Researchers once thought that Asian big-game hunters crossed the Bering Land Bridge to give rise to the first Americans, the Clovis people. New dates show that a crucial Siberian site, thought to be a way station along the Bering road, wasn't occupied until long after the Clovis began killing mammoths in North America.
Who the earliest Americans were and how they got there is one of anthropology's biggest riddles. The first universally acknowledged culture in the Americas is that of the Clovis, who scattered their distinctively fluted projectile tips across North America starting about 13,600 years ago (using corrected radiocarbon dates), before vanishing several centuries later. Their ancestors were thought to have emigrated from northeastern Siberia via a land bridge that became submerged near the end of the last Ice Age. But a handful of pre-Clovis sites, including one in Monte Verde, Chile, dated to about 15,000 years ago, have challenged this idea. One more challenge is published in the 25 July issue of Science .
A team of scientists revisited a key pre-Clovis site on Ushki Lake on Russia's Kamchatka Peninsula, where charcoal in a grave at the site had been dated to 16,800 years ago. But new dates now place the layer at 13,000 years old, according to a team led by paleoanthropologist Ted Goebel of the University of Nevada, Reno. Although the more recent date rules out the Ushki Lake inhabitants themselves as ancestral to the Clovis people, Goebel and his team say it doesn't rule out Clovis origins in Beringia because of slightly earlier sites in Alaska.
However, says David Meltzer, a paleoanthropologist at Southern Methodist University in Dallas, the new finding “removes what was, until now, the critical link in the chain connecting Clovis to Siberia.” The paper “is really thought-provoking,” adds Richard Potts, director of the human origins program at the Smithsonian Institution's National Museum of Natural History in Washington, D.C. “Maybe it's time to consider less obvious sources for the oldest migration to the continent,” he says.