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Human ancestors at West Asian site deemed two species

Disputed fossil study splits a pivotal early Homo species in two

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5:31pm, February 27, 2014

ONE OR TWO  These ancient lower jaws excavated in West Asia come from two different Homo species, a contested study concludes. The assessment conflicts with the proposal by the fossils’ discoverers that they represent a single species.

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A controversial fossil and soil analysis concludes that a key West Asian site hosted not one but two Homo species, one living around 1.8 million years ago and another several hundred thousand years later.

A team that excavated partial skeletons at Dmanisi, in the nation of Georgia, categorized the finds as part of one species, Homo erectus, that lived in Africa and West Asia 1.8 million years ago (SN: 11/16/13, p. 6). But disparities in several skeletal features that emerge early in life distinguish a large Dmanisi lower jaw from two smaller ones, signaling the presence of separate species, asserts a team led by paleoanthropologist José María Bermúdez de Castro of the National Research Center on Human Evolution in Burgos, Spain. The small jaws come from a population that was closely related to early African Homo populations, the scientists conclude February 20 in PLOS ONE. The team suggests the larger jaw belonged to Homo georgicus, a poorly understood species.

Excavation director David Lordkipanidze of the Georgian National Museum in Tbilisi disagrees. Shape similarities among Dmanisi skulls that fit the lower jaws indicate that only one Homo species occupied the site. Geologic studies show that the Dmanisi fossils are no younger than 1.76 million years old, he adds.

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