Science Questions

How did blue eyes evolve?

Sun, 13th Feb 2011

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@S_Mason asked:

We do not evolve from apes, the species you spoke of died out thousands of years ago, they also have a different DNA. if we evolve from apes who all have brown eyes where did blue eyes come from?


Diana -   I would say that actually, yes, we are all in the same family of apes.  A common misconception is that people will say that we evolved from the chimpanzees or the gorillas, but of course, that's not true.  We co-exist with chimpanzees and gorillas, who are also apes, but we have a common ancestor that existed several million years ago.  Now, the species I spoke about was Australopithecus afarensis.  That lived somewhere between 3.7 and 2.9 million years ago and almost certainly had quite different DNA to us.  But, then again, humans have different DNA to each other.  There’s no way we can actually measure what the differences of DNA between ourselves and afarensis would’ve been because of course they're fossils, and there's not going to be much DNA left hanging around there, I don't think.  As for the blue eye adaptation, I believe that mutated sometime around 10,000 years ago and of course, that mutation would’ve occurred in northern European farming populations almost certainly.

Chris -   To add to this, we've also got the point that - because he makes a thing about eye colour - why don't we look at skin colour?  Because chimpanzees and extant apes have pale skin, if you go back 6 million years to the ancestor we last shared with them, that also had pale skin. But the earliest generations of humans had dark skin because they were hairless and therefore needed to evolve some kind of protection against the sun.  When they then leave Africa and come up to northern latitudes and low latitudes later, obviously, then they re-evolve to have paler skin because if you have that dark skin up here where the sun doesn't shine very often, you don't make enough vitamin D, and your bones suffer, and there’s insufficient sunlight for the loss of folic acid, which is a reason to be dark in Africa, for that really to be a problem.

Diana -   Exactly and this whole thing hinges on mutations, on people giving rise to new generations or people who were slightly different.  And so, inevitably, you are going to get people with different shades of skin and different eye colours.  It will happen eventually over a long enough period of time.

Chris -   The evidence for that, just look at how different humans are across the whole surface of the Earth, from one geography to another; and there’s the evidence that we’re extremely genetically diverse, and we’re all the same species.  So, add a few more million years into the mix, and anything can happen.

Diana -   Who knows what we’ll end up looking like?!


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