White dogs are prone to deafness too, along with horrible skin issues and they can get sunburned if out in the open on a sunny day.
Polar bears do not have white fur in the same sense. They have black skin with fur that is hollow and pigmentless. They reflect light and scatter it, making them appear white. That's why in zoos etc they are more of a weird yellowish/very off white color. The black skin absorbs the suns heat to keep them warm (since the fur doesn't block the light like it would if it was actually pigmented).
Also people in Africa can still be born with lighter eye colors due to mutations, either because of distant ancestry from Europe somewhere or various syndromes. It's rare, but it happens. Much of the human genome and appearance factors are the results of mutations and spontaneous happenings, evolution and nature often does not care about usefulness, more 'if it lives to breed, it will pass on, even if its not super useful at the time or ever'.
There are breeds of dog that have ONLY white coats, like Samoyeds, Bichon Frise, and Pyrenees, and they're not all deaf. It depends on the exact gene causing the whiteness, not the whiteness itself, that greatly increased risk of deafness is specifically in dogs or cats which have mixed color coats. Like dalmations and border collies. Albinism specifically is linked to a ton of negative health effects regardless of animal, but genes that make an animal white aren't linked to deafness in all animals either. Piebald sheep don't suffer deafness issues, neither do birds with white feather patterns, or humans with vitilgo. Coloring does link to brain development and related issues in almost every animal, but you can't conflate whiteness with deafness as a general rule or one species' pattern problems to a different species altogether.
And while the appearance of harmless mutations is fairly common and inconsequential, the appearance of solely negative traits historically almost never passed on. Useful traits passed on because they were, hey, useful! It helped you survive to adulthood and beyond, letting you have more children and, in social animals, to guide and protect your group even beyond your fertile years. Random mutations often have zero affect and aren't visible, but the major (I.E. visible) ones are almost always hugely consequential. It's not "random mutations and happenings and stuff", the odd genetic once-off fuck up or the rare dredging up of a harmful gene that's been buried and turned off for generations is not the rule in evolution, it's the exception, the mistake. Even traits we see as net negatives today, like diabetes and sickle cell anemia, were actually useful traits actively passed down once upon a time. Sickle cell anemia can make you sick, but it also makes you completely immune to malaria, which is why sickle cell disease is almost exclusive to Africans from areas where malaria infection is very common. Neanderthal metabolisms worked a bit differently than ours, they almost had a form of insulin resistence which allowed them to supply their muscles with higher levels of more bioavailable energy. In freezing temperatures, this along with their body fat distribution (mostly in the belly) allowed them to survive. Today, with our inherently lazy lifestyles and overly carb-heavy diets, these genes cause diabetes. There are plenty more examples of this.
It wasn't until civilization started increasing the lifespans of the genetically screwed up, and people started intentionally breeding plants and animals and keeping them alive despite serious issues, that we started seeing these things get any kind of commonplace. It's simply not natural - all of these domestic cats and dogs with color-related deafness would have died out long ago without human interference, and isn't that literally what this entire thread is about? Horrific, fucked up abominations who live to suffer and make their owners money when they had no business being born that way in the first place? We get upset because we see these smashed and slammed dogs, the radar dish headed horses, the eyeless and deaf double merles, and we know on some deep, inner level that it's just
wrong, even
cruel because it was, to some degree, completely intentional. It goes against the rules of nature and disturbs the empathetic part of us.
As an aside, I believe that person was saying that blue eyes/light skin was less useful in Africa than in other places, not that it doesn't exist there at all. We do know blue eyes/light skin was a helpful adaptation in humans in the far North.
