08/22/2026
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.
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. 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 modern nuclear family asks one household to do the job dozens of people used to share. 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.
She also studies fatherhood, and her research points to something hopeful: when dads get more involved, mothers' mental health tends to improve. Her book Dad Brain came out in June.
