“Do men need to cheat on their women?” a Playboy headline asked in the summer of 1978. Their not-so-surprising conclusion: Yes! Science says so! The idea that men are promiscuous by nature, while women are chaste and monogamous, is an old and tenacious one. As far back as Darwin, scientists were churning out theory and evidence that backed this up. In this episode, Annie and Elah go back to the 1970s and 1980s, when feminism and science come face to face, and it becomes clear that a lot of animals—humans and bluebirds included—are not playing by the rules.

Angela Saini, author of Inferior: How Science Got Women Wrong

Patricia Adair Gowaty, professor emeritus at UCLA, editor of Feminism and Evolutionary Biology.

Sarah B. Hrdy is an anthropologist, feminist, and a major figure in this chapter of science history. In this book chapter she addresses the myth of the “coy female” and reviews the relevant scientific happenings of the 1970s and 80s, especially in the primatology sphere.

Angus John Bateman’s 1948 paper about fruit fly mating and reproductive success, popularized by this paper from Robert Trivers in 1972. Bateman finds that males have more reproductive success the more females they mate with, and that females don’t benefit as much from mating with multiple males.

Patty Adair Gowaty found holes in Bateman’s study. Bateman didn’t know exactly how many sexual partners his fruit flies had because he didn’t watch them. Instead, he counted up how many offspring they made. Unfortunately, a lot of them had harmful mutations and died—skewing his numbers. Not only do they not meet Mendelian expectations, but in Bateman’s data, he consistently counts more fathers than mothers—which can’t be right, since every baby fly has one mother and one father.

Patty found that eastern bluebird females successfully raise offspring without help from their male partners.

Patty and Alvan Karlin found that eastern bluebird babies aren’t always related to the parents raising them.

True “genetic monogamy,” where bird couples only have sex with each other, appears to be the exception, not the rule in passerines. Polyandry—where females have sex with multiple males—has been found most of the species studied!

In the late ‘70s and early ‘80s, a psychology study at Florida State University found that most men, and no women would accept a sex invitation from a stranger.

In this more recent Germany study, 97% of the women expressed interest in sex with at least one strange man, but only when researchers promised to arrange a (relatively) safe encounter. 

Btw, Patty tells us bluebirds don’t actually have sex in the nest, so having sex “outside the nest” is the norm. We were using the expression figuratively, but worth noting. The nest is really for storing the babies.

This episode was reported and produced by Elah Feder and Annie Minoff. Our senior editor is Christopher Intagliata. Fact checking by Robin Palmer. I Am Robot and Proud wrote our theme. All other music by Daniel Peterschmidt.

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