THE textbook version of how humans evolved in Africa and then travelled out to the rest of the world may have to be torn up. Humans may not after all have had to become highly intelligent, with big brains, to migrate out of Africa.
A surprising new fossil discovery of a small, lightly built species of early human in Central Asia suggests that it wasn鈥檛 only large-brained hominids that had the guile to leave Africa. The individual, found in Dmanisi, Georgia, has a much smaller skull than two others found earlier at the same site.
The skeleton, comprising a skull and jawbone, also combines features found in a number of early human species. This further erodes the textbook view that human evolution was a linear progression from Australopithecines through Homo habilis, Homo ergaster and Homo erectus. The small size of the new individual suggest that there was more variations among hominid populations than supposed.
Advertisement
Two years ago, the discovery of two fossil skulls at Dmanisi showed that the first humans arrived in Eurasia 1.75 million years ago (New Scientist, 20 May 2000, p 6). The fossils appeared to have much in common which those of H. erectus found in Asia and H. ergaster in Africa. The new skull, dated as being from the same time, has a brain volume of just 600 cubic centimetres, putting it in the range of H. habilis (Science, vol 297, p 85). This adds to evidence that early Dmanisi humans did not differ much from their African contemporaries.
The team that discovered the skull, including Reid Ferring of the University of North Texas in Denton and David Lordkipanidze, deputy director of the Georgian State Museum in Tblisi, have 鈥減rovisionally鈥� assigned all three skulls to H. erectus, which they consider equivalent to H. ergaster.
The implications of the find are still unclear, however. Ferring says the three skulls show that there were different types of hominid in Dmanisi at the same time. Lordkipanidze says the fossils show that individuals within a single population of hominids could have varied greatly in size.
Milford Wolpoff of the University of Michigan, who has seen the skulls, has a less radical explanation. He suggests they could simply be showing differences in age and sex. The small skull could be from an immature female, while another jawbone found at the same site could be from a large male, he says.
But anthropologists do agree on the importance of the Dmanisi site, which has yielded a richer collection of early human fossils than any African site. 鈥淭he great value of finds like these is the questions they raise, not the answers they provide,鈥� says Harvard anthropologist Daniel Lieberman.