Consanguinity ("con- (with/together) sanguine (blood) -ity (noun marker)") refers to the property of being from the same kinship as another person. In that respect, consanguinity is the quality of being descended from the same ancestor as another person. Consanguinity is an important legal concept in that the laws of many jurisdictions consider consanguinity as a factor in deciding whether two individuals may be married or whether a given person inherits property when a deceased person has not left a will.
The degree of relative consanguinity can be illustrated with a consanguinity table, in which each level of lineal consanguinity (i.e., generation) appears as a row, and individuals with a collaterally-consanguineous relationship share the same row. See, e.g., table of consanguinity. The Knot System is a numerical notation that defines consanguinity. It is exact.[1]
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Issues of consanguinity arise in several aspects of the law. It is directly relevant in determining whether a couple can marry. These a linked to a jurisdiction's definition of incest, so that couples in an incestuous relationship will not be permitted to marry. Some United States jurisdictions forbid first-cousins to marry, while others limit the prohibition to brothers, sisters, mothers, fathers, aunts and uncles.
Several volumes of Smith's Laws, enacted from 1700 through 1829, contain certain public and private laws of the Province and Commonwealth of Pennsylvania. Several laws with a prescribed punishment against adultery, bigamy, incest and fornication and all combinations of those crimes were enacted in 1705.[2]
Consanguinity is also relevant in issues of inheritance. In regard to the law of intestate succession (when a person dies without a will), under the Uniform Probate Code of the United States section 2-103, after a surviving spouse receives his or her share, the descendants (depending on the circumstances this may include children, grandchildren, or great grandchildren, either biological or adopted) receive the remainder of the intestate estate. If there are no children, the decedent's parent(s) receive the remainder of the estate. If there are neither descendants nor parents, the decedent's estate is distributed to descendants of the decedent's parents (again, depending on the circumstances, brothers and sisters, nieces and nephews, grand nieces and nephews and great grand nieces and nephews). If there are no descendants, parents, or descendants of parents, then the deceased's property passes to descendants of the grandparents of the decedent (uncles and aunts, first cousins, or first cousins once, twice, or thrice removed).
Also, some jurisdictions prohibit individuals from serving on a jury in which they have a certain degree of consanguinity with the defendant.[3]
The connotations of degree of consanguinity varies by context (e.g., Canon law, Roman law, etc.). Most cultures define a degree of consanguinity within which sexual interrelationships are regarded as incestuous (the "prohibited degree of kinship").
In the Roman Catholic Church, unwittingly marrying a closely-consanguineous blood relative is grounds for an annulment, but dispensations were granted, actually almost routinely (the Catholic Church's ban on marriage within the fourth degree of relationship (first cousins) lasted from 1550 to 1917; before that, the prohibition applied to marriages within the seventh degree of kinship). The general rule was that while fourth cousins could marry without dispensation, those more closely related needed dispensation, with it becoming harder and harder to obtain the closer the couple were related.
Adoption may or may not be considered at law to create such a bond; in most Western societies, adoptive relationships are considered blood relationships for these purposes, but in others, including both Japan and ancient Rome, it was common for a couple with only daughters to adopt a son-in-law, making the marriage one between adoptive siblings.
Among the Christian Habesha highlanders of Ethiopia and Eritrea (the predominantly orthodox Christian Amhara and Tigray-Tigrinya), it is a tradition to be able to recount one's paternal ancestors at least 7 generations away starting from early childhood, because "those with a common patrilineal ancestor less than seven generations away are considered 'brother and sister' and may not marry." The rule is less strict on the mother's side, where the limit is about four generations back, but still determined patrilinearly. This rule does not apply to Muslims or other ethnic groups.[4]
The percentage of consanguinity between any two individuals decreases fourfold as the most recent common ancestor recedes one generation. Consanguinity means the amount of shared (identical) DNA, the genetic material. For example, first cousins have four times the consanguinity of second cousins. First cousins once removed have half the shared DNA as full first cousins. Half-fourth cousins sometimes cannot be detected at the DNA level.[5] Finally, double first cousins share twice the consanguinity as first cousins and are as related as half-siblings.
As a working definition, unions contracted between persons biologically related as second cousins or closer (F ≥ 0.0156) are categorized as consanguineous. This arbitrary limit has been chosen because the genetic influence in marriages between couples related to a lesser degree would usually be expected to differ only slightly from that observed in the general population. Globally, the most common form of consanguineous union contracted is between first cousins, in which the spouses share 1/8 of their genes inherited from a common ancestor, and so their progeny are homozygous (or more correctly autozygous) at 1/16 of all loci. Conventionally this is expressed as the coefficient of inbreeding (F) and for first cousin offspring, F = 0.0625. That is, the progeny are predicted to have inherited identical gene copies from each parent at 6.25% of all gene loci, over and above the baseline level of homozygosity in the general population. In some large human populations genetically closer marriages also are favoured, in particular uncle-niece and double first cousin unions where the level of homozygosity in the progeny is equivalent to 0.125.
