Sophisticated hunters not to blame for driving mammoths to extinction

Guardian ^ | Thursday, November 19, 2009 | Ian Sample

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The animals, which included mammoths, elephant-sized mastodons and beavers the size of black bears, were probably picked off by more inept hunters who only much later developed specialised weapons when their prize catches became scarce. "Some people thought humans arrived and decimated the populations of these animals in a few hundred years, but what we've found is not consistent with that rapid 'blitzkrieg' overkill of large animals," said Jacquelyn Gill, a PhD student at the University of Wisconsin, Madison, who led the research team... Gill's team rules this out by putting a more accurate date on the decline and fall of woolly mammoths and more than 30 other large mammals that dominated the landscape as the ice sheets retreated from North America. Among them were giant sloths the size of SUVs. To date the animals' slide to extinction, the scientists examined sediment cores from a lake in Indiana. The deepest sediments were laid down in the distant past, while more recent sediments were nearer the surface. Specifically, the scientists measured levels of a fungus that is known to thrive in the excrement of giant herbivorous mammals and nowhere else. They reasoned that more fungal spores meant more dung, which in turn reflected a larger population of roaming mammals. The sediments also held ancient pollen and charcoal dust, which gave the team clues about the predominant plant life and frequency of wildfires. Writing the US journal Science, the researchers describe how the amount of mammal dung started to fall around 14,800 years ago, long before advanced spearheads became commonplace. The animals had been almost completely wiped out a thousand years later.

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