Final answer:
The Vitamin D hypothesis connects geography and skin pigmentation by explaining that populations farther from the equator have lighter skin to efficiently produce Vitamin D in conditions with less UV radiation.
Step-by-step explanation:
The Vitamin D hypothesis for the correlation between geography and skin pigmentation suggests that as humans migrated away from the equator, they were exposed to varying levels of ultraviolet radiation. Less UV exposure meant less natural production of Vitamin D, essential for bone health and immune functions. Consequently, populations residing farther from the equator evolved to have lighter skin pigmentation to allow for more efficient synthesis of Vitamin D in conditions of reduced sunlight. The Physical Geography of Race postulates that evolutionary adaptations like skin pigmentation occurred to help humans thrive in different climates, adhering to the principle of directional selection, where skin color adaptations are a direct result of the intensity of ultraviolet radiation exposure in different regions.