How did racial differences evolve?

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Jason Fong

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How did racial differences evolve?
« on: 14/10/2009 14:30:04 »
Jason Fong asked the Naked Scientists:
Hi Chris,

I'm currently an economics student and whilst I fully understand evolution when applied to most of the natural world, what confuses me are the origins of certain traits and aspects of human appearance. I have a few questions(along with my hokey armchair theories) all around the same subject matter. Oh and please forgive me if I mix up biological terms or just talk nonsense, I've not taken the subject since my GCSEs!

For example, we as a species originated in Africa millions of years ago, and subsequently spread to the other parts of the globe. Asia, Europe, America etc. I can understand why significant racial differences such as the variety of skin colours we have might come about, e.g. melanin is biologically costly to produce, if there is no environmental need(heat absorption or camouflage) for it eventually people who produce less melanin will tend to reproduce more than those who produce more melanin.

However I don't understand how in evolutionary terms, how key racial traits such as type of hair, facial features and even intelligence can start to differentiate themselves across different races. Take the hair of an African guy and a Chinese guy for example, as I understand black curly hair is curly because the hair strands are flatter and more elliptical than typical hair strands, and this is environmentally useful since it traps more air(heat energy) due to its curliness and it absorbs(and emits) more radiation due to its colour. However Chinese hair is both black and straight, its black colour would suggest that the absorption(and emission) of heat is a priority for the body(head), however the straightness of their hair, and pale skin would suggest otherwise. I know that evolution has no such thing as intent but why does there seem to be a conflict of interest?

What causes the general facial structures which make an African guy and a Chinese guy easily distinguishable from a Caucasian or Indian guy. Are these racially generic facial shapes(trends) brought about by simple evolutionary biology? Or are they a result of some sort of social unnatural selection, in the sense that culturally a society might deem say straight hair as an attractive trait in a partner so eventually that trait dominates. Or that society comes to a consensus that high cheekbones are better than low ones, feminine features in a male are desirable, bigger lips are better than smaller ones, paler skin is more attractive than dark skin and so on.

I read that humans are one of the two animals which has hair which appears to never stop growing at a certain length, as we have hair just for the purpose of grooming, could this social aspect be a factor into the whole straight and curly hair issue?  Then again our hair would mechanically fall out at a much shorter length if we didn't artificially prolong their utility with shampoos and better diets/lifestyles.

Or could it be that genes which are dominant in one race are actually recessive in another race. In the way that since people with similar features are breeding with each other, certain physical features are somehow accentuated and become more apparent. I'm a little hazy on my biology here, but dogs are just a product of unnaturally selected wolves so I guess it's possible.

Also is the racial stereotype which you hear bound around a lot nowadays, that Chinese/asian people are more clever/clever in certain areas(such as maths) than other people, a result of social dynamics or evolution. I read that the chinese counting system which is more logically mathematical helps children grasp the ideas of decimals and sums faster than their western counter parts, could this in turn physically alter the intelligence of subsequent offspring or is it entirely a social thing?

As you've probably thought this could be a sensitive set of questions to discuss on your show so I won't be too miffed if you decide to not answer it on air.

Thanks for your time Chris, I look forward to reading or listening to your response, and of course keep up the great work on the excellent podcasts!

What do you think?


Offline neilep

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How did racial differences evolve?
« Reply #1 on: 14/10/2009 15:45:51 »
In short..Geography and Climate .........(i think !)

Now for some peeps who know how to explain it further !..and perhaps give ewe the right answer !
Men are the same as women, just inside out !