Famous Siberian cave reveals remains of Ice Age mammals

A yak pasta in the mountains in theAlmaty 1st of November 2009. — Photo: REUTERS/Shamil Zhumatov A cave in Siberia, already famous for revealing the first traces of an extinct human lineage called Denisovans -- who once roamed widely across Eurasia -- now presented evidence of a large mammal from the Ice Age hitherto unknown, closely related to the current yak. The researchers claimed to have discovered small bone fragments of the animal in the Denisova Cave, in the Altai Mountains, in southern Siberia, Russia, and obtained DNA indicating that these remains belonged to a bovine species distinct from other already known, both living and extinct. In total, the researchers studied 20 bone fragments of this species -- 14 from the Denisova Cave and 6 from other sites in the region. The oldest specimen dates back to about 250 thousand to 200 thousand years ago, and the most recent, about 27 thousand years ago. The bones themselves were so fragmented that their shape alone did not reveal that they belonged to a large mammal hitherto unknown. But the researchers managed to generate 20 ancient genomes from the bones, and these showed that it was a unique species, whose evolutionary lineage diverged from the ancestors of the current yak about 400 thousand years ago. “It is unusual, especially to recognize a large mammal species from small and unidentifiable fragments,” said the evolutionary geneticist Love Dalén, from the Center for Paleogenetics -- a collaboration between the University of Stockholm and the Swedish Museum of Natural History -- senior author of the research published in the journal Current Biology. READ ALSO: “I would say this is related to advances in the field of ancient DNA, since genetics is a new and powerful source of information applied to ancient materials,” said Alexandre Gilardet, Ph.D. from the Center for Paleogenetics and co-lead author of the study, along with Jonas Oppenheimer, postdoctoral researcher at the Center for Paleogenetics. Genetic evidence alone is not sufficient to allow the attribution of a scientific name to a new species; therefore, the researchers are calling this species “Yak X”. The Ice Age Landscape Dalén said that Yak X lived alongside other bovids, including the steppe bison and the auroch, the wild ancestor of the domesticated cattle. He also shared the Ice Age landscape with woolly mammoths, woolly rhinoceroses, horses, and large predators, such as cave hyenas and brown bears, Dalén said. “I would expect it to look more like a yak than a bison, given its close relationship with modern yaks,” said Dalén. Yaks are robust animals, with horns, long fur, and a hump on their shoulders, somewhat similar to a hairy cow. The males can weigh up to a ton. Wild yaks live exclusively in the highest altitudes of the Tibetan Plateau. The discovery of Yak X deepens the understanding of the diversity of the large mammals of the Ice Age and adds another species to the long list of those that disappeared at the end of that era. “Based on the long period of 200 thousand years of our sampling, we can observe that the species may have suffered a population decline during a warming period about 120 thousand years ago and went extinct some time after our most recent sample, about 27 thousand years ago,” said Oppenheimer. The vast Siberian expanse was a grassland ecosystem called the mammoth steppe, as known for its largest inhabitants. Most of the region was free from the immense layers of ice that covered large areas of North America and Europe. The lineage of Yak X diverged from the ancestors of modern yaks at about the same time as the evolutionary split between the ursine lineages that gave rise to the current brown bears and polar bears. READ ALSO: The Denisovans It was in the Denisova Cave, in 2008, that scientists unearthed a finger bone that provided the first evidence of the existence of the Denisovans, cousins of the Neanderthals and our own species, Homo sapiens. Since then, more remains of Denisovans have been discovered in the cave and in several remote regions of Asia. Some modern human populations, especially those in Melanesia and Papua New Guinea, carry a small percentage of Denisovan DNA, indicating interbreeding with Homo sapiens before the Denisovans disappeared in circumstances that are not yet well understood. The Denisovans were hunter-gatherers who survived in many different types of environments. The Yak X species may have been among the prey they hunted. “It seems reasonable that Yak X was part of the Denisovan diet,” said Dalén. READ ALSO: