Unicorns did exist – until they didn’t
A monstrous rhino species survived until much more recently than thought. Stephen Fleischfresser reports.
What’s four metres long, 2.5 metres high, weighs 3.5 tonnes and has a preposterously large horn in the middle of its face? A really massive unicorn, that’s what.
Research published in the journal Nature Ecology and Evolution has now uncovered the details of the life, history and extinction of a spectacular species dubbed the “Siberian Unicorn”.
A team of international researchers from a range of institutions including the universities of New South Wales and Adelaide in Australia, the University of Durham in the UK, and Leiden University in the Netherlands, led by senior author Adrian Lister of London’s Natural History Museum and lead author Pavel Kosintsev of the Russian Academy of Sciences, have unlocked the secrets deep in the bones of Elasmotherium sibiricum, an extinct member of the rhinoceros family.
E. sibiricum is known colloquially as the Siberian unicorn because of its unusually large horn. It was the largest rhinoceros of the Quaternary period – which ran from roughly 2.5 million to 12 thousand years ago.
Despite its huge size it was lithe and seemed adapted to running across its homelands of central Asia: Kazakhstan, western and central Russia, Ukraine, Azerbaijan and Uzbekistan, and possible areas of Mongolia and China.
Until now, E. sibiricum had been thought to have gone extinct about 200,000 years ago as part of the natural extinction rate that preceded the arrival of humanity, and no one really knew what niche in the ecosystem it inhabited.
For the new work, the researchers sampled 25 examples of E. sibiricum bones, extracting collagen for radiocarbon dating and even DNA for a study of the unicorn’s evolutionary history.
The latter has shows that the animal belonged to a sister taxon to Rhinocerotinae, the group to which all modern rhinoceros belong. The two were thought to have split about thirty-five million years ago, but the current research indicates an even earlier divergence of forty-seven million years ago.
The radiocarbon dating yielded some surprising results, suggesting that the unicorn was still kicking until 39,000 years ago. This places its extinction “firmly within the late Quaternary extinction event”, between 50,000 and four thousand years ago, in which nearly half of Eurasian mammalian megafauna died out. Interestingly, this adds to the evidence of the decline of megafauna just before the ice sheets of the last ice age reached their maximum extension.
And this might help us to understand the reasons for the unicorn’s demise.
The shape of, and the isotopes within, the remains of E. sibiricum suggest that it found its home in herb- and grass-covered steppes, with an extreme adaptation for feeding close to the ground. Perhaps it dug up vegetation up to consume it roots and all.
However, starting about 35 thousand years ago, as the deep cold extended further south, the steppe became more like tundra, denying the unicorn its primary food source, and this was perhaps a decisive factor in its extinction.
The authors also speculate that human might have had something to do with it, although they acknowledge a dearth of supporting evidence.
“The extinction of E. sibiricum,” they write, “could in theory have been exacerbated by human hunting pressure, given the replacement of H. neanderthalensis by H. sapiens in Eurasia around 45–40 [thousand years ago]”.