Once widely roaming across Siberia and North America, the Wooly Mammoth died off more than 10,000 years ago, with a lingering dwarf population lasting on the Wrangel Islands until 4,000 years ago.
In a jumbo analysis of 1,323 wooly mammoth samples, and numerous woodland sample records, a team led by Glen MacDonald of the University of California Los Angeles, reports in the current Nature Communications journal on the gradual disappearance of these remarkable pachyderms. The samples dated to 45,000 years ago in the region called "Beringia" which during the last Ice Age included a land bridge stretching from Siberia to Alaska, the last redoubt of the wooly mammoth.
"Mammoths were open vegetation-adapted with diets dominated by graminoids and soft-shoots of selected woody plants such as willow. Conifer trees, although found in the stomachs of some woolly mammoths, are not nutritious browse. Birch (Betula) can be toxic to cecal digesters, such as mammoths, which lack a rumen for detoxification. While grasses and willows were plentiful, birch was less abundant ... In the north (from 60,000 to 25,000 years ago), with relatively abundant grass and willow cover, may represent an environment closest to the idealized mammoth steppe," says the study.
So, what happened?
First an Ice Age and then a warm-up saw poisonous birch and peatlands, difficult terrain and lousy food, proliferate in the wooly mammoths' territory., says the study. Hunting didn't help:
"Small continental populations of woolly mammoth certainly were present after (12,900 years ag0), but trajectory of these populations towards extinction was being driven by changing habitat and perhaps also through human hunting that had spread to North America. Graminoid, willow and drier herbaceous cover decreased in concert with the establishment of deleterious birch shrubland/woodland throughout Beringia, development of extensive peatlands and wet tundra, and expansion of conifer forest including areas north of the modern treeline across Eurasia as far as the present coastline. Pressure from hunting was also present, as contemporary Paleolithic sites are numerous in both Siberia and now in northwestern North America. Modelling studies show that given the environmental stresses at the time, even limited hunting by humans could have significantly contributed to woolly mammoth extinction."
So there you have it. Not enough willow and too much cold weather, combined with more hunters spelled curtains for the mammoths, concludes the study, where, "final extinction of the island populations signalled the conclusion of the long sunset of the woolly mammoths in Beringia after over 20,000 years of multiple environmental challenges related to changes in climate, habitat and human predation."
As an added note, it is worth mentioning that there is at least one more possible explanation for the demise of the Wooly Mammoth that has been bouncing around over the last decade -- a comet impact with Earth. The idea is pretty contentious, and doesn't explain how island mammoths survived a strike that wiped out their bigger brethren.
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