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.Natural selection is the process by which those heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations.^ Also, a larger population makes it much more likely for mutations to happen.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Whatever genetic traits (advantageous or otherwise) those successful individuals possess will, of course, also have greater representation in the following generations, leading, over time, to a general shift in the genetic profile of the population.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

It is a key mechanism of evolution.
.The natural genetic variation within a population of organisms means that some individuals will survive and reproduce more successfully than others in their current environment.^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Genetic drift in this small mtDNA population would have been much stronger than for autosomal genes, and very much stronger than in most recent human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The project’s homepage includes this short statement: The goal of the International HapMap Project is to compare the genetic sequences of different individuals to identify chromosomal regions where genetic variants are shared.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

For example, the peppered moth exists in both light and dark colors in the United Kingdom, but during the industrial revolution many of the trees on which the moths rested became blackened by soot, giving the dark-colored moths an advantage in hiding from predators. .This gave dark-colored moths a better chance of surviving to produce dark-colored offspring, and in just a few generations the majority of the moths were dark.^ In each generation, only some individuals will produce offspring themselves, and of those that reproduce, some will leave more offspring than others.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Only when all of this has occurred could selection select the animal which survived best and produced more offspring.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ As a result, each generation is assumed to produce animals that are slightly better adapted to local conditions than the previous one.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.Factors which affect reproductive success are also important, an issue which Charles Darwin developed in his ideas on sexual selection.^ Charles Darwin distinguished sexual selection as variance in the number of mates.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Science has a very important paper in the current issue about the evolution of a gene enhancer in hominids, expressed in forelimb development and concentrated toward the first digit.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In many species, adults must compete with each other for mates ( sexual selection ), and success in this competition determines who will parent the next generation.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Natural selection acts on the phenotype, or the observable characteristics of an organism, but the genetic (heritable) basis of any phenotype which gives a reproductive advantage will become more common in a population (see allele frequency).^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Throughout history, you will see natural selection through force by humans who use fear base thinking.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ But balancing selection, for example, can be reduced to density-dependence on an allele's frequency.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Over time, this process can result in adaptations that specialize organisms for particular ecological niches and may eventually result in the emergence of new species.^ The result of this would be the formation of new species."
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Given enough time, this passive process can result in adaptations and speciation (see evolution ).
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ I have also chosen these examples to illustrate how counterbalancing selection can constrain reproductive traits and result in the process of adaptation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.In other words, natural selection is an important process (though not the only process) by which evolution takes place within a population of organisms.^ The consequence of natural selection on the genetic structure and evolution of organisms is complicated.
  • Population Genetics of Plant Pathogens | APSnet Education Center | Natural Selection in Plant Pathosystems 13 January 2010 14:16 UTC www.apsnet.org [Source type: Academic]

^ "Balancing selection is rare in natural populations.

^ Natural selection need not apply only to biological organisms.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Natural selection is one of the cornerstones of modern biology.^ Natural selection is a cornerstone of modern biology.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ We don’t know all the factors involved in “natural selection,” for one.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ Regardless, the alleles that lead to an increase an individuals ability to either secure a mate or to secure the mate of one's choice are selected, at least in part, by a form of natural selection known as sexual selection .

.The term was introduced by Darwin in his influential 1859 book On the Origin of Species,[1] in which natural selection was described as analogous to artificial selection, a process by which animals and plants with traits considered desirable by human breeders are systematically favored for reproduction.^ Throughout history, you will see natural selection through force by humans who use fear base thinking.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ Well, you can breed a thousand plants and select for any trait you want!
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Remarkably, it appeared that natural selection for copper tolerance had indirectly resulted in the evolutionary origin of the hybrid incompatibility (Wu et al.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.The concept of natural selection was originally developed in the absence of a valid theory of heredity; at the time of Darwin's writing, nothing was known of modern genetics.^ Natural selection is a cornerstone of modern biology.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ But so too is his selection of details from nature to support his theory.
  • Sample Chapter for Levine, G.: Darwin Loves You: Natural Selection and the Re-enchantment of the World. 13 January 2010 14:16 UTC press.princeton.edu [Source type: Original source]

^ The genetical theory of natural selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.The union of traditional Darwinian evolution with subsequent discoveries in classical and molecular genetics is termed the modern evolutionary synthesis.^ The modern evolutionary synthesis .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ The Reproductive Powers of Living Beings and the Survival of the Fittest Dobzhansky’s 1937 work Genetics and the Origin of Species is generally viewed as the crystallization point for the origin and growth of the modern synthesis or neo-Darwinian theory of evolution (Lönnig, 1999a).
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ Modern Synthesis is a theory about how evolution works at the level of genes, phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and individuals.

.Natural selection remains the primary explanation for adaptive evolution.^ This paper focuses on the major problems of positing natural selection as the primary explanation for the complexity and diversity universally displayed in the living world.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The fact that this logical outcome of evolution is not found argues against megaevolution by natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Many of the challenges to Darwinian evolution are specifically challenges to natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

Contents

General principles

Darwin's illustrations of beak variation in the finches of the Galápagos Islands, which hold 13 closely related species that differ most markedly in the shape of their beaks. The beak of each species is suited to its preferred food, suggesting that beak shapes evolved by natural selection.
.Natural variation occurs among the individuals of any population of organisms.^ Modern Synthesis is a theory about how evolution works at the level of genes, phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and individuals.

^ Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Favorable variations will therefore accumulate in populations by natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.Many of these differences do not affect survival (such as differences in eye color in humans), but some differences may improve the chances of survival of a particular individual.^ The chimpanzee genome draft had many more sequencing artifacts at that time than the human genome, and these might account for the apparent excess in chimpanzees.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ But if we actually have many hundreds, or even thousands, of recently selected alleles (as we do in humans), then there is a pretty good chance that some of them will look like introgression under the test used here.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Thus, one may demolish a computer in a thousand and more different ways by some accidental procedures.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

.A rabbit that runs faster than others may be more likely to escape from predators, and algae that are more efficient at extracting energy from sunlight will grow faster.^ The problem with that approach is that it's hard to say that some other parameters may not have been more important.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ It is plausible (as a hypothesis) that the enhancer with the most selected substitutions on the human lineage might be more likely than others to have been selected for multiple functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Strong evolutionary change in its sequence may reflect changes in one of those functions, or more than one.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Individuals that have better odds for survival also have better odds for reproduction.^ In fact, natural selection does act on individuals; their characteristics affect their chances of survival and reproductive success.

^ "On rare occasions, however, a mutant allele may actually fit its bearer to the environment better and enhance the reproductive success of the individual.

.If the traits that give these individuals a reproductive advantage are also heritable, that is, passed from parent to child, then there will be a slightly higher proportion of fast rabbits or efficient algae in the next generation.^ Natural selection is differential reproductive success: in the absence of natural selection an organism contributes x gametes to the next generation; in the presence of natural selection an organism contributes < x gametes to the next generation .

^ The power of natural selection will also inevitably depend upon prevailing environmental factors; in general, the number of offspring is (far) greater than the number of individuals that can survive to the next generation, and there will be intense selection of the best adapted individuals for the next generation.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection works on the whole individual, but only the heritable component of a trait will be passed on to the offspring, with the result that favorable, heritable traits become more common in the next generation .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

This is known as differential reproduction. .Even if the reproductive advantage is very slight, over many generations any heritable advantage will become dominant in the population, due to exponential growth.^ We would still know that the Neandertal haplogroup was very common in its population, even if we thought it was only 50%.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ But considering the powerful effect of weak selection over the many generations involved here, and the very large size of the South Asian population during most of that time, genetic drift seems pretty unlikely.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Over the long term, it will never approach fixation, but nor will it become extinct unless the advantages are weak relative to the size of the population.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.In this way the natural environment of an organism "selects" for traits that confer a reproductive advantage, causing gradual changes or evolution of life.^ This process of natural selection is the means of selecting the best of this variety, causing evolution.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The importance attributed to natural selection as a cause of evolution varies widely.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ "The modern synthesis emphasizes the importance of populations as the units of evolution, the central role of natural selection as the most important mechanism of evolution, and the idea of gradualism to explain how large changes can evolve as an accumulation of small changes occurring over long periods of time."

This effect was first described and named by Charles Darwin.
.The concept of natural selection predates the understanding of genetics, which is the study of heredity.^ The genetical theory of natural selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Title: genetical theory of natural selection .
  • genetical theory of natural selection - AbeBooks 13 January 2010 14:16 UTC www.abebooks.com [Source type: General]

^ The key element in understanding natural selection is the concept of fitness .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

In modern times, it is understood that selection acts on an organism's phenotype, or observable characteristics, but it is the organism's genetic make-up or genotype that is inherited. .The phenotype is the result of the genotype and the environment in which the organism lives (see Genotype-phenotype distinction).^ It suggests that arrival in a new environment can result in dramatic changes to an organism within fewer than 40 lifetimes.
  • A Natural Selection - Opinionator Blog - NYTimes.com 13 January 2010 14:16 UTC judson.blogs.nytimes.com [Source type: FILTERED WITH BAYES]

^ All that is required is genotypes, phenotypes, some interaction between the phenotypes and an environment, and natural selection on one property — speed.
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

^ Acting on phenotypes, selection indirectly adapts a population to its environment by increasing or maintaining favorable genotypes in the gene pool ."

.This is the link between natural selection and genetics, as described in the modern evolutionary synthesis.^ Natural selection is a cornerstone of modern biology.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ The modern evolutionary synthesis .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ The genetical theory of natural selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Although a complete theory of evolution also requires an account of how genetic variation arises in the first place (such as by mutation and sexual reproduction) and includes other evolutionary mechanisms (such as gene flow), natural selection is still understood as a fundamental mechanism for evolution.^ "How can such a harmful mutation be so common?"
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Random genetic drift is fairly easy to refute, although it might not appear so at first.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Nomenclature and usage

.The term natural selection has slightly different definitions in different contexts.^ Scientists use several, slightly different definitions of natural selection.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Definitions of natural selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Konrad Lorenz won the Nobel Prize in 1973 for his analysis of animal behavior in terms of the role of natural selection (particularly group selection).
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.It is most often defined to operate on heritable traits, because these are the traits that directly participate in evolution.^ The evolutionary response to natural selection is invariably less than the selection differential because the heritability of any trait is less than 1.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Often, natural selection acts on specific traits of an individual, and the terms phenotype and genotype are sometimes used narrowly to indicate these specific traits.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Variation in most of these genes has only a small effect on the phenotypic value of a trait, and the study of the genetics of these quantitative traits is called quantitative genetics .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.However, natural selection is "blind" in the sense that changes in phenotype (physical and behavioral characteristics) can give a reproductive advantage regardless of whether or not the trait is heritable (non heritable traits can be the result of environmental factors or the life experience of the organism).^ The mechanism of selection of individuals in a population does not "know" which traits are heritable; in this sense, the mechanisms of selection are "blind".
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ "An organism exposes its phenotype its physical traits , metabolism , physiology, and behavior not its genotype , to the environment .

^ Natural selection acts on the phenotype .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Following Darwin's primary usage[1] the term is often used to refer to both the evolutionary consequence of blind selection and to its mechanisms.^ The use of this term is very clear: Its only purpose is to vilify folks who want to explain evolution in terms of Darwin's mechanism.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[2][3] .It is sometimes helpful to explicitly distinguish between selection's mechanisms and its effects; when this distinction is important, scientists define "natural selection" specifically as "those mechanisms that contribute to the selection of individuals that reproduce", without regard to whether the basis of the selection is heritable.^ We can think of this as the "natural” process of selection of individuals to reproduce.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ This article discusses natural selection in this sense of being the mechanisms of selection of individuals to reproduce.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection can achieve a similar effect.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

This is sometimes referred to as "phenotypic natural selection".[4]
.Traits that cause greater reproductive success of an organism are said to be selected for, whereas those that reduce success are selected against.^ I have also chosen these examples to illustrate how counterbalancing selection can constrain reproductive traits and result in the process of adaptation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Moreover, a behavioral shift, whether due to genetic or environemental causes, exposes an organism to novel selective pressures.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Climate change has caused a change in the pattern of selection, by relaxing selection against small individuals who would otherwise have died from food scarcity.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Selection for a trait may also result in the selection of other correlated traits that do not themselves directly influence reproductive advantage.^ Selection for a specific trait can also result in the indirect selection of other traits ("free riders").
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ I have also chosen these examples to illustrate how counterbalancing selection can constrain reproductive traits and result in the process of adaptation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ In other words, behavioral correlates of climate may be a target of selection and introgression -- I would speculate because of the intrinsic rarity of adaptive mutations in these functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

This may occur as a result of pleiotropy or gene linkage.[5]

Fitness

.The concept of fitness is central to natural selection.^ The key element in understanding natural selection is the concept of fitness .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection can also act at the level of gamete generation; obviously an individual who can't make gametes has a Darwinian fitness (and r e lative fitness ) of zero .

