Human Evolution

A chance fossil find along a Russian river has provided researchers with the oldest genomic data ever sequenced from a modern human. The fossil, a nearly complete left femur, was pulled from a bank along the Irtysh River near the Ust’-Ishim district in western Siberia in 2008 by a Russian artist before it made its way to scientists.

For a time, Homo sapiens and Neanderthals shared space in Europe, likely interacting and possibly interbreeding, but roughly 40,000 years ago the Neanderthals died out for unknown reasons. Pinpointing the extinction of the Neanderthals has proved difficult due to limitations in carbon-14 dating techniques, the accuracy of which declines in samples approaching and older than 50,000 years due to a decreasing amount of carbon-14 for testing. Now, using a new dating technique, scientists have confirmed that Neanderthals likely disappeared between 41,000 and 39,000 years ago.

There is widespread agreement among scientists based on fossil and geochemical evidence that modern humans evolved in Africa between 200,000 and 100,000 years ago before spreading around the world. But the timing and route of this dispersal, and whether it occurred as a single exodus or in multiple pulses, remain contested. Now, a new study throws its weight behind a multiple-dispersal hypothesis, suggesting a first group of modern humans left Africa as early as 130,000 years ago, followed by a second about 80,000 years later.

The existence of an ice-free corridor through Canada during  the climax of last glaciation, which allowed the first Americans to cross the Bering land bridge from Siberia and move south (about 13,000 years ago), has long been postulated in North American archaeology. Now, research based on the exposure ages of glacial rocks found in the corridor suggests a puzzling conclusion — that the open pathway closed several thousand years prior to 20,000 years ago and didn’t open again until between 13,000 and 12,000 years ago, well after  first Americans were in the Americas.