A mysterious giant rhino species – called the Siberian unicorn because of its huge single horn – has just survived in western Russia until just 36,000 years ago, according to research published in Nature Ecology & Evolution. This extinction date means that the last days of the Siberian unicorn were shared with the first modern humans and Neanderthals.
Previously, little was known about the creature believed extinct over 200,000 years ago. But genetic analysis and radiocarbon dating have begun to reveal many aspects of how she lived and when she disappeared.
An important finding is that the Siberian unicorn was not extinguished due to modern human hunting, not even the peak of the last Ice Age, which began about 25,000 years ago.
Instead, it succumbed to a more subtle change in the climate that reduced pastures from Eastern Europe to China.
Our new results show that the Siberian unicorn depended on these fields and, unlike other species in the area, such as the Saiga antelope, was unable to adapt to change.
The "Siberian unicorn"
The Siberian unicorn (Elasmotherium) had a single large horn, estimated up to one meter long. It was one of the many different species of rhinos that existed.
In addition to the extinct woolly rhinoceros (which is still found as frozen mummies), there are five species of live rhinoceros. All these creatures are now sadly in trouble, including the white (almost threatened) rhinoceros, the Javanese rhinoceros (critically endangered) and the Sumatran rhino (critically endangered).
The loss of the Siberian unicorn offers a valuable case study showing the poor resilience of rhinos to environmental changes.
The animal in which we work was found in modern Russia, although its scope also extended to areas that now include Kazakhstan, Mongolia, and northern China, where it inhabited a steppe habitat dominated by grasses and grasses.
The Siberian unicorn shared this environment with the Saiga antelope and other species of the Ice Age, including the rhinoceros and the mammoth.
But most of the evidence to date suggests that the Siberian unicorn died out 200,000 years ago, while the rhino and mammoth were extinct some 13,000 and 4,000 years ago, respectively.
So why did the Siberian unicorn become extinct, while other species that lived in the same habitat remained for thousands of years or, like the saiga, still survive today?
A smoking gun
Some unconfirmed evidence has recently suggested that the Siberian unicorn survived even closer to the present, much like the woolly rhinoceros. Thus, we investigated the age of 23 osseous animal samples kept in museum collections in Russia and the United Kingdom.
Instead of 200,000 years, the new dating discovered that the Siberian unicorn was only extinguished just 36,000 years ago.
We then consider how this may have become extinct at this time.
Climate change looks like a likely candidate – but 36,000 years is well before the heyday of the Ice Age, which occurred from 20,000 to 25,000 years ago.
But this date coincides with the moment of a pronounced shift toward colder summers in northern Europe and Asia. This seasonal change has resulted in grasses and grasses becoming more sparse and an increase in species of tundra plants such as mosses and lichens.
A vulnerable expert
So why did a change in climate 36,000 years ago lead the extinct Siberian unicorn but not the woolly rhino or saiga?
To answer this question, our study used fossil bones of the Siberian unicorn, woolly rhinoceros and saiga, and analyzed the nitrogen and carbon they contained – because the differences in these elements reflect the diet of an animal.
We found that, before 36,000 years ago, the Siberian saiga and unicorn behaved very similarly, eating grass almost exclusively. After this point, the carbon and nitrogen in saiga bones showed a major change in diet compared to other types of plants.
But switching from a grass diet proved to be very difficult for the Siberian unicorn, with its collapsible, wear-resistant teeth and a low head hung at grass height. Relatives such as the woolly rhinoceros always ate a more balanced variety of plants, and were much less impacted by a change in habitat.
It is important to note that the change in climate that led to the extinction of the Siberian unicorn was much less pronounced than that of the Ice Age that followed. Or the changes we will face in the near future.
The history of the Siberian unicorn is a timely reminder that even subtle changes in plant distributions can have devastating effects on large animal species.
Worryingly, this is a terrible risk for many animals, such as the surviving cousins of the Siberian unicorn, which, thanks to humans, already have very restricted areas.