Razib Khan One-stop-shopping for all of my content

October 27, 2010

Australian Aboriginal people are one?

Filed under: Aboriginal Genetics,Anthroplogy,Australia,Genetics — Razib Khan @ 12:22 am

ozlang2Richard Broome’s Aboriginal Australians is one of those books which I own which I finally managed to finish recently. It was a quick overview of Australian Aboriginals and their relationship with the settler society, and later in modern Australia. From what I could tell it was a serviceable introduction, though it took a persistent preachy tone whereby one was repeatedly reminded that the Aboriginals were an ever-peaceful people in harmony with nature, notwithstanding their regular burnings of the landscape and inter-tribal brawls. They were in timeless equilibrium with the land that they loved before the white man arrived to destroy their idyll with the shock of modern civilization. The narrative is presented as if the Aboriginals were almost totally static, and perfectly optimized to the environment that was Australia. I personally think this sort of model makes indigenous people less than human, even if it turns them into angels instead of beasts. Of course it’s probably impossible to not have a strong perspective in this sort of material, and I suppose this  type of treatment evens out the ledgers of the past. But one can discern the major themes from the subtle and not-so-subtle polemic easy enough.

One aspect of Aboriginal culture which I have wondered about is its perceived uniformity. The Dreamtime is discussed as if it’s a cultural universal among Australian Aboriginals. Is it? A little poking around indicates that Aboriginals seem to share the idea, though with variations. How’d that come to be? Broome’s model seems to assume that the Dreamtime has deep roots in Aboriginal culture, but we know that the roots likely don’t preexist their arrival in Australia, the people of New Guinea and Melanesia don’t have the concept. It may be that they lost the concept, but I doubt that all of them would. Rather the Dreamtime’s ubiquity in Australia may reflect demographic and cultural change within Australia since the arrival of modern humans ~50,000 years ago.

A paper I reviewed last summer used a thick survey of SNPs to place Australian Aboriginals in their proper global genetic context. One of the major shortcomings of that paper was that it had a small sample size from one specific Aboriginal population, and, that population was heavily admixed with Europeans. With intermarriage rates on the order of 70-80%, and a large load of European ancestry already in the Aboriginal community, the number of “pure” Aboriginals will decline rapidly in the the coming century. So I was curious enough to look for a paper which surveyed a wider range of Australian Aboriginal people. I found one, from 2007, A comprehensive analysis of microsatellite diversity in Aboriginal Australians:

Indigenous Australians have a unique evolutionary history that has resulted in a complex system of inter and intra-tribal relationships. While a number of studies have examined the population genetics of indigenous Australians, most have used a single sample to illuminate details of the global dispersal of modern humans and few studies have focussed on the population genetic features of the widely dispersed communities of the indigenous population. In this study we examine the largest Aboriginal Australian sample yet analysed (N = 8,868) at fifteen hypervariable autosomal microsatellite loci. A comprehensive analysis of differentiation indicates different levels of heterogeneity among indigenous peoples from traditional regions of Aboriginal Australia. The most genetically differentiated populations inhabit the North of the country, in particular the Tiwi of Melville and Bathurst islands, Arnhem Land (itself divided into West and East Arnhem), and Fitzmaurice regions. These tribal groups are most differentiated from other Aboriginal Australian tribes, especially those of the Central Desert regions, and also show marked heterogeneity from one another. These genetic findings are supportive of observations of body measurements, skin colour, and dermatoglyphic features which also vary substantially between tribes of the North (e.g. Arnhem Land) and Central Australian regions and, more specifically, between the Tiwi and West and East Arnhem tribes. This study provides the most comprehensive survey of the population genetics of Aboriginal Australia.

Though not totally representative of the geographic expanse of Aboriginal peoples, the sample size here was still huge. But, they looked only at fifteen microsatellite. Microsatellites mutate fast and so have a lot of variation to draw upon, but fifteen is a rather low number compared to the 160,000 core SNPs used in the paper from last summer. So here you have a trade off between population converge and depth of the genomic survey.

Below are the primary results. First are the Fst values comparing regions, and sub-regions. Second a PCA which shows the relationship between populations. Finally, a fine-grained neighbor-joining tree which shows the geographical clusters.

My Australian readers can make more informed inferences, so I won’t say too much, aside from the impression that genetic distinction seems to correlate well with linguistic distinction. Here’s their conclusion:

The principal findings of this study are that the most differentiated tribal groups are located in three regions, West Arnhem Land, East Arnhem Land and Tiwi, all of which share borders with one another in the Central North of the continent. These tribal groups are most differentiated from other Aboriginal Australian tribes, especially those of the Central Desert regions, and also show marked heterogeneity from one another. These genetic findings are supportive of observations on body measurements….

Citation: Journal of Human Genetics 52, 712-728 (September 2007) | doi:10.1007/s10038-007-0172-z

Image Credit: Wikipedia Commons

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