13
November 2003
The lost mammals: Climate changed
Many of the larger mammal species disappeared from North America towards the end of the Pleistocene, between 20,000 and 10,000 years ago. The apparent coincidence of these extinctions with the arrival of modern humans in the New World has led to suggestions that human activity or 'overkill' may have been the cause. By radiocarbon dating a large number of fossils of horses from Alaska, R. Dale Guthrie now shows that before becoming extinct, horses underwent a precipitous decline in body size. In addition, the new data show that horses did not become extinct at the same time as Alaskan mammoths. Rather than being decimated by enthusiastic human hunters, these two species were probably reacting quite differently to the extreme climatic changes that occurred around 12,500 years ago.
Rapid body size decline in Alaskan Pleistocene
horses before extinction
R. DALE GUTHRIE
Nature 426, 169–171 (2003); doi:10.1038/nature02098
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