Human evolution: Same place, same time
Two fossils discovered in Kenya cast doubt on theories of the early evolution of the genus Homo. They show that the species H. habilis and H. erectus — previously thought to have evolved one after the other — actually lived side-by-side in eastern Africa for almost half a million years. The H. erectus fossil is the smallest ever found, suggesting that this species was not as human-like as once thought.
The east-African hominins H. habilis and the generally larger and later H. erectus are often regarded as part of the same pre-human lineage. The new fossils, uncovered east of Lake Turkana in Kenya, now challenge the relationship between these two species. The researchers attribute the first specimen, fragments of an upper jaw bone, to H. habilis. These bones provide the last known occurrence date for this species — 1.44 million years ago — which is significantly younger than previous estimates. The second fossil, a beautifully preserved H. erectus skull from 1.55 million years ago, is remarkable because it is close to the average size of H. habilis. This indicates that the species displayed substantial sexual dimorphism with the male being much larger than the female, like modern day gorillas.
The new dates show that H. habilis and H. erectus did in fact live at the same time in the Turkana basin for nearly half a million years. Their co-existence makes it unlikely that H. erectus evolved from H. habilis — both species must have originated between 2 and 3 million years ago, a time from which few Homo fossils are known. The authors conclude that, because they stayed as separate individual species for such a long time, they probably each had their own ecological niche and avoided direct competition with each other.

CONTACT:
Fred Spoor (University College London, UK)
Please note the author is currently based in Kenya:
Tel: +254 727 497 787 or +254 20 375 2337
Satellite phone: +88 216 5115 6558
E-mail: f.spoor@ucl.ac.uk

Additional author contacts:
Meave Leakey (Koobi Fora Research Project, Kenya)
Satellite phone: +88 216 5115 6558
E-mail: meaveleakey@gmail.com

Louise Leakey (Koobi Fora Research Project, Kenya)
Tel: +254 722 528 586
E-mail: louiseleakey@gmail.com