Aleut origins and relationships

Michael Balter last week had a news article in Science reviewing archaeological and genetic research into the origins and relationships of Aleut populations Balter:Aleut:2012. The topic has a rich combination of historical and contemporary approaches.

Recent genetic work confirms the distinction: Mitochondrial DNA (mtDNA) from 69 of Hrdli?ka's skeletons showed that Neo-Aleuts, like most modern Aleuts, descend from a common ancestor that carried genetic markers known as haplogroup D, according to recent work by University of Utah geneticist Dennis O'Rourke. But most Paleo-Aleuts were members of haplogroup A, as are most groups now living in Arctic North America.
Hrdli?ka argued that the Neo-Aleut populations came from the Alaskan mainland and replaced the Paleo-Aleuts. But Coltrain and others have found that the newcomers in fact coexisted with the original settlers. The long-headed Paleo-Aleuts were still very much around for several hundred more years, says anthropologist Richard Davis of Bryn Mawr College in Pennsylvania. About two-thirds of living Aleuts belong to haplogroup D and one-third to haplogroup A, according to work by Crawford and his co-workers, and they are presumed to be the result of admixture between Paleos and Neos. Crawford's research with modern Aleuts also suggests that they carry some Paleo-Aleut DNA, because their ancestors branched off from other Arctic peoples about 13,000 years agolong before they colonized the islands, perhaps when they were still in Asia or Beringia.

Such a great case, where today’s scientists can draw upon Hrdli?ka’s models of population history. Still, what I think we are seeing today is only halfway through a revolution in studying human population interactions. In this case, mtDNA haplogroup frequencies are fairly informative – similar to the situation in the Neolithic of Europe. But as we move to whole-genome approaches, it will be possible to attain a much more refined understanding of the relationships and pattern of mixture between what look like distinct groups. Likewise, the distinction between long-headed and broad-headed populations radically oversimplifies what is possible from craniometric comparisons. The biggest limit on craniometrics and genetics is the availability of relevant comparative samples from other early Beringian and American populations. This situation is getting better for genetics, and anthropologists continue to find ways to expand our understanding of New World peopling. The Aleuts are not only an interesting group for their own distinctive history; their ancestry may give them a store of the variability that was present in Eastern Beringia before people moved further south into North America.

The Aleutian islands are a microcosm of the human habitation of other, larger areas of the world. In my opinion, we aren’t going to get the big areas right until we have approaches that work well in cases like this one.