Stone tools found on California's Channel Islands show that early Americans were used to life on the waves. Credit: J. Erlandson

Early Americans were no landlubbers. Settlements recently discovered on the Channel Islands off southern California are littered with the bones and shells of fish, seabirds, and shellfish, as well as worked stone points and blades.

The three island camps, which are between about 11,000 and 12,000 years old, show that some early Americans were well adapted to coastal living, says team member Torben Rick of the National Museum of Natural History in Washington DC. These discoveries, published today in Science1, support the notion that early humans trekked across the Bering land bridge to Alaska and settled the Americas by skirting the Pacific coast all the way down to the tip of South America.

That hypothesis has emerged as an alternative to an inland migration route along a corridor east of the Canadian Rockies, which may not have been clear of glaciers early enough to account for human settlements further south2.

Rising tide

Finds along the Pacific Coast, including a 14,000-year-old settlement in southern Chile3, support a coastal migration. However, the rise in sea level would have erased much of the other evidence of occupation along this route, notes Daniel Sandweiss, an archaeologist at the University of Maine in Orono, who was not involved in the new study. "Anybody who was living right along the shore, their sites are now under water."

Rick, along with Jon Erlandson, an archaeologist at the University of Oregon in Eugene and their team instead scoured the Channel Islands for protected encampments that might have drawn ancient mariners inland. Several years ago, the team stumbled on two such spots on San Miguel Island, and a couple years later they found another settlement on Santa Rosa Island, a few kilometres to the east.

The camps are brimming with animal remains, many with signs of burning, including Canada goose, cormorants, albatross, seals, rockfish, herrings, sardines, mussels, snails, crabs and abalone. Erlandson and Rick's team also found dozens of delicately crafted stone tools and projectile points, which were probably used to hunt and butcher prey.

Because the Channel Islands would have lain some 10 kilometres off the California coast at the time, the hunters must have reached them by boat, Rick says. Once they found the islands, which are visible from present-day Santa Barbara, the mariners would have found ample food and few predators. "They would have found an amazing suite of resources — massive amounts of seabirds, seals and sea lions" not found on the mainland, he says. "In my view it would have seemed like a paradise."

The archaeologists surmise that the people who lived at the Channel Island sites were adept at making a living from the sea, and were not from the interior of North America. The tools found on the Channel Islands are a better match to tools attributed to the Western Pluvial Lakes Tradition in the Pacific Northwest than to the inland Clovis culture, which, also, had disappeared by around 12,000 years ago. "What it tells us is that these weren't people who came from the continental interior and stumbled onto the coast," says Rick.

But where they came from is still an open question, Sandweiss says. "The possibility of a maritime migration is strengthened by the discovery of these sites."

Ted Goebel, an archaeologist at Texas A&M University in College Station, says the stemmed stone points found on the Channel Islands resemble those found in Kamchatka, Russia, dating from 1,000 years earlier, and in Brazil from around the same period. "Could they be evidence of a Pacific coastal migration? Maybe, but the dots between Kamchatka, California and Brazil will have to be connected with more dots in between."