Human fossils are oldest yet

Our species, Homo sapiens, has a new pair of ultimate old-timers. The remains of two ancient individuals, found in Ethiopia in 1967, date to about 195,000 years ago, a research team reports in the Feb. 17 Nature.

The former most-senior H. sapiens fossils were a trio of roughly 160,000-year-old skulls unearthed in 1997 at Ethiopia’s Herto site (SN: 6/14/03, p. 371: African Legacy: Fossils plug gap in human origins).

Ian McDougall of the Australian National University in Canberra and his coworkers trekked to the Kibish formation along Ethiopia’s Omo River, where the 1967 excavators had found a partial H. sapiens skull, associated lower-body parts and another H. sapiens braincase. Scientists had dubbed the two individuals, respectively, Omo 1 and Omo 2.

Features of the Omo 1 fossils closely resemble those of the bones of people today, whereas the Omo 2 fossil recalls ancestors with traits such as a relatively thick braincase. Originally, anthropologists estimated the Omo fossils to be approximately 130,000 years old.

McDougall’s team used isotopic analysis to determine the ages of volcanic-ash layers above and below river sediments that contained the fossils. The results show that Omo 1 and Omo 2 were extracted from sediment that’s extremely close in age to a 196,000-year-old ash layer.

The new analysis of the Omo fossils indicates that, between 200,000 and 150,000 years ago, H. sapiens in eastern Africa possessed varying combinations of “modern” and “primitive” skeletal traits, comments Christopher Stringer of the Natural History Museum in London.