Are Northern Europeans related to Amerindians?

Greg Cochran looks at this issue:

The latest wrinkle is an Amerindian-like component in northern Europeans, accounting for roughly 10% of their ancestry. The French (and the Germans, and the Dutch and Irish) are closer to pure-blooded South American Indians than Italians are. Sardinians are the least close among Europeans – they may have none of this component. Presumably pure-blooded Amerindians in North America would show the same affiliations, but we – the land of the free and the home of the brave – are too crazy to let Reich and Patterson have any samples. This Amerindian-like population must have split off from the group that settled the Americas a long time ago – 20,000 years? More? Amerindians have the East Asian skin color genes, along with some of their own – as far as I know, you don’t see these at all in Europeans. As far as I know, there is zero overlap between Amerindian mtDNA haplotypes and those found in ye olde hunter-gatherers in Europe. There _is_ a weak mtDNA link between Amerindians and modern Europeans (haplogroup X). There are signs that populations related to or influenced by Amerindians once covered much more of northern Eurasia than they do now: for example, most linguists now agree that Ket (and groups with related languages that lived along the Yenisei River in central Siberia) is related to the Na-Dene languages, such as Navaho. Along the same lines, Greenberg thought that there were deep, old relationships between Indo-European and several languages groups in north Eurasia – and with Amerind. You see lots of European-type Y chromosomes among tribal Indians in the eastern United States. The usual assumption is that it’s all recent European admixture, and likely that’s so, but it wouldn’t hurt to look real close. Were the olde European hunters part-Injun? We know that the first farmers in Belgium build log stockades. Sometimes they lost: we’ve found one where the settlers are all dead, full of arrows. Has the wheel made a full turn? If we get a decent quality autosomal DNA sample from some Mesolithic hunters, we’ll know. That should happen soon. Or maybe the Indo-Europeans were a mixed people. Their mythology hints at this: they appeared to have had three castes – warriors, priests, and farmers, and there are signs that the first two castes somehow conquered and incorporated the third. This theme recurs repeatedly in myth and legend – for example, the war between the Aesir and the Vanir.