^ Relative fitness and the selection coefficients employed when mathematically following the impact of selection on a population are essentially identical concepts .

.Broadly, individuals which are more "fit" have better potential for survival, as in the well-known phrase "survival of the fittest". However, as with natural selection above, the precise meaning of the term is much more subtle, and Richard Dawkins manages in his later books to avoid it entirely.^ Evolution by means of natural selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection is then "the survival of the survivors."
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ Natural selection is survival of the fittest, and the tautology hinges on the word fittest .
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

.(He devotes a chapter of his book, The Extended Phenotype, to discussing the various senses in which the term is used).^ Most people were used to discussing protein coding sections of the genome and all evo devo does is shift the location where the random variation happens.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

^ The term intelligence is used here in the classical sense, and does not refer to inherited instincts, without which almost no animal could survive.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.Modern evolutionary theory defines fitness not by how long an organism lives, but by how successful it is at reproducing.^ Long live the neutral theory.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Hense, the modern evolutionary theory is garbage.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

^ For selection to occur, a living organism must exist that is capable of successfully reproducing, and also of ingesting, assimilating, and processing food.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.If an organism lives half as long as others of its species, but has twice as many offspring surviving to adulthood, its genes will become more common in the adult population of the next generation.^ Organisms produce more offspring than can possibly survive (many do at least).
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The more successful species would have more of its offspring around; more would be reproduced, and more would survive.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ A reduction will happen in a single generation as small individuals remain to become adults who would otherwise have been removed.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Though natural selection acts on individuals, the effects of chance mean that fitness can only really be defined "on average" for the individuals within a population.^ The average fitness of the population declines over time.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ "Balancing selection is rare in natural populations.

^ Natural selection can achieve a similar effect.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.The fitness of a particular genotype corresponds to the average effect on all individuals with that genotype.^ Natural selection acts on individuals, but its average effect on all individuals with a particular genotype is the fitness of that genotype.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Consider the average fitness of individuals in a population that has not yet evolved elaborate sexual ornaments compared to the population, which is derived from the original stock, but males have now evolved elaborate ornaments.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Genetic drift, the statistical effect of what happens when the quotient of natural selection is 0, can destroy the allele of interest, or can obliterate all other alleles of a particular gene in a particular species.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

.Very low-fitness genotypes cause their bearers to have few or no offspring on average; examples include many human genetic disorders like cystic fibrosis.^ Genetic drift in this small mtDNA population would have been much stronger than for autosomal genes, and very much stronger than in most recent human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Humans have to be inbred to explain the low genetic variation today.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ So you choose a very conservative cutoff, one that is not likely to include very many women.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Since fitness is an averaged quantity, it is also possible that a favorable mutation arises in an individual that does not survive to adulthood for unrelated reasons.^ Consider the average fitness of individuals in a population that has not yet evolved elaborate sexual ornaments compared to the population, which is derived from the original stock, but males have now evolved elaborate ornaments.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Individuals in the center of the phenotype distribution tend to be favored and have higher fitness than individuals in the "tails" of the distribution.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.Fitness also depends crucially upon the environment.^ Thus, Darwinian fitness is an environment-specific quantity (i.e., it may change depending on environment) .

.Conditions like sickle-cell anemia may have low fitness in the general human population, but because the sickle-cell trait confers immunity from malaria, it has high fitness value in populations which have high malaria infection rates.^ The rate of generation of new neutral mutations is directly proportional to population size (2 N e u for an autosomal locus).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In the long run, this will have not a jot of effect on the neutral substitution rate, but it accounts for most of the neutral evolution of allele frequencies in human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Further, a number of studies have identified a substantial cytoplasmic contribution to fitness and lifespan variance in Drosophila , suggesting that adaptive variation in mtDNA may be segregating within populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Types of selection

.Natural selection can act on any phenotypic trait, and selective pressure can be produced by any aspect of the environment, including sexual selection and competition with members of the same species.^ In this sense, natural selection includes any selection by a natural agent, including sexual selection and kin selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection usually acts on many traits at any point in time.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ But can natural selection produce this specified complexity?
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

.However, this does not imply that natural selection is always directional and results in adaptive evolution; natural selection often results in the maintenance of the status quo by eliminating less fit variants.^ However, direct evidence of natural selection in these cases is lacking.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Evolution by means of natural selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ A prerequisite for natural selection to result in adaptive evolution , novel traits and speciation , is the presence of heritable genetic variation that results in fitness differences.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

The unit of selection can be the individual or it can be another level within the hierarchy of biological organisation, such as genes, cells, and kin groups. .There is still debate about whether natural selection acts at the level of groups or species to produce adaptations that benefit a larger, non-kin group.^ There is still debate, however, about whether natural selection acts at the level of groups or species , (i.e.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ But can natural selection produce this specified complexity?
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

^ Natural selection acts on the phenotype .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Selection at a different level such as the gene can result in an increase in fitness for that gene, while at the same time reducing the fitness of the individuals carrying that gene, in a process called intragenomic conflict.^ The timing of selection at the human FOXP2 gene.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ As Africanized bees have spread across South and into North America, adaptive genes from the existing populations of European bees have introgressed into the Africanized population, increasing under positive selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ So selection on mtDNA has never been a sufficient or necessary hypothesis, even if we assume that other genes carried by Neandertals still survive.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Overall, the combined effect of all selection pressures at various levels determines the overall fitness of an individual, and hence the outcome of natural selection.^ Natural selection can achieve a similar effect.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Natural selection acts on individuals, but its average effect on all individuals with a particular genotype is the fitness of that genotype.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Overall, the combined effect of all selection pressures at various levels determines the overall fitness of an individual, and hence the outcome of natural selection.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.The life cycle of a sexually reproducing organism.^ File:Selection forces.gif Figure 2 : The life cycle of a sexually reproducing organism.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Various components of natural selection are indicated for each life stage.^ Various components of natural selection are indicated for each life stage.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection works on the whole individual, but only the heritable component of a trait will be passed on to the offspring, with the result that favorable, heritable traits become more common in the next generation .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ In any case, as a variant of natural selection theory, it only has the ability to destroy.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

[6]
.Natural selection occurs at every life stage of an individual.^ Natural selection can also act at the level of gamete generation; obviously an individual who can't make gametes has a Darwinian fitness (and r e lative fitness ) of zero .

^ It's worth pointing out that nothing in the approach of Wall and colleagues implies that any of the putative introgression occurred under natural selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Regardless, the alleles that lead to an increase an individuals ability to either secure a mate or to secure the mate of one's choice are selected, at least in part, by a form of natural selection known as sexual selection .

.An individual organism must survive until adulthood before it can reproduce, and selection of those that reach this stage is called viability selection.^ After an individual is born, it has to survive until adulthood before it can reproduce, and selection of those that reach this stage is called viability selection .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection is the process by which individual organisms with favorable traits are more likely to survive and reproduce than those with unfavorable traits.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ We can think of this as the "natural” process of selection of individuals to reproduce.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.In many species, adults must compete with each other for mates via sexual selection, and success in this competition determines who will parent the next generation.^ Sexual selection acts via variance in the number of mates.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Natural selection can also act at the level of gamete generation; obviously an individual who can't make gametes has a Darwinian fitness (and r e lative fitness ) of zero .

^ A reduction will happen in a single generation as small individuals remain to become adults who would otherwise have been removed.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.When individuals can reproduce more than once, a longer survival in the reproductive phase increases the number of offspring, called survival selection.^ The more successful species would have more of its offspring around; more would be reproduced, and more would survive.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ But , of course, survival is a prerequisite for reproducing, and longevity increases fitness if it results in certain individuals leaving more descendants than other individuals leave.

^ Yes, they are much more likely to reduce fitness than to increase it, but many of them are not lethal.
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

.The fecundity of both females and males (for example, giant sperm in certain species of Drosophila)[7] can be limited via "fecundity selection". The viability of produced gametes can differ, while intragenomic conflicts such as meiotic drive between the haploid gametes can result in gametic or "genic selection". Finally, the union of some combinations of eggs and sperm might be more compatible than others; this is termed compatibility selection.^ The chimpanzee genome draft had many more sequencing artifacts at that time than the human genome, and these might account for the apparent excess in chimpanzees.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Possibly, one or more causes of stabilizing selection remain in force (maybe longer development time, but there are other possibilities).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The problem with that approach is that it's hard to say that some other parameters may not have been more important.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Sexual selection

.It is useful to distinguish between "ecological selection" and "sexual selection". Ecological selection covers any mechanism of selection as a result of the environment (including relatives, e.g.^ Our results suggest that the migration of modern humans out of Africa into new environments was accompanied by genetic adaptations to emergent selective forces.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ In principle, it is possible to distinguish between demography and selection, because demography affects all loci in the genome, whereas selection acts upon specific loci.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ Distinguishing the relative contributions of selective sweeps and background purifying selection to the correlations, however, has proven difficult [72] – [76] .
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.kin selection, competition, and infanticide), while "sexual selection" refers specifically to competition for mates.^ In many species, adults must compete with each other for mates ( sexual selection ), and success in this competition determines who will parent the next generation.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Consider the familiar example of runaway sexual selection in which genes underlying mate-choice can lead to the rapid evolution of bizarre and elaborate male ornaments.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Selective mating can be the result of, for example, a change in the physical environment (physical isolation by an extrinsic barrier), or by sexual selection resulting in assortative mating .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

[8]
.Sexual selection can be intrasexual, as in cases of competition among individuals of the same sex in a population, or intersexual, as in cases where one sex controls reproductive access by choosing among a population of available mates.^ In intersexual selection, also called mate choice, individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex.

^ Intrasexual selection is a direct competition among individuals of one sex (usually the males in vertebrates) for mates of the opposite sex.

^ We can distinguish sexual selection into an intrasexual and intersexual selection .

.Most commonly, intrasexual selection involves male–male competition and intersexual selection involves female choice of suitable males, due to the generally greater investment of resources for a female than a male in a single offspring.^ Intersexual selection ( mate choice ) .

^ Female Choice: Intersexual selection, in which females choose males based upon elaborate ornamentation or male behaviors, or Male Competition: Intrasexual selection, in which males compete for territory or access to females, or areas on mating grounds where displays take place.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Males and females often differ phenotypically other than in their possessing different sexual organs .

.However, some species exhibit sex-role reversed behavior in which it is males that are most selective in mate choice; the best-known examples of this pattern occur in some fishes of the family Syngnathidae, though likely examples have also been found in amphibian and bird species.^ It is plausible (as a hypothesis) that the enhancer with the most selected substitutions on the human lineage might be more likely than others to have been selected for multiple functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ I have to select some part to quote for you, so I'll select the passage that would be most likely to come out of my own math in my genetics class: .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ My hypothesis would be natural selection on some significant subset of phenotypic characters, which reduced the phenotypic variance of most of the cranium by pleiotropy.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[9]
.Some features that are confined to one sex only of a particular species can be explained by selection exercised by the other sex in the choice of a mate, for example, the extravagant plumage of some male birds.^ In intersexual selection, also called mate choice, individuals of one sex (usually females) are choosy in selecting their mates from individuals of the other sex.

^ Intersexual selection ( mate choice ) .

^ Genetic drift, the statistical effect of what happens when the quotient of natural selection is 0, can destroy the allele of interest, or can obliterate all other alleles of a particular gene in a particular species.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

Similarly, aggression between members of the same sex is sometimes associated with very distinctive features, such as the antlers of stags, which are used in combat with other stags. .More generally, intrasexual selection is often associated with sexual dimorphism, including differences in body size between males and females of a species.^ Males and females often differ phenotypically other than in their possessing different sexual organs .

^ This would comprise a component of sexual selection that acts on male body size.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Sexual selection (sexual dimorphism, secondary sexual characteristics) .

