Final answer:
Human skin color evolved as an adaptation to UV radiation, with darker skin near the equator and lighter skin in northern regions. Race as a biological concept is inaccurate; human traits like skin color form a continuous spectrum. Social and cultural factors also influence perceptions and standards of skin color.
Step-by-step explanation:
Human skin color has changed over time due to evolutionary adaptations to varying levels of ultraviolet (UV) radiation around the globe. Originally, the dark skin of early humans living in Africa provided protection from intense UV radiation. As humans migrated farther from the equator, into regions with less direct sunlight, lighter skin evolved to allow for more efficient production of Vitamin D in conditions of weaker sunlight.
Physical geography and climate have played significant roles in shaping the phenotypic diversity of humans, which includes skin pigmentation. This process, known as directional selection, highlights how certain traits can confer advantages or disadvantages depending on the environment. Interestingly, the concept of race and delineating humans into distinct categories based on traits like skin color has been debunked by biological anthropologists who assert that human traits vary along a spectrum and cannot be categorized into discrete racial groups.
Societal factors also influence perceptions of skin color; for example, in the United States, cultural practices and beauty standards have fluctuated over time, with desirability once attached to pale skin and later to tanned skin, highlighting changing social norms rather than biological characteristics. Moreover, intermarriage and migration patterns can lead to greater genetic diversity and changes in skin pigmentation within populations over generations.