[Coyoteman]

I’d be curious to know how they went about selecting “native” populations. Did they go deep into the mountains and amazon jungles looking for relatively untouched tribes? The native Americans in the US and Mexico are so interbred with Europeans I would imagine that it would be difficult to obtain pure “native” DNA in these regions.

Mitochondrial DNA is passed unchanged (except for occasional mutations) from mother to children. Mixing with Europeans would either retain the original Native American mtDNA (European male, Native American mother), or retain the European mtDNA (Native American male, European mother). There would be no intermediate mtDNA formed.

And those occasional mutations? That is what this study focused on to track the population movements.

[ElkGroveDan]

I understand how mitochondrial DNA works. If you are testing for external influences in a person's genetic profile, mixing in a population who had external genetic contributions 300 years ago confuses the question of whether such influences were or were not also introduced 3000 years ago.

I used Europeans as an example but what about Polynesians who may have emigrated to America in the 1700s aboard commercial ships? What if they had children with native Americans or native Mexicans in the colonial period? Testing their descendants for the influence of external DNA would be most problematic.

I believe this is a valid study, but I also believe that some sort of precautions would need to have been taken to obtain genetically pure native DNA.

[muawiyah]

Or, rather than the movements of whole populations, the trail of girls traded from tribe to tribe over thousands of years.

Humans trade the girls. So do our cousins the chimps.