These hominids were different. Properly dressed, they could walk down New York City's Fifth Avenue without attracting a second glance. Many of the hallmarks of modern humanity, including art, culture, spoken language and civilization, were probably still tens of thousands of years in the future. But for the first time in history, evolution had produced creatures that looked like us and at least in some ways acted like us as well.
Until now, paleontologists could only speculate about the existence of such people. But an international research team co-directed by Tim White of the University of California, Berkeley, reported in Nature last week that it has finally unearthed the long-sought fossil remains of what could be the very first true Homo sapiens, dated to between 160,000 and 154,000 years ago. And because of the quality of the specimens and where they were discovered, they cast new light on several of paleontology's thorniest questions.
The discovery was largely an accident, one that never would have happened if not for El Nino. Back in 1997, the Pacific Ocean disturbance that affects much of the world's weather triggered punishing rains in Ethiopia. The deluges not only exposed buried fossils but also drove away the people of Herto and their livestock, which would have trampled the fragile bones. When White and the others happened to drive by the village, they noticed a fossil hippo skull poking out of the ancient sand. On closer examination, the skull bore marks indicating that the animal had been gashed with a stone tool. Clearly, human ancestors had once lived there.
When the scientists returned 11 days later, it took them only minutes to find the skulls of two adults, probably male. Six days after that, Berhane Asfaw of Ethiopia's Rift Valley Research Service found a third, the skull of a 6-or 7-year-old child, shattered into about 200 pieces. After years of painstaking cleaning, reassembly and study, the team was confident enough to tell the world that it had found the earliest true Homo sapiens older by at least 1,000 generations than anything previously discovered. "It's not a modern human," says White, "but it's so close that there's no doubt it will become one. The child, in particular, is so like us that you couldn't distinguish it in a population of modern human children."
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."