Historically, some European nobles cited a close degree of consanguinity when they required convenient grounds for divorce, especially in contexts where religious doctrine forbade the voluntary dissolution of an unhappy or childless marriage. Conversely, the consanguinity law of succession requires the next monarch to be of the same blood of the previous one; allowing, for example, illegitimate children to inherit. It is estimated that 55% of marriages between Mirpuri (Kashmiri) Pakistani immigrants in the United Kingdom are between first cousins,[6][7][8] where "preferential patrilateral parallel cousin marriage" (where a boy marries his father's brother's daughter) is often favored.
The offspring of consanguinous relationships are at greater risk of certain genetic disorders. Autosomal recessive disorders occur in individuals who are homozygous for a particular recessive gene mutation. This means that they carry two copies (alleles) of the same gene. Except in certain rare circumstances (new mutations or uniparental disomy) both parents of an individual with such a disorder will be carriers of the gene. Such carriers are not affected and will not display any signs that they are carriers, and so may be unaware that they carry the mutated gene. As relatives share a proportion of their genes, it is much more likely that related parents will be carriers of an autosomal recessive gene, and therefore their children are at a higher risk of an autosomal recessive disorder. The extent to which the risk increases depends on the degree of genetic relationship between the parents; so the risk is greater in mating relationships where the parents are close relatives, but for relationships between more distant relatives, such as second cousins, the risk is lower (although still greater than the general population).[9]
The low genetic heterozygosity associated with increased consanguinity in a population (identified by microsatellite markers) increases its susceptibility to infectious pathogens such as tuberculosis and hepatitis.[10]
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CONSANGUINITY, or Kindred, in law, the connexion or relation of persons descended from the same stock or common ancestor (vinculum personarum ab eodem stipite descendentium). This consanguinity is either lineal or collateral. Lineal consanguinity is that which subsists between persons of whom one is descended in a direct line from the other, while collateral relations descend from the same stock or ancestor, but do not descend the one from the other. Collateral kinsmen, then, are such as lineally spring from one and the same ancestor, who is the stir ps, or root, as well as the stipes, trunk or common stock, whence these relations branch out. It will be seen that the modern idea of consanguinity is larger than that of agnatio in the civil law, which was limited to connexion through males, and was modified by the ceremonies of adoption and emancipation, and also than that of cognatio, which did not go beyond the sixth generation, and was made the basis of Justinian's law of succession. The more limited meaning of consanguinei was brothers or sisters by the same father, as opposed to uterini, brothers or sisters by the same mother. The degrees of collateral consanguinity were differently reckoned in the civil and in the canon law. "The civil law reckons the number of descents between the persons on both sides from the common ancestor. The canon law counts the number of descents between the common ancestor and the two persons on one side only," and always on the side of the person who is more distant from the common ancestor. English law follows the canon law in beginning at the common ancestor and reckoning downwards. The question of consanguinity owes its great importance to the relationship it bears to the laws of marriage and inheritance. For instance, the law forbids marriage between persons within certain degrees of consanguinity and affinity, a prohibition which applies with equal force to a bastard as well as to those born in wedlock. The laws of inheritance and descent are regulated in a great measure according to consanguinity, however much they may vary in different jurisdictions.
Apart from those countries which have made either the civil or the canon law the basis of reckoning degrees of consanguinity (and practically all civilized countries adopt one or other), it is impossible to describe any method or system, for they are as various as the countries and tribes. See, however, the article Indian Law; and consult Lewis H. Morgan, Systems of Consanguinity and Affinity of the Human Family (Washington, 1870); J. F. McLennan, On Primitive Marriage (Edinburgh, 1865): E. A. Westermarck, History of Human Marriage (2nd ed., London, 1894); E. Crawley, The Mystic Rose (1902); A. Lang and J. J. Atkinson, Social Origins and Primal Law (1903); E. B. Tylor, Primitive Culture (4th ed., 1903). See also Affinity; Marriage; Inheritance.
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   | "Consanguinity (in Canon Law)." - CATHOLIC ENCYCLOPEDIA: Consanguinity |
| | Consangwiki - Global resource on Consanguinity - Main Page - ConsangWiki - Consang.net |
| | Assimilation Studies, Part II - Assimilation Studies, Part II by Stanley Kurtz on National Review Online |
| | Ban UK Pakistanis from Marrying Cousing - Ban UK Pakistanis from marrying cousins - Rest of World - World - NEWS - The Times of India |
| | Degrees of Kinship Chart - Degrees of Kinship |
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