The Happiness Hypothesis: Finding Modern Truth in Ancient Wisdom

by Jonathan Haidt

service; only some fine tuning during a few years of childhood play and learning is needed. In humans, however, the rapid rate of embryonic brain growth continues for about two years after birth, followed by a slower but continuous increase in brain weight for another twenty years.32 Humans are the only creatures on Earth whose young are utterly helpless for years, and heavily dependent on adult care for more than a decade. Given the enormous burden that is the human child, women can’t do it on their own. Studies of hunter-gatherer societies show that mothers of young children cannot collect enough calories to keep themselves and their children alive.33 They rely on the large quantity of food as well as the protection provided by males in their peak years of productivity. Big brains, so useful for gossip and social manipulation (as well as hunting and gathering), could therefore have evolved only if men began chipping in. But in the competitive game of evolution, it’s a losing move for a male to provide resources to a child who is not his own. So active fathers, male-female pair-bonds, male sexual jealousy, and big-headed babies all co-evolved—that is, arose gradually but together. A man who felt some desire to stay with a woman, guard her fidelity, and contribute to the rearing of their children could produce smarter children than could his less paternal competitors. In environments in which intelligence was highly adaptive (which may have been all human environments, onc...