Final answer:
The statement is true as skin color is a spectrum that varies across continents due to evolutionary adaptations to sun exposure, and modern conceptions of race are often based more on socioeconomic factors than on biology.
Step-by-step explanation:
The statement 'Skin color varies widely within continents' is true. Studies in biological anthropology have shown that there are no discrete racial categories biologically, and skin color is a trait that varies on a spectrum across the globe. This variation in skin pigmentation is a result of evolutionary adaptations to different levels of ultraviolet rays from the sun, with darker skin evolving in areas with more intense sunlight to protect from harmful radiation and lighter skin evolving in areas with less sunlight to facilitate the production of vitamin D.
As humans migrated out of Africa and across the planet, their skin pigmentation changed in response to their new environments. Socioeconomic factors in modern society often influence racial identity far more than biological qualities such as skin color.