A big new discovery could tell us an astonishing truth about why the woolly mammoths went extinct, and the story paints a truly bizarre end for this ancient giant. Based on a study of their DNA that looked for genetic mutations, it appears the animal had a genetic makeup that was completely messed up just before its demise.

Genetic disease so ravaged the animal that they had lost their sense of smell, they had a shiny coat, and they avoided other mammoths, according to the paper, which was published in PLOS Genetics. This finding is important not just because it could help scientists better understand mammoths, but because it could give clues in helping other species prevent extinction.

Scientists believe that just a few hundred woolly mammoths lived on Wrangel Island in the Arctic Ocean 4,000 years ago, right before its end.

“There is a long history of theoretical work about how genomes might change in small populations. Here we got a rare chance to look at snapshots of genomes ‘before’ and ‘after’ a population decline in a single species,” said Rebekah Rogers, who led the work as a postdoctoral scholar at Berkeley and is now an assistant professor at the University of North Carolina at Charlotte, in a statement on the university’s website. “The results we found were consistent with this theory that had been discussed for decades.”

“Woolly mammoths were one of the most common large herbivores in North America, Siberia, and Beringia until a warming climate and human hunters led to their extinction on the mainland about 10,000 years ago,” the statement from PLOS reads. “Small island populations persisted until about 3,700 years ago before the species finally disappeared. Researchers compared existing genomes from a mainland mammoth that dates back to 45,000 years ago, when the animal was plentiful, to one that lived about 4,300 years ago. The recent genome came from a mammoth that had lived in a group of about 300 animals on Wrangel Island in the Arctic Ocean. The analysis showed that the island mammoth had accumulated multiple harmful mutations in its genome, which interfered with gene functions. The animals had lost many olfactory receptors, which detect odors, as well as urinary proteins, which can impact social status and mate choice. The genome also revealed that the island mammoth had specific mutations that likely created an unusual translucent satin coat.”