The scientists had jokingly nicknamed the hybrid beast – the Higgs bison.
Like the particle long sought by physicists, they were not sure it existed, due to a gap in the fossil record.
“Finding that a hybridisation event led to a completely new species was a real surprise – as this isn’t really meant to happen in mammals,” said Prof Cooper.
“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.”
Radio carbon dating of the bones revealed that each of the bison had been dominant at different times, due to changes in the environment.
The scientists found the age of the cave paintings matched this flux.
The cave paintings came from sites across France and Spain, including Grotte de Lascaux in the Dordogne and Grotte Chauvet-Pont d’Arc in the Ardeche.
Paintings from more than 18,000 years ago show creatures with long horns and hefty forequarters, like the American bison, which is descended from the Steppe bison.
However, more recent paintings (about 12,000 to 17,000 years old) show animals with shorter horns and smaller humps, similar to modern European bison.
“It looks like the cave artists were actually spotting the difference and actually recording them in their art,” said Prof Cooper.
“And so the Higgs bison has been hiding in plain sight for all the time, and no-one recognised. The variation in cave art was put down to cultural or stylistic differences.”
