"A seemingly simple example has been the conclusion that skin, hair,
and eye color are the result of only three genes. Each of these three genes regulate the amount of the light-absorbing pigment called melanin. The genes have two forms, a dark-skin allele (A, B, and C) and a light-skin allele (a, b, and c).
Melanin gives hair and skin its color, specifically shades of brown, red, and black.
Grey hairs contain very few melanin granules spread throughout the hair. White hairs contain no melanin and the whiteness is due to how the hair without pigment reflects light. The pigments’ main function is to protect epidermis cells from damage due to cancer-causing ultraviolet (UV) radiation.
Melanin is produced within melanosomes which are located inside melanin-producing pigment cells called melanocytes. All humans have the same number of melanocytes.
Only the amount of melanin they produce differs, causing a wide scope of human skin- and hair-color variations....melanin-producing melanosomes cause light to scatter to a greater degree in cells with large amounts of melanin.
Side-scatter of flow cytometry was then used to separate cells according to melanin levels. The cells were then analyzed to determine the identity of melanin-modifying genes.
Both new and previously known genes that play important roles in regulating melanin production in humans were located. The researchers determined that there were 169 functionally diverse genes that impacted melanin production, including 135 not previously associated with pigmentation.
One newly discovered gene produced a protein that regulated melanin synthesis by controlling the acidity of the melanosomes...Darker pigmentation was required to protect against ultraviolet radiation in areas of the Earth’s surface closer to the equator and for people who spend hours in direct sunlight. 
For humans living in areas with less-direct sunlight, or fewer hours of daylight, less melanin was required. This condition would then allow them to absorb more sunlight. This is important because sunlight is required to produce critically important vitamin D. Vitamin D has an important role in helping your body absorb calcium and supporting the muscles required to avoid falls.
A previously assumed “simple” system called sun-tanning, which produces various shades of brown skin, has turned out to be enormously complex.
The specific functions for most of the newly identified 135 genes involved in melanin production have yet to be determined.
Likely, if the past is any indicator, these genes will prove to have several functions, not only for melanin production, but also in other human-body operational processes. As a result, the evolution of this once “simple” system has become even less probable than before." CEH
