Scientists have sequenced and analyzed the complete high-quality genomes of two woolly mammoths, which revealed poignant story of their extinction.
Before the world's last woolly mammoth took its final breath, the iconic animals had already suffered from a considerable loss of genetic diversity.
One of those mammoths, representing the last population on Russia's Wrangel Island, was estimated to have lived about 4,300 years ago. The other specimen, from northeastern Siberia, was about 44,800 years old.
The younger of the two specimens showed much lower genetic variation, including large stretches of DNA with no variation whatsoever, the mark of living in a very small population in which related individuals unavoidably mate with each other.
Because an individual's genome is a mosaic of bits and pieces of DNA inherited from a large number of its ancestors, a single genome contains a vast amount of information about a species' population history.
Taking advantage of this, the researchers inferred that woolly mammoth populations suffered a blow in the Middle or Early Pleistocene, some 250,000 to 300,000 years ago, for reasons that weren't at all clear. That more ancient and temporary loss in numbers was followed by a more severe decline at the end of the last glaciation, from which the woolly mammoth never recovered.
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The study is a result of an international collaboration that involved researchers from Sweden, the United States, Canada, and Russia.
The study is published in the Cell Press journal Current Biology.