Possible red eyes?

What it says on the tin, would it be possible for humans to develop red eyes, in addition (or instead of) blue, gree, brown..... we have now.

Feel free to toss in any POD but humans have to develop to OTL form though different colouring is OK (skin, hair.....)
 

NothingNow

Banned
What it says on the tin, would it be possible for humans to develop red eyes, in addition (or instead of) blue, gree, brown..... we have now.

Feel free to toss in any POD but humans have to develop to OTL form though different colouring is OK (skin, hair.....)

It happens as it is. Occular Albinism causes the irises to have a distinctly red hue, among other things.

That said, if you want it to be a mostly benign condition instead of a distinctly disadvantageous one, you'll need to cook up a way to get massive amounts of of Pheomelanin (it's what makes hair and lips red) in the iris, and not much else while still keeping the iris opaque enough to function properly.

You could probably handwave it as a freak genetic mutation (yay!), but would then need to work the founder effect to get it in a large enough population so it doesn't get washed out, since it doesn't give an advantage to survival. Maybe some caveperson thinks red eyes are sexy, or a sign of a good shaman, and things go from there?
 

Curiousone

Banned
It is possible.

Blue eyes have less protection against the Sun than Brown. They were evolved like skin of lighter complexion in higher altitudes. By very random chance it seems

Red eyes would be similar but even more so. Perhaps an ATL can feature naturally red-eyed Nordic blonds traveling to the tropics in aviator sunglasses, SPF 45+.


http://en.wikipedia.org/wiki/Eye_colour#Red_and_violet

Albinism.

"allowing the blood vessels to show through"

http://en.wikipedia.org/wiki/Eye_colour#Blue

In 2008, new research suggested that people with blue eyes have a single common ancestor.
..
The authors concluded that the mutation may have arisen in a single individual probably living in the northwestern part of the Black Sea region 6,000–10,000 years ago during the Neolithic revolution.
..
"In Estonia, 99% of people have blue eyes,"
 
You can give red eyes to some Siberian people. If you want that red eyes become more than just a curiosity, you can give red eyes to Turks or Mongols, remember the population bottleneck caused by Genghis Khan.
 

NothingNow

Banned
Damn you beat me to it.

That I did. Still, you used data. Which is better.

Anyway, having the genes for Pheomelanin production in eyes while providing proper opacity for the iris opens up a whole lot of other things. Combined with Lipochrome it'd make for some cool things.
Hilariously, it seems like violet eyes are much more difficult, since there's no blue pigment normally produced, and most eye colors are actually an effect of Rayleigh scattering.
 

SunDeep

Banned
You did say any POD, right? So maybe in the far future (perhaps with the approval of Project Orion in the 1960's as the POD) the mutation could develop on a colonised planet circling a red dwarf, like Gliese 581g, as an adaptation to the lower intensity of the star in the visible light spectrum?
 
I don't think it is biochemically possible for mammals to have red irises. Plenty of birds, reptiles, amphibians and fish have them, but I cant think of a single mammal - even though many have red fur. This may be in part because human eyes have a natural structural color of gray/blue when depigmented. Most people with blue or green eyes have elevated pheomelanin already, but this structural color overrules any reddish tint.

On the other hand, more prevalent and dramatic amber seems plausible. Plenty of mammals have eyes with more yellow in them than ours do, and people already do have amber eyes (although it's rare, and more a variant of brown than anything).
 

NothingNow

Banned
what about other colours? Yellow? Orange?

A yellow-Amber is possible, with the right amount of Eumelanin (aka, almost none and all brown, with a decent amount of variation in various parts of the iris to get the desired effect.) Orange, I just don't know.

As it is, really thinking about it, Pheomelanin-rich 'Red' eyes would generally range from a series of Greyish-pinks like #DEA5A4 (which would suck as much as having extremely pale blue eyes does IOTL) and violets (like #B57EDC) to very dark reds like Japanese Carmine and web-safe Maroon. Even then, the actual basic color is also dependant on the levels of both kinds of Eumelanin (brown and black) in the iris. And then Ambient light levels combine with that to produce the observed color.

And as a fun fact, under certain light conditions, light blue and grey eyes can tend to appear violet or pinkish anyway.

EDIT:
Most people with blue or green eyes have elevated pheomelanin already, but this structural color overrules any reddish tint.
Which is why you'd need much more of it, and much less Eumelanin. Green Eyes are actually caused by a stroma that is fairly brown Eumelanin-light, with very little black Eumelanin to go with it, and the blue-tone from Rayleigh scattering.

Any 'Red' Eye gene would likely produce reduced levels of eumelanin production in the stroma while elevating pheomelanin production, which would create different tones than we see now.
(But there's no way to really test this without experimentation on cats or something.)
 
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