No Most mutations wouldn't be obvious. They might affect metabolism or some enzymatic pathway. (Isn't it curious that Junior likes cow's milk?) These seem un

No Most mutations wouldn't be obvious. They might affect metabolism or some enzymatic pathway. (Isn't it curious that Junior likes cow's milk?) These seem unlikely to be discriminated against. Even mutations affecting visible features might be gradual and require the accumulation of many mutations over generations and generations to become pronounced. (Height, skull size, dentition) Some features might be due to a single mutation and could be pronounced and obvious in new members of a group. Red hair might be one of these mutations, and perhaps some red headed children were spurned or killed or discriminated against by their group. But this wouldn't easily eliminate red hair. It is caused by a recessive gene so carriers of a single gene won't be redheads themselves. If two non-redheaded carriers of the gene have 4 children on average three will carry the red hair gene but only one will have red hair because they carry two of the genes. I find red hair attractive, and apparently so did our ancestors: red hair was not eliminated from the gene pool. Curiously, humans have evolved to retain juvenile features. This neoteny, as it is called, has resulted in smaller jaws, flatter faces, hairless bodies, larger eyes, and other features. Selection for these traits may be due to our instinctive desire to care for infants. Likewise mutations in the other direction, smaller head to body ratio, etc., could very well have suffered from negative selection pressures as you have raised in your question. I think these speculations are interesting and the answers are not obvious. Why, for example, has a trait such as mental illness, clearly having a negative impact on survival, not been eliminated? Is it just so tricky to get a brain assembled into a mind that there are inevitable difficulties? Or is it caused by interactions with viruses during development that are evolving in competition with us? What about nearsightedness? I wouldn't have been a very good hunter of distant game. Why hasn't myopia been eliminated as a trait? Is it because as I age I can still read without reading glasses? Were there elderly nearsighted arrowhead makers, able to do close work despite age related presbyopia, trading their skillfully made arrowheads for food? One additional observation. Your question mentions non-whiteness, suggesting that more pigmented skin is a mutation. It appears that it is just the reverse. Human evolution started in Africa where pigmentation would have been important because of the more intense sunlight. Lack of pigmentation would be a disadvantageous mutation. So the more accurate question is why would anyone even have light skin? The answer I've heard is that for humans groups that had migrated out of Africa to latitudes that had weaker sunshine, lighter skin allowed for better absorption of the weaker sunlight for the production of vitamin D.