A group of researchers suggest that the last mammoths were probably wiped out by lack of access to freshwater when the Alaska island they were on was cut off from the mainland by rising sea levels.
Scientists based their findings on millennia old layers of sediments from a lake on St. Paul Island in Alaska. Laboratory tests revealed that the last woolly mammoth died about 5,600 years ago, which is about several millennia after the population on the continent had died off.
Co-author of the study Matthew Wooller explained that the furry giants were trapped on the island when the sea engulfed the land bridge. Nevertheless despite being stranded on the island, they managed to outlive their peers on the mainland by 5,000 years.
There were no traces of human inhabitants on the island in that time period.
The research team took sediment samples from the Alaskan lake in 2013. They assessed the amounts of the stable oxygen isotope in the aquatic critters that had lived in the lake during that era and after the woolly mammoth extinction.
From the analysis researchers learned that lake levels changed over time. But the quantity and quality of aquatic organisms also changed over the millennia which prompted researchers reach the conclusion that the lower quality of freshwater in the lake led to the animals’ demise.
Analysis of the nitrogen isotope within the mammoths’ bones revealed that before the major event, weather gradually got drier. Wooller and his team believe that they have gathered enough evidence to prove that the ancient animals ‘died of thirst.’
Restricted access to freshwater resource is the ‘smoking gun’ for the mammoth’s demise, researchers said.
Still, the recent findings not only tell the tragic story of mammoth populations, it also depicts a grim picture of what the future may look like for small island populations under current weather conditions.
Researchers explained that sea level rise reduced the island’s total surface to 42 square miles, but the changes persisted for about 2,000 years before the mammoths went extinct. The research team believes that in our times changes could become more abrupt than that.
The study was funded by the National Science Foundation and was reported Aug. 1 in the Proceedings of the National Academy of Science.
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