Eye colour & Evolution

[Boerseun]

Throughout the human species, eyes coloured other than brown are only to be found amongst people of northern European descent. Why would this be?

 

I have heard plenty arguments that it might have something to do with reflecting the harsh light coming from snowfields, but plenty other humans have lived for thousands of years amongst the snow and haven't come up with the same adaptation. Siberia, North America etc. comes to mind. None of the original inhabitants have coloured eyes. As a matter of fact, friends of mine with blue eyes are more susceptable to headaches caused by glare than friends with brown eyes. So I doubt it, although my sample pool is admittedly small.

 

Could coloured eyes have been selected purely for aesthetical reasons?

 

Matter of fact, I'm hard-pressed to think of any other mammal with coloured eyes, except for maybe the odd border collie with one brown and one blue eye.

 

What gives with eye colour?

[Edella]

Throughout the human species, eyes coloured other than brown are only to be found amongst people of northern European descent.

More common,but not exclusively northern European.Green eyes(for example)are also found from the Middle East to southern Asia.Most of us old enough remember the photograph of Sharbat Gula in National Geographic:http://en.wikipedia.org/wiki/Sharbat_Gula remember her beautiful green eyes.They are common among Pashtuns of Pakistan and Afghanistan.Hungarians have the highest percentage of green eyes of any population, close to 20%.

[DarkColoredLight]

Where was Hitler going with this idea? :)

[InfiniteNow]

The quick answer B is that this was somehow appealing and selected for by members of the opposite sex.

 

Remember the old saying, "the one that sticks out gets nailed hard?"

 

No no no...

 

That was "the nail that sticks out gets hammered down." Never mind. :)

[Boerseun]

The quick answer B is that this was somehow appealing and selected for by members of the opposite sex.

Must be. I can't think of any particular evolutionary benefit. I like the tall nails, though...:)

[ronthepon]

For one thing, eye colour is having a bit complex genetic basis. I'll try to get it out.

 

There are three genes which control eye colour.

 

bey1, bey2 and gey genes they are called.

 

There is a model that uses the bey2 and gey genes to explain the occurances of eye colours. And it's not totally complete, mind.

 

Basically, the bey genes code for blue and brown colours. Brown dominates over blue. (Point: Blue loses the probability game here.:))

 

gey gene codes for green and blue. Here again, blue is not dominant.(Re-Point: Blue loses the probability game here.:doh::eek:)

 

The chances of a blue combination is thus very low in normal cases... only when three genes are coded together for blue, can you get blue eyes.

 

Funny thing about this model is that it says that green is having more chances of getting spread. I've personally seen more blue eyes than green. (Blue= 3, Green= 0 , and I'm not including TV)

 

So, folks, if blue eyes did not seem so beautiful, I dont think the genes coding for blue would remain noticeable at all. :)

 

And, by the way, I'd like to add that brown eyes are so because they have more melanin... the compound which I think is built for the body as a natural anti solar radiation thingy.

 

So I guess blue eyes shall not fare as well in terms of tolerance in the respect...

[Boerseun]

I've personally seen more blue eyes than green. (Blue= 3, Green= 0 , and I'm not including TV)

I, for one, have seen plenty people with green eyes. However, I have never in my life seen someone with three blue eyes!!! Jeez, Ron - how far from that nuclear plant did you say you live? :eek2:

 

On a more serious note, all you've said is true - and I suspect that with more and better movement of peoples around the world, we'll probably see the last blue eyes on this planet in the not-too-distant future...

[ronthepon]

However, I have never in my life seen someone with three blue eyes!!! Jeez, Ron - how far from that nuclear plant did you say you live?

:eek: :) Whoops, forgot the pair picture! ;)

 

 

The only chance for blue eyes to remain significantly noticeable in society is that them blue eyed people spread their genes a lot. The allele won't die out, but the combination will get very very rare.

 

I'm thinking: how would it be if all alleles were equally distributed all over the globe? Then maybe I'd see a green eyed guy or two.

