Wednesday, May 10, 2017

Pre-Columbian European Admixture In Northern Chile?

It is widely held that, except for migrations from Beringia or Siberia, there was no contact between the Old World and the New World prior to the colonization of North America by the Norse in the late 10th century AD. 
Analyses of 23 ancient American DNA samples reveal, however, the presence of European admixture in a sample taken from a Chinchorro mummy of northern Chile dated to 3972-3806 BC. This discovery implies a more complex history of the peopling of the Americas than previously accepted.
R. Smith, "European Admixture in Chinchorro DNA" (May 1, 2017).

Critical commentary here suggests that the article is unlikely to survive peer review or to be published. The author is known on the Internet as Genetiker

Interesting if true, but I'm skeptical of the result, apparently found in just one sample out of 23. This is a very long way from Europe, at around the time that farming had just reached its maximum extent to the Atlantic Coast. The fact that only one in 23 could be recovered suggests that the quality of the one recovered was itself not very good. Contamination of samples seems like a more likely possibility given that it is very hard to come up with any narrative that can explain this data point.

The admixture estimate is more than 30% and less than 40%, which would suggest 3 of 8 great-grandparents were not Amerindian, pushing back a date of migration from Eurasia to North America of those great-grandparents by roughly a century.

This is too recent to plausible pre-date the LGM without leaving a much bigger demographic mark than one ancient DNA sample that leaves no survivors in modern populations. It is too old to be plausible as the result of an intentional global sea voyage. It predates West Eurasian expansion into the Tarim Basin and probable contact with East Asian civilizations by a couple of thousand years. The pottery associated migration across Siberia went the other direction (from East to West).

The Paleo-Eskimo migration which was a genetic source for the Saqqaq, the subsequent Dorset, and the genetically distinctive component of the Na-Dene was around 2400 BCE, which is 1600-1700 years too recent. A variety of other claimed pre-Columbian contacts are even more recent (even an outlier of a claimed New World seed described in India ca. 2000 BCE).

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