DNA yields clues to why mammoths went extinct in arctic regions

The reason mammoths and other large mammals went extinct about 10,000 years ago was a drastic change in available vegetation, Swedish researchers suggest. Scientists at Lund University report new DNA technology shows a sudden change in the dominant vegetation -- from protein-rich herbs to less nutritious grass -- could be behind the demise of many creatures living in the world's tundra regions of northern Russia, Canada and Alaska. Although large parts of those regions were covered in ice from 25,000 to 18,000 years ago, there were also ice-free areas hosting the so-called mammoth steppe, populated by plenty of mammoth, woolly rhinoceros, steppe bison, horse and musk ox, the researchers said. Plant DNA residue in soil samples has yielded an overview of the various plant species that dominated the mammoth steppe, they said. The findings suggest the mammoth steppe was much more dominated by herbs than grass during the last ice age, they said, providing a herb-dominated diet that was much more nutritious than a grass-dominated one. When the last ice age ended and the much more humid interglacial period began, the plant composition on the Arctic tundra changed drastically, the researchers said. "The herbs then became less dominant, and grass took over," Lund geology Professor Per Moller said. The less nutritious food may have been a major contributing factor to why many of the large mammals became extinct about 10,000 years ago, he said.