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White and his colleagues think these hominids are distinctive enough to merit their own subspecies, which the team has dubbed Homo sapiens idaltu. (Idaltu means elder in the Afar language.) But whether or not the nomenclature holds up, says paleoanthropologist G. Philip Rightmire of the State University of New York at Binghamton, "the key point is that they are from the right place at the right time to be, broadly speaking, the ancestor of modern people. It's as near as we're going to get."
The find lays to rest a long-standing dispute about another breed of hominid, the Neanderthals. "It's now clear," says White, "that there were anatomically modern humans in Africa long before there were classic Neanderthals in Europe." This means that the more primitive Neanderthals could not, as some have argued, have been our ancestors. They were almost certainly a side branch on the evolutionary tree, and that branch died out some 30,000 years ago.
Another controversy has to do with where modern humans first appeared. Everyone agrees that a hominid called Homo erectus left its African home some 2 million years ago to populate the Middle East, Asia and Europe. Long after that, argues one camp, Homo sapiens evolved, also in Africa, and began a second exodus. In contrast to this out-of-Africa scenario, the so-called multiregionalists say there was no second sojourn. The far-flung Homo erectus communities and their descendants, the multiregionalists believe, could have interbred enough that Homo sapiens appeared pretty much everywhere at once.
Genetic analysis tends to refute this claim. Among other things, Africans are more genetically diverse than any other people on Earth, which suggests that they have had longer to differentiate. And populations in eastern Africa, where most of the oldest hominid fossils have been found, are the most diverse of all. Finding this most ancient of Homo sapiens in Africa pretty much settles the argument. "It's not just another nail in the coffin for the multiregional view," says Rightmire. "It lowers the coffin into the ground." Declares White: "This is what stepped out of Africa."
Perhaps the most intriguing discovery, however, is that these ancestors behaved like us in at least one poignant way: all three skulls were deliberately tampered with after death, evidently as part of some sort of mortuary practice. "This," says White, "is the earliest evidence of hominids continuing to handle skulls long after the individual died."
"Handle" is an understatement. Cut marks on the skulls indicate that the overlying skin, muscles, nerves and blood vessels were removed, probably with an obsidian flake. Then a stone tool was scraped back and forth, creating faint clusters of parallel lines. The modification of the child's skull is even more dramatic. The lower jaw was detached, and soft tissues at the base of the head were cut away, leaving fine, deep cut marks. Portions of the skull were smoothed and polished.