When bears stand on their hind legs they are pretty 'man-shaped' apart from the muzzle. Maybe there is some kind of chromosomal disorder amongst bears that occurs every now and again, which affects the look of the face and maybe some other characteristics in much the same way as Down's syndrome has wide ranginng but characteristic effects on humans.
That would explain why attempts to find a breeding population have proved fruitless even though sightings are made on a fairly regular basis down through the decades. There would be no breeding population and there is no need to look for an explanation of why such a gene would remain in the population and not be removed by natural selection. This is because the syndrome would be a result of a breakdown of the normal genetic mechanisms rather than the effects of a particular gene.
That would explain why attempts to find a breeding population have proved fruitless even though sightings are made on a fairly regular basis down through the decades. There would be no breeding population and there is no need to look for an explanation of why such a gene would remain in the population and not be removed by natural selection. This is because the syndrome would be a result of a breakdown of the normal genetic mechanisms rather than the effects of a particular gene.