Answer the following question given this paragraph: 

Human skin color is primarily due to the presence of the pigment melanin in the skin. Melanin is not a protein, but it is the product of a biosynthetic pathway. Skin color is a polygenic trait and obviously demonstrates quantitative characteristics. A number of genes factor into determining a person's natural skin color, so modifying only one of those genes changes the color only slightly. It is currently thought that at least three separately inherited genes contribute to skin pigmentation. Let’s call these three genes A, B, and C. A, B, and C are incompletely dominant to a, b, and c, with A, B, and C each contributing a “unit of darkness” to the phenotype. Therefore an AABBCC individual is very dark, darker than an AaBbCc individual, and much darker than a aabbcc individual. A person may have as many as 6 “dark units” to as few as no “dark units,” and any combination in between. This will result in a phenotypic spectrum of color gradation. When graphed, a phenotypic spectrum usually results in a bell-shaped curve, with extreme phenotypes on both ends and more common phenotypes in the center of the curve.


Q: Human skin color is primarily due to the presence of what pigment in the skin?

 Choices:

- tannin

- melatonin

- cytoplasm

- melanin

A:
melanin
