Humans already started it when we killed off all the largest land animals outside of Africa 13 000 years ago. You know Elephants and Mammoths were found all over earth before then. Thank humans for the lack of Elephants in America.
As far as I know, there's only one group of pure-bred bison. All of the other bison in the U.S. are effectively genetic hybrids between bison and cattle.
There were other, pure bred herds (e.g. Yellowstone, Canadian, etc).
And as this points out, the remnants of hybridization efforts were minimal, even in the direct Goodnight, Jones, and Bedson herds:
>> "These brief experiments form the basis for the controversy surrounding cattle genetic introgression in bison today. A study conducted for her Doctoral Dissertation by Lauren Dobson of Texas A&M University concluded that bison descended from those herds have the equivalent of 1 percent cattle genetic introgression within their genome."https://bisoncentral.com/advantage-item/ranchers-role-in-bis...
At the end of the day, bison didn't take (genetically or economically) to hybridization, as the hybrids were less hardy than pure bred bison.
