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Those discoveries led to all sorts of competing theories, but few archaeologists or anthropologists took them seriously until 1997. In that year, a blue-ribbon panel of researchers took a hard look at evidence presented by Tom Dillehay, then at the University of Kentucky, from a site he had been excavating in Monte Verde, Chile. After years of skepticism, the panel finally affirmed his claim that the site proved humans had lived there 12,500 years ago. "Monte Verde was the turning point," says David Meltzer, a professor of prehistory at Southern Methodist University in Dallas who was on the panel. "It broke the Clovis barrier."
Why? Because if people were living in southern Chile 12,500 years ago, they must have crossed over from Asia considerably earlier, and that means they couldn't have used the ice-free inland corridor; it didn't yet exist. "You could walk to Fairbanks," says Meltzer. "It was getting south from Fairbanks that was a problem." Instead, many scientists now believe, the earliest Americans traveled down the Pacific coast — possibly even using boats. The idea has been around for a long time, but few took it seriously before Monte Verde.
One who did was Jon Erlandson, an archaeologist at the University of Oregon, whose work in Daisy Cave on San Miguel Island in California's Channel Island chain uncovered stone cutting tools that date to about 10,500 years B.P., proving that people were traveling across the water at least that early. More recently, researchers at the Santa Barbara Museum of Natural History redated the skeletal remains of an individual dubbed Arlington Springs Woman, found on another of the Channel Islands, pushing her age back to about 11,000 years B.P. Farther south, on Cedros Island off the coast of Baja California, U.C. at Riverside researchers found shell middens — heaps of kitchen waste, essentially — and other materials that date back to the same period as Daisy Cave. Down in the Andes, researchers have found coastal sites with shell middens dating to about 10,500 years B.P.
And in a discovery that offers a sharp contrast to the political hoopla over Kennewick Man, scientists and local Tlingit and Haida tribes cooperated so that researchers could study skeletal remains found in On Your Knees Cave on Prince of Wales Island in southern Alaska. "There's no controversy," says Erlandson, who has investigated cave sites in the same region. "It hardly ever hits the papers." Of about the same vintage as Kennewick Man and found at around the same time, the Alaskan bones, along with other artifacts in the area, lend strong support to the coastal-migration theory. "Isotopic analysis of the human remains," says James Dixon, the University of Colorado at Boulder anthropologist who found them, "demonstrates that the individual — a young male in his early 20s — was raised primarily on a diet of seafood."
Cruising Down the Kelp Highway
Erlandson has found one more line of evidence that supports the migration theory. While working with a group of marine ecologists, he was startled to learn that there were nearly continuous kelp forests growing just offshore all the way from Japan in the western Pacific to Alaska and down the West Coast to Baja California, then (with a gap in the tropics) off the coast of South America. In a paper presented three weeks ago, he outlined the potential importance to the earliest Americans of what he calls the "kelp highway."
"Most of the early sites on the west coast are found adjacent to kelp forests, even in Peru and Chile," he says. "The thing about kelp forests is they're extremely productive." They not only provide abundant food, from fish, shellfish, seals and otters that thrive there, but they also reduce wave energy, making it easier to navigate offshore waters. By contrast, the inland route along the ice-free corridor would have presented travelers with enormous ecological variability, forcing them to adapt to new conditions and food sources as they traveled.
Unfortunately, the strongest evidence for the coastal theory lies offshore, where ancient settlements would have been submerged by rising seas over the past 10,000 years or so. "Artifacts have been found on the continental shelves," says Dixon, "so I'm quite confident there's material out there." But you need submersible craft to search, and, he says, that type of research is a very hard sell to the people who own and operate that kind of equipment. "The maritime community is interested in shipwrecks and treasures. A little bit of charcoal and some rocks on the ocean floor is not very exciting to them."
Multiple Migrations
Even if the earliest Americans traveled down the coast, that doesn't mean they couldn't have come through the interior as well. Could there have been multiple waves of migration along a variety of different routes? One way scientists have tried to get a handle on that question is through genetics. Their studies have focused on two different types of evidence extracted from the cells of modern Native Americans: mitochondrial DNA, which resides outside the nuclei of cells and is passed down only through the mother; and the Y chromosome, which is passed down only from father to son. Since DNA changes subtly over the generations, it serves as a sort of molecular clock, and by measuring differences between populations, you can gauge when they were part of the same group.