Fossils Plug Gap in Human Origins. (African Legacy)

Article excerpt

Three partial skulls excavated in eastern Africa, dating to between 154,000 and 160,000 years ago, represent the oldest known fossils of modern people, according to the ancient skulls' discoverers.

The new finds of Homo sapiens fossils, unearthed near an Ethiopian village called Herto, fill a major gap in the record of our direct ancestors. Modern H. sapiens fossils previously found in Africa and Israel date to about 100,000 years ago. A skull excavated in Ethiopia of a not-yet-modern, so-called archaic H. sapiens is roughly 500,000 years old.

The Herto fossils show that H. sapiens evolved in Africa independently of European Neandertals, says project director Tim D. White, an anthropologist at the University of California, Berkeley. The finds thus bolster the out-of-Africa theory of human evolution (SN: 5/17/03, p. 307). In this view, people originated in Africa between 200,000 and 150,000 years ago and subsequently replaced Neandertals and other closely related groups.

In contrast, supporters of multiregional evolution argue that H. sapiens evolved over the past 2 million years with at least some interbreeding of African, Asian, and European populations.

"Only in the African fossil record can we now see a progression of specimens leading to modern humans," White says.

At Herto in 1997, Whites team found the partial skulls of two adults, one of which retained its facial bones, and of a 6-to-7-year-old child. Removal of sediment from the fossils and their reconstruction, including the assembly of more than 200 pieces of the child's cranium, occurred over the next 3 years. Measurements of argon gas trapped in volcanic ash above and below the finds were used to generate an age estimate. The group describes the Herto discoveries in the June 12 Nature. …