Around 4000 years ago, the last woolly mammoths disappeared from Earth. Those final survivors lived and died on Wrangel Island, off the coast of northeast Russia. Their mainland Siberian relatives had died out some 6000 years before that. Now scientists are one step closer to figuring out what caused these beasts to become extinct.

An international team led by scientists from the Swedish Museum of Natural History has sequenced the entire genome of the woolly mammoth. Their findings, published in Current Biology, provide new insights into the last days of the long-mythologized species.

The team wanted to learn more about the genetic diversity of the Wrangel Island mammoths. The genome of any mammal has two copies of every DNA molecule—one from mom and one from pop. By comparing the two sets of molecules, scientists can determine whether an animal's parents were relatives, and if so, how closely related. Researchers suspected that in such a small and ever-diminishing group, inbreeding was likely.

They took DNA from two mammoth specimens preserved in permafrost. One was soft tissue from a Siberian male from about 44,800 years ago and the other was a tooth from a male on Wrangel Island from about 4,300 years ago. Stem cells from a modern African elephant provided a reference point.

The team found that the Wrangel mammoth population lacked genetic diversity. This finding could lead to greater understanding about whether low genetic diversity diminishes a species' chance of survival. 

"Your genome is like your tool kit for getting out of trouble," Ian Barnes, an evolutionary biologist at the Natural History Museum in London, told The Los Angeles Times. "If you as a species have lots of different tools available, it means some individuals will die when the environment changes or a disease arrives, but there will probably be others that will be resistant and will pass those genes on to the next generation. If you don't have the diversity, it's a challenge."

The data also revealed two significant population drops: one 300,000 years ago and another 12,000 years ago, at the end of the last Ice Age, after which only about 300 to 1000 mammoths remainedWrangel Island separated from the mainland roughly 12,000 years ago due to rising sea levels. 

The breakthrough means we might someday better understand how the species evolved and what makes the elephants of today different from their furry, tusked relatives—and if some scientists have their way, bring woolly mammoths back to life