Even before woolly mammoths (Mammuthus primigenius) went extinct, signs of decline were written in their DNA, researchers report in the May 18 Current Biology.
The team sequenced genomes from a 44,800-year-old specimen from Siberia and a 4,300-year old specimen from Wrangel Island in Alaska, where the last known population of woolly mammoths lived out their days.
Differences between the sequences suggest that woolly mammoths hit two genetic bottlenecks: one in the middle Pleistocene around 285,000 years ago and one exclusively in the Wrangel Island population at the end of the last ice age (116,000 to 130,000 years ago). The Alaskan specimen also showed signs of low genetic diversity and inbreeding.
The researchers posit that such genetic deficits probably contributed to their subsequent demise.