ANTH 5 Chapter Notes - Chapter 4: Melanin, Vitamin D Deficiency
Document Summary
Absorbs sunlight in narrow band of wavelengths (uvb) Uvb poses greatest risk of skin cancer. Dark hair, light skin " our ancestors had light skin. Several million years ago, ancestral humans colonized unforested (bright) african savannas. Ns favored mutations that increased melanin production. Albino africans often die at fairly young age from skin cancer. British immigrants in australia have high rates of skin cancer. Melanin protects against skin cancer but inhibits vitamin d synthesis. Risks of vitamin d deficiency and skin cancer varies inversely. Selection builds facultative adaptations when key environmental challenges vary within lifetimes of individuals. Amount of uvb blocked by melanin varies geographically and seasonally. Facultative adaptations - ability to track and respond to environment in particular ways is designed by selection.
