February 15-21, 2006

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Technology News - Annalee Newitz

Technology News

Interbreeders: 'So the idea of pure, distinct races in humans does not exist'

By Annalee Newitz

THERE IS an anthropologist in St. Louis who used a computer simulation to prove that people interbred with other species for at least a million years. You know what that means: Homo erectus is more ripe for punnage than ever. University of Washington professor Alan R. Templeton published his findings in the recently issued Yearbook of Physical Anthropology, explaining that he had finally disproven the popular "out of Africa" theory, which holds that Homo sapiens zoomed out of Africa roughly 100,000 years ago, killing every hominid that it met (including fellow tool users and fire makers Homo erectus and Homo neanderthalis).

Instead of killing, Templeton found, early humans were more likely having sex with every hominid they encountered on the way out of Africa into Asia and Europe. They also probably migrated out of Africa in three waves, rather than one or two, seeding Asia and Europe with early hominids who later cozied up with newly arrived groups.

Templeton figured this all out using a computer program called GEODIS, which he wrote back during the Clinton administration. The program reconstructs early human mating patterns by doing statistical analysis on population distributions of haplotypes, chunks of genes that get inherited together over long swaths of history.

Based on what he found, Templeton says, "The hypothesis of no interbreeding is so grossly incompatible with the data that you can reject it." It has always struck me as kind of weird that the dominant theory of human evolution—often called the "replacement theory" or "single-origin hypothesis"—holds that Homo sapiens evolved all on its own in Africa, without any interbreeding with its comely hominid neighbors.

The single-origin hypothesis says that when Homo sapiens migrated out of Africa, it simply destroyed (or, in polite anthropology-speak, "replaced") all the other hominids. Even if we assume that Homo sapiens are such a bloodthirsty lot that their response to another form of intelligent life is to battle it, we all know what happens in battles. The conquered are often raped and/or enslaved. This seems like such a time-honored occurrence—even inspiring a snotty little book by some prim profs a few years ago called A Natural History of Rape—that it's hard to believe it wasn't happening in our earliest evolutionary incarnations.

Now you may be saying, sure, humans could have been raping Homo erectus, but that doesn't mean any of them made babies together. That's like saying humans who rape chimps are interbreeding. You'd be right if it turned out to be true that there was only one migration out of Africa 100,000 years ago, when Homo sapiens had diverged enough from its fellow hominids that matings were likely to be sterile.

But Templeton has found that there were three migrations out of Africa—one at 1.5 million years ago, one at about 700,000 years ago and the familiar one we all know and love at 100,000. What Templeton is arguing is that the forbearers of creatures we are today—Homo sapiens sapiens—were interbreeding with the forbearers of other hominid groups.

His theory about the migrations at 700,000 years ago also goes a long way to explaining the sudden expansion in brain-pan size among humans at that time, as well as evidence that tool use began to spring up among hominid groups across Europe and Asia at that time, too.

We are hybrid hominids, not some pure species whose coolness and ingenuity allowed it to sweep over Asia and Europe "replacing" everything we found. We didn't "replace" other hominids; often, we merged with them. Interestingly, Templeton sees his discoveries as a refutation of more than the replacement hypothesis. He sees it as scientific proof that racism has no rational basis.

"You can be 99 percent confident that there was recurrent genetic interchange between African and Eurasian populations," he says. "So the idea of pure, distinct races in humans does not exist. We humans don't have a tree relationship, rather a trellis. We're intertwined."

It's good to remember that for every scientist who wants to prove that Africans are genetically distinct from Europeans, there is one who demonstrates that there is no difference. Especially in conservative times, science is often the enemy of oppressed racial groups (think of the Bell Curve, the Tuskegee syphilis studies and countless "scientific" eugenics programs). But once in a while, an anthropology geek with a cool computer program reminds us that real science does not give answers that fit easily into cultural stereotypes. Good science overturns them.

Annalee Newitz ([email protected]) is a surly media nerd whose ancestors interbred with nanotech smart matter from Jupiter.

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