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. The European bison, or its immediate ancestor, Bison priscus, lived on these grassy plains. As the glaciers retreated, much of the steppes were replaced by forests, and it is thought that the European bison adapted to its new environment by becoming a browser. The others exist in zoos, private preserves, and breeding stations.