The evolution of hominid life-history during the first 20 years of life. The existence time is given below (kya, thousands years ago; mya, millions years ago) and the longevity above. During the evolution of the hominids, childhood and adolescence have been added as new life-history stages as compared with apes and the presumably early hominid Australopithecus afarensis. The chimpanzee serves as a living representative of the assumed Australopithecus afarensis life-history. As childhood emerged and prolonged, infancy was gradually cut shorter, and the latest-introduced adolescence came at the expense of a shorter juvenility.