Palentologists have avoided connecting the great extinctions that brought the Pleistocene to an end 15,000 years ago to climate change by claiming that they were due to a few thousand hunter-gatherers killing millions of animals, all within a span of a few hundred years. Now climate is finally being recognized as the key to the extinctions.
Paleobiologist Dale Guthrie of the University of Alaska says in a study published in Nature this week that climate change, not hunters, brought about the extinction of mammoths and horses in the Yukon Territory, Alaska and Siberia around 12,000 years ago. New dating of fossils shows that the animals did not die off at the same time that hunters arrived, and, in fact, that the appearance of the hunters did not have a measurable effect on herds.
What Guthrie believes is that the end of the ice age around 13,000-15,000 years ago caused the Yukon and Alaska to become much warmer, and drew grazing herds of horses, mammoths, and other animals far to the north. Then the climate changed again, abruptly by geologic standards, over few hundred years. This left the animals stranded without fodder to graze, and the herds diminished and died out.
Why they did not move south with the grass in the same way that they had moved north with it is not explained by the new study. Paleontology has long since dismissed evidence of animals being killed so abruptly that they died with food still in their mouths as fiction. Although such fossils have been found, it is assumed that there must be some other explanation than abrupt weather change to explain the deaths.
Professor Lonnie Thompson of the Byrd Polar Research Institute has found evidence of very abrupt and long-lasting climate change in Peruvian glaciers, which reveal quick-frozen temperate zone plants at their bases, meaning that the plants were killed by a weather event in a matter of minutes, and have remained covered by ice ever since. No animal remains have ever been found in this condition, but storms of an unknown type that can cause such sudden and long-lasting change have certainly happened in the past.
To read our story on Dr. Thompson's findings, click here.
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