"Siberian Unicorns" extinct walked the Earth alongside modern humans


Weighing up to 3,500 kg, Elasmotherium sibiricum– an extinct hairy rhinoceros, popularly known as the "Siberian unicorn" – would have disappeared 200,000 years ago. An updated fossil analysis suggests that this formidable species still existed some 39,000 years ago, and that the conditions of the Ice Age, not the human hunters, contributed to its disappearance.

Paleontologists know about 250 species of rhinoceros, of which only five still exist today. Among the most spectacular of these rhinos was Elasmotherium sibiricum– the Siberian unicorn. For the Neanderthals and modern humans who lived next door and possibly hunted this huge creature in Eastern Europe and Central Asia, it must have been an impressive and deeply intimidating sight. Fossil evidence suggests Elasmotherium weighed more than 3.5 tons, was covered by a thick layer of hair and bore a horn of biblical portions, possibly up to three feet (1 meter) in length.

Impressive as it was, the Siberian unicorns eventually died. The earlier dating of fossils suggested an expiration date somewhere between 200,000 and 100,000 years ago, long before the large-scale Quaternary megafauna that occurred 40,000 years ago died out. New research published this week in Nature Ecology & Evolution is now offering a more reliable estimate, dating to the disappearance of Elasmotherium sometime between 39,000 and 35,000 years ago. The extinction of the Siberian unicorns, therefore, can now be connected to the extinction of the late megafauna, an event that witnessed the end of woolly mammoth, Irish elk and cat with saber teeth.

Writing in their new study, led by Adrian Lister of the London Natural History Museum, the researchers said that "there is no absolute dating, genetic analysis or quantitative ecological assessment of this species." [had] was performed, "which explains why the previous estimate of extinction was so far apart. The new study overcomes these shortcomings and includes the use of up-to-date fossil dating techniques.

For the study, an international team of researchers from the UK, the Netherlands and Russia analyzed in detail Elasmotherium specimens, including a pristine skull kept in the Natural History Museum. An improved radiocarbon dating technique resulted in the revised extinction dates; Many of the samples were slathered into preservation materials, requiring careful preparation for carbon dating.

"Some of the samples we studied were heavily contaminated, which made radiocarbon dating very challenging," said Thibaut Devièse, a researcher at the Oxford School of Archeology and co-author of the study, in a statement. "For this reason, we use a new method of extracting a single amino acid from bone collagen in order to ensure highly accurate results."

In addition, the researchers were able, for the first time, to extract DNA from the Elasmotherium fossils. Subsequent genetic analysis showed that the Siberian unicorns separated from modern rhinoceroses about 43 million years ago, "solving a debate based on fossil evidence and confirming that the two lineages had diverged by the Eocene," the researchers wrote in the study. These Ice Age rhinos are the last species of a "highly distinctive and ancient lineage," according to the survey.

Siberian unicorns lived alongside anatomically modern humans and Neanderthals. That ancient hominids may have preyed on these disproportionate rhinos is not as scandalous a proposition as it sounds. First humans, probably a form of Homo erectuswere hunting rhinos in the Philippines some 700,000 years ago. But while rhinos were on the hominids menu, this new research suggests that climate change, not hunters, was responsible for ElasmotheriumThe death.

These rhinos, as we now know from the new research, lived during the Ice Age just before the Last Glacial Maximum – the stage at which the ice sheets covered their largest area, about 26,500 years ago. The Earth was prone to dramatic climate change during this period, producing droughts, desertification, a drop in sea level and the constant invasion of the glaciers. These climatic disruptions have been fatal to many species, Elasmotherium between them.

For the Siberian unicorn, this meant a loss of habitat and, consequently, the disappearance of a critical source of food, as the new study assumes. In experiments, Lister and his colleagues analyzed the stable isotopic ratios of fossilized rhinos. Researchers have sought to link several plants with the levels of carbon and nitrogen isotopes in their teeth. The Siberian unicorns, as these analyzes revealed, lived in a dry steppe environment, where they chewed hard, dry grasses. Rhinos, with their highly specialized herding lifestyle and naturally low population numbers, were unable to adapt quickly enough to conditions of rapid change, the study suggests.

A changing climate, rather than human, was thus responsible for the disappearance E. sibiricum. Interestingly, it is a finding that combines with similar but unrelated research, in which scientists claim that humans were not responsible for many megafauna extinctions of the Ice Age. Unfortunately, the same can not be said for the current sixth extinction, which is certainly our fault.

[Nature Ecology & Evolution]


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