What can be said, with reasonable confidence based on the evidence available as of the early 2020s, is the following:

The ancient people of Lagoa Santa were Native Americans.

Their genomes show the shared ancestry of all Native American peoples, deriving from the founding population that crossed into the Americas from Beringia.

This is not in question, and no responsible reading of the scientific evidence would suggest otherwise.

Some ancient Lagoa Santa individuals, and some living Indigenous South American populations, show a statistically significant excess allele sharing with Australasian populations — specifically with populations from Australia, New Guinea, and the Andaman Islands.

This signal, which has been named Population Y, is real and has been found in multiple studies using different methods and different datasets.