Scientists used to have to travel to the remotest places on the Earth to find traces of human origins. Now it seems they only need to poke around inside our genes. According to a report in New Scientist, researchers have achieved yet another milestone in using genetic structures to "time" the evolution of our species. As the article puts it:
Analyzing the ways that mitochondrial DNA sequences differ across a large number of living people has helped to establish prehistoric population trends, but this record stretches back only 200,000 years to the point where all humans alive today shared a common female ancestor. That's because mitochondrial DNA passes down from mother to child.
Richard Durbin of the Welcome Trust Sanger Institute in Cambridge, UK, and Heng Li at the Broad Institute in Cambridge, Massachusetts, can push the record back five times as far by reading a single genome.
Taking advantage of the handful of complete human genome sequences now available, the pair looked at how alleles - the two copies of each gene we inherit from our parents - differ within a genome. Many differences between the two copies suggest that they separated some time ago, while similar copies have a more recent separation date.
From even these initial studies the team can claim evidence for severe "bottlenecks" in the evolution of human populations in China and Europe compared to those in Africa. Bottlenecks or "founder" events can play hell with genetic diversity in a group so even these initial studies have shown the utility of the new methods.
By the way, an excellent book on the use of genetic methods in teasing out human origins is Nicholas Wade's Before the Dawn.