A few days ago I saw that Dienekes commented on a recent paper published in The American Journal of Human Genetics where the authors used 10 markers, specifically single nucleotide polymorphisms (SNPs), to discern continental level population differentiation. Dienekes has generated a map which shows the extent of clustering. The authors selected specific SNPs that they assumed would be extremely informative, and so obviated the need to extend their sample of assayed loci into hundreds. They express their results with some caution, and highlight that the inferences need to be judged in light of the assumptions and biological realities. Additionally, the loci in question are informative on the continental level precisely because they seem to be regions subject to powerful positive selection.
This is somewhat of a banal observation in the post-genomic HapMap age, but, for those of you who want to read the full article and don't have institutional access, I found that google's HTML conversion of the PDF is available! Click while it works.
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Most of the things I've seen of this type have been meataxe lumping of major population groups, as here. I'd like to see something on isolated and unique groups, however small, such as the !San, original Australians, Andaman Islanders, etc. (A look at linguistic-isolate groups such as Yukagirs, Basques, Burushaski, etc. might also be interesting).
The PDF can be accessed here: http://vetinari.sitesled.com/snp.pdf (copy+paste)
John--
Agreed, to some extent. But you know, you don't go to press with the data you want, you go to press with the data you have. The Human Genome Diversity Project got its ass kicked in a propaganda war, so people have pretty much just had to make do.
Also note that the necessary data on isolated groups are being gathered in the context of gene mapping. For example, the Kosrea and the Hutterites. An ambitious person could put it all together, if they wanted.
Here's the question, though: Why genotype a ton of autosomal markers to find those that distinguish isolated populations from the rest of the world? I can think of couple reasons not to bother:
1. In terms of looking for natural selection, forget it: the genetics of these populations is more determined by drift and inbreeding than selection.
2. In terms of ancestry, if I'm not mistaken (I might be; I'm wandering away from what I know best), Y chromosome and mitochondrial DNA studies have already shown that isolated populations are, well, isolated, but still somewhat related to mainland populations. what more do you want to know?
It's frickin' expensive to gather a lot of marker data from a lot of people, so if there's no real pressing question to be asked, it's tough to find a way to do it.
PS. from the wikipedia entry on the human genome diversity project, I went to the entry for the Genographic Project, which I'd never heard about. Sounds pretty cool, and gets around the cost issue a bit by charging people to give them their Y chromosome and mitochandrial lineages.
I'd like to see something on isolated and unique groups, however small, such as the !San, original Australians, Andaman Islanders, etc. (A look at linguistic-isolate groups such as Yukagirs, Basques, Burushaski, etc. might also be interesting).
time & $$$. when the techniques get cheap it will come, and hey, it might even get cheap enough that you can transfer them to animals and starting doing some real assaying of genetic variation in the interests of conservation. btw, i suspect small human groups will be assayed first, though patchily, because they'd have 'interesting' variation.
small human groups *are* being assayed first, as they are ideal for linkage diseqilibrium mapping. The links are in my post from a while ago, which is apparently being extensively scanned for spam...