Thursday, February 17, 2005

This Week In Nature

In the Current issue of Nature: Vol 433 No 7027 pp669-784:

Stratigraphic placement and age of modern humans from Kibish, Ethiopia
Nature 433, 733 - 736 (17 February 2005)

The Oldest Homo Sapiens
A new study of a 1967 fossil site at Kibish, Ethiopia, indicates the earliest known members of Homo sapiens lived in Africa about 195,000 years ago, 65,000 years older than the previously published date. The discovery adds yet more weight to the argument that Africa, and Ethiopia in particular, was the birthplace of humans. The dating sits well with genetic analyses of modern populations, which suggest that H. sapiens first appeared in Africa around 200,000 years ago.
"It pushes back the beginning of anatomically modern humans," says geologist Frank Brown, a co-author of the study and dean of the University of Utah's College of Mines and Earth Sciences. "These are the oldest well-dated fossils of modern humans (Homo sapiens) currently known anywhere in the world," the scientists say in a summary of the study.
The researchers dated mineral crystals in volcanic ash layers above and below layers of river sediments that contain the early human bones. The fossils, called Omo I and Omo II, were found in 1967 at Kibish, near Ethiopia's Omo River, by the famed fossil-hunter Richard Leakey. They conclude the fossils are much older than a 104,000-year-old volcanic layer and very close in age to a 196,000-year-old layer.