Postpartum Depression Isn’t in Our Biology, It’s What Happens When You Strip a New Mom of the Village She Evolved to Have

We were built to raise kids in groups, with grandmothers, aunts, siblings, and neighbors passing the baby around all day. Now we hand one exhausted person a newborn, an empty house, and a deadline to get back to work.

Humans are what scientists call cooperative breeders, meaning we evolved to share the work of raising children across a whole community rather than pile it onto one or two people. No single parent was ever meant to carry the load alone, and for nearly all of our history, none did.

That’s the argument USC psychologist Darby Saxbe made on the Modern Wisdom podcast, pushing back on the idea that postpartum depression has some built-in evolutionary purpose. If depression were an adaptation, the thinking goes, it would serve some function — signaling a need for help, say, or steering resources toward a struggling mother. Saxbe isn’t convinced. She thinks it’s closer to a mismatch between how we’re wired and how we live.

For most of human history, new mothers had constant hands-on help. In some communities, a baby is held almost nonstop and passed among as many as 10 caregivers, from fathers to grandmothers to older kids. The mother was rarely the only adult in the room, let alone the only one who knew how to soothe a crying infant. Care was distributed, and so was the exhaustion.

Compare that to now. The modern nuclear family asks one household to do the job dozens of people used to share, often behind a closed front door in a neighborhood where no one else is home during the day. Saxbe points to isolation, the devaluing of caregiving, and pressure to return to work before parents feel ready as the forces that leave new moms drained. None of those are personal failings, she argues — they’re features of the environment we’ve built, and they’d wear down almost anyone.

That framing matters, because it shifts the question from what’s wrong with a struggling mother to what’s missing around her. If postpartum depression is partly a symptom of lost support, then rebuilding some version of that support becomes part of the treatment.

She also studies fatherhood, and her research points to something hopeful on that front: when dads get more involved, mothers’ mental health tends to improve. The village doesn’t have to be a whole community — sometimes it starts with the other parent in the house. Her book Dad Brain came out in June.