Once upon a time, about 36,000 years ago, colossal unicorns frolicked across the Siberian plains. They were huge—3.5 metric tons apiece—with a single horn protruding majestically from between their ears. They were also exceptionally ugly. Forget Lisa Frank pictures or Starbucks’ unicorn-themed Frappuccinos; Elasmotherium sibiricum, or the Siberian unicorn, as it’s sometimes called, looked much like today’s living rhinos, but larger, shaggier, and with a decidedly larger horn.

Now, according to an international team of researchers from Adelaide, Sydney, London, the Netherlands, and Russia, we have a better idea of why we no longer see these monstrous creatures snacking on Siberian grassland. In new research published in the journal Nature Ecology and Evolution, the scientists say the Siberian unicorn seems to have become extinct during the Ice Age, when climate change reduced its grassy habitat around present-day Russia, Kazakhstan, Mongolia, and Northern China.

The study hypothesizes that the animals died out around 165,000 years later than originally thought, meaning that they roamed the Earth at the same time as Neanderthals and our human ancestors. But, for once, this is a case where we don’t seem to have been at fault for an extinction. ”The Siberian unicorn appears to have been badly hit by the start of the ice age in Eurasia,” said study co-author and climate scientist Chris Turney, from the University of New South Wales, in a statement. “A precipitous fall in temperature led to an increase in the amount of frozen ground, reducing the tough, dry grasses it lived on and impacting populations over a vast region.”

By analyzing the animal’s DNA, the researchers discovered that, despite appearances, the Siberian unicorn was only a very distant relative of today’s living rhinos, and in fact the last surviving member of a unique mammal family. “The ancestors of the Siberian unicorn split from the ancestors of all living rhinos over 40 million years ago,” said study co-author and University of Adelaide genetics researcher Kieren Mitchell, in a statement. “That makes the Siberian unicorn and the African white rhino even more distant cousins than humans are to monkeys.” Their genetic connection to prettier, and allegedly mythological, non-Siberian unicorns remains a mystery.