First we learned to love, then we learned to be smart

Natalie Angier is my favorite science writer. Often I’ll be a couple of paragraphs into a science story, notice how well written it is, and realize it must be one of hers.

Her latest is a preview of a new book by Sarah Blaffer Hrdy, “Mothers and Others: The Evolutionary Origins of Mutual Understanding,” which will be published by Harvard University Press in April.

The thesis of the book is that we evolved cooperation and social intelligence through learning to love babies. As Angier puts it:

…human babies are so outrageously dependent on their elders for such a long time that humanity would never have made it without a break from the great ape model of child-rearing. Chimpanzee and gorilla mothers are capable of rearing their offspring pretty much through their own powers, but human mothers are not.

Unlike chimps, our closest relatives, we spend a lot of time sharing child-care, even giving and receiving help from unrelated adults.

Our capacity to cooperate in groups, to empathize with others and to wonder what others are thinking and feeling — all these traits, Dr. Hrdy argues, probably arose in response to the selective pressures of being in a cooperatively breeding social group, and the need to trust and rely on others and be deemed trustworthy and reliable in turn. Babies became adorable and keen to make connections with every passing adult gaze. Mothers became willing to play pass the baby. Dr. Hrdy points out that mother chimpanzees and gorillas jealously hold on to their infants for the first six months or more of life. Other females may express real interest in the newborn, but the mother does not let go: you never know when one of those females will turn infanticidal, or be unwilling or unable to defend the young ape against an infanticidal male.

By contrast, human mothers in virtually every culture studied allow others to hold their babies from birth onward, to a greater or lesser extent depending on tradition.

Hrdy believes that cooperative childrearing arose a long time before our brains exploded in size. It’s a nice idea, that we learned to trust, and this allowed us to develop as more intelligent primates:

With helpers in the nest, women could give birth to offspring with ever longer childhoods — the better to build big brains and stout immune systems — and, paradoxically, at ever shrinking intervals. The average time between births for a chimpanzee mother is about six years; for a human mother, it’s two or three years. As a result of our combined braininess and fecundity, humans have managed to colonize the planet.

This suggests that love and cooperation are an absolutely central part of what it is to be human, not just in terms of our individual experience, but in terms also of our evolutionary history.

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