Human skin and hair pigmentation varies within and between populations due to MC1R genetics. Natural selection shaped pigmentation variation including MC1R. MC1R mutations associate with normal skin color variation. MC1R receptor switches eumelanin production to pheomelanin via alpha-MSH and ASIP. Loss-of-function MC1R causes pheomelanin overproduction like yellow mouse coat. MC1R highly polymorphic across humans. MC1R variants link to red hair and fair skin phenotypes. MC1R mutations reduce tanning ability. Pheomelanin produces free radicals under UV raising skin cancer risk. MC1R review covers global human polymorphism not just Europeans. Review examines MC1R selection role. Review includes MC1R evolution in non-human primates. Human MC1R at chromosome 16q24.3 with 951 bp coding. Alternative MC1R splice variant MC1RB exists with unknown function. MC1R mutations in transmembrane domains affect hormone binding and pigmentation. MC1R intracellular loops critical for signaling and pigmentation effects.