Russell Means said this quote

Golden eagles don`t mate with bald eagles, deer don`t mate with antelope, gray wolves don`t mate with red wolves. Just look at domesticated animals, at mongrel dogs, and mixed breed horses, and you`ll know the Great Mystery didn`t intend them to be that way. We weakened the species and introduced disease by mixing what should be kept seperate. Among humans, intermarriage weakens the respect people have for themselves and for their traditions. It undermines clarity of spirit and mind.