Cave paintings match DNA analysis to confirm the existence of the “Higgs bison”

New study fills in the modern European bison’s family tree.

The origin of modern European bison had long been a mystery due to gaps in the fossil records. Now, a study published today in Nature Communication shows that they originated over 120,000 years ago through the hybridization of the extinct steppe bison and the extinct ancestor of modern cattle, aurochs.

Researchers corroborated ancient DNA analysis with 15,000-year-old cave paintings, which depicted the previously unknown hybrid species of bison.

“Finding that a hybridization event led to a completely new species was a real surprise – as this isn’t really meant to happen in mammals,” says study leader Alan Cooper, University of Adelaide. “Normally, when you get hybridization between mammals, the hybrid form isn’t optimized for the environment, and so it gets subsumed back into one of them. You see mixing going on, but it never forms a new species; here it did.”

Modern European bison (or wisent - Bison bonasus) from the Białowieża Forest in Poland. Credit: Rafał Kowalczyk
Modern European bison (or wisent - Bison bonasus) from the Białowieża Forest in Poland. Credit: Rafał Kowalczyk.

Ancient DNA extracted from radiocarbon-dated bones and teeth found in caves across Europe, the Urals, and the Caucasus was used to trace the genetic history of the populations. They found a distinctive genetic signal from many fossil bison bones, which was quite different from the European bison or any other known species.

“The genetic signals from the ancient bison bones were very odd, but we weren’t quite sure a species really existed – so we referred to it as the Higgs Bison,” says Cooper.

Radiocarbon dating showed that the mystery species dominated the European record for thousands of years at several points, but alternated over time with the Steppe bison, which had previously been considered the only bison species present in Late Ice Age Europe.

“The dated bones revealed that our new species and the Steppe Bison swapped dominance in Europe several times, in concert with major environmental changes caused by climate change,” says lead author Julien Soubrier, University of Adelaide. “French cave researchers told us that there were indeed two distinct forms of bison art in Ice Age caves, and it turns out their ages match those of the different species. We’d never have guessed the cave artists had helpfully painted pictures of both species for us.”

The cave paintings were being drawn exactly as bison dominance was switching from the steppe bison to this new hybrid. The art depicted creatures with long horns and large forequarters, like American Bison, or animals with shorter horns and smaller humps, similar to modern European bison.

Reproduction of a painting at the the Pergouset cave (Ardèche, France - ~17,000 years old), probably representing a European bison (or wisent - Bison bonasus) from the hybridisation of Aurochs and Steppe bison. Credit: Carole Fritz and Gilles Tosello
Reproduction of a painting at the the Pergouset cave (Ardèche, France - ~17,000 years old), probably representing a European bison (or wisent - Bison bonasus) from the hybridisation of Aurochs and Steppe bison. Credit: Carole Fritz and Gilles Tosello.

Reproduction of the blurred black charcoal drawing of a steppe bison (Bison priscus) from the Aurignacian period - Chauvet-Pont d’Arc cave (Ardèche, France). Credit: Carole Fritz and Gilles Tosello

Reproduction of the blurred black charcoal drawing of a steppe bison (Bison priscus) from the Aurignacian period - Chauvet-Pont d’Arc cave (Ardèche, France). Credit: Carole Fritz and Gilles Tosello.

“When we contacted the cave researchers their reaction was ‘ah finally we can make sense of what we have been saying to our colleagues for years’: the cavemen could not have painted these bison with only one model,” says Soubrier.

Ironically, the new hybrid bison not only survived but actually turned out to be the largest European mammal to survive the mass extinctions at the end of the ice age.

“Once formed, the new hybrid species seems to have successfully carved out a niche on the landscape, and kept to itself genetically,” says Cooper. “It dominated during colder tundra-like periods, without warm summers, and was the largest European species to survive the megafaunal extinctions.”

What the species almost didn’t survive was the communist revolution: “It almost went extinct in the 1920s, because the game parks that had been preserved under Czarist rule for hunting were all abandoned. The locals went in and killed a lot of these animals for food, so the whole species got down to 12 individuals,” says Cooper.

While numbers are now above 6,000, those 12 individuals formed a “genetic bottleneck.” As a result, the modern European bison is actually quite different genetically from the ancient ancestor identified in the study.

Featured Image courtesy of D. Viat.