We live in an age when we have a lot of SNP data on a lot of populations. This allows for a very fine level of granularity in terms of analysis. To illustrate, Genetics recently published Nationwide Genomic Study in Denmark Reveals Remarkable Population Homogeneity, which analyzes hundreds of Danes with hundreds of thousands of SNPs. In The History and Geography of Human Genes, published twenty years ago, most of the analysis was grounded in pairwise comparisons between populations using hundreds of markers. Not only do we have much greater resources in terms of data, but we have various analytic frameworks which in concert allow for richer, more precise, inferences. Today we can actually assign ancestry regions of an individual’s genome!
The first author of the Genetics paper, Yorgos Athanasiadis, has put up a post where does a walk-through of the various methods step-by-step. It’s useful for anyone who has an inclination to do something similar for another data set.
This portion jumped out at me:
The six Danish regions showed highest affinity with a cluster that we call BRI(tish), because it’s mostly made up by British samples, followed by the NOR(wegian) and SWE(dish) clusters. This is not to say that Danes are about 40% made up by British DNA, as some enthusiastic twitters have mentioned. The BRI cluster also includes German, Belgian and Dutch samples, meaning that it might as well be reflecting some other ethnic component; in lack of a better name, we called it BRI. Another interesting fact is that because of the presence of this cluster, haplotype sharing with other Scandinavians was about 40%….
I think the implications of this are something I’m going to have to chew on for a while. Some of these genetics results aren’t straightforward in terms of what they mean in a vacuum, though the historical inference is obvious.
Anyway, read the whole thing, On the genetic structure of Denmark.
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