Their family goes back to Miocene times, around 20-million years ago. During this period roughly fifteen genera existed, most being from Asia. By the late Miocene, some 10-mya, there are seventy new bovid genera, and by the Pleistocene, there were over one hundred. Today, there is about half that number. It is presumed the family evolved from the tropical regions of the world.
Scientists believe both species descend from an ancient relative in India.
As the herds traveled north from India, some went east into Siberia and eventually crossed the Bering land bridge into the New World, while other members of the herd headed west into the European forests. Bison priscus, the immediate ancestor of the European bison went extinct, during the last glaciation. Some scientists believe the European bison was at one time a grazer. During the Ice Ages of the Pleistocene epoch, much of Europe and Asia was covered by glaciers. The remaining landscape consisted of steppes.