Los nativos americanos comparten afinidad genetica con los nordicos

DNA study reveals third group of ancient ancestors of modern Europeans | Science | theguardian.com

It has long been recognised that modern Europeans are descended from an initial migration of hunter-gatherer people who replaced H. neanderthalensis about 40,000 years ago. This lifestyle was then replaced by a farming-based culture which spread out from the Middle-East about 8,000 years ago, probably via Anatolia and the Balkans.

It had been assumed that this was a cultural change as neighbouring people recognised the superiority of agriculture and adopted the techniques and technology of their neighbours. Now techniques of DNA recovery from ancient remains are enabling scientists to build a much more complete picture, showing, for example, that this second wave was a real wave of genetically distinct peoples rather than a spread of cultures as had previously been assumed based on archaeological evidence alone.

And this analysis has revealed that a third population was involved. Beginning about 5,000 years ago, people from northern Eurasia migrated into Western Europe. Their DNA came from the same population as the 24,000 year-old boy found at Mal'ta near Lake Baikal in eastern Siberia - the same people who have been shown to be ancestral to most Native American people.

Abstract
We sequenced the genomes of a ~7,000-year-old farmer from Germany and eight ~8,000-year-old hunter-gatherers from Luxembourg and Sweden. We analysed these and other ancient genomes with 2,345 contemporary humans to show that most present-day Europeans derive from at least three highly differentiated populations: west European hunter-gatherers, who contributed ancestry to all Europeans but not to Near Easterners; ancient north Eurasians related to Upper Palaeolithic Siberians, who contributed to both Europeans and Near Easterners; and early European farmers, who were mainly of Near Eastern origin but also harboured west European hunter-gatherer related ancestry. We model these populations’ deep relationships and show that early European farmers had ~44% ancestry from a ‘basal Eurasian’ population that split before the diversification of other non-African lineages.

Ancient human genomes suggest three ancestral populations for present-day Europeans
Iosif Lazaridis, Nick Patterson, et al.; Nature 513, 409–413 (18 September 2014) doi:10.1038/nature13673

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It became very clear that all Europeans have hunter-gatherer as well as early farmer DNA to varying degrees, but it was also very clear that something was missing here in the makeup of modern Europeans.

Johannes Krause, Institute for Archaeological Sciences, University of Tübingen, Germany
Analysis of DNA from different populations also shows that the proportions of DNA from these two populations also varies considerably pointing to different reactions when these two peoples came into contact. In Sardinia, for example, people are 80% 'farmer', 29% 'hunter-gatherer' and only 1% 'Eurasian'. In England the mix is closer to 50:36:16 respectively whilst in Scotland it is 40:43:17 although differences of this order may not be significant.

Given that, as we can see from language analysis, the history of Western Europe, as elsewhere, was a constant reflux of different populations such as the 'Western Mediterraneans', the Celts and the Germanic tribes of the 'Völkerwanderung', the replacement from northern Europe of the Finns to leave a remnant population in Latvia and northern Fino-scandinavia, and the frequent explosive intrusion of nomadic Central Asian people such as the Turks, Mongols, Magyars and Hunns into Eastern Europe, these present day ratios are more a product of later mixing rather than reflecting the initial contacts between the three peoples.

To me, the interesting thing in this finding is how it illustrates how genes flow through a population and how, after diversifying in relative isolation, the genes from different populations can recombine when populations come back into contact. Who would have thought, for example, that when the first Europeans reached the Americas, they would be carrying the same genes that had evolved in northern Eurasia in people who were ancestral, in part, to both them and the people they found there and who had come there by going round the Earth in the opposite direction.

It is absurd to think of ourselves as racially distinct or having some notion of racial purity. As studies like this show, we can't even take a single population and say they all came from one ancestral stock in anything like recent history. The best we can say is that we diversified and differentiated from archaic hominids somewhere in East Africa and spread out from there, both in Africa itself and then into the rest of the world, even interbreeding with earlier archaic hominids as we did so.

And of course, the timescale involved absolutely rules out the infantile Bronze-Age notion of an ancestral single couple or even a single surviving family just a few thousand years ago. There would simply not have been enough time for this diversification ***owed by migrations and remixing to have occurred. Besides, some of the remains, such as the Mal'ta boy, predate even the Bronze-Age when the myths were invented, by tens of thousands of years, by which time his people had been around for long enough to have evolved a distinct DNA from that of the rest of the people of Europe - which is why we can recognise it today.

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