Final answer:
Human skin color is determined by polygenic inheritance, where melanin production by melanocytes plays the central role. Carotene and hemoglobin also contribute to skin color, especially in light-skinned people. Skin color is an evolutionary adaptation to local UV radiation levels and differs from socio-economic constructs of race.
Step-by-step explanation:
Human skin color is the result of a type of complex inheritance known as polygenic inheritance. This form of inheritance means that multiple genes contribute to the phenotype, resulting in a wide spectrum of skin color variation. These variations are evolutionary adaptations to different levels of exposure to ultraviolet rays from the sun. The pigment melanin in the epidermis is the primary substance that determines the color of human skin. However, carotene and hemoglobin also play a role, especially in lighter-skinned individuals. The production of melanin is carried out by specialized cells called melanocytes, located in the stratum basale of the epidermis. The melanin is then transferred to keratinocytes, which are the predominant cells in the epidermis.
Geographical and environmental factors have historically shaped the physical characteristics of human populations. The concept of race has often been associated with skin color but is a complex socio-economic construct rather than solely a biological one. It's important to understand that the social construction of race differs significantly from genetic inheritance and evolutionary adaptations, such as skin pigmentation, which is a direct response to regional differences in sunlight exposure and the consequent need for varying degrees of protection against ultraviolet radiation or the synthesis of Vitamin D.