Scientists at Durham University in England say the new findings challenge accepted theories that humans played a large part in the extinction of woolly mammoths, woolly rhinos and cave lions through hunting, competition for land and pressure on habitats, Science Daily.com reported Tuesday.
Instead, a massive reduction in grasslands and the spread of forests may have been the primary cause of the decline, they say.
The researchers studied data on climate and vegetation in the Northern Hemisphere during and after the height of the last Ice Age, 21,000 years ago.
Over a huge part of the Earth's surface, they say, there was a massive decline in the productivity and extent of grasslands due to climatic warming and the spread of forests.
"Woolly mammoths retreated to northern Siberia 14,000 years ago whereas they had roamed and munched their way across many parts of Europe, including the U.K., for most of the previous 100,000 years or more," Professor Brain Huntley said.
"The change from productive grasslands across large areas of northern Eurasia, Alaska and Yukon to less productive tundra-like habitats had a huge effect on many species.
"We believe that the loss of food supplies from productive grasslands was the major contributing factor to the extinction of these mega-mammals."
He called the findings "a model for what may happen as a result of rapid climate change over the next century linked to human activity."
"It is food for thought in these times of global warming and human-induced habitat change," he said. "There may well be a lesson to learn."