DNA from Siberian Cave Reveals Extinct Ice Age “Yak X” Species

Ancient DNA Unearths an Unknown Ice Age Bovine in Siberian Denisova Cave

Denisova Cave in Russia’s Altai Mountains, famous for yielding the first remains of the extinct human lineage known as Denisovans, has now produced genetic evidence of a previously unknown large Ice Age mammal closely related to the modern yak, Reuters reported on October 19.

Genomic Sequencing of Fragmentary Remains

Researchers studied 20 bone fragments recovered from Denisova Cave and other regional sites, discovering that the specimens belonged to a distinct bovine species. The physical pieces were too small and fragmentary for visual identification. However, scientists extracted ancient DNA to generate 20 genomes, revealing an evolutionary lineage that split from modern yak ancestors roughly 400,000 years ago.

The oldest specimen dates back approximately 250,000 to 200,000 years, while the youngest sample is about 27,000 years old. Because genetic data alone does not satisfy the requirements for formal taxonomic naming, the team designated the animal “Yak X.”

“It is unusual, especially to recognize a large mammal species from small, unidentifiable fragments,” said evolutionary geneticist Love Dalén of the Centre for Palaeogenetics, a collaboration between Stockholm University and the Swedish Museum of Natural History, senior author of the research published in the journal Current Biology.

Alexandre Gilardet, a doctoral student at the Centre for Palaeogenetics and co-lead author alongside postdoctoral researcher Jonas Oppenheimer, attributed the discovery to modern technological progress. “I’d say that this is related to the advances in the field of ancient DNA, as genetics is a powerful new layer of information applied to ancient materials,” Gilardet explained.

The Mammoth Steppe Ecosystem

Yak X inhabited a vast grassland ecosystem known as the mammoth steppe, sharing the landscape with woolly mammoths, woolly rhinoceroses, horses, steppe bison, aurochs, and large predators including cave hyenas and brown bears. According to Dalén, the animal likely bore a strong resemblance to a modern yak—possessing a sturdy build, horns, long fur, and a shoulder hump—rather than a bison.

Photo: srnnews.com

The evolutionary divergence time between Yak X and modern yaks mirrors the split between the ursine lineages that produced today’s brown bears and polar bears. The discovery illustrates the diverse megafauna that populated Eurasia before vanishing at the close of the Ice Age epoch.

Population Decline and Extinction Timeline

Analysis of the 200,000-year sampling span indicates that Yak X faced a population reduction during a period of warming around 120,000 years ago. The species ultimately went extinct some time after the youngest sample, approximately 27,000 years ago.

The cave where the fossils surfaced also holds immense paleoanthropological significance. In 2008, scientists unearthed a finger bone in Denisova Cave, identifying the Denisovans—extinct cousins of Neanderthals and our own species, Homo sapiens. Modern human populations in Melanesia and Papua New Guinea retain a small percentage of Denisovan DNA from ancient interbreeding.

Researchers suggest that Yak X likely served as a food source for these hominins. “It seems reasonable that Yak X was on the Denisovan menu,” Dalén stated.

More on this story: Troves of Denisovan Fossils and Tools Discovered in Southwest China Cave