The 'Higgs Bison'

The two living species of bison (European and American) are among the few terrestrial megafauna to have survived the late Pleistocene extinctions. Despite the extensive bovid fossil record in Eurasia, the evolutionary history of the European bison (or wisent, Bison bonasus) before the Holocene (<11.7 thousand years ago) remains a mystery. 

More than 15,000 years ago.Ice Age cave artists recorded ancestral bison and cattle species. Bovids in Europe at this time consisted of two forms: the Aurochs (Bos primigenius), ancestor of modern cattle, and Steppe bison (Bison priscus). Interestingly , the cave paintings depict bison with either long horns and large forequarters (more like the American bison, which is descended from the Steppe bison) or with shorter horns and small humps, more similar to the wisent. It turns out the artists had also recorded a hybrid species. This mysterious new species, known affectionately by the researchers as the Higgs Bison because of its elusive nature, originated over 120,000 years ago through the hybridisation of the Aurochs  and the Steppe Bison. 

Ancient DNA research by an international team has revealed that the Higgs Bison eventually became the ancestor of the modern wisent, which today survives in protected reserves such as the Białowieża forest between Poland and Belarus. The team studied ancient DNA extracted from radiocarbon-dated bones and teeth found in caves across Europe, the Urals, and the Caucasus to trace the genetic history of the populations. Radiocarbon dating showed that the Higgs Bison 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.

Once formed, the new hybrid species seems to have successfully carved out a niche on the landscape, and kept to itself genetically. It dominated during colder tundra-like periods, without warm summers, and was the largest European species to survive the megafaunal extinctions. However, the modern European bison looks genetically quite different as it went through a genetic bottleneck of only 12 individuals in the 1920s, when it almost became extinct. That's why the ancient form looked so much like a new species.