hairdos of other apes and acquire hair that required continual attention. Geneticists have calculated a date for the birth of the hairdressing industry. Keratin, the protein in hair, comes in a large number of different varieties, each prescribed by a different gene. Humans, chimpanzees and gorillas have much the same set of keratin genes but with a striking difference. One of these genes, the human version of which is known as phi hHaA, produces a working keratin protein in chimpanzees and gorillas but is inactive in people of all ethnic groups. Although the genetic regulation of human hair growth is not yet understood, it seems likely that the inactivation of the phi-hHaA gene is the step by which the hair follicles of the human head have escaped from the orderly cycle imposed on chimp and gorilla hair follicles. By comparing the mutations in various versions of the human and ape gene, researchers have calculated that the
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