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"This is a truly revolutionary scientific discovery." Howell added that these anatomically modern humans pre-date most neanderthals, and therefore could not have descended from them, as some scientists have proposed.
The international team is led by White and his Ethiopian colleagues, Berhane Asfaw of the Rift Valley Research Service in Addis Ababa, Ethiopia, and Giday Wolde Gabriel of Los Alamos National Laboratory in New Mexico.
The fossils date precisely from the time when biologists using genes to chart human evolution predicted that a genetic "Eve" lived somewhere in Africa and gave rise to all modern humans.
"We've lacked intermediate fossils between pre-humans and modern humans, between 100,000 and 300,000 years ago, and that's where the Herto fossils fit," said paleoanthropologist Tim White, professor of integrative biology at the University of California, Berkeley, and a co-leader of the team that excavated and analyzed the discovery site.
Many of the modern human comparison skulls came from a worldwide sample of skeletal remains in the collection of UC Berkeley's Hearst Museum of Anthropology."Back in 1982, when Becky Cann and Allan Wilson of UC Berkeley were using molecules to study evolution, they concluded that the common ancestors of all modern humans lived in Africa 100,000 to 200,000 years ago.For the last 20 years we've been looking for good, well-dated fossil evidence of that antiquity." Previously found fossils were younger, from sites scattered around Africa, often poorly dated and incomplete.The results of the find will be reported in two papers in the June 12 issue of the journal Nature.The research team also unearthed skull pieces and teeth from seven other hominid individuals, hippopotamus bones bearing cut marks from stone tools, and more than 600 stone tools, including hand axes.