Iain Mathieson and the Reich-Patterson crew have a new paper out on natural selection over the past 8,000 years in Europe, much fortified by the availability of ancient DNA and knowledge of the ancestral mix.
The first point is that lactose tolerance is a fairly late development in Europe, not common (unseen in these samples) until almost the bronze age (first seen in a Bell Beaker skeleton). In particular they don’t see it (not common) in the Yamnaya, which must mean that it wasn’t a driver of the Indo-European expansion: we were wrong. I suspect it did exist in the early Indo-Europeans, since we see the same haplotype in India, but one guy wandering around can change the distribution of an adaptive allele. I also don’t understand how they got such a low estimate of its selective advantage (1.5%), but maybe I can winkle that out.
It looks as if there was selection for greater height among the Yamnaya – a possible parallel with Nilotics?
The strong light-skin allele, SLC24A5, does look to be mainly introduced by the early neolithic farmers, but there’s weirdness. It’s not found in the western hunter-gatherers, but it is there in Scandinavian hunter-gatherers, where you also see the well-known EDAR 370A mutation. It’s even possible that it originated there – but it’s rare in Europeans today, although you see it in Finns a little.