About five years ago researchers discovered that there was some affinity between people in the Amazon and populations in Australasia. This was very strange but robust. After that, an ancient sample from Brazil also showed this affinity.
Now PNAS has a paper with a bigger data set that finds this ancestry more widely in South America:
Different models have been proposed to elucidate the origins of the founding populations of America, along with the number of migratory waves and routes used by these first explorers. Settlements, both along the Pacific coast and on land, have been evidenced in genetic and archeological studies. However, the number of migratory waves and the origin of immigrants are still controversial topics. Here, we show the Australasian genetic signal is present in the Pacific coast region, indicating a more widespread signal distribution within South America and implicating an ancient contact between Pacific and Amazonian dwellers. We demonstrate that the Australasian population contribution was introduced in South America through the Pacific coastal route before the formation of the Amazonian branch, likely in the ancient coastal Pacific/Amazonian population. In addition, we detected a significant amount of interpopulation and intrapopulation variation in this genetic signal in South America. This study elucidates the genetic relationships of different ancestral components in the initial settlement of South America and proposes that the migratory route used by migrants who carried Australasian ancestry led to the absence of this signal in the populations of Central and North America.
The intrapopulation variation makes me suspicious. If it has been tens of thousands of years I would have expected intra-population variation to disappear.
The statistic looks correct. But we still don’t know what that means. The hypothesis presented about a coastal migration seems reasonable enough. But who knows?
What could be other plausible alternatives ? That they were not an ancient migration, but a separate but a later migration via sea or land?
Compare and contrast this to the migration of Indic people to Australia about 4000 years ago that has left detectable genetic and possible linguistic legacy amongst native Australians but we were able to date that event more precisely.
Why not this event(s) ?
Don’t see a link or a reference
click image nick
Could the intrapopulation variance be due to more recent admixture events? There’s certainly been a lot of demographic upheaval in South America over the last few hundred years.
“The screaming loud problem with the hypothesis that this is associated with the Founding population of the Americas is that there is material and large interpopulation and intrapopulation variability in the signal, in populations spread across South America.
Inter-population variability could be plausible for populations in isolated Amazonian tribes, or groups with strong endogamy norms. But immense intra-population variability simply should not survive for 14,000 years (about 500 generations). The law of averages catches up with that kind of variability surprisingly quickly in the case of traits that are ancestry informative but not distinguishable as a visible phenotype without extreme population structure, which a trait spread across myriad different pre-Columbian cultures simply couldn’t maintain.
Instead, the wide variability and wide geographic range points to a source of this genetic component in much more recent mariners, certainly no older than the arrival of the Paleo-Eskimo ancestors of the Na-Dene in Alaska (ca. 4500 years ago), but more likely (since this ancestry is not seen anywhere outside South America) via Polynesian mariners in the last 1500 years or less (about 30 generations or less), where solid evidence already shows sign of some slight recent admixture of South Americans into Polynesian gene pools nearest to South America, and where evidence from remains of flora and fauna native to the Americas in Polynesia and native to Polynesia on the Pacific Coast has established that some limited pre-Columbian maritime trade via the Pacific Ocean had to have taken place in about that time frame. The likely epicenter from which the admixture radiates also coincides with one of the most likely loci of South American source admixture into Polynesians ca. 1200 CE.”
http://dispatchesfromturtleisland.blogspot.com/2021/03/paleo-asian-ancestry-in-amazon-is.html