If everyone’s got a kink, mine is having my breasts touched during sex. It’s almost as if there’s an electric wire from my chest to my pants—when my boyfriend touches me up here, I feel it down there.
I’d never really thought of this sensation as more than what it feels like—pleasure. Until I came across a paper in the aptly named journal Medical Hypotheses that raised a fascinating question: Could "breast sex" have evolved to feel good because it's good for us?
The paper’s theory went like this: When women’s breasts are sexually stimulated, we release the same chemicals as when we breastfeed—and given that breastfeeding comes with health benefits, perhaps sexual stimulation brings the same benefits.
The paper even posits that sexual stimulation of breasts may be “instrumental in reducing the risk in women of sexual dysfunction, poor emotional health, cancers of the ovary, uterus, and cervix, and breast cancer." Come again?
Intrigued, I set out to explore whether it’s possible that having one’s boobs caressed holds the secret to good health, asking biologists and evolutionary anthropologists—could this win-win be for real?
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Given how prominent women’s breasts are in our culture, we know surprisingly little about their purpose when it comes to mating.
Humans are the only species to incorporate breasts into sex—and in order for a behavior to be naturally selected, it has to be biologically advantageous. But why is still a mystery.
We’re not even sure why female breasts are the globes we’ve come to know and love. While other female primates have engorged mammaries only when they're nursing, human females look as if they're always lactating. "It appears there has been some selection to make breasts bigger" in humans, compared to other primates, said Steven Gaulin, a professor of anthropology at University of California, Santa Barbara. But beyond that, ¯\_(ツ)_/¯.
These are the mysteries that Valerie Robinson, the paper’s author, is attempting to solve—or at least get people to think about. Robinson, who is 78 years old and holds a Master’s degree in biology, has spent much of her life thinking about this issue. The journal in which her paper is published bills itself as “a forum for ideas” that aims to publish “interesting and important theoretical papers that foster the diversity and debate upon which the scientific process thrives.”
And Robinson’s argument will likely stir debate. In the paper, she suggests that what distinguishes human breasts is the fact that they’re meant to be sexual—and that not engaging them sexually could even be harmful to women.
"The failure of women to engage in the healthful activity of nipple stimulation during sex, specifically to aid in sexual arousal and in achieving orgasm, is counter to a unique species typical practice, and such failure puts a woman’s sexual satisfaction, emotional health, and physical health in jeopardy,” Robinson speculates.
Basically, our breasts need sexual love—and if they don’t get it, we could pay a price.
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If you’re wondering how breastfeeding factors in—well, brace yourself.
When a woman breastfeeds, the act benefits not only the child but the mother. Breastfeeding triggers the release of oxytocin from the brain into the bloodstream, which helps her bond with her child. Breastfeeding also lowers her risk of developing breast cancer, as well as in-situ cervical cancer and ovarian cancer.
While experts don't know exactly why breastfeeding can help prevent disease, most research theorizes that the hormonal changes that occur while nursing—including a dip estrogen levels—as well as the elimination of carcinogens through breast milk and increased oxytocin play a role. These benefits are great, but some argue that failing to breastfeed can, by the same token, elevate a woman’s risk for disease.
Robinson takes similar logic. She first explains that breast sex triggers the same oxytocin release as breastfeeding, and thus helps a woman bond with her adult partner. She then posits that because breastfeeding has been shown to help prevent breast cancer, breast sex might mimic those results. She writes, "Because of similarities to breastfeeding, sexual breast love, that is, nipple eroticism may also reduce the risk of cancer by a parallel mechanism."
Robinson points to a group of women, the Chinese Tanka (or boat people), who construct their clothing with an opening on only the right side. Thus, when breastfeeding, often only the right breast is used. Research into this group of women has shown that there's a significant increase of cancer risk in the unused breast.
This same rationale could be applied to breast stimulation, she argues. "Because of underlying biological factors, the 'non-sexual breast' may be found to carry a breast cancer risk similar to that of the 'non-breastfeeding breast'."
But there may be another link between breast sex and breastfeeding that’s uncomfortable to think about: It’s possible that the reason breast stimulation feels good during sex is because our boobs are wired to feel good during breastfeeding.
Researchers theorize that nipple stimulation feels good to encourage mothers to breastfeed longer. "Its pleasurable because it's a reward for engaging in nursing," said Elisabeth Lloyd, a professor of biology at Indiana University who has studied the female orgasm extensively. Many women even orgasm while breastfeeding, she told me, adding that "It's not often spoken of but it’s very well documented."
Robinson also brings this up in her paper, writing, "Infant breast feeding has a pleasurable link to the uterus—a hushed up connection and a somewhat delicate topic."
This connection between breastfeeding and breast stimulation is really the heart of Robinson's hypotheses. Essentially, she argues that benefits introduced from nursing can be simulated by the caressing or suckling of breasts by a partner.
While the experts I spoke with agreed that breastfeeding can help prevent cancer, they could not confirm that breast play or breast suckling by a partner could have the same effect—but the theory didn't strike them as crazy, either.
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It’s also possible breast play evolved to feel good simply because it increases women’s chances of having an orgasm—which comes with its own set of benefits.
“Some women say their nipples are directly connected to their clitoris,” said Lloyd, adding that she's encountered women who can orgasm based on breast stimulation alone.
The evolutionary purpose for the female orgasm is as much as mystery as the role of boobs during sex, but one (albeit controversial) theory argues that it could actually be an adaptive behavior—that orgasming could serve a functional role to the female. According to David Puts, a professor of anthropology at Pennsylvania State University, orgasm helps sperm get sucked up for increased fertility, helps pair bonding with the release of oxytocin, and could even play a role in partner selection.
(Yes, a lack of orgasm might be a signal to the female that she's with the wrong mate. "Research has shown that women were more likely to have orgasms, and orgasm sooner, with men who were more genetically compatible with them," said Puts.)
While Puts didn't want to make a direct link between breast play and health benefits, he acknowledges that there's some sort of evolutionary mechanism in place for breast stimulation to feel good from nursing, and the sexual element could be partly a byproduct of that—but also acknowledges that "selection could also have worked to favor it as a sexual area."
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So what’s the takeaway? Sure, it’s possible that breast sex could contribute to women’s health—and a lack of breast sex could harm us. But as the title of the journal in which the paper was published suggests, this is just a theory. While the anthropologists I spoke with didn’t disregard it, a mountain of research would be needed to draw any real conclusions. For now, our breasts will remain shrouded in mystery.
In the meantime, I didn’t uncover any downsides to breast sex in my reporting. So if you’re looking for something to do this weekend—feel free to unshroud yours for your honey.
Taryn Hillin is Fusion's love and sex writer, with a large focus on the science of relationships. She also loves dogs, Bourbon barrel-aged beers and popcorn — not necessarily in that order.