Final answer:
Variation in human skin color is influenced by a combination of genetics, environmental factors like sun exposure, and adaptation to UV radiation levels. While genetics dictate the potential range of skin colors, environmental interactions and evolutionary pressures have led to a spectrum of skin tones across human populations. Moreover, the concept of race based on skin color is not supported by biological anthropology.
Step-by-step explanation:
When considering the statements that apply to the variation in human skin color, it is important to understand that skin color is determined by a combination of factors including genetics, environmental influences, and evolutionary adaptation to different levels of UV radiation. Skin color is predominantly determined by melanin, and while genetics play a major role, environmental factors such as sun exposure can cause skin to darken. Adaptation to UV radiation is evident in the gradient of skin tones observed in human populations living at different distances from the equator. While newborns may have lighter skin tones, they do not have identical skin color at birth; rather, skin tone can change with age and UV exposure.
The traditional theory of directional selection suggests that darker skin evolved to protect against the sun's UV rays in sunny regions, and lighter skin evolved in regions with less sun to help produce adequate amounts of vitamin D. Research in biological anthropology, such as the works by Nina Jablonski and Agustín Fuentes, supports the idea that human traits, including skin color, vary along a spectrum, and the social construction of race based on skin color is not indicative of discrete biological categories.