[10]

Examples of natural selection

Resistance to antibiotics is increased though the survival of individuals which are immune to the effects of the antibiotic, whose offspring then inherit the resistance, creating a new population of resistant bacteria.
A well-known example of natural selection in action is the development of antibiotic resistance in microorganisms. Since the discovery of penicillin in 1928 by Alexander Fleming, antibiotics have been used to fight bacterial diseases. .Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations.^ Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, primarily as the result of mutations .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Natural selection results in the reduction of genetic variation through the elimination of maladapted individuals and, through that, of the mutations that causes the maladaptation.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ However, populations of bacteria are enormous, and so a few individuals will have beneficial mutations.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them slightly less susceptible.^ When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them a little less susceptible.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ This is an example of what is sometimes called an ' arms race ', in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Slight genetic mistakes or imperfection called mutations may result in some new traits.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.If the exposure to antibiotics is short, these individuals will survive the treatment.^ If the exposure to antibiotics is short, these individuals will survive the treatment.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.This selective elimination of maladapted individuals from a population is natural selection.^ This selective elimination of maladapted individuals from a population is natural selection in action .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ We can think of this as the "natural” process of selection of individuals to reproduce.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ This article discusses natural selection in this sense of being the mechanisms of selection of individuals to reproduce.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.These surviving bacteria will then reproduce again, producing the next generation.^ These surviving bacteria will then reproduce again, producing the next generation.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ In each generation, only some individuals will produce offspring themselves, and of those that reproduce, some will leave more offspring than others.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.Due to the elimination of the maladapted individuals in the past generation, this population contains more bacteria that have some resistance against the antibiotic.^ Due to the elimination of the maladapted individuals in the past generation, this population contains more bacteria that have some resistance against the antibiotic.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ This selective elimination of maladapted individuals from a population is natural selection in action .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ In general, there is a lot more polymorphism in wild populations than one might otherwise expect .

.At the same time, new mutations occur, contributing new genetic variation to the existing genetic variation.^ At the same time, new mutations occur, contributing new genetic variation to the existing genetic variation.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ At the same time, new mutations occur, resulting in a mutation-selection balance .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ For example, selection on standing variation rather than new mutations could contribute to divergence but leave little signature in polymorphism data [118] – [120] , potentially leading to higher McDonald-Kreitman-based estimates.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.Spontaneous mutations are very rare, and advantageous mutations are even rarer.^ Spontaneous mutations are very rare, very few have any effect at all, and usually any effect is deleterious.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ At stake is many millions of dollars which can be gained even if the breeding produces only a very small advantage.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Any of these changes might have an effect that is highly advantageous or highly disadvantageous, but large effects are very rare.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

.However, populations of bacteria are large enough that a few individuals will have beneficial mutations.^ Finally, even if an optimal allele can in theory be reached mutationally, expect within large populations the needed mutation likely will not be achieved .

^ Many differences between species may also be neutral, if the fraction of newly arising neutral mutations is large enough to offset their low chance of fixation.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ In turn, the 100-kb scale may be large enough to include both a strongly beneficial substitution and the reduction in diversity that it caused, but may be too large for the effects of weakly beneficial substitutions to be detected.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic.^ If the creature survives a mutation which is not harmful enough to impede early survival, it will likely be passed on to one's offspring.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Yes, they are much more likely to reduce fitness than to increase it, but many of them are not lethal.
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

^ Basically, in a population which is not well mixed (i.e., not highly mobile) individuals more likely mate with neighbors than with non-neighbors (the guy next door versus the guy 8,000 miles down the road) .

.Given enough time, and repeated exposure to the antibiotic, a population of antibiotic-resistant bacteria will emerge.^ Individuals sampled at any given time in the population sink are overwhelmingly likely to have ancestors not in the sink but in one or more source populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Thus, three alleles (or many more) can exist in a population (with associated allele frequencies) but only up to two alleles at a time can exist within a given individual .

^ According to Dembski's argument we would not need to worry: bacteria infecting a patient could not evolve antibiotic resistance.
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

.This new changed population of antibiotic-resistant bacteria is optimally adapted to the context it evolved in.^ The last section shows the distribution of resistance in a new generation of bacteria.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ This is an example of what is sometimes called an ' arms race ', in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ Therefore, the fewer polymorphisms, the less ably a population can respond to environmental change (i.e., the population is less able to adapt ) .

.At the same time, it is not necessarily optimally adapted any more to the old antibiotic free environment.^ It is also assumed that those that survive to reproduce are more likely to be better adapted to the environment, and are generally biologically superior.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Environments change all the time, not necessarily catastrophically, but change nonetheless .

^ And if it did so, why could it not then become adapted to still more demanding conditions, and so expand its geographic range (or its altitudinal or habit distribution) indefinitely over the course of time?
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

.The end result of natural selection is two populations that are both optimally adapted to their specific environment, while both perform substandard in the other environment.^ "Balancing selection is rare in natural populations.

^ Selection for a specific trait can also result in the indirect selection of other traits ("free riders").
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ "Of all the causes of microevolution, only natural selection generally adapts a population to its environment.

The widespread use and misuse of antibiotics has resulted in increased microbial resistance to antibiotics in clinical use, to the point that the methicillin-resistant Staphylococcus aureus (MRSA) has been described as a "superbug" because of the threat it poses to health and its relative invulnerability to existing drugs.[11] .Response strategies typically include the use of different, stronger antibiotics; however, new strains of MRSA have recently emerged that are resistant even to these drugs.^ Recently, several new strains of MRSA have emerged that are resistant to vancomycin and teicoplanin {{#if:Schito GC .
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ However, the widespread use and especially misuse of antibiotics has led to increased microbial resistance against antibiotics, to the point that the methicillin-resistant Staphylococcus aureus (MRSA) has been described as a ' superbug ' because of the threat it poses to health and its relative invulnerability to existing drugs.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

[12]
.This is an example of what is known as an evolutionary arms race, in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them.^ This is an example of what is sometimes called an ' arms race ', in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

^ He acknowledges that "the development of antibiotic resistance by pathogens via the Darwinian mechanism is experimentally verified and rightly of great concern to the medical field" (Dembski 2002: 38).
  • Has Natural Selection Been Refuted? The Arguments of William Dembski | NCSE 13 January 2010 14:16 UTC ncse.com [Source type: FILTERED WITH BAYES]

^ If a new mutation reduces their susceptibility to an antibiotic, these individuals are more likely to survive when next confronted with that antibiotic.
  • Natural selection - Hwiki 13 January 2010 14:16 UTC hwiki.fzk.de [Source type: Academic]

A similar situation occurs with pesticide resistance in plants and insects. Arms races are not necessarily induced by man; a well-documented example involves the elaboration of the RNA interference pathway in plants as means of innate immunity against viruses.[13]

Evolution by means of natural selection

.A prerequisite for natural selection to result in adaptive evolution, novel traits and speciation, is the presence of heritable genetic variation that results in fitness differences.^ Jerry, genetic drift is just a simple variant of natural selection.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

^ The importance attributed to natural selection as a cause of evolution varies widely.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Selection depletes additive genetic variation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.Genetic variation is the result of mutations, recombinations and alterations in the karyotype (the number, shape, size and internal arrangement of the chromosomes).^ Hence, the net result of larger numbers of gene mutations can mean overall degeneration of a species instead of ‘upward‘ evolution.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ Thus, the number of significant genes in the European-American sample, after incorporating recombination and correcting for multiple tests, is very similar to the initial results where recombination was ignored and multiple tests were not corrected for.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ The project’s homepage includes this short statement: The goal of the International HapMap Project is to compare the genetic sequences of different individuals to identify chromosomal regions where genetic variants are shared.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Any of these changes might have an effect that is highly advantageous or highly disadvantageous, but large effects are very rare.^ Very reliable since changing modes is not a consequential command, you can undo the effect of a mistaken command by just doing the right command.
  • Natural Selection: 13 January 2010 14:16 UTC www.piemenus.com [Source type: General]

^ However, keep in mind that mutations are not only rare but also often represent random changes in highly evolved (i.e., information laden) nucleotide sequences .

^ By drawing parallels between these two sets, the enchantment effect of the contemporary morphings might be enhanced” (50).
  • Sample Chapter for Levine, G.: Darwin Loves You: Natural Selection and the Re-enchantment of the World. 13 January 2010 14:16 UTC press.princeton.edu [Source type: Original source]

.In the past, most changes in the genetic material were considered neutral or close to neutral because they occurred in noncoding DNA or resulted in a synonymous substitution.^ Changes in population size make absolutely no difference to the neutral substitution rate.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ According to the press release, they identify a number of cases in which sites inferred to be under selection are actually not the functional change, because other functional changes have been identified by experiment.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In the long run, this will have not a jot of effect on the neutral substitution rate, but it accounts for most of the neutral evolution of allele frequencies in human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.However, recent research suggests that many mutations in non-coding DNA do have slight deleterious effects.^ Find this article online Charlesworth B (1994) The effect of background selection against deleterious mutations on weakly selected, linked variants.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Find this article online Andolfatto P (2005) Adaptive evolution of non-coding DNA in Drosophila.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ I think once the “non-coding” DNA leg is kicked out from underneath them they’ll flounder in the statistics.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

[14][15] .Although both mutation rates and average fitness effects of mutations are dependent on the organism, estimates from data in humans have found that a majority of mutations are slightly deleterious.^ In the long run, this will have not a jot of effect on the neutral substitution rate, but it accounts for most of the neutral evolution of allele frequencies in human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Therefore, the rate of neutral evolution in humans really has accelerated , as a function of hitchhiking on new adaptive mutations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[16]
The exuberant tail of the peacock is thought to be the result of sexual selection by females. This peacock is an albino; selection against albinos in nature is intense because they are easily spotted by predators or are unsuccessful in competition for mates.
.By the definition of fitness, individuals with greater fitness are more likely to contribute offspring to the next generation, while individuals with lesser fitness are more likely to die early or fail to reproduce.^ Darwinian fitness is the allelic contribution an individual makes to the next generation .

^ Thus, the more likely an individual is to survive and reproduce (i.e., to contributes its alleles to the next generation), the higher that individual's Darwinian fitness .

^ Natural selection can also act at the level of gamete generation; obviously an individual who can't make gametes has a Darwinian fitness (and r e lative fitness ) of zero .

.As a result, alleles which on average result in greater fitness become more abundant in the next generation, while alleles which generally reduce fitness become rarer.^ Furthermore, the longer a population remains at a reduced size, the greater the effect of genetic drift on allele frequency .

^ More generally, our results have important implications for mapping genes underlying complex human diseases.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ More generally, our results have several implications for mapping genes underlying complex human diseases.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

.If the selection forces remain the same for many generations, beneficial alleles become more and more abundant, until they dominate the population, while alleles with a lesser fitness disappear.^ A reduction will happen in a single generation as small individuals remain to become adults who would otherwise have been removed.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In general, there is a lot more polymorphism in wild populations than one might otherwise expect .

^ Possibly, one or more causes of stabilizing selection remain in force (maybe longer development time, but there are other possibilities).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.In every generation, new mutations and recombinations arise spontaneously, producing a new spectrum of phenotypes.^ The rate of generation of new neutral mutations is directly proportional to population size (2 N e u for an autosomal locus).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The fast rate of generation of new adaptive mutations means that the rate of neutral evolution by hitchhiking has vastly accelerated in the recent past.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ A useful measure of the amount of selection during a given generation is the difference in the mean between the phenotype distribution before and after selection, but before the next generation of progeny is produced.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.Therefore, each new generation will be enriched by the increasing abundance of alleles that contribute to those traits that were favored by selection, enhancing these traits over successive generations.^ I have also chosen these examples to illustrate how counterbalancing selection can constrain reproductive traits and result in the process of adaptation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ That is, natural selection serves to reduce certain genotypes relative to others in terms of their contribution of alleles to the gene pool .

^ That is, mutation places alleles into a gene pool, other microevolutionary forces can serve to increase the frequency of the allele, but selection acts to selectively remove maladaptive alleles (mutation in, selection out) .

