ON CEDROS ISLAND IN MEXICO—Matthew Des Lauriers got the first inkling that he had stumbled on something special when he pulled over on a dirt road here, seeking a place for his team to use the bathroom. While waiting for everyone to return to the car, Des Lauriers, then a graduate student at the University of California, Riverside, meandered across the landscape, scanning for stone tools and shell fragments left by the people who had lived on the island in the past 1500 years.
As he explored, his feet crunched over shells of large Pismo clams—bivalves that he hadn’t seen before on the mountainous island, 100 kilometers off the Pacific coast of Baja California. The stone tools littering the ground didn’t fit, either. Unlike the finely made arrow points and razor-sharp obsidian that Des Lauriers had previously found on the island, these jagged flakes had been crudely knocked off of chunky beach cobbles.
“I had no idea what it meant,” says Des Lauriers, now a professor at California State University (Cal State) in Northridge. Curiosity piqued, he returned for a test excavation and sent some shell and charcoal for radiocarbon dating. When Des Lauriers’s adviser called with the results, he said, “You should probably sit down.” The material dated from nearly 11,000 to more than 12,000 years ago—only a couple thousand years after the first people reached the Americas.
That discovery, in 2004, proved to be no anomaly; since then, Des Lauriers has discovered 14 other early sites and excavated two, pushing back the settlement of Cedros Island to nearly 13,000 years ago. The density of early coastal sites here “is unprecedented in North America,” says archaeologist Loren Davis of Oregon State University in Corvallis, who joined the project in 2009.
The Cedros Island sites add to a small but growing list that supports a once-heretical view of the peopling of the Americas. Whereas archaeologists once thought that the earliest arrivals wandered into the continent through a gap in the ice age glaciers covering Canada, most researchers today think the first inhabitants came by sea. In this view, maritime explorers voyaged by boat out of Beringia—the ancient land now partially submerged under the waters of the Bering Strait—about 16,000 years ago and quickly moved down the Pacific coast, reaching Chile by at least 14,500 years ago.
Findings such as those on Cedros Island bolster that picture by showing that people were living along the coast practically as early as anyone was in the Americas. But these sites don’t yet prove the coastal hypothesis. Some archaeologists argue that the first Americans might have entered via the continental interior and turned to a maritime way of life only after they arrived. “If they came down an interior ice-free corridor, they could have turned right, saw the beaches of California, and said, ‘To hell with this,’” says archaeologist David Meltzer of Southern Methodist University in Dallas, Texas.