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Study sheds light on mammoth extinction
Penn State researchers Stephan Schuster, Webb Miller and colleagues have already reported a novel way of recovering ancient DNA from hair. Now, they have used this technique to examine the genetic make-up of woolly mammoth populations.
Mitochondrial DNA reveals distinct mammoth groups
Using hair from museum specimens, the scientists examined the mitochondrial DNA sequences of 18 individual mammoths. These sequences fell into 2 distinct groups: Clade I and Clade II.
Clade I mammoths were found in sites across Russia, and in North America. By contrast, Clade II mammoths were only found in a 450km-wide area of Siberia. The genetic diversity within each group was fairly low.
Phylogenetic analysis suggested that the two groups diverged from each other some time between 1 and 2 million years ago. (The analysis also suggested that mammoths split off from Asian elephants around 6 million years ago, and from African elephants nearly 8 million years ago).
Different extinction dates
Not only were Clade II mammoths restricted to a small geographical range, they also appear to have died out tens of thousands of years before Clade I mammoths went extinct.
Hunting by humans is unlikely to have played a part in the demise of Clade II mammoths. Instead, it is possible that some kind of local population extinction (perhaps due to climate change or disease) wiped them out.