 A high level of genetic similarity has been found among North American cougar populations , suggesting they are all fairly recent descendants of a small ancestral group . Culver et al. propose the original North American population of P. concolor was extirpated during the Pleistocene <unk> some 10 @,@ 000 years ago , when other large mammals , such as <unk> , also disappeared . North America was then <unk> by a group of South American cougars . 
