Advances in the analysis of ancient DNA have upended the scientific community’s view of how human populations migrated both into and around the North and South American continents, illustrating the rapid and complex movement of humanity into the western hemisphere towards the end of the last ice age. Aside from unraveling more of the mystery of the origins of the Americas’ first inhabitants, the studies also aided in the repatriation of a long-lost ancestor of a Native American tribe in Nevada, and the discovery of an individual with DNA from Australia that lived on the east coast of modern-day Brazil — over 10,000 years ago.

The findings were unveiled in two separate studies, and used newly-sequenced DNA that was gathered from 64 individuals that represented more than ten millennia of genetic history. The samples were recovered from sites stretching from Alaska in the north to Argentina’s Patagonia region in the south; previously, the genetic maps of only six individuals older than 6,000 years were available, with the new sequences providing a treasure trove of knowledge for researchers.

The studies uncovered a complex path traveled by the various peoples that flooded into the Americas at the end of the Pleistocene. For instance, a group belonging to North America’s Clovis culture, a prehistoric tool-making culture that disappeared roughly 13,000 years ago, appears to have been behind the rapid population spread across the two continents, with genetic markers found in ancient remains from both Nevada and Brazil tracing their lineage back to the only known human Clovis remains, an individual called the Anzick child, discovered by accident in Montana in 1968.

But the opening of this window to the past yielded not only new insights on the early years of the Americas’ founding populations, but it also helped solidify the link between present-day people with their distant ancestors: For the past twenty-one years, the Fallon Paiute-Shoshone Tribe in Nevada has been trying to repatriate the remains of an individual they believe is one of their ancestors, the Spirit Cave mummy. Excavated from the Spirit Cave in 1940, this mummy was initially assumed to only be a few thousand years old, until more modern carbon-dating techniques revealed that the individual was actually 10,700 years old, making it the oldest human mummy found in North America. In 1997, the Paiute-Shoshone made a Native American Graves Protection and Repatriation Act (NAGPRA) claim of cultural affiliation with the mummy, to have the body returned to them for reburial. However, the Bureau of Land Management disputed the tribe’s claim, on the grounds that there wasn’t enough evidence to establish the remains’ affiliation with the tribe necessary to honor the claim.

In 2015, evolutionary geneticist Eske Willerslev, from the University of Copenhagen, approached the Paiute-Shoshone for permission to carry out genetic testing on the mummy, permission that was granted by the tribe: aside from the valuable data that would be uncovered by the tests, the outcome would settle the issue of the tribe’s claim once and for all. The results of the tests established that the remains belonged to an individual that was indeed related to the Paiute-Shoshone, despite the advanced antiquity of the mummy. The remains were given back to the Paiute-Shoshone in 2016, and a private re-burial ceremony was held earlier this year to return their long-lost ancestor to the earth.

This link also overturns a long-standing theory called the Paleoamerican Hypothesis, that posits that the Americas were originally populated by a Paleoamerican group of peoples, unrelated to today’s Native Americans. "Our study proves that Spirit Cave and Lagoa Santa were actually genetically closer to contemporary Native Americans than to any other ancient or contemporary group sequenced to date," Willerslev explains of the Paiute-Shoshone’s ancestor, and another found in Lagoa Santa, Brazil. "Looking at the bumps and shapes of a head does not help you understand the true genetic ancestry of a population—we have proved that you can have people who look very different but are closely related."

But while one mystery was solved, the studies presented another, perplexing conundrum: The remains of an individual that lived 10,400 years ago, in modern-day Lagoa Santa on Brazil’s east coast, was found to have Australasian DNA, originating from the area of Australia and New Zealand. Although one might assume that the individual’s ancestors had slowly spread northward through Asia, across the Bering Land Bridge, and then south through the Americas, the team found no trace of these genetic markers in any of the other samples they had available, making it appear as if the people that those genes belonged to have "somehow [leaped] over all of North America in a single bound," according to study co-author and archaeologist David Meltzer, of Southern Methodist University. Meltzer assumes that this DNA may have belonged to a group that somehow remained genetically isolated from other Native American groups on their long migration south — no small feat, considering the extent to how the America’s Indigenous populations traveled and commingled over the past ten millennia.