This week’s Nature reports that DNA from an ancient human has been recovered and sequenced. The DNA is from a hair sample found several decades ago in Greenland, and just now recognized as human. It came from a male of the Saqqac Culture, which was active in Alaska, Canada, and Greenland from about 5,000 to about 2,500 years ago.
Surprisingly, the authors found that DNA could be sequenced from a hair lacking a follicle; apparently some cells were trapped in the hair shaft. About 80% of the genome was sequence-able. What does it tell us about this guy? A few things:
1. He had type A blood and was Rh positive. That’s a common blood type in Siberians and Asians.
2. He had a haplotype consistent with having brown eyes. No surprise there.
3. Other SNPs (single-nucleotide polymorphisms) associated with physical trait suggested that the man had darker skin, thick, dark hair, dry earwax (!), and a tendency to baldness (but remember, the DNA came from a thick swatch of hair). A combination of SNPs from different areas of the genome suggested that he had a stocky body. That’s no surprise, either. (This, by the way, conforms to “Allen’s Rule,” the biogeographic observation that populations from colder areas have relatively smaller protruding limbs and parts, and stockier frames—all of which conserve heat.) All of these genotypes are consistent with what we know about people who lived in northern Asia and Alaska.
It’s great that they could find out this stuff, but it’s really no surprise. What made the paper Nature-worthy is the recovery and sequencing of ancient DNA from a human. Oh, and the really interesting result is this: the DNA suggests that the individual had components of genes still present in East Asian and Siberian populations, but not found in modern-day Inuits or people from South and Central America. This suggests that there were two separate invasions of North America from Asia: the one that gave rise to native Americans, South Americans, and modern Inuit on the one hand, and that leading to the presence of Saqqaq in Greenland. Those latter individuals probably came across the Bering Strait, and then, hugging the Arctic, made their way eastward across North America and then to Greenland.
That conclusion is of course tentative because it’s based on only this single genome. Still, based on the sequence, and the tentative phylogeny showing that this individual’s ancestors split off from the ancestors of their closest living relatives (the Chukchis of eastern Siberia) about 5,000 years ago, anthropologists may have to revise their conclusion that there was one invasion of North America from eastern Asia around 18,000 years ago.
Rasmussen, M. et al. (lots of authors!). 2010. Ancient human genome sequence of an extinct Palaeo-Eskimo. Nature online, doi:10.1038/nature08835. Note that this group previously published a sequence of mtDNA from this individual (Gilbert, M. T. P. et al., 2008. Science 320:1787-1789)