>>11326646Your body only produces a finite amount of the chemicals that color hair throughout your lifetime. That means as you age and produce more hair in your lifetime, your color supplies start running out, causing grey hairs. Best analogy I got is the ink cartridge one, thinking of your body as being covered in tiny ink cartridges that will run out for each hair follicle throughout your lifetime depending on how much hair grows in that spot.
In gorillas their backs have hair that uses up their ink cartridges very quickly compared to the rest of their body, causing silver hair.
