Mystery beast in ice age cave art revealed as cow-bison hybrid

By Alice Klein

Mystery of the European bison ancestor solved

Rafał Kowalczyk

Cow, bison or both? DNA fingerprinting has revealed that a strange bovine creature painted by European cave artists during the ice age was a cross between a cow ancestor and bison.

Ancient European paintings depict two types of bison: one with long horns, a large hump and robust forequarters, and the other with short horns and a small hump. The former is more common in cave art painted more than 22,000 years ago, while the latter emerges about 17,000 years ago.

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Until recently, the two depictions were thought to reflect a change in art style, because only one species of bison – the now-extinct steppe bison – was believed to have inhabited Europe during this period (move the slider, below, to see the two types of cave art).

Carole Fritz and Gilles Tosello

But DNA sequencing of bones and teeth from 64 ancient bison has revealed that there was another species in the mix. Over 120,000 years ago, interbreeding between steppe bison and aurochs – the now-extinct ancestors of modern cattle – created a hybrid animal.

The finding explains why the two bison forms appear in ancient paintings, and why bison bones uncovered from the ice age are not uniform in size and morphology.

It also helps to solve the long-running mystery of where modern European bison – or wisent – come from. These animals are genetically distinct from American bison, which are descended from steppe bison.

Julien Soubrier at the University of Adelaide, Australia, and his colleagues analysed ancient bison DNA to show that European bison are descended from the hybrid bison. Analysing the DNA of modern animals was not sufficient to understand this process because they went through a genetic bottleneck of only 12 individuals in the 1920s, due to decline in habitat and hunting.

American bison are descended from the now-extinct long-horned steppe bison  

Carole Fritz

Cave art and fossil dating suggest that the short-horned hybrid bison and long-horned steppe bison swapped dominance multiple times from at least 55,000 years ago.

This was most likely a response to major environmental shifts, says Soubrier. “We know there were dramatic changes in temperature occurring every few thousand years in the late Pleistocene,” he says. “It’s possible that when it became colder, the steppe bison migrated elsewhere, while the hybrid found a niche and stayed.”

While it is not uncommon for closely related species like cows and bison to interbreed, it is unusual for the resulting hybrids to survive, Soubrier says.

“Usually, the hybrid has low fertility and is less well adapted because it is half one species and half another so it is not optimised to the landscape,” he says. “Most of the time, it will disappear after one or two generations or get re-engulfed by one of the parent species.”

Journal reference: Nature Communications, DOI: 10.1038/NCOMMS13158

Read more: Reviving Europe’s long-lost beasts through mass rewilding