Scientists had long thought that woolly mammoths were one large homogeneous group, but an international group of scientists studied the mitochondrial DNA - the DNA in the genes of the mitochondria structures within cells - to paint a new picture of the ancient pachyderms.
They extracted the DNA from frozen hair samples obtained from individual woolly mammoth specimens, found throughout a wide swath of northern Siberia. They compared 18 complete genomes of mitochondrial DNA and found evidence of two genetically distinct clades, or groups of the elephant-like beasts.
"The population was split into two groups, then one of the groups died out 45,000 years ago, long before the first humans began to appear in the region," said study team leader Stephan C. Schuster of Penn State University.
Schuster and his team also found that each group had a low genetic diversity - in other words, individuals within each of the woolly-mammoth groups were very closely related to one another.
"This low genetic divergence is surprising because the woolly mammoth had an extraordinarily wide range: from Western Europe, to the Bering Strait in Siberia, to North America," said study team member Webb Miller, also of Penn State. He added that this low genetic diversity "may have degraded the biological fitness of these animals in a time of changing environments and other challenges."
In their paper, which appears in the June 9 issue of the journal Proceedings of the National Academy of Sciences, the researchers note that the smaller clade appears to have died out before the larger clade, possibly as a result of genetic drift, or the frequencies with which certain forms of a gene are passed to later generations, purely as a matter of chance. Because the population had such a small range, the lack of diversity could have left them vulnerable to a sudden change in their environment.
Interesting! Now, an equally interesting question would be where the smaller range was would be extremely interesting. Especially if someone were to compare it to the paleoenvironment. Were they confined because of glaciers? What was the mechanism that isolated their range? Was it something else? Forests? Water bodies? Something to ponder.