Transcript Skin Color Factors - College of Charleston

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