We usually think of woolly mammoths as purely Ice Age creatures. But while most did indeed die out 10,000 years ago, one tiny population endured on isolated Wrangel Island until 1650 BCE. So why did they finally go extinct?
Wrangel Island is an uninhabited scrap of land off the northern coast of far eastern Siberia. It's 37 miles from the nearest island and 87 miles from the Russian mainland. It's 2,900 square miles, making it roughly the size of Delaware. And until about 4,000 years ago, it supported the world's last mammoth population. For 6,000 years, a steady population of 500 to 1,000 mammoths endured while their counterparts on the mainland disappeared.
It's truly remarkable just how recent 1650 BCE really is. By then, the Egyptian pharaohs were about halfway through their 3000-year reign, and the Great Pyramids of Giza were already 1000 years old. Sumer, the first great civilization of Mesopotamia, had been conquered some 500 years before. The Indus Valley Civilization was similarly five centuries past its peak, and Stonehenge was anywhere from 400 to 1500 years old. And through all that, with all of humanity in total ignorance of their existence, the mammoths lived on off the coast of Siberia.
So then, what finally killed off the mammoths? That's been the subject of a four-year research project by British and Swedish researchers, and they now believe that the final extinction of the mammoths was not inevitable, that they could have survived indefinitely if a couple circumstances had worked out differently. Co-author Love Dalen explained to BBC News:
"We wanted to find out why these mammoths became extinct. Wrangel Island is not that big and it was initially thought that such a small population could have suffered problems of inbreeding and a lack of genetic diversity. But the problem is mammoths don't display that much genetic variation - especially towards the end of their line. The DNA investigations found there was a 30% loss in genetic diversity as the population levels dropped - but that was to be expected. But when we examined the samples from the island, there reached a point when this reached a plateau and there was no more loss. This stage continued until the creatures became extinct. This therefore rejects the inbreeding theory. The mammoths on the island were isolated for nearly 6,000 years but yet managed to maintain a stable population."
Instead, Dalen and the rest of the team believes some drastic change must have occurred on Wrangel Island to kill off the mammoths, and there are two likely culprits: humans and climate. Archaeological evidence suggests that humans reached Wrangel Island at roughly the same time the last mammoths vanished, but there's no evidence yet to indicate that they ever hunted the mammoths. The more likely answer is climate change, which as a side effect might well have made it easier for humans to reach the island to serve as witnesses to the mammoths' final days.
Whatever the exact cause of the mammoth extinction, the fact that they did not succumb to inbreeding is very good news for conservation. According to the Dalen, this means that a small population of even a large animal can maintain genetic diversity and survive indefinitely on a small piece of land. And hey, if anyone ever does figure out how to clone a mammoth, I've got a very good idea where we should put their nature preserve.