Some mutations occur in so-called regulatory genes. .Changes in these can have large effects on the phenotype of the individual because they regulate the function of many other genes.^ Genetic drift, the statistical effect of what happens when the quotient of natural selection is 0, can destroy the allele of interest, or can obliterate all other alleles of a particular gene in a particular species.
  • Jerry Fodor: Natural Selection Has Gone Bust | Uncommon Descent 13 January 2010 14:16 UTC www.uncommondescent.com [Source type: Original source]

^ In other words, behavioral correlates of climate may be a target of selection and introgression -- I would speculate because of the intrinsic rarity of adaptive mutations in these functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ According to the press release, they identify a number of cases in which sites inferred to be under selection are actually not the functional change, because other functional changes have been identified by experiment.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Most, but not all, mutations in regulatory genes result in non-viable zygotes.^ Hence, the net result of larger numbers of gene mutations can mean overall degeneration of a species instead of ‘upward‘ evolution.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ The changes, he lamented, were almost all small so that if a thousand mutations were combined in a single fruit fly, a new species would not result but, at most, only a weird fruit fly which probably would not survive birth (Goldschmidt, 1952, p.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Note that assortative mating serves to constrain the breadth of one's gene pool potentially resulting in inbreeding and all of the consequences of inbreeding discussed above .

Examples of nonlethal regulatory mutations occur in HOX genes in humans, which can result in a cervical rib[17] or polydactyly, an increase in the number of fingers or toes.[18] .When such mutations result in a higher fitness, natural selection will favor these phenotypes and the novel trait will spread in the population.^ "Balancing selection is rare in natural populations.

^ Favorable variations will therefore accumulate in populations by natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The absence of such "positive mutations" results in limits for natural selection.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

X-ray of the left hand of a ten year old boy with polydactyly.
.Established traits are not immutable; traits that have high fitness in one environmental context may be much less fit if environmental conditions change.^ Depending on the number of computers and how often and for how long one proceeds to act this way, one may collect a nearly endless number of non-functional changes.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ When selection acts to change one trait, the other trait will change because the genetic response to selection involves the same genetic locus.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Therefore, the fewer polymorphisms, the less ably a population can respond to environmental change (i.e., the population is less able to adapt ) .

.In the absence of natural selection to preserve such a trait, it will become more variable and deteriorate over time, possibly resulting in a vestigial manifestation of the trait.^ The absence of such "positive mutations" results in limits for natural selection.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ Natural selection usually acts on many traits at any point in time.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.In many circumstances, the apparently vestigial structure may retain a limited functionality, or may be co-opted for other advantageous traits in a phenomenon known as preadaptation.^ In other words, behavioral correlates of climate may be a target of selection and introgression -- I would speculate because of the intrinsic rarity of adaptive mutations in these functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

A famous example of a vestigial structure, the eye of the blind mole rat, is believed to retain function in photoperiod perception.[19]

Speciation

.Speciation requires selective mating, which result in a reduced gene flow.^ (CORRECTION (2008/04/18): If selection were on a linked site, then Neandertals might share the human-derived amino acids as a result of ancient shared ancestry with humans, while the linked selected sweep might be absent in Neandertals, not necessitating any gene flow.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Examples of that kind may not be rare in nature, although in many instances selection may increase population size only to result in added pressure to various prey species, which then reduce the carrying capacity.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Selective mating can be the result of, for example, a change in the physical environment (physical isolation by an extrinsic barrier), or by sexual selection resulting in assortative mating.^ Our results suggest that the migration of modern humans out of Africa into new environments was accompanied by genetic adaptations to emergent selective forces.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ Mankind is moving (evolving) from a physical, environment changing, competitive being into a Pneumatic, environment building, cooperative being.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ Why couldn't the Icelandic genetic changes have been the result of selection that favored some mtDNA lineages rather than others?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Over time, these subgroups might diverge radically to become different species, either because of differences in selection pressures on the different subgroups, or because different mutations arise spontaneously in the different populations, or because of founder effects – some potentially beneficial alleles may, by chance, be present in only one or other of two subgroups when they first become separated.^ Still, one may hope to do better at identifying selected alleles.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ They were able to trace many QTL's of small effect with relation to the major differences in life history and moisture requirements in ecogeographic races of M. guttatus , to show that the within-population variation for these traits is caused by high-frequency (likely balanced) alleles rather than mutation-selection balance or rare alleles, and to find the correlated responses to selection of different plant traits based on different QTL's.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ They do allow for an alternative -- perhaps the two amino-acid-coding mutations were not the target of selection, but instead some linked locus.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.A lesser-known mechanism of speciation occurs via hybridization, well-documented in plants and occasionally observed in species-rich groups of animals such as cichlid fishes.^ Such deleterious interlocus interactions, usually referred to as Dobzhansky–Muller (D-M) incompatibilities, are thought to be the major cause of low hybrid fitness in plants and animals (reviewed in Coyne and Orr, 2004).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[20] .Such mechanisms of rapid speciation can reflect a mechanism of evolutionary change known as punctuated equilibrium, which suggests that evolutionary change and particularly speciation typically happens quickly after interrupting long periods of stasis.^ For example, the relatively long thumbs of the Hadar hominids (compared to chimpanzees and gorillas) suggest that the sequence of changes started early in hominid evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ But if adaptive substitutions are as common as the McDonald-Kreitman-based estimates suggest, then divergence reflects similar contributions of both neutral and adaptive changes.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Strong evolutionary change in its sequence may reflect changes in one of those functions, or more than one.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Genetic changes within groups result in increasing incompatibility between the genomes of the two subgroups, thus reducing gene flow between the groups.^ Gene flow between populations ( migration ) .

^ First, I consider how we might use information theoretic concepts to test the hypothesis of independence between two genetic loci.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Why couldn't the Icelandic genetic changes have been the result of selection that favored some mtDNA lineages rather than others?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Gene flow will effectively cease when the distinctive mutations characterizing each subgroup become fixed.^ An introgressive allele might be linked to several other unique mutations that happened during the long period of limited gene flow between ancient populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ These are genetic drift (i.e., sampling error), migration (i.e., gene flow ), and mutation .

.As few as two mutations can result in speciation: if each mutation has a neutral or positive effect on fitness when they occur separately, but a negative effect when they occur together, then fixation of these genes in the respective subgroups will lead to two reproductively isolated populations.^ The effect of positive and negative selection on linked neutral sites.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Some of these include chance recombination of existing genes which produce positive, negative or neutral characteristics (neutral meaning of equal survival value compared to the parent gene structure), population fluctuations due to chance factors, geographical factors such as oceans or mountains which cause breeding isolation, gene flow, and changes in the length of reproduction and fertility periods.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ They do allow for an alternative -- perhaps the two amino-acid-coding mutations were not the target of selection, but instead some linked locus.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.According to the biological species concept, these will be two different species.^ These are two drastically different explanations of the same pattern -- one based on adaptational causes, the other based on constraints on organismal design.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ In other words, these two methods are complimentary and may potentially detect selection operating over different time scales.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

Historical development

The modern theory of natural selection derives from the work of Charles Darwin in the nineteenth century.

Pre-Darwinian theories

.Several ancient philosophers expressed the idea that nature produces a huge variety of creatures, apparently randomly, and that only those creatures survive that manage to provide for themselves and reproduce successfully; well-known examples include Empedocles[21] and his intellectual successor, Lucretius,[22] while related ideas were later refined by Aristotle.^ Bees also now provide a strong example of adaptive introgression -- in this case, within a very tightly timed dispersal with known climatic conditions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[23] The struggle for existence was later described by Al-Jahiz, who argued that environmental factors influence animals to develop new characteristics to ensure survival.[24][25][26] .Abu Rayhan Biruni described the idea of artificial selection and argued that nature works in much the same way.^ Take a look at the way it describes natural selection: .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In the same manner the variations of each creature are determined by fixed and immutable laws; but these bear no relation to the living structure which is slowly built up through the power of selection, whether this be natural or artificial selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In particular, both selection and genetic drift (and for that matter, mutation) are described by the same equations that describe demography.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[27] Similar ideas were later expressed by Nasir al-Din Tusi[28] and Ibn Khaldun.[29][30] Such classical arguments were reintroduced in the 18th century by Pierre Louis Maupertuis[31] and others, including Charles Darwin's grandfather Erasmus Darwin. .While these forerunners had an influence on Darwinism, they later had little influence on the trajectory of evolutionary thought after Charles Darwin.^ Darwin didn’t make these people killers but he helped explain why they are killers.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

Until the early 19th century, the prevailing view in Western societies was that differences between individuals of a species were uninteresting departures from their Platonic idealism (or typus) of created kinds. However, the theory of uniformitarianism in geology promoted the idea that simple, weak forces could act continuously over long periods of time to produce radical changes in the Earth's landscape. The success of this theory raised awareness of the vast scale of geological time and made plausible the idea that tiny, virtually imperceptible changes in successive generations could produce consequences on the scale of differences between species. .Early 19th century evolutionists such as Jean Baptiste Lamarck suggested the inheritance of acquired characteristics as a mechanism for evolutionary change; adaptive traits acquired by an organism during its lifetime could be inherited by that organism's progeny, eventually causing transmutation of species.^ My point is that if an organism, especially in a variable climate, that carried this gene would be at a selelctive advantantage if that trait were inherited.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ A source-sink model would appear consistent with the continued evolution of such traits during the Upper Paleolithic—a time when the extinction and replacement hypothesis predicts no change in these characters.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The inheritable “trait” being the ability to retain ancient DNA. Also, this trait could be inherited in pieces spread over more than one organism, which are recombined through hybridization with the same results.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[32] This theory has come to be known as Lamarckism and was an influence on the anti-genetic ideas of the Stalinist Soviet biologist Trofim Lysenko.[33]

Darwin's theory

.In 1859, Charles Darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation.^ Even Darwin recognized that the natural selection theory had serious problems.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The genetical theory of natural selection.
  • NATURAL SELECTION 13 January 2010 14:16 UTC www.weloennig.de [Source type: Academic]

^ Adaptation and natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.He defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".[34] The concept was simple but powerful: individuals best adapted to their environments are more likely to survive and reproduce.^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Throughout this chapter and elsewhere I have spoken of selection as the paramount power, yet its action absolutely depends on what we in our ignorance call spontaneous or accidental variability.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In the same manner the variations of each creature are determined by fixed and immutable laws; but these bear no relation to the living structure which is slowly built up through the power of selection, whether this be natural or artificial selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.As long as there is some variation between them, there will be an inevitable selection of individuals with the most advantageous variations.^ Selection is defined as some sort of functional relationship between fitness and phenotype and we can easily describe fitness in terms of three kinds of curves: .
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ It includes a long passage covering the significant mismatch between mtDNA variation and effective population sizes across animals (but not mammals).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ I have to select some part to quote for you, so I'll select the passage that would be most likely to come out of my own math in my genetics class: .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.If the variations are inherited, then differential reproductive success will lead to a progressive evolution of particular populations of a species, and populations that evolve to be sufficiently different eventually become different species.^ Modern Synthesis is a theory about how evolution works at the level of genes, phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and individuals.

^ Within each population, men differ by their genotype, and yet the species Homo sapiens has not modified its plan or structure or functions.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Evolution in Action This interactive feature shows how random mutations can lead to species-wide change.
  • Evolution Library: Topic Page 13 January 2010 14:16 UTC www.pbs.org [Source type: Academic]

[35]
Darwin's ideas were inspired by the observations that he had made on the Beagle voyage, and by the work of two political economists. .The first was the Reverend Thomas Malthus, who in An Essay on the Principle of Population, noted that population (if unchecked) increases exponentially whereas the food supply grows only arithmetically; thus inevitable limitations of resources would have demographic implications, leading to a "struggle for existence" as a divinely ordained law "in order to rouse man into action, and form his mind to reason" for the greater good despite the "partial evil" limiting population.^ We would still know that the Neandertal haplogroup was very common in its population, even if we thought it was only 50%.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ As Africanized bees have spread across South and into North America, adaptive genes from the existing populations of European bees have introgressed into the Africanized population, increasing under positive selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Following these assumptions, on average all the mtDNA genomes at 15,000 years ago would descend from only 4 or 5 ancestral copies in the population 40,000 years ago.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[36] The second was Adam Smith who, in The Wealth of Nations, identified a regulating mechanism in free markets, which he referred to as the "invisible hand", which suggests that prices self-adjust according to supplies and demand.[37] .When Darwin read Malthus in 1838 he was already primed by his work as a naturalist to appreciate the "struggle for existence" in nature and it struck him that as population outgrew resources, "favourable variations would tend to be preserved, and unfavourable ones to be destroyed.^ And a new mutation would not tend to be surrounded by high F ST polymorphisms, until it got to be very common in the population -- up above 50 percent.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Favorable variations will therefore accumulate in populations by natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Find this article online Aguade M, Miyashita N, Langley CH (1989) Reduced variation in the yellow-achaete-scute region in natural populations of Drosophila melanogaster.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.The result of this would be the formation of new species."^ The result of this would be the formation of new species."
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The changes, he lamented, were almost all small so that if a thousand mutations were combined in a single fruit fly, a new species would not result but, at most, only a weird fruit fly which probably would not survive birth (Goldschmidt, 1952, p.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

[38]
.Once he had his theory "by which to work", Darwin was meticulous about gathering and refining evidence as his "prime hobby" before making his idea public.^ Modern Synthesis is a theory about how evolution works at the level of genes, phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and individuals.

