Biology Of Skin Color

(Sub-Saharan African, Indian, Southern European, and Northern European)

We are all one color…Brown

• The only difference is the shade

• There are no people who actually have true black, white, red, or yellow skin.  These are commonly used color terms that do not reflect biological reality.

Skin color and race

• There are NO reliable genetic markers for race. (ie. There is no gene for race)

• The concept of race is questionable!– The “false” concept of race can be traced to

the history of European colonization

• As a species, all humans originated in Africa.

Subtle Differences• The brown color we all share is melanin

produced my the melanocytes at the lowest level of the epidermis.– Protection for UV light

• The skin uses UV light to produce vitamin D, BUT approximately an hour a week is all that is needed.

• ALSO, and important to human evolution, UV breaks down folic acid (Vitamin B) in the body.– A lack of folic acid can lead to birth defects &

deformed sperm

Geography

• Near the equator the amount of sunlight is much more than what is needed.– Too much exposure increases the risk of birth

defects, defective sperm & skin cancer.

• Thus, an increase in melanin (which absorbs UV and protects the folic acid & DNA)

Evolution of Skin Color

• Evolution of humans near the equator in Africa would thus benefit from an increase in the production of melanin.

• As people migrated, particularly far north of the equator (less intensity and length of light) the need for UV (vitamin D) outweighed the protection from destruction of folic acid & UV (birth defects & cancer).

(Data for native populations collected by R. Biasutti prior to 1940.)

Amounts of Melanin and Other Color Factors

• European Ancestry:– Low levels of melanin produced– Skin slightly transparent because of this– Pinkish hue comes form blood in the capillaries of the

skin

• Asian Ancestry:– May have a slight yellowish tinge– Carotene (a red-orange pigment) is found in the

dermis and the highest level of the epidermis

Shallowness of Skin Color

• Very little of the skin is actually involved in skin-color difference.– Everyone has

melanin.

• The ONLY difference is the presence or absence of carotene and the amount of melanin.