Friday, January 30, 2009
Homo Erectus Update
It has long been assumed that the first human ancestors to leave Africa were representatives of the species Homo Erectus, which was thought to have originated in East Africa approximately 1.8 million years ago. Recently, though, redating of geological layers at the African find sites makes it appear that the earliest appearance of Homo Erectus in Africa dates to around 1.65 million years ago [here]. Also Homo Erectus remains, dating to approximately 1.8 million years ago were found in the Republic of Georgia [here]. There are some interesting morphological differences between the Georgian and African specimens, but the real significance of the find is that the fossils outside Africa are significantly older than anything found there. This calls into question the whole "out of Africa" scenario for early human development which is the currently ruling paradigm, raising the possibility that Homo Erectus evolved from earlier hominids, as yet unidentified, somewhere in Asia. That possibility has just been given an important boost by a report of Homo Erectus remains dating to approximately 1.83 million years ago found in Malaysia [here].
It is too early to declare the "Out of Africa" scenario dead -- the fossil record is far too spotty to support such a conclusion. Moreover, genomic analysis still points strongly to an African origin for modern humans. But what just a few years ago seemed to be a clear and straightforward story of human evolution has become much more problematic.
That's the way science seems to work. Just when a clear and ideologically satisfying developmental scenario seems to be screaming out at you, things get complicated again. Policy makers would do well to remember that.
According to John Hawks, what was found in Malaysia was not human remains but human artifacts, tools of a type commonly associated with Homo Erectus. He notes that this is not in itself surprising, since there is other evidence of early homo in the region, but that the method of dating is a bit "wonky" and may not be very accurate. [here]