At the End of the Nineteenth Century, American Bison Were

Short Answer

At the end of the nineteenth century, American bison were bred with domestic cattle in an attempt to rescue their declining populations. The resulting hybrids were bred with true bison. After many generations, animals that look like bison may still contain some ancestral cattle DNA. Conservation geneticists have considered isolating bison that show no cattle ancestry by the mitochondrial DNA test and breeding them to maintain a group of "pure" bison. The number of bison with no cattle genes is estimated at 15,000 animals (The New York Times, 23 April 2002, "Genetically, bison don't measure up to frontier ancestors"). List one reason this might not be a good idea.