African Eve or multiregional origins? Maybe both
WASHINGTON (Reuters) The out-of-Africa theory is not dead, anthropologists and other experts say this week, despite two recent studies that challenge the idea we are all descended from a single African "Eve."
U.S. and Australian researchers published two reports that used physical and genetic evidence to suggest there may have been mixing of pre-humans with modern species.
They said they had proved wrong the mainstream out-of-Africa theory that the ancestors of all living humans emerged from Africa some 50,000 years ago and either killed off or out-competed all other humanlike creatures who settled across much of the world.
One study used genetic evidence that suggested "Mungo Man," an Australian skeleton dated to between 40,000 and 60,000 years ago, is genetically unrelated to Africans. The researchers, Gregory Adcock of Australian National University and colleagues, said their finding showed the first modern humans evolved in Australia, not Africa.
Another, published in Friday's issue of the journal Science, analyzed physical features of early human skulls to suggest there must have been interbreeding among the migrating Africans and resident Neanderthals and even Homo erectus species of prehumans.
"There never was a marauding band of Africans," University of Michigan anthropologist Milford Wolpoff, who led the second study, said in a telephone interview.
"It certainly means that the "Eve" theory, the replacement theory, seems to be wrong."
The Australian team and Wolpoff and colleagues belong to the "multiregionalist" school of human evolution. They believe humans evolved around the world at roughly the same time, and that they probably mixed with earlier species such as Neanderthals and Homo erectus.
The out-of-Africa school says that all earlier humans died out and were replaced by a small group from Africa who quickly conquered the world.
Some experts say the two theories are not incompatible, although they predict a fight over the latest studies.
"There might be a lot of finger-pointing and name calling and debate that is more heat than light," says Peter Underhill of Stanford University, who has published genetic studies that date our common ancestors to an African man who lived 59,000 years ago and an African woman who lived 143,000 years ago.
"But I don't think it torpedoes the recent out-of-Africa scenario at all. I don't think these two papers are going to turn the world of human evolution on its head."
It does not matter whether early humans mixed or evolved into "modern" forms in more than one place, Underhill says. The out-of-Africa theory holds only that one lineage finally held sway, either through luck, better genes, or a combination of the two.
We are all descended from that lineage, he says. "Everyone on Earth today is very closely related," he says.
"It might suggest that there was some hybridization with moderns and possibly other modern lineages that existed 60,000 years ago that are now extinct, or it is possible there was some kind of hybridization with some sort of archaic human that lived in the past," Underhill adds.
"But no one is walking around so far in Europe with Neanderthal genes."
So if both theories can coexist, why argue?
"Egos, egos egos," Underhill says. "Scientists are human."
Clark Howell, a professor emeritus of human evolution at the University of California Berkeley, agrees.
"There is a tendency in some instances for some people at some times to jump to very wide, sweeping conclusions," he says. "In my view these two studies don't upset any applecarts."
In other words, modern humans may have indeed evolved in places other than Africa. They may even have mated occasionally with Neanderthals, who did live at the same time and in the same places. But genetically, they have since died out.
"If we are looking for the ancestry of modern people, where people alive today came from, where their genes came from if there was such hybridization it is negligible. It is impossible to find today," says Chris Stringer, head of human origins at London's Natural History Museum and an architect of the out-of-Africa theory.