A ball of hair tangled around a whalebone comb was preserved in the arctic permafrost for nearly 4,000 years. Found in the 1980s and stored in a Denmark museum, it was only in 2010 that evolutionary biologist Eske Willerslev, PhD, professor and director of University of Copenhagen’s GeoGenetics Centre, used shotgun DNA sequencing to reconstruct the genetic history of the first entire ancient human genome from the hair. He found it came from a Saqqaq man—the earliest known people to settle in Greenland.

Willerslev says, “Over the past decade human history has been fundamentally changed thanks to ancient genomic analysis—and the incredible findings have only just begun.”

Willerslev and his longstanding collaborator David Meltzer, PhD, an archaeologist and professor of prehistory in Southern Methodist University’s Dedman College in Texas recount discoveries  sparked by the world’s first analysis of the ancient human genome in their Nature article, “Peopling of the Americas as inferred from ancient genomics.

“The last ten years has been full of surprises in the understanding of the peopling of the Americas. What has really blown my mind is how resilient and capable the early humans we have sequenced DNA from were—they occupied extremely different environments and often populated them in a short space of time,” Willerslev says. “We were taught in school that people would stay put until the population grew to a level where the resources were exhausted. But we found people were spreading around the world just to explore, to discover, to have adventures.”

Analysis of the ancient human genome has led to insights on human adaptability and behavior that would not have been possible through archeological findings alone.

It was previously thought, that there were early non-Native American people in the Americas but the ancient DNA analysis so far has shown that all of the ancient remains found are more closely related to contemporary Native Americans than to any other population anywhere else in the world.

“Genomic evidence has shown connections that we didn’t know existed between different cultures and populations and the absence of connections that we thought did exist. Human population history been far more complex than previously thought,” says Meltzer. “A lot of what has been discovered about the peopling of the Americas could not have been predicted. We have seen how rapidly people were moving around the world when they have a continent to themselves, there was nothing to hold them back. There was a selective advantage to seeing what was over the next hill.”

In 2013, scientists mapped the genome of a four-year-old boy who died in south-central Siberia 24,000 years ago. Sequencing of the Siberian child’s genome showed the existence of a previously unsampled population that contributed to the ancestry of Siberian and Native American populations.

In 2015, Willerslev and his team published the first ancient Native American genome, sequenced from the remains of a baby boy ceremonially buried more than 12,000 years ago in Anzick, Montana. Their ancient genomic analysis was able to solve the mystery of the 9,000-year-old remains of the Kennewick Man, one of the oldest, most complete and controversial skeletons found in the Americas. The controversy stormed around lawsuits between the United States Army Corps of Engineers and five Native American tribes who claimed ownership of the man they called Ancient One.

Willerslev, mindful of cultural sensitivities when searching for ancient DNA, explained the details of his work to tribal community members, seeking their support. Members of the Colville Tribe, based in Washington State where the remains were found, donated DNA samples to allow Willerslev and his team to investigate if there was a genetic link between them and Kennewick Man.

Jackie Cook, a descendant of the Colville Tribe and the repatriation specialist for the Confederated Tribes of the Colville Reservation says, “We had spent nearly 20 years trying to have the Ancient One repatriated to us. There has been a long history of distrust between scientists and our Native American tribes but when Eske presented to us about his DNA work on the Anzick child, the hair on my arms stood up. We knew we shouldn’t have to agree to DNA testing, and there were concerns that we would have to do it every time to prove cultural affiliation, but our Council members discussed it with the elders and it was agreed that any tribal member who wanted to provide DNA for the study could.”

The Ancient One was returned to the tribes and reburied when Willerslev’s team established that the Kennewick Man’s genome, like the Anzick baby, was a direct ancestor of living Native Americans.

Willerslev team also identified the origins of the world’s oldest natural mummy called Spirit Cave, unlocking the secrets of the Ice Age tribe in the Americas. Genetic analysis of 15 ancient genomes from a series of famous and controversial remains across North and South America allowed the scientists to track the movements of the first humans as they spread across the Americas at an “astonishing” speed during the Ice Age and how they interacted with each other.

The team discovered that the Spirit Cave remains came from a Native American while dismissing a longstanding theory that a group called Paleoamericans existed in North America before Native Americans. As a result of these studies, Spirit Cave was returned to The Fallon Paiute-Shoshone Tribe based in Nevada for burial.