Climate Change Killed the ‘Siberian Unicorn,’ Study Says

Weighing over 7,700 pounds and sporting what was likely the largest rhino horn of all time, Elasmotherium sibiricum—popularly known as the “Siberian unicorn”—must have been an incredible sight to behold.

But despite this extinct rhino’s spectacular appearance, very little is known about it. That changed Monday with the publication of a paper in Nature Ecology & Evolution presenting the first DNA analysis of Siberian unicorn fossils.

Led by Pavel Kosintsev, a paleontologist at the Ural Branch of the Russian Academy of Sciences, a team of researchers concluded that the Siberian unicorn died out around 39,000 years ago, suggesting that modern humans and Neanderthals shared Eurasia with this epic beast during its final years on Earth. Previous estimates held that the rhino went extinct 200,000 years ago.

Though humans have been implicated in the extinctions of many megafauna species, like woolly mammoths and giant sloths, Kosintsev and his colleagues think our ancestors kept their distance from this rhino and that climate change was likely the main factor in its demise.

"It is unlikely that the presence of humans was the cause of extinction,” said co-author Chris Turney, a climate scientist at the University of New South Wales, in a statement. "The Siberian unicorn appears to have been badly hit by the start of the Ice Age in Eurasia when 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."

The traditional timeline of the Siberian unicorn’s extinction was first challenged by an E. sibiricum skull unearthed in Kazakhstan in 2016. The skull was dated to just 29,000 years ago, but the measurement was deemed unreliable because its collagen composition was not ideal for radiocarbon dating.

Kosintsev and his colleagues decided to follow up on the odd measurement with multiple lines of evidence. The team performed radiocarbon dating on 23 E. sibiricum specimens, extracted DNA from six specimens, and conducted an ecological assessment of the rhino’s habitat from fossil and geological evidence.

The specimens were dated between 39,000 and 50,000 years old, a period associated with the emergence of anatomically modern humans across Eurasia. This also coincides with the late Quaternary extinction event, a period that lasted from 50,000 to 4,000 years ago, and included dramatic climate shifts. Approximately 40 percent of northern Eurasian mammal species weighing over 45 kilograms (100 pounds) died out during this climate event, according to the study.

There is heated debate over the extent to which natural climate change or human pressures pushed some of these species off the brink.

To inform the impact of climate change on the Siberian unicorn, researchers conducted isotope analysis of E. sibiricum tooth fossils to reconstruct its probable food sources, and found that these animals were highly specialized steppe grazers. Eurasian herbivores with more diversified diets, such as the saiga antelope, managed to survive the climate changes that occurred 40,000 years ago. But as grasslands decreased from these disruptions, the Siberian unicorn may have been slowly edged into extinction.

There’s always a possibility that humans may have played a role in the eventual end of this animal. But E. sibiricum is rarely depicted in human cave art and there’s no record of its bones in human settlements from this period, so the two species probably didn’t interact much, according to the study.

Still, it’s amazing to think that humans were around to witness the final days of the Siberian unicorn, one of the most majestic megafauna of the Pleistocene period.

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