text: why are western people white, african people black and indian people somewhere in between?   some evolutionary biologists believe that skin tone is directly correlated with uv exposure.  historically speaking, humans who have lived in relatively 'sunny' places near the equator (e.g. central africa), have been exposed to relatively large amounts of uv.  since fair-skinned humans show a greater increase in mortality in response to increased uv exposure (thanks to skin cancer) than do dark-skinned humans, it logically follows that indivuduals with darker skin should have been more likely to survive in 'high uv' regions.  natural selection at its best!    of course, this theory doesn't explain why fair-skinned people predominate in areas where uv exposures are relatively low.  that is, dark- and fair-skinned individuals should, according to this logic, both have similar survivability rates in an area where uv exposure is not a major cause of mortality.  and yet, in countries like norway or scotland, where uv eposures have historically been quite low, all natives seem to have extremely low melanin levels.  do fair-skinned people somehow have increased survivability in these regions?  i suppose it's possible, but i can't quite see how.  or perhaps natural selection isn't only force at work? i'd be interested if anyone else could shed some light on the issue. :)