TOWARD A LIFE-HISTORY OF THE HOMINIDAE

Two new developments promise to greatly improve our ability to reconstruct the evolution of the human life cycle: 1. the introduction of the comparative methodology of life history into anthropology and 2. research on bone and dental development that reveals a world of life history preserved in the fossil record. Comparative study suggests that the human strategy depends on rich energy sources and low mortality and that our general rate of growth and aging evolved in parallel with brain size. It now appears that the australopithecines were a substantially primitive grade of hominid with life histories more like apes than humans. The life cycle of early Homo erectus was probably unlike any living hominoid: Evidence suggests that it grew up somewhat faster than living humans, it lacked an adolescent growth spurt, and H. erectus infants were more helpless than those of chimpanzees (but conceivably of more mature body proportion and motor advancement than our own). The appearance of fully modern life histories is still not fully resolved: Early Pleistocene Homo probably did not share them, and late Pleistocene hominids probably did, but life history is still little documented in the intervening million years. Although many details remain to be uncovered, the combination of advancing method and theory should soon lead to more robust models of human origins.