PALEOPEDIATRICS - OR WHEN DID HUMAN INFANTS REALLY BECOME HUMAN

Modern human children take about twice as long as their closest biolog ical relative, the chimpanzee, to mature. One standard explanation for the evolution of ''delayed maturation'' at an early stage of human ev olution is that it provided the time necessary for immature individual s to learn complex skills, most notably those relating to tool-making abilities. However, after comparing dental maturational profiles of ea rly hominids from South Africa (who apparently did make and use stone tools) (Susman [1994] Science 265:1570-1573) to those of extant humans and chimpanzees, we find no evidence to document an association betwe en ''delayed maturation'' and tool-making abilities in the early stage s of human evolution. This also suggests that the assumed association between prolonged childhood dependency and other behaviors often assoc iated with the advent of tool-making such as cooperative hunting, food sharing, home bases, sexual division of labor, etc., is also suspect. Instead, we must look for other, or additional, selective pressures f or the evolution of ''delayed maturation,'' which may postdate the aus tralopithecine radiation. (C) 1995 Wiley-Liss, Inc.