An international team of paleontologists in Africa has unearthed the oldest known fossil remains of modern humans. Working in the remote Afar Valley of Ethiopia, the researchers found 160,000-year-old skulls of two adults and one child. In a report published in the journal Nature, the scientists say their finding confirms that anatomically modern Homo sapiens emerged, not from Neanderthals in Europe, but from a different human ancestor in Africa. Tim White, professor in the Department of Integrative Biology at the University of California at Berkeley and a leader of the team that excavated and analyzed the fossils, told VOA's Rosanne Skirble that the fossils give a better picture of what our direct ancestors looked like.
Tim White: "We compared the child and we found out that it was well within the range of anatomically modern people today. We know that from how the teeth were erupting. We recovered the erupting teeth. On the adult, when we examined it, we compared it with about 6,000 modern human skulls, from all around the world. And we found that this is right at the edge of the range. This is a very large, massive, robust individual with very strong neck muscle attachments, very prominent brow ridges, but not like earlier hominids or Neanderthals, rather they are like ours. And so we recognized these minor differences from modern humans by giving it a different sub-species name. We call it 'Homo sapiens Idaltu.' We used an Afar name, which means elder.
Rosanne Skirble: "I'd like to talk about the debate the 'Out of Africa' theory of which you are a proponent, and the 'multi-regional' approach. Can you tell us about those two theories of the origin of humans, and how this discovery adds to the debate."
Tim White: "The debate actually is over a century and a half old and it stems back to the 1800s when Neanderthals were first found in Europe. People looked at these and some people thought that these were just a primitive stage of humans and we evolved from these Neanderthals. And, of course these were some of the first fossils found in Europe. Other people said, no, that they looked very strange and that we [modern humans] must have come from somewhere else. And over the last century and a half a lot more Neanderthal fossils have been found in Europe and now we have some earlier Neanderthals and later Neanderthals and [we know] that they persisted in Europe until about 30,000 years ago. We know a great deal about how the glaciers came and went in time through many, many cycles. We have Neanderthal children whose remains have been found in caves in Europe. Yet Africa has remained fairly mute in its contribution to this problem. Although the studies of modern human genetics have pointed to Africa as a potential source of Homo sapiens, the evidence has been very, very poor until now. And, now with the child and the adult from Ethiopia dating to a time that is more remote than even the average Neanderthal, we see an anatomy that is so similar to anatomically modern people that we can clearly show that this evolution of our species happened in Africa at the same time that Europe was inhabited by Neanderthal people, people that ultimately went extinct."
Project leader Tim White says the fossil-rich site also yielded skull pieces and teeth from seven other hominids, hippopotamus bones bearing cut marks from stone tools and hundreds of other artifacts including hand axes, flake tools, and rare blades.
Professor White adds that some sophisticated technology helped researchers locate the fossils.
"We use a lot of satellite imagery and aerial photography to target the outcrops of exposed rocks," he said. "These sediments look very different from a lava flow, which isn't going to have any fossils in it. Then you have to have people on the ground to be able to walk these outcrops and who recognize what is coming out. And it is not an easy job. The graduate student from Berkeley who found, for example, the complete adult cranium, didn't find the complete skull there on the sand.
"He found one piece, but then by doing the detective work we figured out where the rest of it was and we extracted it," he continued. "Dr. Berhane, when he found the piece of child's cranium, this was a piece that was about as big as the size of an American quarter [about 2.5 centimeters in diameter]. But he knew right away that it was a hominid. How did he know that? He is an anatomist. He is trained. He knows the detailed anatomy of hominids. So it is not a matter of chance. It is a scientific investigation. We are aiming to recover evidence and the evidence is very hard to recover, and to do it you have to have a really good team and that's what we have here in Ethiopia."
That team includes more than 45 scientists from 14 countries who specialize in geology, archaeology and paleontology. In the single study area the team has found fossils dating from the present to more than six million years ago. Project leader Tim White says the team will continue to monitor the site, but in their next excavation, the scientists plan to examine rock that dates back 250,000 years, in search of fossil remains of an even earlier human ancestor.