Minor climate change, hunters killed off North American mammoths

Nov 7, 2011, 14:40 GMT

Washington - The first hunters, coupled with a relatively minor change in the climate, could have spelled the end of the North American mammoth, according to a US team that studied the tooth enamel of the large elephant-like mammals.

A team led by Jessica Metcalfe from the University of Western Ontario made deductions from the plant material the animals fed on and the water content in their surroundings some 11,000 years ago, and published their findings in the Proceedings of the National Academy of Sciences.

While the rainfall in the relevant period might have declined slightly, the scientists have ruled out the severe or extended drought that had previously been put forward for the mammoth's extinction.

It is possible that the animals, much like the elephant of today, sought out the greenest parts of their range during the summer months. And in these confined low-lying areas they might well have been easy prey for early hunters.

The American mammoth and other large North American animals died out about 11,000 years ago, and archaeological finds dating to the time shortly before reveal carefully crafted stone arrowheads, demonstrating the arrival of people from the so-called Clovis culture.

An old spearhead found between mammoth ribs even showed recently that early humans hunted the huge animals about 13,000 years ago, well before the Clovis era.

The scientists analyzed the proportions of the various oxygen isotopes in the tooth enamel from mammoth finds in the San Pedro Valley in California, deducing that the climate had been relatively warm and dry. But there had been sufficient summer rain for the plants that they fed on.

The team also called into question the previous theory that there had been a lengthy drought, by looking at the concentration of the carbon-14 isotope in the tooth enamel.