Question

How has natural selection affected the distribution of (native) skin pigmentation across the world?

1. Background information regarding what skin pigmentation is and/or why humans have skin pigmentation
2. An exploration of the environmental pressures responsible for native skin pigmentation distribution (i.e. what was killing/reducing reproductive rates) in both:
   1. Equatorial areas
   2. High latitudes
   3. Why dark pigmentation is an adaptation to the selective pressure(s) found near the equator
   4. Why light pigmentation is an adaptation to the selective pressure(s) found at higher latitudes

Answer 1

How natural selection affects skin pigmentation distribution:

There are many factors that affect or that results in various skin type of pigmentation type of humans around the world. In evolution skin pigmentation is developed by the natural selection that is, its ability to sustain in a particular environment.Dark pigmentation is found to be from ancestral origin and is maintained due to exposure to to high Uv radiation. Melanin is the compound that is responsible for the pigmentation in humans. If its content is low this is due to the exposure to to lower UV radiation that is, the geographical condition which is seen particularly in in higher latitudes.

What is skin pigmentation:

A person's skin pigmentation is the result of his or her parents' genetic makeup and also the effect of sun. The compound cold melon in is the primary substance that influence skin pigmentation. Highest concentration of melanin, darker is the skin colour. And such type of skin can decrease the effect of UV on their body.

Effect of environmental pressure on pigmentation:

Firstly sun is the factor that is responsible for the variation in skin pigmentation around the world. People living near the equator where the exposure to sunlight is much higher will be having a dark coloured skin due to the presence of a type of melanin (eumelanin) that will protect the skin from effects of such radiation. What in the case of people which are living near higher latitudes is not allotted with such high concentration of Sunlight so the pheomelanin which is a form of melanin that accumulate a lighter skin tone to the people.

Secondly, the geographical location is another factor for the variation in skin pigmentation. It is also having and indirect relation with the exposure to Sun.

Thirdly, the ancestral genetic makeup is another factor that influence variation in skin tone. Several genetic traits can be inherited from the ancestors so that whatever the geographic location is the individual will show the genetic dominance over the the surrounding condition.

Equatorial region

As we know such region is exposed to high amount of Sunlight or direct ultraviolet radiation is accumulated over the people living in this region. This exposure can damage the skin so the adaptation was to evolve darker skin protection from the sun's rays.

Higher latitude region

This region is having a low exposure to the sun and the vitamin D which is necessary for different process like calcium development, hence the skin is lighter for maximum absorption of the sunlight.