This search turned up 75 locations in the United States and one in Canada that Grayson and Meltzer evaluated. Forty-seven of the sites did not exhibit minimally acceptable evidence showing an association between artifacts and extinct mammals. Most of these sites were rejected because they were not sufficiently described or documented.
"In many cases there is no published material, and when something is not published we are not able to weigh evidence of a human connection," said Grayson. "In other cases there was just an anecdotal suggestion of artifacts or remains, or there were very sketchy drawings."
Of the remaining 29 sites only 14 survived closer study. To determine this, the researchers looked for settings in which artifacts and animal remains were so closely associated that there was little doubt that their relationship was not accidental. In addition, Grayson and Meltzer searched published evidence for signs of human hunting and butchering and processing. This included cases where projectile points were found among bones or where there was solid evidence of human-caused bone breakage or cut marks.
Mammoth and mastodon bones were the most commonly found remains at the 14 confirmed predation sites, but horse, camel and bison bones also were identified. However, Grayson said there was no evidence that the two horse bones and one camel bone, all from extinct genera, came from animals that had been hunted by humans. There was quite a bit of evidence of human predation of bison, but this genus did not become extinct.
The survey produced no evidence that humans hunted the 33 other genera of extinct animals, which also include sloths, tapirs, bears and sabertooth cats. In fact, only 15 genera can be shown to have survived beyond 12,000 years ago and into Clovis times, said Grayson.
"There is absolutely no evidence that Clovis people were involved with 33 of the extinct genera. Where's the spear point sticking out of a camel or a ground sloth? If you can kill a mammoth you can kill a lumbering ground sloth. Clovis people absolutely did not chase these now-extinct animals relentlessly across the North American landscape," he said.
"The bottom line is that we need to stop wasting our time looking at people as the cause of these extinctions. We suspect the extinctions were driven by climate change. We need to know what aspects of climate change were involved. We have to tackle this species by species, one at a time, and look at the interaction of each species with the climate and vegetation on the ground."
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Adapted from materials provided by University Of Washington.
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