1. Skin Color Factors Melanin - Pigment in skin, eyes, hair
Carotene - a copper-colored pigment
Skin Thickness
Reflection of Blood Vessels

2. Skin Color Distribution

3. Why? Natural Selection In Tropics Reduces frequency of skin cancer
Reduces likelihood of severe sunburn which interferes with sweating
Melanin screens sunlight passing through skin
Regulates Vitamin D Production
Which Regulates deposition of Calcium
Too Much Calcium > Calcification of soft tissues
In Higher Latitudes
Too Little Calcium > Rickets; Reduced Size of Birth Canal

4. Lower production of melanin, especially in females of reproductive age,
would be reinforced through differences in reproductive success, and
the genes coding for this variant would be differentially transmitted to offspring.
There are two variants of the gene SLC24A5.
The first variant has a frequency of 99% among European Americans.
The other has a frequency of 93 to 100% among East Asians