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What trait is human skin color?

Human skin color is determined by the amount and type of melanin pigments produced in the skin. Melanin is produced by cells called melanocytes and protects the skin from damage caused by ultraviolet (UV) radiation from the sun. The major pigments that determine skin color are eumelanin and pheomelanin.

Melanin and Skin Pigmentation

Eumelanin produces darker colors and is found in larger amounts in people with darker skin tones. Pheomelanin produces a red-yellow color and is found more abundantly in people with lighter skin tones. The ratio and distribution of these two pigments accounts for the range of human skin colors.

Higher levels of overall melanin act as a natural sunscreen and provide more protection against UV radiation. People living near the equator generally have more eumelanin in their skin as an adaptation to shield them from intense sun exposure that can damage DNA and cause skin cancer.

Genetics of Skin Color

The amount and type of melanin produced is primarily determined by genetics. The main gene that regulates pigmentation is called the melanocortin 1 receptor (MC1R) gene. Variants of this gene alter the production and ratio of eumelanin and pheomelanin. Other genes involved in melanin synthesis also influence skin tone.

Our genetic makeup regulates the functioning of melanocytes, causing some people to have more active melanin production and darker skin, while others have less active melanocytes and lighter skin. Genetic variations leading to reduced melanin synthesis likely arose as humans migrated to higher latitudes where sunlight is less intense.

Evolution of Human Skin Tones

All modern humans originally had dark skin suited for the intense UV radiation near the equator. As populations migrated north out of Africa, lower UV levels meant that lighter skin was advantageous to produce enough vitamin D from weaker sunlight.

Lighter skin likely emerged around 30,000 to 50,000 years ago as an adaptation to environmental conditions in northern regions. Different skin tones arose as groups spread across the globe to environments that favored particular levels of melanin pigmentation.

Region Typical Skin Tone
Africa Dark brown to black skin
Asia Light to olive skin
Europe Very pale to light olive skin
Americas Tan to brown skin

This table shows broad trends in skin tones adapted to different world regions over thousands of years.

Biological Impact of Skin Pigmentation

Levels of melanin affect how susceptible people are to sunburn, skin cancer, and vitamin D synthesis.

Darker skin contains more melanin and minimizes UV damage but can inhibit vitamin D production. Lighter skin allows more vitamin D synthesis but is more prone to sunburn and skin cancer.

Melanin also plays other biological roles related to skin function and health that scientists are still working to understand.

Misconceptions About Skin Color

There are no biological race groupings that correlate precisely with skin color variations. The concept of biological race as determined by skin tone is a social construct without genetic basis.

Skin tone exists on a continuum and is overlapping across human populations. Darker and lighter skin have both appeared across all continents over time depending on sun exposure and other pressures.

All people have essentially the same skin structure and pigment-producing capacity. Our shared history of adaptation from early humans originated in Africa means all modern humans can produce significant melanin.


In summary, human skin color is an evolutionary adaptation related to latitude, sun exposure, and vitamin D synthesis. It arises primarily from genetic differences regulating melanin production and ratios of the two key pigments eumelanin and pheomelanin.

Modern humans share an African origin with uniformly dark skin where intense UV radiation necessitated heavy melanin production. As populations migrated north, lighter skin tones emerged at higher latitudes where sunlight was less intense.

The genetics governing skin color are complex and gradient, with no sharp divides between predefined races. Variations in skin tones represent remarkably recent evolutionary fine tuning as our species spread across the planet.