DNA and ancient remains suggest that most mammoths had died out around 10,000 years ago - but why did they go extinct?
Credit: Wikipedia
These mammoth populations in Alaska and Siberia became isolated from each other during a period of warmer climate, when higher sea levels submerged the land bridge. Then around 100,000 years ago, the land bridge reopened as the climate cooled, allowing the two groups intermingle once more.
DNA further suggests that at around 43,000 years ago, the original Siberian lineage died out, leaving only the lineage of the Alaskan immigrants alive at the time of the mammoth's last gasp. This builds on previous work using the fossil record, also by Barnes, and co-author Adrian Lister of University College London.
Set up for extinction
"Around 20,000 years ago, before humans start to become a real predation threat to most of the [large] species in Siberia, we find a significant cooling across the Northern Hemisphere, with an increase in the size of glaciers, and considerable environmental change, and this seems to have been important in setting up the conditions for extinction too," said Barnes.
As the climate warmed 12,000 years ago, forests once again took over the steppe-tundra of Europe and the mammoths vanished. The last population of mammoths survived in Siberia until around 10,000 years ago.
"This study is a great first step in understanding the complexities of the recently extirpated mammoth populations," commented Hendrik Poinar, an anthropologist at McMaster University in Ontario, Canada. Poinar has worked on sequencing parts of the mammoth genome.
Past insights
However, "it's too early, with too few individuals to really tell what happened to the mammoths, whether or not the population was structured at all, and when the migrations to North America took place," cautioned Poinar. "But with more data, from more mammoths, this should become clearer."
"At a time when we should be very concerned about the potential extinction of many existing large mammals, studying those that occurred in the geologically recent past can provide many insights," said Lister. "Our work, together with that of others, shows that the conditions for extinction can be set up long before the actual extinction event."
