Researchers believe that the last population of woolly mammoths may have been wiped out by a “random event,” despite signs of inbreeding and low genetic diversity. The last population of the species was isolated on Wrangel Island, off the coast of Siberia, some 10,000 years ago due to rising global sea levels at the start of the Holocene period. Their numbers dropped to as few as less than 10 individuals before the population recovered to between 200 and 300 within 20 generations, according to a study published on Thursday in the journal Cell. Some 6,000 years later the mammoth species became …