The gully-trap method took more planning, and reduced the risks to the hunters. The herding method probably involved every able-bodied person in the group, including women and older children, said Bement.
The bison are from a cow-calf herd, he said, adding that "10 to 15 bison would probably feed the same number of people as one or two mammoths."
The animals were butchered at the site. First the legs were cut off and passed up to people on the rim, who stripped the meat from the bone. The main part of the carcass was processed at the bottom of the gully.
Whether all the meat was consumed immediately is unclear. There is no nearby evidence showing that it was processed and dried for later consumption, but the sun would have been hot and winter was coming, said Bement.
"The site is proof that Clovis hunters had developed gully-style bison hunts much earlier than previously thought," said Bement. "Before this it was thought that the hunting style emerged only in the Folsom period."
Folsom culture and technology followed the Clovis era, and lasted from about 10,800 to 10,200 years ago. Whether the two cultures overlapped, and whether the Folsom culture evolved from the adaptations the Clovis made to a changing environment or the Clovis simply died out and were replaced by the Folsom, are also hotly debated issues.
Overkill versus Climate Change
Another point of contention is the role of the Clovis in the extinction of the large mammals of the Ice Age, sometimes referred to as megafauna.
When the Clovis first arrived, North America was home to mastadons, beavers the size of bears, giant sloths, camels, mammoths, and other large mammals. Less than 1,000 years later, these giant creatures were on the brink of extinction. Proponents of the overkill theory argue that the animals were hunted to extinction by humans.
Others argue that the extinction resulted from the loss of food and habitat associated with climate change.
"The [Jake Bluff] bison kill provides ample proof that Clovis people were actively hunting bison. Why didn't they become extinct?" said Russell Graham, a paleontologist and chief curator at the Denver Museum of Nature and Science. "We have no evidence that they were hunting camels or horses, or many of the other Ice Age megafauna that did become extinct."
The find "puts another chink in the armor of the overkill fight," he said.
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