Scandinavia’s aurochs died out from several pressures at once, ancient DNA shows

The wild cattle called aurochs vanished from Scandinavia after a squeeze from several directions at once, according to ancient DNA from bones found in southern Sweden and Denmark. The study, led by Lund University doctoral student Erika Rosengren and published in The Holocene, traces a population that arrived about 11,700 years ago, lost genetic diversity on the way, was cut off when the sea rose, and then faced hunters and a changing forest. Rosengren’s conclusion is that no single cause was enough.

A shrinking gene pool on the road north

Aurochs, the wild ancestors of modern cattle, once ranged across Europe, Asia and northern Africa. They began colonising Scandinavia 11,700 years ago, after the end of the last Ice Age, Lund University’s release on the study says. The newcomers were a subset of the mainland herd, and the DNA shows it: a population bottleneck during the migration reduced genetic diversity, and diversity fell further moving north from mainland Europe through Jutland, then across Zealand and into Scania.

Mikkel-Holger Sinding, an associate professor at the University of Copenhagen and the senior author, called it a textbook example of a bottleneck in evolutionary genetics. A small founding group carries only a sliver of a species’ variation, and every step of an expansion into new ground can strip away more of it.

Rosengren, a doctoral student in historical osteology at Lund University, is the lead author, and the work pairs her bone-based approach with Sinding’s genetics at Copenhagen. That combination is what lets the paper say something about both who the animals were and how many of them there were. Genetic diversity describes the first question; counts of radiocarbon-dated specimens and the age mix of bones at different sites speak to the second. Where the evidence lines up, the case for a compound cause is stronger than either method could make alone.

Cut off by the sea around 8,000 years ago

Earlier work held that the Scandinavian animals became isolated around 10,000 years ago. The new genetic evidence points to contact with the main European population after that date. The land bridge connecting Scandinavia to the European mainland was flooded around 8,000 years ago, and from then on the northern herd was completely isolated.

The straits that formed at that time coincided with intense human hunting, according to the study. The result was a sharp decline in the Swedish population and the complete disappearance of aurochs from Zealand, Denmark. The team drew those conclusions from several lines of evidence: ancient DNA from bones recovered from bogs and archaeological settlement sites, the frequency of radiocarbon-dated specimens and the number of bones over time, and a comparison of the age composition of bones across sites.

Forest, hunters and a last stand in southern Sweden

Southern Sweden’s population hung on in low numbers until at least 6,500 years ago. That is roughly 1,500 years after the land bridge flooded, so the isolated herd did not collapse overnight; it dwindled across many human generations while hunters, a denser forest and a thin gene pool all pressed on it. The release places the final survivors in southern Sweden, while on Zealand the animals disappeared entirely once the straits had formed. The pattern therefore differs from place to place, and the study’s compound explanation fits that unevenness better than any single trigger would. In Sweden, open landscapes gave way to dense forest, which the authors say likely harmed the species and contributed to its disappearance. The researchers related their results to regional palaeoenvironmental and archaeological records, which is how habitat change entered the account alongside genetics and hunting.

The authors conclude that the extinction resulted from combined genetic depletion, human pressure, and habitat fragmentation and degradation. The wider story is long: the decline of aurochs across Europe lasted about 8,000 years and ended with their disappearance from Poland in the 17th century, so Scandinavia’s loss was one early chapter of a drawn-out retreat. Which pressure mattered most is something the release does not rank. Its framing is that bottleneck, isolation, hunting and forest change stacked on one another, and that a herd already thinned by one of them had less room to absorb the next.

Conservation lessons from a lost herd

Rosengren draws a lesson for conservation. Species rarely disappear because of a single factor, she argues, and “conservation plans must therefore be comprehensive and consider multiple stressors at the same time.” She also supports ecological corridors for threatened wildlife in place of isolated nature reserves, an idea that follows directly from the Scandinavian story, where isolation and shrinking numbers made each later pressure more damaging.

As Rosengren put it, “these ancient case studies reveal long-term patterns” of vulnerability and human impact. The article is titled “The immigration history and extinction dynamics of the Scandinavian aurochs (Bos primigenius)” and can be found through its DOI. Lund has released images of an aurochs skull and a reconstruction of an aurochs, and EurekAlert’s archaeology news page gathers related work.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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