Ethiopian skulls oldest known of human species

Two human skulls discovered in Africa have been confirmed as the oldest known examples of our species. The remains, unearthed in Kibish, Ethiopia, are estimated to be about 195,000 years old and come from around the time that modern humans are thought to have emerged.

The fossils, called Omo I and Omo II, were found in 1967, but experts have previously disagreed over their ages. In a report published yesterday in the journal Nature, scientists said the fossils were the same age - and humankind's oldest relics - even though Omo I's features were distinctly more "modern" than those of its companion.

Ian McDougall, of the Australian National University, and his colleagues examined the rate of decay of unstable isotopes of the element argon in the rocks where the specimens were found. The fossils were found above a layer of rocks composed of compacted volcanic ash which was 196,000 years old, but below a layer dated at 104,000 years old.

The team concluded the deposition of each layer of the rock formation was probably rapid and that the fossils were close to 196,000 years old. The report said: "We suggest that hominid fossils Omo I and Omo II are relatively securely dated to 195,000 years old, plus or minus 5,000 years, making Omo I and Omo II the oldest anatomically modern human fossils yet recovered."

Previously, the oldest examples were thought to have been found in Herto, Ethiopia, and were dated between 154,000 and 160,000 years old. Separately, scientists are closer to finding an answer to ageing. Researchers in California said they have isolated youth-preserving molecules in the bloodstreams of animals. They found that when the circulatory systems of young and old mice were connected, the elder rodent increased its ability to regenerate damaged tissue.

In contrast, the younger mouse showed a decrease in its rejuvenation abilities. The researchers, from Stanford University School of Medicine and the Geriatric Research, Education and Clinical Centre, said the effects were due to something in the younger mice's bloodstream activating "progenitor cells" in the older animals. This suggests the slow-down in an animal's ability to renew cells - one of the defining aspects of ageing - could be reversed.

- INDEPENDENT