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Homo ergaster
Fossil range: Pleistocene
Skull KNM-ER 3733 discovered by Bernard Ngeneo in 1975 (Kenya)
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: H. ergaster
Binomial name
Homo ergaster
Groves and Mazák, 1975

Homo ergaster (from the Greek ἔργον,[1] "work") is an extinct species (or subspecies) of hominid that lived in eastern and southern Africa from the end of the Pliocene epoch to the early Pleistocene, about 1.8-1.3 million years ago.[2] There is still disagreement on the subject of the classification, ancestry, and progeny of H. ergaster, but it is now widely thought (though not agreed) to be the direct ancestor of later hominids such as Homo heidelbergensis, Homo sapiens and Homo neanderthalensis rather than Asian Homo erectus.[3] It is one of the earliest members of the genus Homo, possibly descended from, or sharing a common ancestor with, Homo habilis.[4]

Contents

Discovery and representative fossils

South African palæontologist John T. Robinson first discovered a mandible of a new hominid in southern Africa in 1949; he named the species Telanthropus capensis, though it is now recognised as a member of Homo ergaster.[5] The name was first applied by Colin Groves and Vratislav Mazák to KNM-ER 992, a mandible discovered near Lake Rudolf (now Lake Turkana), Kenya in 1975, which became the type-specimen of the species. The most complete skeleton of H. ergaster (and one of the most complete extinct hominids to date), KNM-WT 15000, was discovered at Lake Turkana, Kenya, in 1984 by paleoanthropologists Kamoya Kimeu and Alan Walker. They nicknamed the 1.6-million-year-old specimen "Turkana Boy".

Classification and special distinction

Many paleoanthropologists still debate the definition of H. ergaster and H. erectus as separate species. Some call H. ergaster the direct African ancestor of H. erectus, proposing that H. ergaster emigrated out of Africa and into Asia, branching into a distinct species.[6] Most dispense with the species-name ergaster, making no distinction between such fossils as the Turkana Boy and Peking Man. Though "Homo ergaster" has gained some acceptance as a valid taxon, H. ergaster and H. erectus are still usually defined as distinct African and Asian populations of the larger species H. erectus. (For the remainder of this article, the name "Homo ergaster"will be used to describe a distinct species for the convenience of continuity in reading.)

H. ergaster may be distinguished from H. erectus by its thinner skull-bones and lack of an obvious supraorbital sulcus. It may be distinguished from Homo heidelbergensis by its thinner bones, more protrusive face, and lower forehead. Derived features separating it from earlier species include reduced sexual dimorphism,[7] a smaller, more orthognathous (less protrusive) face, a smaller dental arcade, and a larger cranial capacity (700-900cm³ in earlier ergaster-specimens, and 900-1100 in later specimens).[8] It is estimated that H. ergaster stood at 1.9 metres (6.2 ft) tall[citation needed]. Remains have been found in Tanzania, Ethiopia, Kenya, and South Africa.

Divergence

Homo habilis is generally accepted as the putative ancestor of the genus Homo,[9] and often of H. ergaster most directly. This taxon's status as a legitimate species within "Homo", however, is particularly contentious. H. habilis and H. ergaster coexisted for 200,000-300,000 years, possibly indicating that these species diverged from a common ancestor.[10] It is unclear the genetic influence that H. ergaster had on later hominids. Recent genetic analysis has generally supported the Out-of-Africa hypothesis, and this may designate H. ergaster the role of ancestor to all later hominids.[11]

Origin and extinction

H. ergaster diverged from the lineage of H. habilis between 1.9 and 1.8 million years ago; the lineage that emigrated Africa and fathered H. erectus diverged from the lineage of H. ergaster almost immediately after this. These early descendants of H. ergaster may have been discovered in Dmanisi, Georgia.[12] H. ergaster remained stable for ca. 500,000 years in Africa before disappearing from the fossil record around 1.4 million years ago. No identifiable cause has been attributed to this disappearance; the later evolution of the similar H. heidelbergensis in Africa may indicate that this is simply a hole in the record, or that some intermediate species has not yet been discovered.

Use of tools

Homo ergaster used more diverse and sophisticated stone tools than its predecessors: H. erectus, however, used comparatively primitive tools. This is probably because H. ergaster first produced Oldowan tools, and later refined the style to develop the first Acheulean bifacial axes:[13] while the use of Acheulean tools began ca. 1.6 million years ago, the line of H. erectus diverged some 200,000 years before the general innovation of Acheulean technology. Thus the Asian migratory descendants of H. ergaster made no use of any Acheulean technology.

Sociality

Sexual dimorphism in H. ergaster is greatly reduced from its australopithecine ancestors (around 20%[14]), but still greater than dimorphism in modern humans. This diminished competition for mates between males, implied by the reduction in sexual dimorphism, may also correspond to the more modern social practices of ergaster. Not only was H. ergaster like modern humans in body, but also more in organisation and sociality than any earlier species. It is conceivable that H. ergaster was the first hominin to harness fire: whether as the containment of natural fire, or as the lighting of artificial fire, is still a matter of contention. It is now assumed, however, that erectus did have control of fire,[15] as well as each other hominin sharing a common ancestor with ergaster. The social organisation of H. ergaster probably resembled that of modern hunter-gatherer societies. Unlike australopithecines, ergaster males presumably did not compete at all for females, which had themselves increased in size greatly in proportion to males. This reduced competition and dimorphism also coincided with an increase in brain size and efficiency of stone tools.

Homo ergaster skull reconstruction of the Nariokotome Boy from Lake Turkana, Kenya. Museum of Man, San Diego.

