Not us this time?

Another look at the Pleistocene decline of a large North American mammal, although in this case the species survived. And, perhaps more surprisingly, this time we're not the agent of disaster. A study coming out in the new PNAS looks at the dramatic reduction in numbers of musk ox which began about 12,000 years ago and concludes that the major cause was climate change, rather than human impacts.

The researchers analyzed mitochondrial RNA from musk ox remains up to 60,000 years old from areas across their former range. They then applied statistical techniques to investigate changes in the genetic diversity of musk ox over their North American history. They found that genetic diversity, an indicator of population size, declined several times over the last 65,000 years. They also found that changes fluctuations in the size of musk ox populations did not mirror those of other North American megafauna like mammoths and bisons, suggesting that population declines can not be attributed to an invading horde of overzealous human hunters.

The more I read about Pleistocene extinctions, the more convinced I become that there's simply not an easy answer.