The American Journal of Human Genetics has published an article titled, “Correcting for Purifying Selection: An Improved Human Mitochondrial Molecular Clock,” in which a more accurate method of dating ancient human migration, even when no corroborating archaeological evidence exists, is announced.
How does was this done?
The authors started with a sample of 2,000 fully sequenced mtDNA genomes. Not only does this increase the accuracy, but also the precision, ultimately allowing for more narrow temporal ranged. Furthermore, the new method integrates the process of natural selection, which normally skews migration results. In doing so, they authors confirmed that their new methodology works by comparing it against known colonization of Polynesia in the Pacific (approximately 3,000 years ago), and the Canary Islands (approximately 2,500 years ago) extracted from archaeological data.
Aside from confirmation, some more ‘surprising’ results have also been extracted. Last author, Martin B. Richards comments,
“We can settle the debate regarding mankind’s expansion through the Americas. Researchers have been estimating dates from mtDNA that are too old for the archaeological evidence, but our calculations confirm the date to be some 15,000 years ago, around the time of the first unequivocal archaeological remains.
Furthermore, we can say with some confidence that the estimate of humanity’s ‘out of Africa’ migration was around 60-70,000 years ago — some 10-20,000 years earlier than previously thought.”
The press release says that the team has made their simple calculator freely available on on the University of Leeds website. But I can’t seem to find it, but the supplemental data includes an Excel spreadsheet version of the calculator for you to use and dissect. Anyone got the link to the online calculator?
- Pedro Soares, Luca Ermini1, Noel Thomson, Maru Mormina, Teresa Rito, Arne Röhl, Antonio Salas, Stephen Oppenheimer, Vincent Macaulay, & Martin B. Richards (2009). Correcting for Purifying Selection: An Improved Human Mitochondrial Molecular Clock American Journal of Human Genetics