Explaining the Logic Behind Skin Color

[Wannabeagenius]

Hi All,

I know that the environment is responsible for people of African descent having black skin and people of Scandinavian descent have white skin but I cannot figure out the logic behind this.

I thought it had to do with the absorption of Vitamin D from the sun and the Scandinavian people developed white skin in order to absorb more sunlight per unit time due to living in a climate with less sunlight. However, the problem with this is that white skin reflects more sunlight than black skin so by my reasoning, Africans should be white and Scandinavians black.

What is wrong with my logic?

Thank you,
Bob

 

[dacruick]

I think this is a basic evolution principle that I have no credibility in saying, I just assumed I was correct, so someone please correct me if I am wrong. I don't think its the fact that one reflects more than the other. In Africa there is a lot of sun, and the sun burns your skin. What makes skin the colour it is, is called melanin. I think that after thousands and thousands of years of being under the sun, evolution produced more melanin so that the burns were less severe.

 

[Smachine]

I think its to do with DNA protection, as melanin is located at the top of nucleus in the keratinocytes. Europeans are normally exposed to less sunlights UV radiation so they normally don't need that much of it.

 

[Moonbear]

Actually, people of all skin colors produce roughly about the same amount of melanin. The difference is mostly in the abundance of enzymes to break down the melanin, and how much of that melanin is transported nearer the skin surface. The melanin is there and ready to be released upon more skin exposure (i.e., getting a tan).

White skin is also not bright white, it's more appropriate to just refer to it as a lighter skin color than "white", and it isn't particularly reflective, so that line of reasoning really isn't very accurate.

 

[JerryClower]

I thought it had to do with the absorption of Vitamin D from the sun and the Scandinavian people developed white skin in order to absorb more sunlight per unit time due to living in a climate with less sunlight. However, the problem with this is that white skin reflects more sunlight than black skin so by my reasoning, Africans should be white and Scandinavians black.

People from Europe didn't develop white skin to absorb more sunlight per unit time. That is actually very illogical thinking. Logically, black absorbs all light and white reflects it. Meaning a darker color, the warmer/hotter your skin would get. The function of melanin is to protect the epidermis from sun burns. African people live in a hotter climate with more sunlight, So, their melanocytes produced more melanin to protect them. The Scandinavians, however, didn't live in such a hot climate. Sunburn was not as big of a threat to their survival, so their melanocytes produced less melanin. By the way, the more melanin you have, generally the darker your skin is.

 

[Monique]

People from Europe didn't develop white skin to absorb more sunlight per unit time. That is actually very illogical thinking.

This is not correct. This is clearly shown by the fact that people with a very dark skin color in countries in the northern hemisphere are more likely to get a vitamin D deficiency, while people with a lighter skin color are not (vitamin D production requires exposure to sunlight).

Melanin is the natural UV-filter of the skin. Regions around the equator get more intense sunlight, so need stronger protection from the harmful rays of the sun. That is why people with an ancestry in that region have a type and quantity of melanin in their skin that turns their skin a dark color. The melanin absorbs the UV radiation and stops it from penetrating the skin. That's the clue why you need less or different melanin when the sunlight is less intense: some of the light needs to be absorbed by regular skin cells in order to make vitamin D.
Also, you will have less selection on skin containing a lot of melanin. Why put a lot of energy in producing melanin when you do not really need it to prevent sunburn?

 

[ROFLBBQ]

Interesting article. It only took one search in google to find this. Use it.
http://www.pbs.org/wgbh/evolution/library/07/3/text_pop/l_073_04.html

 

[skeptic2]

Scientific American had an article on this issue a number of years ago. If I remember correctly, its point was that skin color evolved to balance the effects of too much exposure such as skin cancer with the effects of too little exposure such as rickets.

http://www.scientificamerican.com/article.cfm?id=skin-deep