Delicate stone arrowheads and tools and a wide variety of marine and bird skeletons unearthed on the Channel Islands off the coast of California provide strong evidence that North America was settled by two separate groups of immigrants some 13,000 years ago, one that came overland from Asia and a second group of maritime explorers who sailed along the coast.
Archaeologists generally agree that one group of hunters migrated from northern Asia across the land bridge that connected Asia and North America through the region known as Beringia, slaughtering large mammals with spears and arrows fitted with characteristic stone tips known as Clovis points.
But a slowly growing body of evidence hints that a separate group of people, who originated perhaps in Japan, sailed along the coasts of both continents, traveling as far south as Tierra del Fuego and migrating as far inland as the glacial lakes of the Pacific Northwest.
The problem with proving it is that the ocean level was about 200 feet lower then. As sea levels have risen, they have inundated most of the coastal sites where the ancient seafarers may have lived.
To get around the problem, archaeologist Jon M. Erlandson of the University of Oregon and his colleagues studied caves on the Channel Islands that remained above the rising waters. They reported this week in the journal Science that they had discovered middens — garbage disposal areas — containing many bones and tools.
The arrowheads, made of a locally obtained rock called chert, were of two main types: barbed arrowheads with a stem to which a shaft could be attached, and broad crescents. The barbed arrowheads are so delicate, Erlandson said, that they could only have been used for killing fish and similar prey. The broader crescents would have minimized the accuracy required for shooting at birds; in that way, they were like the arrow equivalent of a shotgun, he said.
Similar points dating from 16,000 years ago have been found in Japan. Points contemporaneous with those found on the Channel Islands have also been found in the Great Basin and Columbia Plateau areas in the Pacific Northwest and in the Paisley Caves in eastern Oregon.
In contrast, the Clovis points used by the people who lived further inland are much heavier and cruder, and have a flute or indentation to hold the shaft. No fluted points have been found on the islands, Erlandson said.
The team also found the remains of shellfish, seals, geese, cormorants and a variety of fish.
Archaeologists who favor the theory of a single migration to the New World over a land bridge have argued that the people who made the Clovis points — so named because they were first found at a site near Clovis, N.M. — eventually migrated to the shore, where they changed their technology to make arrowheads and spears more suitable for fishing.
Erlandson, however, argues that the maritime culture migrated inland up rivers in some areas, leaving evidence of their presence near the glacial lakes and at other sites.