The European bison is a bovine animal similar to the American bison but from the Eurasian continent.
European bisons, according to DNA analysis, carry aurochs genes, so it is likely that their ancestors interbred.
At one point the European bison has been hunted to extinction, but enough live specimens remained in captivity that it is was possible to reintroduce them to the wild.
While European bison numbers are up in the wild, and the species is no longer considered to be endangered, the species has lost a significant part of its genetic diversity, which can hurt them on the long run.
Still the story of the European bison appears to be one of the few success stories, when humans managed, in the last minute, to reverse the damage they have done.
Further Readings:
Bison bonasus on ADW.
The Remarkable Story of How the Bison Returned to Europe.
European Bison – European Bison Conservation Center.