Ancient DNA Reveals Extinct Bovine Species in Southern Siberia

DNA analyses of ancient remains have revealed a previously unknown extinct bovine species that inhabited southern Siberia during and even before the last Ice Age. The extinct species was related to modern yaks, but followed a separate evolutionary path for hundreds of thousands of years. The findings are published in Current Biology.

"This is a remarkable discovery of a large extinct species based on small non-diagnostic bones," says Love Dalén, senior author and Professor of Evolutionary Genomics at the Centre for Palaeogenetics, a joint collaboration between Stockholm University and the Swedish Museum of Natural History.

The discovery was made from remains found in Denisova Cave and other sites in southern Siberia. By analysing ancient DNA from unidentifiable bone fragments, researchers from the Centre for Palaeogenetics in Stockholm, the University of California, Santa Cruz, and the University of Vienna generated 20 ancient genomes spanning 200,000 years.

Comparisons with other bovine genomes showed that the fossils belonged to a previously unknown species. The researchers estimate that it began diverging from modern yaks around 400,000 years ago and became fully separated around 250,000 years ago.

A useful comparison for when this lineage originated is the divergence between brown bears and polar bears, which has also been estimated to have occurred around 400,000 years ago. This age overlaps with a particularly strong warm climatic period, which could have prompted population isolation and, ultimately, speciation."

Alexandre Gilardet, one of the lead authors and PhD student, Center for Palaeogenetics

A Region of Remarkable Discoveries

An earlier study on trace amounts of DNA had suggested something special about some of the bone fragments found in and around Denisova Cave. The discovery also has a notable parallel in the same region.

"These findings mirror the discovery of the Denisovans, a group of archaic humans, from a single fossil in 2010 and highlights the Altai region as a possible biodiversity hotspot and refugium across Ice Ages," says Love Dalén.

However, in contrast to the hybridization observed among different ancient humans, the scientists detected negligible evidence for interbreeding between this new species and other bovines in the area, such as steppe bison or aurochs, the extinct wild ancestor of cattle.

Population Changed During a Warmer Period

The results also suggested that a population replacement occurred during the last interglacial warm period, accompanied by a loss of genetic diversity.

"This could reflect the genetic consequences of climate warming around 120,000 years ago on a cold-adapted species. The long time span of our dataset is really rare in ancient DNA, and allows us to look across whole glacial cycles to see how they might have impacted biodiversity," says Jonas Oppenheimer, the other lead author of the study and a postdoctoral researcher at the Centre for Palaeogenetics.

The youngest specimen analysed is around 27,000 years old. The species became extinct sometime after that, but the exact timing and causes remain unknown.

Further Research Needed to Classify the Species

The extinct relative of modern-day yaks was detected at Denisova Cave and in the broader Altai-Sayan Mountains and southern Siberian region. In contrast, modern wild yaks are nowadays restricted to higher elevations of the Tibetan Plateau. Genetic evidence alone is not sufficient to formally classify and name a new species. Going forward, the researchers therefore plan to compare the findings with previously described yak-like remains from the region to determine whether they belong to the same species.