Human childhoods last about a quarter of our lives, longer than those of any other species, says Brenna Hassett in The Guardian. We spend “25-odd years” growing up, and that’s what makes us “Earth’s most complex animal”. There are multiple ways we “invest in the slow growth of the next generation”. One is monogamy, which about 90% of animals have “dismissed as unworkable”, but in our case gives us “genetic co-investors” – dads, in other words. This means less competition for mates, and as such, our genitals are “remarkably unremarkable”. If we had the same reproductive habits as mouse lemurs, for example, men’s testes would be the size of grapefruits.
We women “pour so much physical investment into our babies that they nearly kill us”: children are born big-brained, and with 15% body fat, compared to “the sleek 3% of a chimpanzee”. We take infants “off the breast” far sooner than any of our primate relatives. Instead, they get an extended period learning from friends, family and wider society. And bar a few whales, no other female animals stop reproducing before they die – in humans, this mid-life cut-off produces the grandmother, “a parenting ally no other species has managed”. Historical approaches to childhood vary: some children were sent down the mines at 12; I was still doing a degree at 30. But in general, the longer the better. It takes time to “learn to be a better monkey”.