[pgrmdave]

Where I live, there are nearly as many blue eyes as brown eyes. In one of my english classes, somebody once commented on how rare the combination of dark hair and blue eyes was, we looked around and out of about 25 people, 7 had blue eyes and dark hair, and another 4 had blue eyes and light hair. I've seen a few green eyes, but I usually think they're blue unless somebody tells me they're green and I'm looking closely.

[Cedars]

This page discusses vitamins as a potential reason:

 

http://www.thetech.org/genetics/ask.php?id=160

 

A couple of gifs:

 

http://www.gnxp.com/blondehair.gif

 

http://www.gnxp.com/blueeyes.gif

[Raskolnikov]

A possibility which hasn't been considered here is that eye color wasn't selected for at all. It's conceivable that eye color doesn't have any bearing on a person's ability to reproduce, and hence that it's just a fluke that there are so many people with colorful eyes in Europe.

[InfiniteNow]

A possibility which hasn't been considered here is that eye color wasn't selected for at all. It's conceivable that eye color doesn't have any bearing on a person's ability to reproduce, and hence that it's just a fluke that there are so many people with colorful eyes in Europe.

That is an interesting possibility Raskolnikov, however, I have a difficult time seeing how "natural selection" and evolution WOULDN"T be a part of this. Maybe you would elaborate some on your point above? :cup:

 

 

Cheers. :)

[Pyrotex]

A possibility which hasn't been considered here is that eye color wasn't selected for at all. It's conceivable that eye color doesn't have any bearing on a person's ability to reproduce, and hence that it's just a fluke that there are so many people with colorful eyes in Europe.

Many aspects of physiology are clearly selected for by evolution, like our binaural vision, bony ridges to protect the eyes, eye lashes, color vision. However, there is no necessity for ALL aspects of physiology to be specifically selected for.

 

Remember, our genes select for proteins, NOT physiological features. There may be dozens of genes that produce the proteins (in the right order) that result in shape of our eye sockets and faces. Many of those proteins have OTHER consequences as well. Some of those will be Benign/Neutral Features. Most if not all our genes encode for at least one BNF.

 

The trick is, to determine if a feature, like eye color, discriminates our fitness to survive or breed, or attract a mate. Peacock feather colors probably started out as a BNF but increased probability of attracting a mate. Does eye color work that way for Humans? I don't know. They might be a BNF, like the pattern of lines across our palms. :cup:

[DarkColoredLight]

It's only a fluke if it's not proven to be significant. Therefore, Raskolnikov, your nay saying is unnessicary. We all have the ablity to say nay, but most don't have the ablity to say YAY.

 

I'm down for considering that eye color has been an effect of evolution, but haven't found evidence to prove that is can lead to anything else. Other than to aid lust. Don't fornicate with the ugly eyed people and there'll be less ugly eyed people, in theory. Good luck defining "ugly eyed people." ROFL

[Boerseun]

Friends of mine with blue eyes are more susceptable to headaches and even migraines than those with dark eyes. If this is indicative of the larger population, it might even be that blue eyes are detrimental to survival. After all, you can't fight a wolf or a bear or a lion as effectively as a brown-eyed dude if you're struck with a migraine.

 

Any truth to this? How do your blue-eyed friends perform on the headache scale?

[Critter]

 

The trick is, to determine if a feature, like eye color, discriminates our fitness to survive or breed, or attract a mate. Peacock feather colors probably started out as a BNF but increased probability of attracting a mate. Does eye color work that way for Humans? I don't know. They might be a BNF, like the pattern of lines across our palms. :hihi:

 

I've heard it said that we associate blonde hair and blue eyes with youth and thus health which may lead to a subconscious selection based on perceived fitness to breed. A young healthy woman is more likely to successfully carry healthy babies to term.

 

Many people born with lighter hair and eyes have them darken as they age.

 

I used to have rather blonde hair as a child but now it is decidedly brown. Oh and my eyes are hazel! Not sure if they've changed though. They tend to look different shades depending on what I am wearing.

[Tormod]

Any truth to this? How do your blue-eyed friends perform on the headache scale?

 

Blue eyed, migraine plagued, here.