How Did People Reach the Americas?

Ancient DNA sheds light on the prehistoric humans who colonized a hemisphere.

From ancient DNA, Eske Willerslev teases out answers to prehistoric puzzles.

From ancient DNA, Eske Willerslev teases out answers to prehistoric puzzles.


The success of ancient DNA analysis is likely to open up valuable new sources of archaeological information in the United States. Coprolites—stored in the thousands in museums all over the country—may yield answers from the distant past without infringing on American Indian beliefs about the sanctity of burial remains.

The technique has promise—and a quickly growing track record—in other arenas, as well. In 2002, Penn State researcher Beth Shapiro, then at the University of Oxford, successfully sequenced the DNA of the dodo bird, extinct for more than three centuries—and discovered it was a close relative of the pigeon. In 2006, Hendrik Poinar, a geneticist at McMaster University in Canada, sequenced most of a woolly mammoth's genome from fragments of bone, proving—at least in theory—that cloning one might be possible. And a lab in Germany has been researching the genetics of Neanderthals to see how closely they were related to modern humans—and if the two species interbred.

Willerslev, meanwhile, is probing other genetic remains for further discoveries. Last summer, he announced the recovery of the oldest intact DNA ever found. It came from a soup of plants and animals, now buried under a mile of Greenland glacier, that made up a forest at least 450,000 years ago. The discovery showed that Greenland was once covered in lush forest—and helps refine climate models of global warming. He has also just announced another find from the frozen north: a human hair sample from Greenland that yielded a complete human genome more than 3,400 years old. The DNA matches modern Siberians but not the Inuit who live in Greenland today, suggesting that the wrinkled prehistory of the Americas has yet to be fully ironed out. Now, Willerslev is planning a trip back to Greenland to hunt for more ancient DNA. With traditional archaeology in one hand and cutting-edge genetic techniques in the other, he may soon have more to tell us about the Americas' earliest immigrants.