^ According to Gould, Darwin's work consisted of uncompromising philosophical materialism in contrast to other evolution theories, most of which utilized vitalism or elements of a theistic evolution.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Yes, the work of Darwin “evolved” into a manifesto that supports “might make right” and provides the justification to kill in order to survive.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

He was in the process of writing his "big book" to present his researches when the naturalist Alfred Russel Wallace independently conceived of the principle and described it in an essay he sent to Darwin to forward to Charles Lyell. .Lyell and Joseph Dalton Hooker decided (without Wallace's knowledge) to present his essay together with unpublished writings which Darwin had sent to fellow naturalists, and On the Tendency of Species to form Varieties; and on the Perpetuation of Varieties and Species by Natural Means of Selection was read to the Linnean Society announcing co-discovery of the principle in July 1858.[39] Darwin published a detailed account of his evidence and conclusions in On the Origin of Species in 1859. In the 3rd edition of 1861 Darwin acknowledged that others — notably William Charles Wells in 1813, and Patrick Matthew in 1831 — had proposed similar ideas, but had neither developed them nor presented them in notable scientific publications.^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Remarkably, it appeared that natural selection for copper tolerance had indirectly resulted in the evolutionary origin of the hybrid incompatibility (Wu et al.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Filed under history natural selection non-primate Monday July 7 2008 8 26 pm .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[40]
.Darwin thought of natural selection by analogy to how farmers select crops or livestock for breeding, which he called "artificial selection"; in his early manuscripts he referred to a 'Nature' which would do the selection.^ Selection: artificial and natural.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Support for natural selection depends heavily upon the validity of its analogy with artificial selection (Tinkle, 1976).
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Filed under Darwin natural selection quotes Wednesday December 24 2008 2 35 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.At the time, other mechanisms of evolution such as evolution by genetic drift were not yet explicitly formulated, and Darwin believed that selection was likely only part of the story: "I am convinced that [it] has been the main, but not exclusive means of modification."^ Population genetics of mutation-selection drift.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Is "genetic drift" that much more likely than selection?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ As my conclusions have lately been much misrepresented, and it has been stated that I attribute the modification of species exclusively to natural selection....
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

[41] .In a letter to Charles Lyell in September 1860, Darwin regretted the use of the term "Natural Selection", preferring the term "Natural Preservation".[42] For Darwin and his contemporaries, natural selection was essentially synonymous with evolution by natural selection.^ The study upends the belief that natural selection is a dominant feature of evolution, noting that climate can trump that card.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ It's time to get the message -- natural selection has been the major force driving recent human evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Filed under Fst HapMap natural selection Friday September 5 2008 3 24 pm .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.After the publication of The Origin of Species, educated people generally accepted that evolution had occurred in some form.^ Some people confuse the idea of adaptive evolution with the idea of neutral evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Animals with more complex brains are also often less able than lower forms to withstand some of the major environmental pressures that supposedly originally caused their evolution, especially temperature and food supply pressures (Colinvaux, 1978).
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.However, natural selection remained controversial as a mechanism, partly because it was perceived to be too weak to explain the range of observed characteristics of living organisms, and partly because even supporters of evolution balked at its "unguided" and non-progressive nature,[43] a response that has been characterized as the single most significant impediment to the idea's acceptance.^ The study upends the belief that natural selection is a dominant feature of evolution, noting that climate can trump that card.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Filed under history natural selection non-primate Monday July 7 2008 8 26 pm .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ It's time to get the message -- natural selection has been the major force driving recent human evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[44] .However, some thinkers enthusiastically embraced natural selection; after reading Darwin, Herbert Spencer introduced the term survival of the fittest, which became a popular summary of the theory.^ Even Darwin recognized that the natural selection theory had serious problems.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ There is a tendency to lump together evolution (a fact which was known as early as Aristotle), natural selection (which was hinted at by al-Jahiz in the ninth century but first systematically propounded by Darwin), “survival of the fittest” (a tautology propounded by Social Darwinists) and eugenics (which is the precise opposite of natural selection) and so forth.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[45] The fifth edition of On the Origin of Species published in 1869 included Spencer's phrase as an alternative to natural selection, with credit given: "But the expression often used by Mr. Herbert Spencer, of the Survival of the Fittest, is more accurate, and is sometimes equally convenient."[46] .Although the phrase is still often used by non-biologists, modern biologists avoid it because it is tautological if "fittest" is read to mean "functionally superior" and is applied to individuals rather than considered as an averaged quantity over populations.^ Consider the average fitness of individuals in a population that has not yet evolved elaborate sexual ornaments compared to the population, which is derived from the original stock, but males have now evolved elaborate ornaments.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Basically, in a population which is not well mixed (i.e., not highly mobile) individuals more likely mate with neighbors than with non-neighbors (the guy next door versus the guy 8,000 miles down the road) .

^ In the case of female choice and male ornaments, the average fitness of individuals in the population can decline as the frequency and intensity of the bizarre male ornaments increases in the population.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

[47]

Modern evolutionary synthesis

.Natural selection relies crucially on the idea of heredity, but it was developed long before the basic concepts of genetics.^ His ideas on natural selection remained private.
  • “Natural Selection” by 2007 Literary Awards Program Winner, Jacob Appel 13 January 2010 14:16 UTC sfwp.org [Source type: General]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Bad vibes and good viruses Co-creators – far away and long ago → Natural Selection and Natural Born Killers .
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

Although the Austrian monk Gregor Mendel, the father of modern genetics, was a contemporary of Darwin's, his work would lie in obscurity until the early 20th century. .Only after the integration of Darwin's theory of evolution with a complex statistical appreciation of Gregor Mendel's 're-discovered' laws of inheritance did natural selection become generally accepted by scientists.^ Even Darwin recognized that the natural selection theory had serious problems.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Given the above, why then is natural selection accepted?
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The Hardy-Weinberg theorem is important conceptually and historically because it shows how Mendels theory of inheritance plugs a hole in Darwin s theory of natural selection The Hardy-Weinberg theorem explains how Mendelian inheritance preserves genetic variation from one generation to the next.

The work of Ronald Fisher (who developed the required mathematical language and the genetical theory of natural selection),[2] J.B.S. Haldane (who introduced the concept of the "cost" of natural selection),[48] Sewall Wright (who elucidated the nature of selection and adaptation),[49] Theodosius Dobzhansky (who established the idea that mutation, by creating genetic diversity, supplied the raw material for natural selection: see Genetics and the Origin of Species),[50] William Hamilton (who conceived of kin selection), Ernst Mayr (who recognised the key importance of reproductive isolation for speciation: see Systematics and the Origin of Species)[51] and many others formed the modern evolutionary synthesis. .This synthesis cemented natural selection as the foundation of evolutionary theory, where it remains today.^ His ideas on natural selection remained private.
  • “Natural Selection” by 2007 Literary Awards Program Winner, Jacob Appel 13 January 2010 14:16 UTC sfwp.org [Source type: General]

^ Evolutionary theory: the unfinished synthesis.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Remarkably, it appeared that natural selection for copper tolerance had indirectly resulted in the evolutionary origin of the hybrid incompatibility (Wu et al.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Impact of the idea

Darwin's ideas, along with those of Adam Smith and Karl Marx, had a profound influence on 19th century thought. .Perhaps the most radical claim of the theory of evolution through natural selection is that "elaborately constructed forms, so different from each other, and dependent on each other in so complex a manner" evolved from the simplest forms of life by a few simple principles.^ For me the most profound aspect of the Theory of Evolution is the notion that life forms evolve.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ Throughout history, you will see natural selection through force by humans who use fear base thinking.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ The study upends the belief that natural selection is a dominant feature of evolution, noting that climate can trump that card.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

This claim inspired some of Darwin's most ardent supporters—and provoked the most profound opposition. .The radicalism of natural selection, according to Stephen Jay Gould,[52] lay in its power to "dethrone some of the deepest and most traditional comforts of Western thought". In particular, it challenged long-standing beliefs in such concepts as a special and exalted place for humans in the natural world and a benevolent creator whose intentions were reflected in nature's order and design.^ Another scenario that could mimic introgression under this statistical approach is long-standing balancing selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The study upends the belief that natural selection is a dominant feature of evolution, noting that climate can trump that card.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ It's time to get the message -- natural selection has been the major force driving recent human evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Social and psychological theory

.The social implications of the theory of evolution by natural selection also became the source of continuing controversy.^ The study upends the belief that natural selection is a dominant feature of evolution, noting that climate can trump that card.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Find this article online Hahn MW (2008) Toward a selection theory of molecular evolution.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ The fact that this logical outcome of evolution is not found argues against megaevolution by natural selection.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

.Friedrich Engels, a German political philosopher and co-originator of the ideology of communism, wrote in 1872 that "Darwin did not know what a bitter satire he wrote on mankind when he showed that free competition, the struggle for existence, which the economists celebrate as the highest historical achievement, is the normal state of the animal kingdom".[53] Interpretation of natural selection as necessarily 'progressive', leading to increasing 'advances' in intelligence and civilisation, was used as a justification for colonialism and policies of eugenics, as well as broader sociopolitical positions now described as Social Darwinism.^ He or she is forced to simplify, because reality is so complicated that you don’t know it in any detail, and even if you did know it and used math describing it faithfully, the analysis would be impossible to carry through.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Remarkably, it appeared that natural selection for copper tolerance had indirectly resulted in the evolutionary origin of the hybrid incompatibility (Wu et al.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Filed under Darwin natural selection quotes Wednesday December 24 2008 2 35 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Konrad Lorenz won the Nobel Prize in Physiology or Medicine in 1973 for his analysis of animal behavior in terms of the role of natural selection (particularly group selection).^ In his mind, artifical selection and the production of domesticated animals and plants was a powerful anology for the action of natural selection.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ The analysis of selection on single traits which is presented above (even the analysis of single traits during successive episodes) simplifies the action of natural selection.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Methods that are described in the chapter on the phylogenetic analysis of behavior may allow us to date when a particular behavioral or morphological trait arose during the evolutionary history of a group.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

However, in Germany in 1940, in writings that he subsequently disowned, he used the theory as a justification for policies of the Nazi state. He wrote "... selection for toughness, heroism, and social utility...must be accomplished by some human institution, if mankind, in default of selective factors, is not to be ruined by domestication-induced degeneracy. The racial idea as the basis of our state has already accomplished much in this respect."[54] .Others have developed ideas that human societies and culture evolve by mechanisms that are analogous to those that apply to evolution of species.^ In terms of primates, the evolution of large brain size has been an evolutionary trend that distinguishes homo sapiens from other primates, and all of primates from other terrestrial vertebrates (many marine mammals or cetacea have evolved relatively large brains that rival the human brain).
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Shooting your classmates is not objectively wrong, but the idea has evolved to ‘appear’ wrong so that we all don’t turn on each other with a semi-automatic.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

^ I've argued that introgression may have occurred under selection in ancient humans, but so far few other people have looked at the question with the idea of ancient selection in mind.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[55]
.More recently, work among anthropologists and psychologists has led to the development of sociobiology and later evolutionary psychology, a field that attempts to explain features of human psychology in terms of adaptation to the ancestral environment.^ In this case, we have many more recent humans than fossil ones, and many more archaic humans and Neandertals than "early modern" humans.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ It's not proof that the Neandertals, or any other particular group of ancient humans, survived and passed their genes on to more recent people.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Their results show that human HACNS1 drives expression in the mesenchyme of the early developing forelimb, and later developing hindlimb, in these mouse embryos.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.The most prominent such example, notably advanced in the early work of Noam Chomsky and later by Steven Pinker, is the hypothesis that the human brain is adapted to acquire the grammatical rules of natural language.^ It is plausible (as a hypothesis) that the enhancer with the most selected substitutions on the human lineage might be more likely than others to have been selected for multiple functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The other nonrandom hypothesis is natural selection, which would presumably have favored one or more modern human types while eliminating the original Neandertal haplogroup.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[56] .Other aspects of human behavior and social structures, from specific cultural norms such as incest avoidance to broader patterns such as gender roles, have been hypothesized to have similar origins as adaptations to the early environment in which modern humans evolved.^ They measure a high phenotypic variance within the sample they refer to early modern humans.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In other words, the selective scenario proposed by the authors cannot account readily for patterns of variation in modern humans.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The early modern human sample includes the African and Levantine crania complete enough for analysis.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.By analogy to the action of natural selection on genes, the concept of memes – "units of cultural transmission", or culture's equivalents of genes undergoing selection and recombination – has arisen, first described in this form by Richard Dawkins[57] and subsequently expanded upon by philosophers such as Daniel Dennett as explanations for complex cultural activities, including human consciousness.^ The timing of selection at the human FOXP2 gene.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ It's time to get the message -- natural selection has been the major force driving recent human evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ But it's simply not true that researchers have shown "many more genes" under selection in humans than chimpanzees.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[58] .Extensions of the theory of natural selection to such a wide range of cultural phenomena have been distinctly controversial and are not widely accepted.^ Given the above, why then is natural selection accepted?
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Neutral mutations minimally disrupt the adaptedness of an organism, e.g., impacts extremely minimally on phenotype , in such a way that natural selection cannot distinguish alleles .

