How did we evolve eye colour?

Chris Smith put this to zoologist Chris Basu...

Chris B - The question of which apes did human beings evolve from? That’s a big, big, big question and that’s the reason why this area of science, the study of human ancestors, is such a big and active area. That’s because the honest answer is we don’t yet know.

We do know little pieces of the puzzle. So we know that by looking at DNA the last common ancestor between human beings and chimpanzees lived about 7 million years ago and when we look at fossils from around this time we do find that these fossils do have things in common with human beings.

So fossils from West Africa are starting to show the really early signs of things like bipedalism. But one of the challenges of this area is, when we look at these fossils, we’re not looking at our direct ancestor. It’s like if I’m studying a photograph of my great uncle and I’m trying to imagine what my great grandfather looked like. So it’s one of these challenges that we’re trying to work out what our ancestors looked like from our distant relatives.

But going to the question of the eye colour yes, our early human ancestors likely had brown eyes. And the diversity in the eye colour that we see today comes from mutation in our genome. So, for example, the mutation that give us blue eyes, we can pin down to about six thousand years ago. And perhaps one of the reasons we do see a lot of variety in eye colour in humans is because of our white sclera. So the whites of our eyes really makes our eyes really stand out, really punch out when you look at them and that’s probably because of things like non-verbal communication, so facial features, are really important in our society. That’s we’re drawn to look at eyes.