Perhaps, as Davis and other archeologists suggest, those people came from northeast Asia by boat, moving south along the Pacific coastline and setting up camps along the way. “The Pacific coast is the most likely candidate—it seems like it would have had areas of exposed and habitable land between about 17,000 and 16,000 years ago,” says Geoffrey M. Smith, executive director of the Great Basin Paleoindian Research Unit at the University of Nevada Reno, who was not involved in the new research. “It may have been more short trips in some sort of watercraft between exposed and habitable patches along the coast.”
But this scenario presents some archeological challenges: First, there aren’t any boat artifacts from this period that’d suggest people had the technology to get from Asia to the Americas by sea. (That’s not to say the boats didn’t exist. Humans got from Asia to Australia 60,000 years ago, Davis says, which would presumably require long-range boating.) And as the world transitioned into the warmer climate we enjoy today, all that ice melted and drove up sea levels, shifting the Pacific coastline and submerging any potential artifacts.
Why exactly people would have made the journey is also an open question—and perhaps an unanswerable one. “It’s hard to know what motivated people to make that move from Northeastern Asia to Northwestern North America,” says Smith. “Those areas were connected by land, so it wasn’t like people said, ‘OK, we’re getting in this boat and we’ll never see you again.'” Instead, it could have been much more of an organic, slow process in which people crept down the Pacific coastline, maintaining contact with Asian communities.
Davis and his colleagues don’t know if the groups from Japan and the Americas were genetically related—they don’t have the genetic material to actually back up such a theory. But the similarity of the projectile points each group produced could suggest a sort of ancient social network, the sharing of technology. “It doesn’t matter, necessarily, if their genetics are the same,” says Davis. “You meet somebody from some other part of the world and you’re holding an iPhone, you have the same technology as that person—it doesn’t mean you’re genetically related.”
It would make sense that as humans flowed from Asia to the Americas, they would use similar projectile points. “By bringing in the northern Japan connection, we’ve got a pretty good hypothesis about linking up Old and New World assemblages in a comparable time period,” says David Hurst Thomas, senior curator in residence of North American archeology at the American Museum of Natural History, who wasn’t involved in the research. It’s an early theory that’ll need critiquing and further evidence, he adds, “but I think it’s groundbreaking.”
Davis also thinks this may not have been a singular connection between Asia and the Americas during that time period. Perhaps after these people brought the knowledge of the projectile points with them on their journey, other groups kept coming, keeping the ocean-spanning technological network alive—adding more intriguing wrinkles to the enormously complicated history of the peopling of the Americas. “It’s hard to know much about how such a network operated over time and space with only two far-apart data points,” says Davis of the artifacts discovered in Japan and Idaho. “But it’s a place to start.”