^ I discuss this theory to hilight how sexual selection as a process is unique relative to natural selection.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

[59]

Information and systems theory

.In 1922, Alfred Lotka proposed that natural selection might be understood as a physical principle which could be described in terms of the use of energy by a system,[60] a concept that was later developed by Howard Odum as the maximum power principle whereby evolutionary systems with selective advantage maximise the rate of useful energy transformation.^ Remarkably, it appeared that natural selection for copper tolerance had indirectly resulted in the evolutionary origin of the hybrid incompatibility (Wu et al.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ As I mentioned above, a recent positively selected mutation could in principle create a pattern like that described for an introgressive allele -- at least under the statistics used in this paper.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In principle, it could be evolutionarily neutral, manifesting its disadvantages only late in life; alternatively, its disadvantages could be outweighed by advantages early in life, or in a different environment, so that it could have been positively selected.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Such concepts are sometimes relevant in the study of applied thermodynamics.
.The principles of natural selection have inspired a variety of computational techniques, such as "soft" artificial life, that simulate selective processes and can be highly efficient in 'adapting' entities to an environment defined by a specified fitness function.^ In principle, it could be evolutionarily neutral, manifesting its disadvantages only late in life; alternatively, its disadvantages could be outweighed by advantages early in life, or in a different environment, so that it could have been positively selected.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ But at present evolutionary theory offers a multiplicity of models suggesting a thousand avenues whereby the morphology, physiology, and behavior of organisms can be related to the environment in such a way that a selection process is set in motion.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ If the deletion was favored by some selection, that would probably be antagonistic , that is, acting against the fitness cost of the deletion late in life.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[61] For example, a class of heuristic optimization algorithms known as genetic algorithms, pioneered by John Holland in the 1970s and expanded upon by David E. Goldberg,[62] identify optimal solutions by simulated reproduction and mutation of a population of solutions defined by an initial probability distribution.[63] Such algorithms are particularly useful when applied to problems whose solution landscape is very rough or has many local minima.

Genetic basis of natural selection

.The idea of natural selection predates the understanding of genetics.^ His ideas on natural selection remained private.
  • “Natural Selection” by 2007 Literary Awards Program Winner, Jacob Appel 13 January 2010 14:16 UTC sfwp.org [Source type: General]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In his treatise on the Natural Selection in the Wild , John Endler (1986) considered natural selection a process that is inseparable the genetic transmission of the successful traits.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.We now have a much better idea of the biology underlying heritability, which is the basis of natural selection.^ Because natural selection is selectively removing the extreme phenotypes rather than the now by-definition better-adapted intermediate phenotypes.

^ Selection on maternal investment should have a genetic basis if the trait is to respond to natural selection and indeed egg size of the mother is positively correlated with egg size of daughter's.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ While this may be an artifact of laboratory selection, large population size in nature may maintain high levels of heritability in the face of sexual selection.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

Genotype and Phenotype

See also: Genotype-phenotype distinction.
.Natural selection acts on an organism's phenotype, or physical characteristics.^ Understanding natural and sexual selection entails visualizing the relationship between a phenotypic trait and one of these components of the life history.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ While natural selection on a single trait can simultaneoulsy move two or more traits that are linked by pleiotropy or physical linkage, the reverse can also be true.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ My hypothesis would be natural selection on some significant subset of phenotypic characters, which reduced the phenotypic variance of most of the cranium by pleiotropy.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Phenotype is determined by an organism's genetic make-up (genotype) and the environment in which the organism lives.^ We cannot consider behavioral traits in isolation from the other morphological and physiological traits that make up what is referred to as the "whole-organism".
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ We have known for over half a century that the genome encodes the heritable phenotypes of an organism and that this genetic information is maintained and modified by natural selection on randomly arising mutations.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Because of their phenotypes , which are due to the amalgam of traits that make up an individual, some individuals do better than others.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.Often, natural selection acts on specific traits of an individual, and the terms phenotype and genotype are used narrowly to indicate these specific traits.^ Natural selection usually acts on many traits at any point in time.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ I have also chosen these examples to illustrate how counterbalancing selection can constrain reproductive traits and result in the process of adaptation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Throughout history, you will see natural selection through force by humans who use fear base thinking.
  • Natural Selection and Natural Born Killers | The Intention Experiment 13 January 2010 14:16 UTC www.theintentionexperiment.com [Source type: Original source]

.When different organisms in a population possess different versions of a gene for a certain trait, each of these versions is known as an allele.^ Population genetics is essentially the study of allele and genotype fr e quencies within populations of organisms .

^ In the subsequent sections, we develop approaches to address these issues with the dual goals of identifying genes that possess strong evidence of natural selection and of inferring population demographic history.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ Modern Synthesis is a theory about how evolution works at the level of genes, phenotypes, and populations whereas Darwinism was concerned mainly with organisms, speciation and individuals.

.It is this genetic variation that underlies phenotypic traits.^ Phenotypic variance is not a measure of genetic variance .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ If we see a population that has a large measure of phenotypic variability, it does not mean that the population had much genetic variability.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In recent years, other researchers have suggested that it might informative to measure selection on phenotype independent of the genetic transmission of the trait.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.A typical example is that certain combinations of genes for eye color in humans which, for instance, give rise to the phenotype of blue eyes.^ An example is the so-called simpler eyes of insects or ears of certain animals which are more effective than the same structure in humans.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ It gives an extremely good example of the importance of developmental regulation to human evolution.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In transgenic mice, the human version of this enhancer triggers gene expression in the forelimb, concentrated toward the thumb side, and some other parts of the body, notably the pharyngeal arches (which give rise to elements of mouth, throat and larynx), eye and ear.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.(On the other hand, when all the organisms in a population share the same allele for a particular trait, and this state is stable over time, the allele is said to be fixed in that population.^ The most commonly considered case is where one allele increases while the population remains the same size.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Under genetic drift, these allelic demographies are in all cases of similar form to the demography of the population in which those alleles are embedded.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Several SNPs in this region show an unusual degree of divergence among the HapMap groups, on the basis of the rank percentile of their FST values (Wright's coefficient, a measure of variance in allele frequencies among populations) among all autosomal SNPs with the same overall frequency in the HapMap.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

)
.Some traits are governed by only a single gene, but most traits are influenced by the interactions of many genes.^ Thus, the European-American sample contained nearly three times as many significant genes as the African-American sample, and only three genes were significant in both samples (ABO, IL1RN, and TNFRSF1B) .
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

.A variation in one of the many genes that contributes to a trait may have only a small effect on the phenotype; together, these genes can produce a continuum of possible phenotypic values.^ These may be partly independent in their effects on the total variance, or they may not be.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Darwinists believed that these slight variations gradually, almost imperceptibly, could have changed a species into a new one.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ The importance of these effects also varies with the intensity of purifying selection.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

[64]

Directionality of selection

.When some component of a trait is heritable, selection will alter the frequencies of the different alleles, or variants of the gene that produces the variants of the trait.^ That comes down to viability of small young individuals and the non-heritable (environmental) component of variance in size, in a fairly complicated way.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Specifically, four of the high-confidence selection genes have been implicated in various complex diseases ( Table 3 ).
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ But balancing selection, for example, can be reduced to density-dependence on an allele's frequency.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Selection can be divided into three classes, on the basis of its effect on allele frequencies.^ In the long run, this will have not a jot of effect on the neutral substitution rate, but it accounts for most of the neutral evolution of allele frequencies in human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Relative to the expectations of the Neutral Theory, recurrent selective sweeps alter both diversity levels and allele frequencies [57] – [59] .
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ These effects decrease with genetic distance between the neutral and selected alleles, as recombination uncouples their dynamics.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

[65]
.Directional selection occurs when a certain allele has a greater fitness than others, resulting in an increase of its frequency.^ For example, both positive selection and increases in population size lead to an excess of low-frequency alleles in a population relative to what is expected under a standard neutral model (i.e., a constant-size, randomly mating population at mutation-drift equilibrium).
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ If fitness is increased by the number of progeny, and if a larger animal should be able to produce more offspring, then why don't large primates produce more than a single offspring?
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ A linear regression describes directional selection and provides the best fit linear relationship between the trait being selected and the measure of fitness (survival, number of mates, etc).
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

This process can continue until the allele is fixed and the entire population shares the fitter phenotype. It is directional selection that is illustrated in the antibiotic resistance example above.
.Far more common is stabilizing selection (which is commonly confused with purifying selection[66] [67]), which lowers the frequency of alleles that have a deleterious effect on the phenotype – that is, produce organisms of lower fitness.^ Possibly, one or more causes of stabilizing selection remain in force (maybe longer development time, but there are other possibilities).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ But balancing selection, for example, can be reduced to density-dependence on an allele's frequency.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In the long run, this will have not a jot of effect on the neutral substitution rate, but it accounts for most of the neutral evolution of allele frequencies in human populations.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.This process can continue until the allele is eliminated from the population.^ We are used to thinking of the process of natural selection as leading to better and better adapted individuals in the population owing to the continued refinement of natural selection.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

.Purifying selection results in functional genetic features, such as protein-coding genes or regulatory sequences, being conserved over time due to selective pressure against deleterious variants.^ The timing of selection at the human FOXP2 gene.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Meanwhile, drift looks even more unlikely, since the chances of a mutation growing from 1 copy to 4 percent against such selection are nil.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Why couldn't the Icelandic genetic changes have been the result of selection that favored some mtDNA lineages rather than others?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Finally, a number of forms of balancing selection exist, which do not result in fixation, but maintain an allele at intermediate frequencies in a population.^ "Balancing selection is rare in natural populations.

^ But balancing selection, for example, can be reduced to density-dependence on an allele's frequency.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In diversifying selection it is the intermediate form that is selected against .

