From Denver, at the Annual Meeting of the Society for American Archaeology
Many North American mammal species died out around 11,000 years ago, roughly coinciding with the arrival of humans on the continent. Some scientists contend that these so-called Clovis people, who made deadly spear points out of stone, hunted mammoths and all sorts of other prey to extinction in just a few hundred years.
That scenario oversimplifies what probably happened, according to Russell Graham of the Denver Museum of Nature and Science. A new set of radiocarbon dates for fossil animal bones collected throughout North America indicates that a major wave of mammal extinctions occurred 11,500 years ago, before the arrival of Clovis folk, Graham says. Two further waves of extinction took place around the time of their arrival–11,000 years ago and again 10,800 years ago, when mammoths and mastodons died out.
A recently developed process for chemically purifying small samples of fossil bone makes the new radiocarbon dates more reliable than previous ones, which did not indicate nearly as many pre-Clovis extinctions, Graham asserts.
The number of spear points found at Clovis sites indicates that there were too few hunters to have wiped out entire species on their own, adds Stuart J. Fiedel of John Milner Associates, an archaeological contracting firm in Alexandria, Va. He says it’s likely that hunting by these early North Americans magnified the effects of a series of sharp shifts between warm and cold climates that either wiped out or depleted many mammal populations. These findings contrast with recent results indicating that human hunting is the likely cause of New Zealand’s prehistoric bird extinctions (SN: 3/23/02, p. 190: Early hunters are guilty as charged).