JUANA SUMMERS, HOST:
A squishy, slippery blob that's incredibly needy - that's how pretty much every person is born. And those needs, that huge amount of care, well, in America, much of that responsibility often falls to one person, usually the mother. But a new study with a group of hunter-gatherers suggests that humans probably didn't evolve to take care of babies all on their own. Reporter Michaeleen Doucleff has the story.
MICHAELEEN DOUCLEFF, BYLINE: The study takes place in the rainforest of the Republic of Congo with the Bayaka people, who acquire their food primarily by hunting, foraging and fishing. Nikhil Chaudhary led the study. He's an evolutionary anthropologist at the University of Cambridge. In this study, he closely watched 18 babies and toddlers.
NIKHIL CHAUDHARY: So you follow a child for a total of 12 hours.
DOUCLEFF: Every 20 seconds, he wrote down details about the child's care.
CHAUDHARY: Who the caregiver was, whether the caregiver was, like, bathing or feeding the child or soothing them or carrying them. So you're just writing that down constantly.
DOUCLEFF: When Chaudhary and his colleagues analyzed the data, they found a striking pattern.
CHAUDHARY: The numbers were really quite amazing.
DOUCLEFF: Each baby had 15 to 20 different caregivers. Many of them simply watched the child. But...
CHAUDHARY: In terms of caregivers who actually are providing hands-on care, the average was about eight.
DOUCLEFF: Eight different people, besides the mom and the dad, bathing, feeding, physically loving the child. Scientists call these extra helpers alloparents, which means other parents. The study appears this month in Developmental Psychology. And together with other studies on communities worldwide, the findings suggest that throughout most of human evolution, mothers weren't taking care of babies alone, but instead they had a lot of help from a few alloparents. In other words, it doesn't take a village to take care of a baby. It takes a handful of extra people.
EMILY EMMOTT: The idea we have in evolutionary anthropology is that humans evolved this system of cooperative child rearing. So it's just, like, physically impossible for an individual person to look after a child successfully.
DOUCLEFF: That's Emily Emmott. She's a biological anthropologist at the University College London and wasn't involved in the study. She says in Western culture, there's an evolutionary mismatch. On the one hand, we're often expected to take care of babies on our own, but humans have evolved to care for babies in another way - that is with lots of help.
EMMOTT: And when we look cross-culturally, it's a system of quite complex care we often find. So it's beyond, you know, just the partner. It's often beyond kind of family members.
DOUCLEFF: It's like friends, neighbors, older children and paid help. Emmott thinks this mismatch is a key reason for the high rates of postpartum depression in the U.S.
EMMOTT: I think lots of women are put in this impossible situation where, actually, they're just set up to fail. And then it's not really surprising that a lot of women feel depressed.
DOUCLEFF: Because looking after a baby alone in a house, she says, can be quite hard and depressing.
I'm Michaeleen Doucleff for NPR News.
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