JUANA SUMMERS, HOST:
With Valentine's Day on the horizon, maybe you're thinking about that one special person. Well, a recent study looked across different mammals and ranked how monogamous they are. Humans register fairly high on the commitment scale, but we're edged out by a few other species like beavers and Ethiopian wolves. NPR's Katia Riddle reports on what monogamy in the animal world tells us about ourselves.
KATIA RIDDLE, BYLINE: When he goes on research trips, Greg O'Corry-Crowe stays out on the ice for weeks observing beluga whales and their mating strategies. He says recent developments in technology, better sensors and smaller instruments now allow him and his colleagues unprecedented access to observe the whales' behavior.
GREG O'CORRY-CROWE: So we can go anywhere, set up a camp and then just deploy with a very small team. And oh, my God, it's mind-blowing what you get to see.
RIDDLE: One such trip was off the coast of Alaska, observing a community of 2,000 whales. They studied the way these whales choose mating partners. They didn't necessarily think that the whales were monogamous, but they did think it was the males who were primarily seeking out multiple partners. Turns out the females also want to mix things up.
O'CORRY CROWE: All our predictions based on, you know, big, powerful males dominating the breeding season hasn't held up.
RIDDLE: He wonders if the females are working to establish a big whale village rather than a small nuclear family. This strategy is similar to one that some primates use, says Kit Opie. He studies evolutionary anthropology at University of Bristol. Chimpanzee and baboon females mate with multiple males. That keeps their offspring safe, says Opie.
KIT OPIE: Because all the males think, I could be the father of the subsequent infant, so I'm not going to harm it. And it's a really good strategy.
RIDDLE: Other primates, says Opie, do have more monogamous arrangements where both parents protect and care for their young, like the small apes called gibbons. They can form long-term bonds in small family units.
OPIE: In the gibbons, the male and the female and their offspring will have a really, really heavy-duty border around their territory, and they keep every adult out.
RIDDLE: Humans, says Opie, have an unusual combination of these two strategies. We have monogamous partnerships within big groups. We likely evolved into this arrangement hundreds of thousands of years ago.
OPIE: This is the theory of the origin of language, the origin of culture, why humans are here, why we're talking on Zoom and all the rest of it.
RIDDLE: Humans have mostly been practicing something they call pair-bonded monogamy since then, anthropologists say, but not 100%. Human behavior is especially flexible. It's culture rather than biology that determines the way we deviate from the one-partner-at-a-time model. Opie points to this example. Once humans started to accumulate property, polygamy - or the practice of having multiple partners - became more prevalent.
OPIE: It's better to go with a rich man, even if you're kind of second or third wife, than to go for a kind of an average-income man and be the only wife.
RIDDLE: When humans move toward exclusively monogamous cultures, there's usually a belief system, like religion, involved. That's according to Robin Dunbar, who studies evolutionary psychology at University of Oxford.
ROBIN DUNBAR: The rest that are monogamous are almost always in forced monogamies, which, of course, is universal for Christianity with very few exceptions.
RIDDLE: With modern Americans drifting away from Christianity in recent decades and with the relatively recent invention of birth control, some surveys show that Americans are today more open to the practice of multiple partners and unconventional family arrangements, especially young people. But Americans, says Dunbar, should not have the hubris to think they invented this practice.
DUNBAR: America has retained its religious base, so maybe it's a bit more of a shock to contemporary Americans.
RIDDLE: At our core, says Dunbar, on the question of monogamy, we are conflicted. That's part of what makes us human.
Katia Riddle, NPR News.
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