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The Long Human Childhood

April 12, 2008

Book Review

The Benefits of a Long Childhood

Ethan Remmel

Why Youth Is Not Wasted on the Young: Immaturity in Human Development. David F. Bjorklund. xii + 276 pp. Blackwell Publishing, 2007. $24.95.

Why do children take so long to grow up? From an evolutionary perspective, the fact that humans reach maturity so slowly, relative to other species, is a puzzle, because the leisurely pace of their development clearly has costs: It requires greater parental investment and increases the risk that offspring will die before reproducing.

One possible explanation for our slow rate of maturation is that it is an adaptation—that is, natural selection may have favored a long childhood because it had benefits that outweighed its costs. However, most scientists who have examined this issue have assumed that immaturity has no inherent advantages and that our extended period of development must therefore be a by-product of selection for some other characteristic.

The most popular candidate has been intelligence. A big and complex brain takes a lot of time to develop, and in humans much of that development must occur after birth, because bipedalism limits birth-canal width, which has in turn constrained the head size of newborns. More specifically, social intelligence has often been postulated as the driving factor. In this view, as humans achieved ecological dominance, they became one another’s principal competition for resources. Consequently, the ability to manage social relations and alliances was selected for, in what evolutionary biologist Richard Alexander has characterized as a cognitive “arms race” within the species. The result is that we are much smarter than we would need to be simply to succeed at hunting and gathering, and we are thus capable of creating complex cultures.

David F. Bjorklund, an influential leader in the emerging area of evolutionary developmental psychology, does not dispute the foregoing account in his new book, Why Youth Is Not Wasted on the Young. But he does question the assumption that extended immaturity has no benefits. He suggests that a long period of development, although it may have arisen as a by-product of other factors, does confer advantages—behavioral flexibility, for example—that have contributed to our success as a species. In other words, he believes that childhood is an evolutionary spandrel (although he doesn’t use the term)—a side effect, which in this instance turns out to be adaptive itself.

hard Alexander has characterized as a cognitive “arms race” within the species. The result is that we are much smarter than we would need to be simply to succeed at hunting and gathering, and we are thus capable of creating complex cultures.

David F. Bjorklund, an influential leader in the emerging area of evolutionary developmental psychology, does not dispute the foregoing account in his new book, Why Youth Is Not Wasted on the Young. But he does question the assumption that extended immaturity has no benefits. He suggests that a long period of development, although it may have arisen as a by-product of other factors, does confer advantages—behavioral flexibility, for example—that have contributed to our success as a species. In other words, he believes that childhood is an evolutionary spandrel (although he doesn’t use the term)—a side effect, which in this instance turns out to be adaptive itself. …more

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