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Author Topic: Why so few eye colours?  (Read 3363 times)

Offline DoctorBeaver

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Why so few eye colours?
« on: 14/08/2007 10:19:03 »
I was going to ask this in Ozric's thread about eye colour but decided to start a new thread instead.

Why are eye colours limited to so few? Why does no-one have, say, purple or orange eyes?

Obviously, our genes aren't coded for such colours. But why should that be? Is there any evolutionary benefit to the colours we have? Could eyes once have been lots of different colours but those colours have evolved out? Or bred out?


 

Offline dentstudent

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Why so few eye colours?
« Reply #1 on: 14/08/2007 10:52:01 »
I think it has to do with the base blue colour and the amount of melanin the is produced. There are only so many colours that can be created like this, and I guess that purple isn't one of them.

There is this thread from last month.....

http://www.thenakedscientists.com/forum/index.php?topic=8758.0

and particularly this

http://en.wikipedia.org/wiki/Eye_color
 

Offline DoctorBeaver

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Why so few eye colours?
« Reply #2 on: 14/08/2007 11:12:58 »
Thanks, Stuart.
 

another_someone

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Why so few eye colours?
« Reply #3 on: 14/08/2007 12:36:15 »
Actually, in a sense, this question is rather racially specific.  As far as I am aware, people who have no European ancestry only have eyes that are various shades of brown (just as is also true of hair colour).
 

Offline DoctorBeaver

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Why so few eye colours?
« Reply #4 on: 14/08/2007 13:15:56 »
George - I appreciate that, but it doesn't explain the whys and wherefores.
 

another_someone

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Why so few eye colours?
« Reply #5 on: 14/08/2007 13:30:09 »
George - I appreciate that, but it doesn't explain the whys and wherefores.

Yes, but it does seem to indicate that the whys cannot be very strong, as most of the human race make do with a very much narrower range of eye colours; and if there is a why, it can only really apply to Europeans.

It also highlights the fact that as Europeans already have a much wider range of colours than most humans, it seems a bit churlish to demand even more colours :)

I suspect the eye colour in Europeans is little more than a byproduct of reduced melanin in the skin (although I am not aware if other high latitude people's  (e.g. Siberian and Alaskan peoples who do not have Indo-European ancestry) have the same spectrum of hair and eye colour.

What certainly must be the case is that one cannot consider the spectrum of eye colour in the absence of looking at the spectrum of hair colour.
 

Offline DoctorBeaver

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Why so few eye colours?
« Reply #6 on: 14/08/2007 13:36:12 »
Sure, I agree about hair colour.

So, can we assume that eye colour is basically down to blue and melanin?
 

Offline dentstudent

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Why so few eye colours?
« Reply #7 on: 14/08/2007 13:45:15 »
Unless they're albino, in which case there is no pigmentation at all, and you can see the red colouring of the blood in the iris.



 

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Why so few eye colours?
« Reply #7 on: 14/08/2007 13:45:15 »

 

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