I've been interested in human evolution for many years but have yet to find any coherent information on the the two subjects above.

The first question is, of course, why, when evolving in a diverse continent where evolution chose to keep our fellow primates and particularly our close relatives the apes hairy, did we lose our hair? Hair doesn't preserve or fossilise well over millenia so there are no clues in the record as to when or why this change began or how many millenia it took to completion, bearing in mind that some of us males are still hairy enough for the change to be considered less than complete on a pan-species basis. So, I'd be interested to know if there's any accepted wisdom on the subject.

Secondly, skin colour is something that facinates us, some us for entirely the wrong reasons. Now, I realise that having divested ourselves of hair at some point, skin colour changes from the dark colour amenable to a tropical climate could be stimulated by humans moving out of Africa into climate zones where sunlight was less of an issue and heat retention became a little bit more important. But how long did this take? Is there some information say, in the genome, perhaps some spoor in the mitochondrial dna for instance, that could put a timescale on this? Also, did it happen more than once or simultaneously as different and disparate small groups of our species spread thinly across the European and Asian land masses? And would paler skins revert to darker skins as groups moved into hotter climates. In other words, are we, from a species point of view, flexibly photosensitive from a skin colour point of view?

And finally, I do hope that everybody understands, considering the sensitivity surrounding skin colour, that I am asking this only out of curiosity.