Not long ago, most paleoanthropologists thought that intercontinental travel was reserved for hominids who were long of limb and big of brain. But now researchers have unearthed a skull--the smallest and most primitive hominid skull ever found outside Africa--that appears to bury the notion that big brains spurred our first exodus from that continent.
Until very recently, the fossil evidence suggested that early humans did not journey out of Africa until they could walk long distances and were smart enough to invent sophisticated tools. Then, 2 years ago, a team working at Dmanisi, Georgia, shook up those ideas. It reported finding two small skulls dated to a surprisingly ancient 1.75 million years ago and associated with only primitive stone tools (Science, 12 May 2000, p. 948 ).
The latest find, described in the 5 July issue of Science , was made by the same team, led by David Lordkipanidze at the Georgian State Museum in Tbilisi, Georgia, and Philip Rightmire of the State University of New York, Binghamton. The researchers classify their find like the other two, as Homo erectus, a long-legged, big-brained species considered to be the first to leave Africa. But some features of the diminutive new skull--the small cranial capacity and the thin but well-developed brow ridges, for example--also resemble H. habilis, an African hominid that some believe was ancestral to H. erectus.
Lordkipanidze and Rightmire suggest that the Dmanisi hominids might be descended from H. habilis–like ancestors that had already left Africa. If so, then soon after our genus arose--and before its members had reached the brain size and stature of H. erectus--it was already pushing into new continents. Such a primitive traveler also raises the heretical possibility that H. erectus itself evolved outside Africa, long considered the cradle of human evolution, notes Tim White of the University of California, Berkeley.
Still, other researchers favor different scenarios, and exactly where the remains fit on the hominid family tree is still a matter of much debate. However, one thing is already clear, says Rightmire: "It wasn't a full-blown Homo erectus and a big brain ... that enabled people to push out of Africa. The first pushing was done by little people."