Before becoming extinct, the last mammoths accumulated harmful genetic mutations that may have altered their behaviour and appearance.

Woolly mammoths (Mammuthus primigenius) disappeared from North America and Siberia 10,000 years ago, but small groups survived on islands until about 4,000 years ago. Rebekah Rogers and Montgomery Slatkin at the University of California, Berkeley, compared two published genome sequences — one from a Siberian mainland specimen dated to 45,000 years ago, when mammoths numbered more than 12,000, the other a 4,300-year-old specimen from Wrangel Island in the Arctic Ocean, which had a population of just 300 individuals.

They found that the island mammoth had more harmful mutations, including many gene deletions. The mutations may have affected the animals' social behaviour and sense of smell; given them a silky, translucent coat; and contributed to their demise. Conserving small, isolated animal populations may not be enough to save endangered species from genetic harm, the authors warn.

PLoS Genet. 13, e1006601 (2017)