the book i'm reading (jared diamond - the third chimpanzee) suggests that it's more a matter of sexual selection that makes skin colors (and other traits) different. perhaps it started out by people getting lighter as they moved away from africa or something, but that's not what keeps it around. and it's not necessarily a racist idea. we all know that we imprint on people around us when we are young as to whom we will look for as a sex partner/spouse... animals do too. it's simply an expression of that. people biologically want to mate with someone who is genetically close (but not too close) to them. it ensures that mating will be successful. why are there interracial marriages and stuff in spite of this? you don't have to imprint on a family member, just anyone who was around before you turned six.
just some theories the book puts forth. it seems plausible. apparently darwin wrote a second (less popular) book on sexual selection after his natural selection book. at first he kept all sexual selection stuff out of his book because it (the idea of sexual selection) is so explosive...
but that dpoesn't account for so many people. there are vvery white people in the south pacific and aborigines are some of the darkest people around. there are many, many more that break that 'rule' and it simply doesn't match the genetics. it's really more likely that the removed time between the individual 'tribe' and the exit from africa is the highest factor. nothing else really works. your information is the old thought. there is a great deal of newer research. do some more studying before you make a decision.
yes and that would be a good and meaningful argument if all the exceptions to the lighter-higher/darker-middle association were recent migrants... but they simply aren't. there are light-skinned peoples who have been in the south pacific for thousands and thousands of years and the aborigines in australia have been traced to be the next oldest population from africa.
it seems that the skin tone thing is more a genetic separation from africa or something.
well see i was involved in this topic a long time ago and then it was very clear that sexual selection was responsible for skin tone (at least the furtherance of darker or lighter varieties in a given area). but now i might just be arguing.
because caucasians decided that they liked white skin better. that they found it more attractive. lighter people had lighter families and were attracted to other lighter people. it may have been driven by a purpose, but the aborigines haven't lost their melanin and they've been closer to the pole for longer than anyone has been anywhere outside of africa. why?
ok how's this. lighter skinned black women are becoming more and more prevalent while darker skinned black women are becoming rarer. darker skinned black men are becoming more and more prevalent and lighter skinned black men rarer. why? because that is what is (and has been for a long time) viewed as attractive. so it is sexually selected for (by choosing partners esp. that the alternative do not reproduce as often... well this is the general idea.). this has no relationship to latitude.
i think you and i may be arguing different ideas entirely (this is not new...) you may be arguing the purpose and reason for an adaptation and i may be arguing why it was allowed to continue. basically. if no one had found the first dark or light person attractive, they would not have reproduced and the trait would have been lost.
i'm not talking about popular culture in america. i'm talking about partner selection among particular groups. look at black couples... generally, the woman has lighter skin and the man has darker. this is not a new trend brought on by hollywood aesthetic. look at old african-american short stories and novels. amos fortune: free man describes the sister as being very beautiful because of her carmel skin.