Explain why there are a wide variety of phenotypes for skin color in humans?

Question

Explain why there are a wide variety of phenotypes for skin color in humans

Answer 1

There is a wide variety of phenotypes for skin color because there is a wide variety of environments with differing UV radiation for humans AND there is a wide variety of disease which effect humans that are linked to the level of melanism in the skin.

Darker skin has an increased amount of melanin in the epithelial cells, which prevents damage from UV radiation. Humans that evolved in environments with high amounts of UV radiation (i.e. the African continent, Australian aboriginal populations, and certain Asian and South American/Central American regions) were naturally selected for high melanin in their epithelial cells due to high levels of skin cancer in these locations for people with low amounts of melanin in their epithelial cells. High rates of skin disease led to high death rates, which pushed natural selection towards darker skin color.

At the same time, there is an alternative selection in areas with lower UV radiation (areas near the poles such as Scandanavia). These areas had low amounts of UV radiation, and therefore their problem was the lack of sunlight. Sunlight provides essential nutrients to the body (I believe it is Vitamin A or E, I can't remember - I think it's A) through absorption of photons via the skin. Darker skin with high levels of melanin end up with a lack of Vitamin A (E?) which can lead to a disability called rickets - a bone disorder. Humans with this disorder were selected against as it may lead to death and loss of genetic prowess in the population. Therefore, less melanin in the skin was selected for in areas with less UV radiation.

Answer 2

Exactly the same way non-creationist do. According to the Bible, the people of the earth dispersed into same groups (tribes and families) where they had a limited gene pool, and so certain characteristcs (such as skin color or hair types) became common in those groups. Just as you see the same charactistics in all the people who are genetic members of a single family today. The only difference is that the Bible gives us the names and shows us the dispersal pattern of those tribes. (Genesis 10-11). And whether you like the idea or not, modern science today teaches that all humans decided from a single male and female. So it is in agreement with the Bible on that point.

Answer 3

Because of polygenic effects. Many alleles contribute to skin color, some more than others in effect. So, in any population you will have a continuous distribution of color tone. Rather like the distribution of height; some loci of genes having an additive effect, thus increasing the trait, whether melanin or height.

Answer 4

The previous poster has the correct answer, except ... it's Vitamin D.

Answer 5

in flowers, a white gene and a pink gene are both dominant, so codominance causes pink flowered offspring.
skin color is similar(although white is reccesive) so when you mix mocha with caramel, you get chocolate colored skin

Answer 6

www.wikipedia.com