Why is human skin limited to shades of light and dark?

vastly different eye colors, and hair - red, white, black, brown, all in our own species, but no "real" range in skin colour? why do other species come in so many colours but not our own?

Why is human skin limited to shades of light and dark?

Great question. I guess the simple answer is that we and our ancestors don't have any genes for skin color other than those that lead to melanin production. As far as I remember, neither do our closest relatives, the apes. On the other hand, baboons aren't too distantly related, and they do have dramatic blue and red pigmentation in certain areas. A lot of the differences in hair, eye color are due to absence of pigmentation. Red hair, however is due to a gene called the "ginger gene" which leads to a pigment closely related to melanin.

Just found this: Melanin can be used to produce colors in baboons:

"the red and blue markings are also caused by melanin, in the latter case by the refraction of light due to specific spatial arrangements of the pigment granules in the skin areas involved."

http://www.reference.com/search?q=pigmen...

So we could presumably modify how we use melanin as a way of generating colors (or possibly express the ginger gene in skin to get red) . However, this might take thousands or millions of years of evolution, and there may be selective pressure against it--maybe we don't find blue people attractive. And I don't see why there would be any particular reason that humans would have evolved in that direction.

One final possibility is that some types of coloration may block the UV light that is required for vitamin D synthesis. After all, they are found on the highly exposed, fur-free regions of baboons, and they presumably need some protection from UV in the blazing African sun.

Thought I should add: the red of birthmarks is caused by a high concentration of blood vessels.

Finally, there is the case of the blue people--the Fugates of Kentucky. There was a bit of inbreeding, which led to a recessive blood disease characterized by a faint bluish purple color, stronger at the lips and fingernails. There are reports of people at certain times being much more "blue"--such as infants. Here's a link about them--a very interesting story.

http://www.rootsweb.com/~kyperry3/Blue_F...

Why is human skin limited to shades of light and dark?

maybe the animals have a low range for skin color. r all dogs the same skin color, probably. Plus, humans do have a range, think about Flavor Flav and Punkin

Why is human skin limited to shades of light and dark?

its all in the genes.

we have eveolved not to need colours. we dont need to hide or nything like that. the composition of our skin is made to suit all our needs. and that composition has the end result of whatever our skin colour is

Why is human skin limited to shades of light and dark?

the reason there are more black people than white people in africa is because usually there is very little light so people with black skin become invisible leaving white people to be killed but in europe there is alot of snow so people with white skin blend in whereas people with black skin stand out and get killed, in the dessert where the sand is brown, people with brown skin blend it leaving white and black people to get killed so each skin has an advantage

Why is human skin limited to shades of light and dark?

Those species with so varied colours use them to attract the other gender, or to camouflague itself, or to show that they are poisonous. I think you dont need either.