sometimes interbreeding with local populations,
who came from where? Makes the whole of this ‘study’ a p[lea from more grant money. Everyone knows that American Indians were created here - a claim which forms the basis for their legal claims for superior rights and special master status in various venues.
Except that they really don't have it because they are a miniscule voting block and don't really vote as a block, particularly in the two states where they are most numerous (Oklahoma and North Carolina) and spread out amoung the population.
Do you hear much about the Osage (Oklahoma) or Lumbee (North Carolina)? Probably not, because they are wealthier than the local population from oil and banking/real estate, respectively.