What are two theories put forth to explain human variation in color?

Question

What are two theories put forth to explain human variation in color?

Answer 1

Skin color is the amount of melanin in your skin.

One reason for why it is darker closer to the equator is because when the sun hits your skin it destroys folic acid, which is needed to carry a baby to full term. So they're skin needs to be darker to protect that folic acid.

Yet,  the sun also stimulates vitamin D production. Vitamin D is necessary in healthy bone growth. It can lead to things such as rickets if you don't get enough.

These two things are why there is so much variation in color among people. There must be this balance between vitamin D production and the amount of folic acid left. And this also explains the innuits in Alaska and why they're so dark. You'd think they would need to be lighter based on this theory, but their diet is so vitamin D enriched that they don't need the sun to stimulate the production, so their skin is darker to protect their folic acid.

I don't know if that's what you're looking for.

Answer 2

Diet & Environment

Answer 3

As for skin color:

"In their analysis of human evolutionary history, Jablonski and Chaplin concluded that modern humans most likely evolved in the tropics, where they were exposed to high UV levels. But as they moved into regions away from the equator, where UV levels are lower, humans became fairer so as to allow enough UV radiation to penetrate their skin and produce vitamin D, the "sunshine vitamin," also obtained from eating fish and marine mammals. Vitamin D is essential for maintaining healthy blood levels of calcium and phosphorous, and thus promoting bone growth.

Skin color, according to Jablonski and Chaplin, basically becomes a balancing act between the evolutionary demands of photo-protection and the need to create vitamin D in the skin.

One of the important implications of Jablonski and Chaplin's work is that it underlines the concept of race as purely a social construct, with no scientific grounds. DNA research has shown that genetically all humans, regardless of skin color and other surface distinctions, are basically the same. In an April 2001 article titled, "The Genetic Archaeology of Race," published in the Atlantic Monthly, Steve Olson writes "the genetic variants affecting skin color and facial features are essentially meaningless —they probably involve a few hundred of the billions of nucleotides in a person's DNA. Yet societies have built elaborate systems of privilege and control on these insignificant genetic differences."

http://ngm.nationalgeographic.com/ngm/02...

"Before the mass global migrations of people during the last 500 years, dark skin color was mostly concentrated in the southern hemisphere near the equator and light color progressively increased further away, as illustrated in the map below. In fact, the majority of dark pigmented people lived within 20° of the equator. Most of the lighter pigmented people lived in the northern hemisphere north of 20° latitude."

http://anthro.palomar.edu/adapt/adapt_4....

Answer 4

All the folks with lighter skin did not do well - they got sun stroke and what not.  The people who did not over heat and die procreated and had a bunch of kids who could better withstand heat and sunlight.   Over thousands of years.  What is this theory called again?

Answer 5

I think humans settled in certain places and then were isolated by mountain ranges or oceans, then after thousands of years of breeding people in Northern Europe became paler due to lack of sunshine especially in the winter. Chinese and other eastern peoples, must've been a reason they developed, the way they are. Can't explain

Answer 6

Well, two theories would be heredity and environment.

Answer 7

natural selection

sexual selection

Answer 8

the sun,weather depends on where u live ur skin will be darker or lighter  E.G in africa the people have very dark skin cos it protects them from the sun,in iceland ppl are very pale cos they dont need to be protected from the sun or  (uv lights)

(but it depends on the skin color of ur parents)

Answer 9

location on earth, thus implying the amount of sun. but im pretty sure everyone has the same pigment it just how it reacts to sun light

Answer 10

Why do you want 2 theories when it is known perfectly well what causes variation in colour.

The brown colour is caused by melanin - the more melanin the darker your skin.

Natural selection accounts for different population having genes which code for different levels of melanin.

In practice it is not quite as simple as one gene coding for melanin, but the principle stands.

http://creationontheweb.com/images/pdfs/...

http://creationontheweb.com/images/pdfs/...

Answer 11

it all has to do with the sun and the amount of pigment in your skin