Woolly mammoths suffered genetic 'meltdown' before extinction

Before woolly mammoths went extinct thousands of years ago, their dwindling population suffered a series of genetic mutations that hampered their ability to survive, researchers said Thursday.Woolly mammoths were once among the most common herbivores inNorth America and Siberia, but came under threat from increased hunting pressure and a warming climate.Experts analyzed the genome of one of the last known woolly mammoths ever found -- a 4,300-year-old specimen from Wrangel Island, off the northe