gttjohn said:
hi all i just wondered why asian people have different shaped eyes from me and why do african people look so different from me also ,im from ireland ,i am white have blue eyes and a large nose , now i think my skin is white because we get very little sun light my nose might be large because it has to heat up the air as it goes into my lungs( colder climate )i don't know why my eyes are blue though ,i know that african people have dark skin because of the sun but why are there noses wide ,,,, and if its a case that asian people are evolved as a result of their climate and latitude why do other people at the same climate and latitude look different ,please help its very strange
Evolution of different appearance is an intellectual puzzle. Some of the stuff published is speculative.
Some evolutionary divergence is RANDOM not driven by any environmental or other fitness factor.
I respect people's efforts to solve these puzzles, just like any other scientific conundrum, for their own sake.
I remember hearing years ago that the important thing about a big nose was that in a dry climate like a desert it would MOISTURIZE the air going into your lungs (protecting delicate moist lung tissue) and then RECOVER moisture on the way out, which it would then recycle to the next dry air going in.
I remember hearing that the nice thing about a little nose or a flat nose is that it wouldn't be so likely to get frostbite in a cold climate. You want a more spherical layout to minimize surface area, to reduce heat loss. Possibly shorter arms legs fingers too. In extreme cold you don't want things to stick out so much.
Any of this might be wrong. Divergence in human appearance might be largely random.
I heard that darker skin pigmentation evolved four times----like when lighter skin people moved down into southern India their skin became darker. There have been several north to south migrations, and I was told several cases where extra pigmentation evolved.
Blue eyes are a puzzle. It's recessive and I can't think of any simple fitness advantage. Yet some subpopulations in northern Europe are or were blue-eyed to substantial extent. Why would a blue-eye male be interested in mating with a blue-eye female, preferentially, and contributing to support of her children? If he did act on such a preference, what advantage accrued? If there is no advantage, and no tendency to adopt that preference, why wouldn't the recessive gene have gotten scattered and the phenotype have disappeared?
Does anybody know of one or more conjectured explanations. Am I missing an obvious one?
Anyway, good for GttJohn for bringing up a bunch of intriguing human evo and natural selection puzzles.