Melanin is a hormone that regulates your day night cycle(disregard that I got it confused with melatonin). Melanocytes, the glands that secrete melanin are on your skin, but also inside your major organs. They are part of your immune system, maybe it is connected to the "cosmic energy" or at least part of your "yellow" chakra since your ribcage has all your bone marrow and your heart which is the "yellow" energy. You also have neuromelanin created by your brain. Anyway it's just a powerful anti-oxidant, and white people can still tan.