Human beings are born too soon. Within hours of arriving in the world, a baby antelope can clamber up to a wobbly standing position; a day-old zebra foal can run from hyenas; a sea-turtle, newly hatched in the sand, knows how to find its way to the ocean. Newborn humans, on the other hand, can’t hold up their own heads without someone to help them. They can’t even burp without assistance. Place a baby human on its stomach at one day old – or even three months old, the age at which lion cubs may be starting to learn to hunt – and it’s stranded in position until you decide to turn it over, or a sabre-toothed tiger strolls into the cave to claim it. The reason for this ineptitude is well-known: our huge brains, which make us the cleverest mammals on the planet, wouldn’t fit through the birth canal if they developed more fully in the womb. (Recently, cognitive scientists have speculated that babies may actually be getting more useless as evolution proceeds; if natural selection favours ever bigger brains, you’d expect humans to be born with more and more developing left to do.)
This is why humans have “parenting”: there is a uniquely enormous gap between the human infant and the mature animal. That gap must be bridged, and it’s difficult to resist the conclusion that there must be many specific things adults need to get right in order to bridge it. This, in turn, is why there are parenting advice manuals – hundreds and hundreds of them, serving as an index of the changing ways we have worried about how we might mess up our children.