East African fossils cast new light on the origins of Homo

Reconstructed skull of Homo rudolfensis (KNM ER 1470)
Wikipedia Commons (CC) Durova

This week two important papers address the antiquity and diversity of the genus Homo.

A study published in Nature (here) takes a fresh look at Homo habilis, "The Handy Man," first described half a century ago (see previous post). The mandible (lower jaw) of the type specimen (OH 7) is badly distorted, but has been reconstructed using state-of-the-art computer tomography and 3D imaging technology. Comparison with other fossil mandibles from the region shows that not all can be ascribed to H. habilis. Indirectly. this supports the validity of Homo rudolfensis (pictured) as a distinct species.

A similar approach yielded a new estimate for the endocranial volume of OH 7 (a proxy for brain size). Interestingly, similar values are obtained for H. habilis, H. rudolfensis and H. erectus. 

A new fossil from Ethiopia, described in Science (here and here), is too incomplete to assign to a species. It is exciting because it can be assigned to the genus Homo and is 400,000 years older than all previous fossils. It pushes the origin of our genus back to at least 2.8 million years ago. There could well be overlap with Australopithecus afarensis best known from the skeletal remains of "Lucy"