A publication of the Archaeological Institute of America
What wiped out the mammoths? What about the camels, horses, and giant armadillo-like glyptodonts that thrived in North America until the end of the last Ice Age? The popular overkill theory, first put forth by ecologist Paul Martin of the University of Arizona in 1967, holds that humans are the culprits in the massive wave of extinctions. Martin thinks the Clovis people annihilated some 30 genera of mammals soon after they entered the New World around 11,000 years ago. Now Don Grayson, a zooarchaeologist at the University of Washington, has gone on a hunt of his own. His quarry--the overkill hypothesis.
"There is no reason to believe that the early peoples of North America did what Martin's argument says they did," says Grayson, who in two recently published papers argues that climate change did in the mammoths and other large mammals. He points out that similar extinctions occur at the same time in northern Siberia and southwestern France, areas that did not experience a sudden influx of hunters but did undergo radical climate change. Moreover, of the more than two dozen species that went extinct, only mammoth remains appear in Clovis sites.
According to Grayson, "overkill was a useful theory when it was first proposed, but now it's an article of faith." He points out that, excepting Martin, archaeologists and paleontologists familiar with the period no longer think the evidence supports human-induced extinctions. "I think the reason overkill is still popular with ecologists and the public is the Old Testament nature of it--humans causing vast environmental damage. But it's not science."
Martin isn't convinced. "I think that archaeologists have always washed their hands of human complicity in large extinctions," he says.