What makes the discovery extraordinary is the humble nature of the evidence. The species was not identified from a complete skeleton, a horn core, or any diagnostic morphology at all, but from small bone fragments that could not be assigned to any known animal by sight. This is a remarkable discovery of a large extinct species based on small non-diagnostic bones, says Love Dalén, senior author of the study and Professor of Evolutionary Genomics at the Centre for Palaeogenetics. Only through the extraction and sequencing of ancient DNA preserved within the fragments could the team determine that the bones belonged to an animal unknown to science.

The remains were recovered from Denisova Cave and other sites in southern Siberia, a region that has become one of the most important windows into the Ice Age world. By analysing ancient DNA from the unidentifiable fragments, the researchers succeeded in generating twenty ancient genomes spanning an astonishing 200,000 years of evolutionary time. Datasets of this temporal depth are exceptionally rare in ancient DNA research, and they allow scientists to track how populations changed across entire glacial cycles rather than merely sampling a single moment in the past. When the team compared these genomes with those of other bovine species, the result was unambiguous: the fossils belonged to a lineage entirely distinct from any bovine described to date.

The genomic comparisons allowed the researchers to estimate when this mysterious lineage split from its closest living relatives. According to their analysis, the species 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, says Alexandre Gilardet, one of the lead authors and a PhD student at the Centre for Palaeogenetics. This age overlaps with a particularly strong warm climatic period, which could have prompted population isolation and, ultimately, speciation. In other words, a prolonged warm interval may have fragmented ancestral yak populations, cutting groups off from one another long enough for them to evolve into separate species.

The parallel with another landmark discovery from the very same landscape is striking. Denisova Cave is already world-famous as the site where, in 2010, DNA analysis of a single finger bone fragment revealed the Denisovans, an entire group of archaic humans previously unknown to science. 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 Dalén. The idea that the Altai Mountains and surrounding areas served as a refugium, a place where populations survived through climatic extremes and diversified in isolation, gains considerable weight from the fact that two entirely new branches of the tree of life, one human and one bovine, have now been identified from the same region largely through genetic rather than anatomical evidence.

Yet the new bovine species appears to have had a very different evolutionary history from the Denisovans in at least one crucial respect. When different groups of archaic humans met in Eurasia, they frequently interbred, leaving traces of hybridization in the genomes of their descendants, including present-day people. In contrast, the scientists detected negligible evidence for interbreeding between the new species and other bovines living in the area at the time, such as the steppe bison or the aurochs, the extinct wild ancestor of domestic cattle. This reproductive isolation reinforces the conclusion that the animal was a genuinely separate species rather than a regional population or hybrid lineage, and it suggests that biological boundaries between these large Ice Age herbivores remained firmly in place even when their ranges overlapped.

The deep genomic time series also captured dramatic changes within the species itself. The results 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, says Jonas Oppenheimer, the other lead author of the study and a postdoctoral researcher at the Centre for Palaeogenetics. 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. The last interglacial, a period when global temperatures were warmer than today in many regions, appears to have squeezed cold-adapted fauna into smaller refugia, eroding their genetic variation and reshuffling populations in ways that left permanent signatures in their DNA.

The timeline of the species’ disappearance remains only loosely constrained. The youngest specimen analysed in the study is around 27,000 years old, placing the animal squarely within the last Ice Age, at a time when mammoths, woolly rhinoceroses, steppe bison and other megafauna still dominated the Siberian landscape. The species became extinct sometime after that point, but the exact timing and the causes of its demise remain unknown. Whether it succumbed to rapid climate warming at the end of the Pleistocene, to the spread of humans through the region, to competition with other large herbivores, or to some combination of these pressures is a question that future discoveries may help to answer.

Geographically, the extinct relative of modern-day yaks was detected at Denisova Cave and in the broader Altai-Sayan Mountains and southern Siberian region. The contrast with its living relatives is telling: modern wild yaks are today restricted to the high elevations of the Tibetan Plateau, where they survive in some of the most extreme cold environments on Earth. The new findings suggest that yak-like bovines once occupied a much broader distribution across mid-latitude Asia, and that southern Siberia harboured a distinct lineage that has since vanished without leaving any obvious trace in the fossil record as traditionally studied.

A formal species name, however, must wait. Genetic evidence alone is not sufficient to formally classify and name a new species under the rules of zoological nomenclature, which require comparison with diagnostic physical material. Going forward, the researchers therefore plan to compare their genomic findings with previously described yak-like remains from the region, in the hope of determining whether any of those fossils belong to the same species. If a match is found, the scattered bones in museum collections could suddenly acquire a new identity, and the ghost bovine of the Altai could finally receive both a name and a face. For now, the discovery stands as a powerful demonstration of how ancient DNA can reveal entire species hidden inside fragments too small and too degraded for traditional identification, and as a reminder that even the best-studied Ice Age ecosystems still hold surprises waiting in the sediment.

Subject of Research: Ancient DNA analysis of Ice Age bovine remains from Siberia revealing an extinct yak-relative species

Article Title: Previously unknown extinct bovine species discovered in Siberia

Article References: Previously unknown extinct bovine species discovered in Siberia. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: ancient DNA, bovine, yak, Siberia, Denisova Cave, Ice Age, extinction, speciation, Altai Mountains, palaeogenetics, Current Biology, megafauna