Linguistic use

Homo ergaster was probably the first hominid to use a human voice, though its symbolic cognition was probably somewhat more limited. It was thought for a long time that H. ergaster was restricted in the physical ability to regulate breathing and produce complex sounds. This was based on Turkana Boy's cervical vertebrae, which were far narrower than in later humans. Discoveries of cervical vertebrae in Dmanisi, Georgia some .3 million years older than those of Turkana Boy are well within the normal human range.[16] It has been established, furthermore, that the Turkana Boy probably suffered from a disease of the spinal column that resulted in narrower cervical vertebrae than in modern humans[17] (as well as the older Dmanisi finds). While the Dmanisi finds have not been established definitively as H. ergaster; they are older than Turkana Boy (the only definite ergaster-vertebrae on record), and thereby suggest kinship to ergaster. Turkana Boy, therefore, may be an anomaly. There is no archaeological evidence that Homo ergaster made use of symbolic thought (no physical symbols, e.g. writing, art, &c.), but the well evolved brain and physical capabilities (along with reconfiguration of ergaster's breathing-apparatus) suggest some form of linguistic or symbolic communication.

Notable fossils

See also

Footnotes

  1. ^ ergon
  2. ^ Hazarika, Manji (16-30 June, 2007). "Homo erectus/ergaster and Out of Africa: Recent Developments in Paleoanthropology and Prehistoric Archaeology". 
  3. ^ G. Philip Rightmire (1998). "Human Evolution in the Middle Pleistocene: The Role of Homo heidelbergensis". Evolutionary Anthropology. 
  4. ^ F. Spoor, M. G. Leakey, P. N. Gathogo, F. H. Brown, S. C. Antón, I. McDougall, C. Kiarie, F. K. Manthi & L. N. Leakey (9 August 2007). "Implications of new early Homo fossils from Ileret, east of Lake Turkana, Kenya". Nature 448 (448): 688–691. doi:10.1038/nature05986. 
  5. ^ Wood, Bernard, and Mark Collard (2001). "The Meaning of Homo". Ludus Vitalis 9 (15): p. 63-74. 
  6. ^ Tattersall, Ian and Jeffrey Schwartz (2001). Extinct Humans. 
  7. ^ McHenry, Henry M. (1994). "Behavioral ecological implications of early hominid body size". Academic Press Limited. 
  8. ^ Hazarika, Manji (16-30 June, 2007). "Homo erectus/ergaster and Out of Africa: Recent Developments in Paleoanthropology and Prehistoric Archaeology". 
  9. ^ Wood, Bernard, and Mark Collard (2001). "The Meaning of Homo". Ludus Vitalis 9 (15): p. 63-74. 
  10. ^ Urquhart, James (8 August, 2007). Finds Test Human Origins Theory. 
  11. ^ Hazarika, Manji (16-30 June, 2007). "Homo erectus/ergaster and Out of Africa: Recent Developments in Paleoanthropology and Prehistoric Archaeology". 
  12. ^ Tattersall, Ian (2008). "An Evolutionary Frameworks for the Acquisition of Symbolic Cognition by Homo sapiens". 
  13. ^ Beck, Roger B.; Linda Black, Larry S. Krieger, Phillip C. Naylor, Dahia Ibo Shabaka, (1999). World History: Patterns of Interaction. Evanston, IL: McDougal Littell. ISBN 0-395-87274-X. 
  14. ^ McHenry, Henry M. (1994). "Behavioral ecological implications of early hominid body size". Academic Press Limited. 
  15. ^ Goren-Inbar, Naama, et al. (30 April, 2004). "Evidence of Hominin Control of Fire at Gesher Benot Ya 'aqov, Israel". Science 304 (5671): pp. 725-727. 
  16. ^ Bruce Bower (6 May, 2006). "Evolutionary Back Story: Thoroughly Modern Spine Supported Human Ancestor". Science News Online 169 (18): 275. 
  17. ^ Wong, Kate (November 2003). "Stranger in a new land". Scientific American. 

References

External links


Wiktionary

Up to date as of January 15, 2010

Definition from Wiktionary, a free dictionary

Translingual

Etymology

Latin homo man + ?

Proper noun

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Home ergaster

  1. a taxonomic species, within genus Homo - "working man" (extinct)
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Wikispecies

Up to date as of January 23, 2010

From Wikispecies

Homo ergaster

Taxonavigation

Main Page
Cladus: Eukaryota
Supergroup: Unikonta
Cladus: Opisthokonta
Regnum: Animalia
Subregnum: Eumetazoa
Cladus: Bilateria
Cladus: Nephrozoa
Cladus: Deuterostomia
Phylum: Chordata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Superclassis: Tetrapoda
Classis: Mammalia
Subclassis: Theria
Infraclassis: Placentalia
Ordo: Primates
Subordo: Haplorrhini
Infraordo: Simiiformes
Parvordo: Catarrhini
Superfamilia: Hominoidea
Familia: Hominidae
Subfamilia: Homininae
Tribus: Hominini
Subtribus: Hominina
Genus: Homo
Species: †Homo ergaster

Name

Homo ergaster Groves & Mazak, 1975

Type specimen: KNM-ER 992

Vernacular names

Eesti: Töötav inimene
עברית: הומו ארגסטר
日本語: ホモ・エルガステル

Simple English

Homo ergaster
Fossil range: Pleistocene
File:Homo
A Homo ergaster skull
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Family: Hominidae
Genus: Homo
Species: H. ergaster
Binomial name
Homo ergaster
Groves & Mazak, 1975

Homo ergaster ("working man") is an extinct hominin species (or subspecies, according to some authorities) which lived throughout eastern and southern Africa between 1.9 to 1.4 million years ago with the advent of the lower Pleistocene and the cooling of the global climate.









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