We now know why the last of the mammoths died

20 Oktober 2019

Mammoths once roamed far and wide across much of Eurasia, yet owing to a changing climate and relentless human predation they died out four millennia ago. Their final toehold was on Wrangel Island in the Arctic Ocean, where the wholly giants persisted for a while. Yet even there their life on the planet came to an end in a short space of time.

We may now know why exactly that happened. An international team of scientists from the University of Helsinki, the University of Tübingen and the Russian Academy of Sciences have reconstructed the scenario that probably caused mammoths to go extinct on the remote island in what is now Russia.

During the last Ice Age, between 100,000 years and 15,000 years ago, woolly mammoths were widespread in the Northern Hemisphere from Spain all the way to Alaska. Yet a warming climate that began 15,000 years ago, their habitat in Northern Siberia and Alaska shrank while human hunters also predated in the pachyderms, causing most mammoths to perish. Some of the survivors ended up on Wrangel Island, cut off from the mainland by rising sea levels. They lingered on for another 7,000 years there.

Yet not even there were they ultimately safe. Their isolated habitat, extreme weather events and the spread of prehistoric man may all have contributed to the animals’ demise, the researchers argue in a study published in Quaternary Science Reviews. Backed up into their final stronghold, the last few mammoths were largely defenseless against environmental stresses.

The researchers, who come from Finland, Germany and Russia, examined the isotope compositions of carbon, nitrogen, sulfur and strontium from a large set of mammoth bones and teeth from Northern Siberia, Alaska, the Yukon, and Wrangel Island. They did so to see what they could deduce from them when it came to changes in diet and habitat disturbances.

What they found was that in mammoths on Wrangel Island collagen carbon and nitrogen isotope compositions did not shift as the climate warmed up by 10,000 years ago. “The values remained unchanged until the mammoths disappeared, seemingly from the midst of stable, favorable living conditions,” they explain in a press release.

Early human hunters took a toll on mammoth populations. (illustration: Wikimedia Commons)

“This result contrasts with the findings on woolly mammoths from the Ukrainian-Russian plains, which died out 15,000 years ago, and on the mammoths of St. Paul Island in Alaska, who disappeared 5,600 years ago,” they add.

“In both cases, the last representatives of these populations showed significant changes in their isotopic composition, indicating changes in their environment shortly before they became locally extinct.”

Mammoths in Siberia and those on Wrangel Island showed a marked difference in how they stored fats and carbohydrates. “We think this reflects the tendency of Siberian mammoths to rely on their reserves of fat to survive through the extremely harsh ice age winters, while Wrangel mammoths, living in milder conditions, simply didn’t need to,” said Dr. Laura Arppe, from the Finnish Museum of Natural History Luomus at the University of Helsinki, who led the research team.

Evidence also indicated that the quality of the mammoths’ drinking water worsened on the island over time. Then, a sudden extreme weather event may have spelled doom for the mammoths by depriving them of enough food, causing their population to drop even further.

“It’s easy to imagine that the population, perhaps already weakened by genetic deterioration and drinking water quality issues, could have succumbed after something like an extreme weather event,” explains Prof. Hervé Bocherens, from the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen.

Roaming bands of human hunters may too have taken their toll on the last few mammoths, speculate the researchers, whose work shows that large mammals, once their populations have greatly diminished, are at heightened risks of going extinct as a result of environmental factors and human behaviors. “An important takeaway from this is that we can help preserve species by protecting the populations that are not isolated from one another,” they write.

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