Very little in science is truly settled, but publishers of grade-school textbooks featuring the consensus view of the settlement of the Americas—that pioneers from Siberia trekked across the Bering Strait on a land bridge some 12,000 years ago—can breathe easy, at least for now. Confirming the archaeological and anthropological evidence, geneticists have ruled out the alternative, that multiple migrations from several regions in Asia or Polynesia were the first Americans. Instead, the genetic analysis points to the continents’ settlement by a small band of intrepid explorers who originally made their home in a single region.

Writing in the open-access journal PLoS Genetics, a team of researchers (who seem to be as numerous as those early migrants) describe their analysis of variations at 678 key locations on the DNA of present-day members of 29 Native American populations. The scientists compared that variation to the genetic profiles of two populations from Siberia. Both genetic diversity within the Native American groups and genetic similarity to the Siberian populations decrease the farther a native population is from the Bering Strait—strong evidence that that was the path the migrants took from Asia to America.

It was not a trip that many were persuaded to make, it seems. One unique genetic variant, previously found in no other populations outside Siberia, is prevalent in Native Americans across both North and South America. That suggests what geneticists call a founder population, a single migration or, at most, a few waves from a single source, not multiple crossings from many different spots in Siberia. It wasn’t as if the new arrivals sent back word that everyone in the old country should follow them.

“If there were a large number of migrations, and most of the source groups didn’t have the variant, then we would not see the widespread presence of the mutation in the Americas,” says co-author Noah Rosenberg, assistant professor of human genetics at the University of Michigan Medical School.