The human ancestral family tree just got a lot bushier: a newly discovered fossil supports the notion that Homo habilis may not have evolved into the larger Homo erectus. Researchers have found an H. habilis jawbone near Kenya's Lake Turkana that dates to 1.44 million years ago, when H. erectus also roamed the area. If the two early hominids coexisted, then they probably evolved separately from a common ancestor. The oldest habilis and erectus fossils found in East Africa date to 1.9 million years ago, indicating that they cohabited in the region for half a million years and that the species' shared ancestor would have had to have lived two million to three million years ago. But whether it was much different from both or resembled the older habilis is unknown: the only remains from this time are some skull fragments and a few teeth. Dig up the study in the August 9 Nature.
This article was originally published with the title "Cohabitating Hominids" in Scientific American 297, 4, 38 (October 2007)