Why do humans have such long childhoods?

The leading explanations hold that a long childhood gives humans time to learn difficult skills and to explore before adult life demands focused action. Human children are slow-growing and depend on others for a long time, and the evidence reviewed here points to learning as a central benefit. Social learning and cooperation are also named as part of the picture. [1] [2] [3]

One review notes that chimpanzees produce as much food as they eat by about age 7, while even in forager cultures human children are not self-sufficient until at least 15. Fossil evidence suggests Homo sapiens had a longer period of immaturity than other hominins, including Neanderthals. The same source says the young brain is expensive: more than 60 percent of a 4-year-old's resting calories go to it, against around 20 percent in adults. [2]

Humans cope with this cost through unusually varied caregiving, including pair-bonded fathers, related and unrelated alloparents, and post-menopausal grandmothers. Other species show some of these, but none appears to have all of them. One popular account puts the investment at 20 to 30 years' worth. [2] [4]

Embodied capital theory says that much of the human diet consists of hard-to-acquire, energy-rich resources, and that collecting them takes coordination, strength and knowledge built up over a long development. The low output of childhood is then repaid by high productivity across a lifetime. A study of child and adolescent foragers in 28 societies tested this idea. Returns from tubers and game, which are harder to extract, rose slowly and peaked in adulthood. Returns from fruit and fish or shellfish reached adult levels by adolescence. The authors concluded that the results support long childhoods evolving as a period for learning complex resource extraction. [1]

The same study found that by age 10 children achieved about half the productivity of 20-year-olds, so children can forage fairly independently well before adulthood. Returns still kept rising at least until adulthood for all resources. [1]

The sources present several explanations, and they are not strictly rivals. The pooled energy model argues that children's contributions to the family economy, through an age-graded division of labor, helped favor long childhoods. The study above notes that earlier research has reached inconsistent conclusions on how foraging skill relates to niche complexity, and its own findings favor the learning view. [1]

A separate argument, based on explore-exploit trade-offs, holds that childhood is a protected period of broad exploration, curiosity and play, which trades off against the focused, goal-directed skills of adults. On this view, early exploration lays the groundwork for the whole range of human cognitive skills. Another source stresses that humans live in societies, so a long childhood also makes us a social, long-learning species. The search results do not say which of these accounts most specialists currently favor. [2] [3]