.This can occur in diploid species (that is, those that have two pairs of chromosomes) when heterozygote individuals, who have different alleles on each chromosome at a single genetic locus, have a higher fitness than homozygote individuals that have two of the same alleles.^ A reduction will happen in a single generation as small individuals remain to become adults who would otherwise have been removed.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The project’s homepage includes this short statement: The goal of the International HapMap Project is to compare the genetic sequences of different individuals to identify chromosomal regions where genetic variants are shared.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Under genetic drift, these allelic demographies are in all cases of similar form to the demography of the population in which those alleles are embedded.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.This is called heterozygote advantage or overdominance, of which the best-known example is the malarial resistance observed in heterozygous humans who carry only one copy of the gene for sickle cell anemia.^ This is one of the genes that makes us human.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In humans, there are a number of recently selected genes whose advantage comes from relaxing density dependence (that is, increasing carrying capacity), for example by allowing greater resource extraction from the environment.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Maintenance of allelic variation can also occur through disruptive or diversifying selection, which favors genotypes that depart from the average in either direction (that is, the opposite of overdominance), and can result in a bimodal distribution of trait values.^ Why couldn't the Icelandic genetic changes have been the result of selection that favored some mtDNA lineages rather than others?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The adaptive value of functional (coding) portions of Western European genomes could be related to positive selection on novel variation in West European bees, to positive selection on novel hybrid gene combinations, and/or to selection for heterozygous genotypes.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ What if an ancient trait were again valuable as climate swings or other environmental opportunites and are now again favorable.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Finally, balancing selection can occur through frequency-dependent selection, where the fitness of one particular phenotype depends on the distribution of other phenotypes in the population.^ But balancing selection, for example, can be reduced to density-dependence on an allele's frequency.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Possibly, one or more causes of stabilizing selection remain in force (maybe longer development time, but there are other possibilities).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Consequently, if the frequency of the haplotype changes, the average recombination rate will increase for one sex and decrease for the other, but the sex-averaged recombination rate of the population can stay relatively constant.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.The principles of game theory have been applied to understand the fitness distributions in these situations, particularly in the study of kin selection and the evolution of reciprocal altruism.^ The study upends the belief that natural selection is a dominant feature of evolution, noting that climate can trump that card.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Clearly, a better understanding of the selective pressures in Drosophila awaits a better characterization of these adaptations.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Find this article online Hahn MW (2008) Toward a selection theory of molecular evolution.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

[68][69]

Selection and genetic variation

.A portion of all genetic variation is functionally neutral in that it produces no phenotypic effect or significant difference in fitness; the hypothesis that this variation accounts for a large fraction of observed genetic diversity is known as the neutral theory of molecular evolution and was originated by Motoo Kimura.^ Phenotypic variance is not a measure of genetic variance .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Evolutionary implications of non-neutral mitochondrial genetic variation.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The project’s homepage includes this short statement: The goal of the International HapMap Project is to compare the genetic sequences of different individuals to identify chromosomal regions where genetic variants are shared.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.When genetic variation does not result in differences in fitness, selection cannot directly affect the frequency of such variation.^ Selection depletes additive genetic variation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ This classification admittedly ignores many known phenomena, such as epistatic interactions among mutations, frequency-dependent selection, heterozygous advantage, and spatially and temporarily varying selective pressures within species [10] , [11] —all of which can substantially affect fates of mutations in populations.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ The project’s homepage includes this short statement: The goal of the International HapMap Project is to compare the genetic sequences of different individuals to identify chromosomal regions where genetic variants are shared.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.As a result, the genetic variation at those sites will be higher than at sites where variation does influence fitness.^ Individuals in the center of the phenotype distribution tend to be favored and have higher fitness than individuals in the "tails" of the distribution.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Why couldn't the Icelandic genetic changes have been the result of selection that favored some mtDNA lineages rather than others?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ If we see a population that has a large measure of phenotypic variability, it does not mean that the population had much genetic variability.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

[65]

Mutation selection balance

.Natural selection results in the reduction of genetic variation through the elimination of maladapted individuals and consequently of the mutations that caused the maladaptation.^ Population genetics of mutation-selection drift.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Selection depletes additive genetic variation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ Read more Filed under demography genetic drift Iceland mtDNA natural selection Monday January 19 2009 1 40 am .
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.At the same time, new mutations occur, resulting in a mutation-selection balance.^ Our results suggest that the migration of modern humans out of Africa into new environments was accompanied by genetic adaptations to emergent selective forces.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ But a new mutation under positive selection would start out weakly linked to nearby polymorphisms, each of which already exists at some substantial frequency in the population.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In particular, both selection and genetic drift (and for that matter, mutation) are described by the same equations that describe demography.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.The exact outcome of the two processes depends both on the rate at which new mutations occur and on the strength of the natural selection, which is a function of how unfavorable the mutation proves to be.^ I have also chosen these examples to illustrate how counterbalancing selection can constrain reproductive traits and result in the process of adaptation.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ It's worth pointing out that nothing in the approach of Wall and colleagues implies that any of the putative introgression occurred under natural selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In other words, behavioral correlates of climate may be a target of selection and introgression -- I would speculate because of the intrinsic rarity of adaptive mutations in these functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Consequently, changes in the mutation rate or the selection pressure will result in a different mutation-selection balance.^ Changes in population size make absolutely no difference to the neutral substitution rate.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Consequently, if the frequency of the haplotype changes, the average recombination rate will increase for one sex and decrease for the other, but the sex-averaged recombination rate of the population can stay relatively constant.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Why couldn't the Icelandic genetic changes have been the result of selection that favored some mtDNA lineages rather than others?
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Genetic linkage

.Genetic linkage occurs when the loci of two alleles are linked, or in close proximity to each other on the chromosome.^ The linkage between genes is not a physical linkage where two loci lie in close proximity on the same chromosome.
  • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

^ First, I consider how we might use information theoretic concepts to test the hypothesis of independence between two genetic loci.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ The effects of both positive and negative selection at linked loci on the dynamics of neutral alleles can be ignored.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.During the formation of gametes, recombination of the genetic material results in reshuffling of the alleles.^ These effects decrease with genetic distance between the neutral and selected alleles, as recombination uncouples their dynamics.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.However, the chance that such a reshuffle occurs between two alleles depends on the distance between those alleles; the closer the alleles are to each other, the less likely it is that such a reshuffle will occur.^ These effects decrease with genetic distance between the neutral and selected alleles, as recombination uncouples their dynamics.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ There are two samples here that have a high average distance between nearest neighbors in the sample: "archaic" humans and early modern ones.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Well, you can see that must depend on the values of no less than six other parameters.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.Consequently, when selection targets one allele, this automatically results in selection of the other allele as well; through this mechanism, selection can have a strong influence on patterns of variation in the genome.^ Possibly, one or more causes of stabilizing selection remain in force (maybe longer development time, but there are other possibilities).
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ In other words, behavioral correlates of climate may be a target of selection and introgression -- I would speculate because of the intrinsic rarity of adaptive mutations in these functions.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Other Sections▼ Abstract Introduction Results Discussion Materials and Methods Supporting Information References Introduction Despite intense study and interest, a detailed understanding of the evolutionary and demographic forces that have shaped extant patterns of human genomic variation remains elusive.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

.Selective sweeps occur when an allele becomes more common in a population as a result of positive selection.^ The chances are low for any randomly chosen mutation under positive selection, because a new positively selected mutation isn't likely to be linked to other rare mutations -- it's much more likely to be linked to common polymorphisms.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ As I mentioned above, a recent positively selected mutation could in principle create a pattern like that described for an introgressive allele -- at least under the statistics used in this paper.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ As Africanized bees have spread across South and into North America, adaptive genes from the existing populations of European bees have introgressed into the Africanized population, increasing under positive selection.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.As the prevalence of one allele increases, linked alleles can also become more common, whether they are neutral or even slightly deleterious.^ If deleterious mutations and adaptive substitutions occur at similar rates throughout the genome, their effects on neutral polymorphism should be greater in regions with lower recombination, where a neutral allele is linked to a larger number of selected sites.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ The most commonly considered case is where one allele increases while the population remains the same size.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ If you access Amazon through one of my links, Amazon will give 6% of every purchase (and more for certain items or rentals) to the site.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

This is called genetic hitchhiking. .A strong selective sweep results in a region of the genome where the positively selected haplotype (the allele and its neighbours) are essentially the only ones that exist in the population.^ Detecting recent positive selection in the human genome from haplotype structure.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ For example, both positive selection and increases in population size lead to an excess of low-frequency alleles in a population relative to what is expected under a standard neutral model (i.e., a constant-size, randomly mating population at mutation-drift equilibrium).
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ Because recent selective sweeps are expected to produce sharp dips in levels of polymorphism ( Figure 3 ), regions with frequent adaptations should exhibit not only reduced levels of diversity but also greater contrasts between minimal and background levels of polymorphism (i.e., greater heterogeneity in diversity levels).
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.Whether a selective sweep has occurred or not can be investigated by measuring linkage disequilibrium, or whether a given haplotype is overrepresented in the population.^ Sweep 3 occurred recently, but was associated with a weaker selective coefficient, thereby reducing polymorphism in a smaller region.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Haplotype diversity and linkage disequilibrium at human G6PD: recent origin of alleles that confer malarial resistance.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ The sweep labeled 1 was driven by strong selection and occurred very recently, leading to a sharp decrease in diversity at linked sites.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.Normally, genetic recombination results in a reshuffling of the different alleles within a haplotype, and none of the haplotypes will dominate the population.^ Within each population, men differ by their genotype, and yet the species Homo sapiens has not modified its plan or structure or functions.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ These effects decrease with genetic distance between the neutral and selected alleles, as recombination uncouples their dynamics.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Consequently, if the frequency of the haplotype changes, the average recombination rate will increase for one sex and decrease for the other, but the sex-averaged recombination rate of the population can stay relatively constant.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

.However, during a selective sweep, selection for a specific allele will also result in selection of neighbouring alleles.^ What has been debated, however, is the specific selective advantage conferred by lactase persistence ( Holden and Mace 1997 ).
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

^ Distinguishing the relative contributions of selective sweeps and background purifying selection to the correlations, however, has proven difficult [72] – [76] .
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Relative to the expectations of the Neutral Theory, recurrent selective sweeps alter both diversity levels and allele frequencies [57] – [59] .
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

.Therefore, the presence of strong linkage disequilibrium might indicate that there has been a 'recent' selective sweep, and this can be used to identify sites recently under selection.^ But if we actually have many hundreds, or even thousands, of recently selected alleles (as we do in humans), then there is a pretty good chance that some of them will look like introgression under the test used here.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

^ Sweep 3 occurred recently, but was associated with a weaker selective coefficient, thereby reducing polymorphism in a smaller region.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ There are probably too many genes on these lists for all of them to reflect selective balances or recent positive selection -- there are a lot of recently selected genes, but few of them will have the specific kind of linkage that would show up as significant in this study.
  • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

Background selection is the opposite of a selective sweep. .If a specific site experiences strong and persistent purifying selection, linked variation will tend to be weeded out along with it, producing a region in the genome of low overall variability.^ Because purifying selection in a genomic region is the evolutionary hallmark of its importance to the organism, these findings suggest that most of the euchromatic portion of the Drosophila genome is functionally important [26] – [28] .
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ The importance of these effects also varies with the intensity of purifying selection.
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ What has been debated, however, is the specific selective advantage conferred by lactase persistence ( Holden and Mace 1997 ).
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

.Because background selection is a result of deleterious new mutations, which can occur randomly in any haplotype, it produces no linkage disequilibrium.^ Because recent selective sweeps are expected to produce sharp dips in levels of polymorphism ( Figure 3 ), regions with frequent adaptations should exhibit not only reduced levels of diversity but also greater contrasts between minimal and background levels of polymorphism (i.e., greater heterogeneity in diversity levels).
  • PLoS Genetics: Pervasive Natural Selection in the Drosophila Genome? 13 January 2010 14:16 UTC www.plosgenetics.org [Source type: Academic]

^ Only when all of this has occurred could selection select the animal which survived best and produced more offspring.
  • Some Biological Problems With The Natural Selection Theory 13 January 2010 14:16 UTC www.rae.org [Source type: FILTERED WITH BAYES]

^ Our results suggest that the migration of modern humans out of Africa into new environments was accompanied by genetic adaptations to emergent selective forces.
  • Population History and Natural Selection Shape Patterns of Genetic Variation in 132 Genes 13 January 2010 14:16 UTC www.ncbi.nlm.nih.gov [Source type: Academic]

