Y chromosome

Dienekes comments on a new paper that attempts to estimate the age of a Y chromosomal clade:

I am constantly amazed by how the tremendous amount of effort required to identify, sample, catalogue, process, and genotype great numbers of people from around the world is accompanied by an apparently complete lack of interest in checking the basic premises on which interpretation of this data is based.

There are too few people who understand the assumptions underlying the computer programs they're using -- which, after all, are intended to be useful in a broad range of species, not just humans. Yet few species have demographic histories anything like humans.

The BBC has a story about Y chromosome matches between German Bronze Age skeletons and a couple of guys living in the same area now:

"I didn't expect it at all, to end up being the direct descendant of the cavemen. It's amazing, especially as on that particular day I had such a dry mouth, I thought the DNA sample wouldn't work," he said.

Looks like the Y chromosome equivalent of the Cheddar Man mtDNA match from 10 years ago. The import of both stories is roughly the same -- considerable local genetic survival from prehistoric times.

Sharon Begley covers a recent paper by Joanna Mountain on Y chromosome migrations and African pastoralists:

The novel mutation arose in eastern Africa about 10,000 years ago and was carried by migration to southern Africa about 2,000 years ago not by Bantu-speakers, in whom the mutation is absent, but in speakers of what’s called the Nilotic language. These unsuspected ancestors first brought herds of animals to southern Africa before the Bantu migration.

To me, this is one of the most useful applications of genetics to prehistory: finding migrations that have been largely obscured by later movements. But it's tricky, and faces a major problem in the fact that recent selection has also generated demographic forces. Of course, if the migrations were somehow connected to the selection, that would be less of a problem...

Dienekes details his argument for why date estimates based on Y-chromosome STRs are overestimated. I'd like to see him publish it!