Sunday, May 11, 2008


A new, simplified family tree of humanity has dealt a blow to those who contend that the enigmatic hominids known as Neanderthals intermingled with our forebears. Neanderthals were a separate species to Homo sapiens, as anatomically modern humans are known, rather than offshoots of the same species, the new organigram published Sunday by the journal Nature declares.

The method, invented by evolutionary analysts in Argentina, marks a break with the conventional technique by which anthropologists chart the twists and turns of the human odyssey. That technique typically divides the genus Homo into various classifications
according to the shape of key facial features -- "flat-faced," "protruding-faced" and so on.

The authors of the new study, led by Rolando Gonzalez-Jose at the Patagonian National Center at Puerto Madryn, Argentina, say the problem with the conventional method is that, under evolution, facial traits do not appear out of the blue but result from continuous change. The team goes back over the same well-known set of specimens, but uses a different approach to analyze it, focusing in particular on a set of fundamental yet long-term changes in skull shape.

They took digital 3D images of the casts of 17 hominid specimens as well as from a gorilla, chimpanzee and H. sapiens. The images were then crunched through a computer model to compare four fundamental variables -- the skull's roundness and base, the protrusion of
the jaw, and facial retraction, which is the position of the face relative to the cranial base.
When other phylotogenic techniques are used, the outcome is a family tree whose main lines closely mirror existing ones but offers a clearer view as to how the evolutionary path unfolded.

The paper suggests that, after evolving from the hominid Australopithecus afarensis, the first member of Homo, H. habilis, arose between 1.5 and 2.1 million years ago. We are direct linear descendants of H. habilis. H. sapiens started to show up around 200,000 years ago.

Neanderthals are declared "chronological variants inside a single biological heritage," in other words, evolutionary cousins but still a separate species from us.

The squat, low-browed Neanderthals lived in parts of Europe, Central Asia and the Middle East from around 170,000 but traces of them disappear some 28,000 years ago, their last known refuge being Gibraltar. Why they died out is a matter of furious debate, because they co-existed


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