See also

References

  1. ^ a b Darwin C (1859) On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life John Murray, London; modern reprint Charles Darwin, Julian Huxley (2003). The Origin of Species. Signet Classics. ISBN 0-451-52906-5.  Published online at The complete work of Charles Darwin online: On the origin of species by means of natural selection, or the preservation of favoured races in the struggle for life.
  2. ^ a b Fisher RA (1930) The Genetical Theory of Natural Selection Clarendon Press, Oxford
  3. ^ Works employing or describing this usage:
    Endler JA (1986). Natural Selection in the Wild. Princeton, New Jersey: Princeton University Press. ISBN 0-691-00057-3. 
    Williams GC (1966). Adaptation and Natural Selection. Oxford University Press. 
  4. ^ Works employing or describing this usage:
    Lande R & Arnold SJ (1983) The measurement of selection on correlated characters. Evolution 37:1210-26
    Futuyma DJ (2005) Evolution. Sinauer Associates, Inc., Sunderland, Massachusetts. ISBN 0-87893-187-2
    Haldane, J.B.S. 1953. The measurement of natural selection. Proceedings of the 9th International Congress of Genetics. 1: 480-487
  5. ^ Sober E (1984; 1993) The Nature of Selection: Evolutionary Theory in Philosophical Focus University of Chicago Press ISBN 0-226-76748-5
  6. ^ Modified from Christiansen FB (1984) The definition and measurement of fitness. In: Evolutionary ecology (ed. Shorrocks B) pp65–79. Blackwell Scientific, Oxford by adding survival selection in the reproductive phase
  7. ^ Pitnick S & Markow TA (1994) Large-male advantage associated with the costs of sperm production in Drosophila hydei, a species with giant sperm. Proc Natl Acad Sci USA 91:9277-81; Pitnick S (1996) Investment in testes and the cost of making long sperm in Drosophila. Am Nat 148:57-80
  8. ^ Andersson, M (1995). Sexual Selection. Princeton, New Jersey: Princeton University Press. ISBN 0-691-00057-3. 
  9. ^ Eens M, Pinxten R. (2000). Sex-role reversal in vertebrates: behavioural and endocrinological accounts. Behav Processes 51(1-3):135-147. PMID 11074317
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  39. ^ Wallace, Alfred Russel (1870) Contributions to the Theory of Natural Selection New York: Macmillan & Co. [3]
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  41. ^ Darwin 1859, p. 6
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     Maurice E. Stucke. "Better Competition Advocacy". http://works.bepress.com/cgi/viewcontent.cgi?article=1000&context=maurice_stucke. Retrieved 2007-08-29. "Herbert Spencer in his Principles of Biology of 1864, vol. 1, p. 444, wrote “This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called ‘natural selection’, or the preservation of favoured races in the struggle for life.”" 
  46. ^ Darwin 1872, p. 49.
  47. ^ Mills SK, Beatty JH. [1979] (1994). The Propensity Interpretation of Fitness. Originally in Philosophy of Science (1979) 46: 263-286; republished in Conceptual Issues in Evolutionary Biology 2nd ed. Elliott Sober, ed. MIT Press: Cambridge, Massachusetts, USA. pp3-23. ISBN 0-262-69162-0.
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  51. ^ Mayr E (1942) Systematics and the Origin of Species Columbia University Press, New York. ISBN 0-674-86250-3
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  53. ^ Engels F (1873-86) Dialectics of Nature 3d ed. Moscow: Progress, 1964 [5]
  54. ^ Quoted in translation in Eisenberg L (2005) Which image for Lorenz? Am J Psychiatry 162:1760 [6]
  55. ^ e.g. Wilson, DS (2002) Darwin's Cathedral: Evolution, Religion, and the Nature of Society. University of Chicago Press, ISBN 0-226-90134-3
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  60. ^ Lotka AJ (1922a) Contribution to the energetics of evolution [PDF] Proc Natl Acad Sci USA 8:147–51
    Lotka AJ (1922b) Natural selection as a physical principle [PDF] Proc Natl Acad Sci USA 8:151–4
  61. ^ Kauffman SA (1993) The Origin of order. Self-organization and selection in evolution. New York: Oxford University Press ISBN 0-19-507951-5
  62. ^ Goldberg DE. (1989). Genetic Algorithms in Search, Optimization and Machine Learning. Addison-Wesley: Boston, MA, USA
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  65. ^ a b Rice SH. (2004). Evolutionary Theory: Mathematical and Conceptual Foundations. Sinauer Associates: Sunderland, Massachusetts, USA. ISBN 0-87893-702-1 See esp. ch. 5 and 6 for a quantitative treatment.
  66. ^ Lemey, Philippe; Marco Salemi, Anne-Mieke Vandamme (2009). The Phylogenetic Handbook. Cambridge University Press. ISBN 978-0-521-73071. 
  67. ^ http://www.nature.com/scitable/topicpage/Negative-Selection-1136
  68. ^ Hamilton WD. (1964). The genetical evolution of social behaviour I and II. Journal of Theoretical Biology 7: 1-16 and 17-52. PMID 5875341 PMID 5875340
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Further reading

  • For general audiences
    • Dawkins, Richard (1996) Climbing Mount Improbable. Penguin Books, ISBN 0-670-85018-7.
    • Dennett, Daniel (1995) Darwin's Dangerous Idea: Evolution and the Meanings of Life. Simon & Schuster ISBN 0-684-82471-X.
    • Gould, Stephen Jay (1997) Ever Since Darwin: Reflections in Natural History. Norton, ISBN 0-393-06425-5.
    • Jones, Steve (2001) Darwin's Ghost: The Origin of Species Updated. Ballantine Books ISBN 0-345-42277-5. Also published in Britain under the title Almost like a whale: the origin of species updated. Doubleday.^ Filed under disease life history natural selection Zimmer "flounders" Carl Zimmer puts in a nice entry on the new flounder evolution paper, covering the history of the question including the debate between Darwin and Mivart about the evolution of the upward-facing flounder eye position.
      • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

      ^ Filed under cardiovascular disease genetic drift India natural selection population genetics recent selection Quote: Selection, stochasticity Reading through P. A. P. Moran's book, The Statistical Processes of Evolutionary Theory , I found this passage (p.
      • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

      ^ Filed under natural selection non-primate rapid evolution Quote: Elliott Sober on the force of selection Elliott Sober's book, The Nature of Selection , discusses the philosophical underpinnings of evolutionary explanation in relation to other sciences.
      • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

      ISBN 1-86230-025-9.
    • Lewontin, Richard (1978) Adaptation. Scientific American 239:212-30
    • Weiner, Jonathan (1994) The Beak of the Finch: A Story of Evolution in Our Time. Vintage Books, ISBN 0-679-73337-X.
  • Historical
    • Zirkle C (1941). .Natural Selection before the "Origin of Species", Proceedings of the American Philosophical Society 84 (1), p. 71-123.
    • Kohm M (2004) A Reason for Everything: Natural Selection and the English Imagination. London: Faber and Faber.^ Remarkably, it appeared that natural selection for copper tolerance had indirectly resulted in the evolutionary origin of the hybrid incompatibility (Wu et al.
      • natural selection | john hawks weblog 13 January 2010 14:16 UTC johnhawks.net [Source type: FILTERED WITH BAYES]

      ^ He did not attend the reading of his seminal paper, The Origin of Species , at the Linnean Society on July 1, 1858.
      • “Natural Selection” by 2007 Literary Awards Program Winner, Jacob Appel 13 January 2010 14:16 UTC sfwp.org [Source type: General]

      ^ Despite the paucity of actual examples of disruptive selection, the process is thought to play a major role in the process of speciation or the origin of new species (Templeton, 198X).
      • Introduction to Natural and Sexual Selection 13 January 2010 14:16 UTC bio.research.ucsc.edu [Source type: Academic]

      ISBN 0-571-22392-3. For review, see [8] van Wyhe J (2005) Human Nature Review 5:1-4

External links


Simple English

Natural selection is a central concept of evolution, sometimes called the survival of the fittest. It was an idea of Charles Darwin and Alfred Russel Wallace.[1] Darwin chose the name as an analogy with artificial selection (selective breeding).

Natural selection is the process where organisms with favourable traits are more likely to reproduce. In doing so, they pass on these traits to the next generation. Over time this process allows organisms to adapt to their environment. This is because the frequency of genes for favourable traits increases in the population.

Members of a species are not all alike, partly because of differences in heredity (genetics). This is true even with children of the same parents. Some of these differences might make one organism better at surviving and reproducing than others in a particular habitat. When this organism reproduces, it passes along the genes, which gave it the advantage, to its children. Some adaptations are extremely long-lasting, useful in many habitats. The evolution of wings in birds is an example. Others are good only as long as the environment stays the same. If the environment changes enough, then another organism might do better.

Contents

The process

Natural selection explains why living organisms change over time to have the anatomy, the functions and behaviour that they have. It works like this:

  1. All living things have such fertility that their population size could increase rapidly forever.
  2. We see that the size of populations does not increase to this extent. Mostly, numbers remain about the same.
  3. The food and other resources are limited. Therefore, there is competition for food and resources.
  4. No two individuals are alike. Therefore, they will not have the same chances to live and reproduce.
  5. Much of this variation can be inherited. The parents pass such traits to the children through their genes.
  6. The next generation can only come from those that survive and reproduce. After many generations of this, the population will have more helpful genetic differences, and fewer harmful ones.[2] Natural selection is really a process of elimination.[3] The elimination is being caused by the relative fit between the individuals, and the environment they live in.

Examples

There are now quite a number of examples of natural selection in natural populations.[4]

Antibiotic resistance

A well-known example of natural selection in action is the development of antibiotic resistance in microorganisms. Since the discovery of penicillin in 1928 by Alexander Fleming, antibiotics have been used to fight bacterial diseases. Natural populations of bacteria contain, among their vast numbers of individual members, considerable variation in their genetic material, as the result of mutations. When exposed to antibiotics, most bacteria die quickly, but some may have mutations that make them slightly less susceptible. If the exposure to antibiotics is short, these individuals will survive the treatment. This selective elimination of maladapted individuals from a population is natural selection.

Given enough time, and repeated exposure to the antibiotic, a population of antibiotic-resistant bacteria will emerge. This leads to what is known as an evolutionary arms race, or co-evolution, in which bacteria continue to develop strains that are less susceptible to antibiotics, while medical researchers continue to develop new antibiotics that can kill them.[5] Response strategies typically include the use of different, stronger antibiotics; however, new strains of MRSA have recently emerged that are resistant even to these drugs.[6] A similar situation occurs with pesticide resistance in plants and insects, and with malarial resistance to quinine.

Camouflage

Some day-flying moths were light in colour, and some of the moths were dark. At first, the light coloured moths survived better because they were camouflaged against the white colour of the nearby trees. This made it hard for birds to see them. When factories were built, it caused pollution that made all the trees look black. Now the light coloured moths were obvious against the dark bark. The dark coloured moths now had the advantage, after the environment changed. The genes controlling dark colour spread through the population of moths.

Mimicry

Another example: Some harmless insects mimic other insects which are dangerous, or which taste foul. Mimicry evolves because the better mimics survive better. They live to produce more offspring than the less good mimics. The genes of the better mimics become more common in the species. Over time, mimic species get closer to their models. This is the process of evolution by natural selection.

Sexual selection

showing the Tufted Coquette Lophornis ornatus, female on left, ornamented male on right.]]

Sexual selection is a special kind of natural selection. It is a theory of Charles Darwin that certain evolutionary traits can be explained by competition within a species. Darwin defined sexual selection as the effects of the "struggle between the individuals of one sex, generally the males, for the possession of the other sex".[7] It is usually males who fight each other. Traits selected by male combat are called secondary sexual characteristics (including horns, antlers, etc.) and sometimes referred to as 'weapons'. Traits selected by mate choice are called 'ornaments'.

Females often prefer to mate with males with external ornaments—exaggerated features of morphology. Genes that enable males to develop impressive ornaments or fighting ability may simply show off greater disease resistance or a more efficient metabolism—features that also benefit females. This idea is known as the 'good genes' hypothesis. Sexual selection is still being researched and discussed today.[8]

References

  1. Darwin, Charles (annotated by James T. Costa). 2009. The annotated Origin: a facsimile of the first edition of On the Origin of Species. Harvard, Cambridge, Mass.
  2. Evolution 101: Natural Selection from the Understanding Evolution webpages made by the University of California at Berkeley
  3. Mayr, Ernst. 2001. What evolution is. Harvard. p117.
  4. Endler J.A. 1986. Natural selection in the wild. Princeton, New Jersey: Princeton University Press. ISBN 0-691-00057-3.
  5. "MRSA Superbug News". http://www.inboxrobot.com/news/MRSASuperbug. Retrieved 2006-05-06. 
  6. Schito GC (2006). [Expression error: Unexpected < operator "The importance of the development of antibiotic resistance in Staphylococcus aureus"]. Clin Microbiol Infect 12 Suppl 1: 3–8. doi:10.1111/j.1469-0691.2006.01343.x. PMID 16445718.  [1]
  7. Darwin C. 1871. The Descent of Man and selection in relation to sex John Murray, London
  8. Cronin, Helena 1991. The ant and the peacock: altruism and sexual selection from Darwin to today. Cambridge University Press.

Citable sentences

Up to date as of December 23, 2010

Here are sentences from other pages on Natural selection, which are similar to those in the above article.








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