Scientists Found an Ice Age Yak X Cousin in Denisova Cave

A little-known Siberian cave has produced a new extinct mammal. Researchers analyzing 20 bone fragments found in Denisova Cave in the Altai Mountains of southern Siberia found DNA showing the remains belonged to a bovine species distinct from every other known species, living and extinct. Fourteen of the fragments came from Denisova Cave itself and six from other sites in the broader region, according to reporting by ReutersThe team is calling the animal Ice Age Yak X, and the study was published in the journal Current Biology. The team generated an ancient genome from each of the twenty fragments, building a picture of a whole population rather than a single stray animal.

Denisova Cave is already famous in palaeontology. It yielded the first remains of the Denisovans, an extinct human lineage that once ranged widely across Eurasia. The cave's cold, stable conditions preserve genetic material for hundreds of thousands of years, which is why researchers keep returning to its sediment layers and museum drawers full of bone shards that no morphologist could name by shape alone. Genetic analysis of those fragmentary bones has now revealed a distinct bovine lineage that lived in Siberia before disappearing around the end of the Ice Age, and the cave once again proves to be one of the richest archives of vanished life on the planet.

DNA did what eyes could not

The bones of Ice Age Yak X were so fragmentary that their physical shape gave no hint they belonged to a previously unknown large mammal. Instead, the researchers extracted ancient DNA and generated a genome from every fragment. The genetic data showed a unique species whose evolutionary lineage diverged from the ancestors of the modern-day yak approximately 400,000 years ago. That split means Ice Age Yak X was a close cousin of the modern yak, not a direct ancestor: the two branches went their separate ways while both lineages kept evolving. Love Dalén, an evolutionary geneticist at the Centre for Palaeogenetics, a collaboration between Stockholm University and the Swedish Museum of Natural History, was the senior author of the paper.

Dating puts the oldest specimen at roughly 250,000 to 200,000 years old, and the youngest at about 27,000 years old, meaning the lineage was still roaming Siberia near the end of the last Ice Age before disappearing. That late date matters because many large Ice Age mammals vanished in the same window, so Yak X may have faced the same mix of pressures. That long survival through repeated glaciations makes its extinction a question the team wants to pursue, since climate shifts, habitat loss, or human pressure could each have played a part.

Why the discovery matters

Dalén said it is unusual to recognize a large mammal species from small, unidentifiable fragments, and credited the result to how far ancient DNA technology has come. Alexandre Gilardet, a doctoral student at the Centre for Palaeogenetics and a co-lead author of the study alongside postdoctoral researcher Jonas Oppenheimer, said genetics has become a powerful new layer of information applied to ancient materials. The Ice Age Yak X result matters because natural history museums hold drawers of bone fragments too broken to classify by eye, and each one is now a potential unknown species. Sediment samples add another frontier: DNA preserved in cave dirt has already identified animals that left no recognizable bones behind, which means the list of extinct mammals may grow simply by re-reading ground that researchers have already walked.

Genetic evidence alone is not sufficient to give the animal a formal scientific name, so Ice Age Yak X is a provisional working name rather than an official label. The researchers wrote in Current Biology that more complete skeletal material would be needed before the species gets its permanent name. Finding that material may take patience, since the fragments identified so far survived only because cave conditions froze them in time. Until then, Yak X is a reminder that the Ice Age still has mammals hiding in plain sight, one DNA extraction at a time.