unless i'm missing something, the "mystery population" can easily be identified with refugees of the ice sheets, who lived in small pockets of melting in the northern hemisphere, hunted mammoths and generally make up the bulk of the cave man stereotype. the population would be ancestral to the kurgan groups that spread the indo-european population around the steppes. existing literature refers to these people as "nordic" and considers the basques, picts and others amongst their possible descendents.

http://www.nature.com/news/ancient-european-genomes-reveal-jumbled-ancestry-1.14456

i mean, i get that they're denying a strict separation, but nobody ever really claimed that separation existed in the first place. and the idea is well-established.

lol. i think maybe nature is avoiding the topic in the fear that ignorant people might label them racists.

the northern nordics were ancestral to the indo-europeans, but were not them. the southern hunter gatherers would have been displaced by the nordics that came in after the ice sheets melted. they themselves would have mostly been displaced by middle eastern farmers. the indo-europeans came after that. aryanism is something different altogether and certainly didn't make it's way into anthropology books written in the 90s. but people have a hard time keeping up...

anyways, unless i'm missing something, the mystery population is easy to identify.

as for eye colour, i've long argued that it's spread is probably not due to natural selection. you'll hear people say things about the angle the sun hits europe. that's weak, to say the least. and is an ability to adjust to sunlight going to overpower other traits? it's such a triviality, that i couldn't see it overpowering anything at all. how can people argue with a straight face that it increases survival?

i've seen a few arguments that suggest that the genes that determine eye colour are also genes that provide heightened immunity, and the eye colour followed as a coincidence of the immunity. i think it was for malaria, actually. that makes more sense to me, and correlates with the above ideas better. but i think this is controversial.

if you look at the spread of the mutation from somewhere in north-central europe, it just strikes me as entirely random. it looks like an ink blot that spread around by chance for no real reason whatsoever.

it's just genetic drift, in other words. but it's a type of variation that doesn't seem to have any kind of actual advantage. meaning, it's just the result of a genetic process that fucked up (genetic processes fucking up being the source of mutations and therefore evolution). there's not a reason it fucked up. there's no benefit to it fucking up. it just fucked up.

skin colour and skull size seem to be more complicated than that, but they're highly plastic. again, the correlation between sunlight and skin colour isn't nearly as strong as some may suggest. and, you really want to tell an african that they're less likely to survive in sweden? i'm not sure i could honestly apply that to an australopithecine. it seems entirely trivial.

so, genetic drift? i think it's a little more complicated if you go backwards a few millennia. in today's world, it's probably all there is to it. the sahara and the himalayas aren't the boundaries they once were. we could talk about systemic racism, but that's not readily biological (maybe the psychology has a biological explanation, but it's not at the level of selection) and it's only of questionable relevance at a reproductive level (consider jefferson for an obvious example). so, the only thing acting on skin colour today is drift, and that will be the foreseeable future unless something catastrophic happens.