What’s the most disgusting sentence that’s ever been spoken out loud? Doubtless there are loads of contenders for this, but the one that I’d instantly nominate is a throwaway line a friend of mine used to say now and again, and which more than once I saw provoking an actual, physical gag reflex in people who heard it. It went like this: You might ask her something innocuous like, “Shall we put a movie on?” or “Want to head out for coffee?” And if she wasn’t so inclined, instead of a normal, courteous “no thanks,” she’d frown, look you in the eye, and reply: “I’d rather go down on my dad.”
As the most extreme talk-to-the-hand available to language, it was always a hilarious move, but also so very deeply disturbing. Friends would gasp in horror; siblings would storm out genuinely furious; imaginary teacups would smash on the floor. Years later, it’s clearly stuck with me as eight words I’ll never be able to un-recoil from for as long as I live. And now, neither will you. (Sorry about that.)
Most of us don’t have the social steel to joke this freely about incest (and stomach-trigger warning: More on that shortly), but that’s only one side of the grossness going on here. The other is that there’s a usually lead-lined partition in our minds that keeps anything to do with our parents fully insulated from any sort of pornographic imagery, and any catastrophic breach like this tends to lead to full core meltdown and much mental fallout. Even though, if pushed, we all might grudgingly admit that the people who conceived us almost certainly used sex to do so, when graphically confronted with this inescapable fact, all we want to do is escape from it, and as fast as possible.
“It’s difficult to imagine mom lying on the bed or the floor with her legs spread, and dad penetrating her,” says Gary Brown, an L.A.-based marriage and family therapist, cheerily illustrating the repulsive power of parent-on-parent pleasuring. “That image is just horrifying. Or as our children might say: TMI.” Brown says his own three grown-up kids are as much in denial about this as anyone else. “They say, ‘Okay, we know you and mom did it at least three times, because we don’t believe in immaculate conception. But we don’t want to know about it. We don’t want to hear about it. And we definitely don’t want to know the details.’”
If you haven’t by now clicked away, erased your browsing history and thrown all your electronic devices into a furnace, then you might as well stick with me to find out why. Because, by and large, we want our parents to be happy, right? Just as long as it’s not (and never, ever will be) happiness found in the throes of orgasm. This, though, seems selfish and bratty on our part. What the hell is our problem?
The repugnance felt toward acknowledging parents as sexual beings “seems pretty universal,” says Brown, and is “uniform across cultures as well.” In his view, the difficulty we have in coping with our parents’ sexuality — or even a whiff of sex in any parentalized context; why, say, it’s virtually impossible to watch R-rated scenes on TV with your folks in the room without silently suffering an inward nervous breakdown — might be down to the fact that we associate their presence so strongly with the innocence of our own early childhood. To safeguard the sanctity of that time in our imaginations, he says, “we really want to see our parents as ‘purer,’ for want of a better word,” than they really are, “and not tethered to sexuality.”
He warns that this is conjecture on his part, though, since it’s not a topic that he encounters too often, either in practice or in academic research — possibly because the revulsion it inspires is too strong for all but the most intrepid psychologists to want to venture anywhere near it. “The paucity of information,” he suggests, “is mute testimony to the fact that, even in this day and age, there still are some taboos.”
Disgust, Discussed
“Disgust researchers have recognized this,” says Debra Lieberman, evolutionary psychologist at the University of Miami, and co-author of the book Objection: Disgust, Morality and the Law. “I find it funny, but I do think that there’s the stigma, the stink, of studying the taboo.” When people introduce her at parties saying, “She studies incest,” she likes to correct them: “Avoidance. Incest avoidance…”
According to Lieberman, who has conducted extensive research into the phenomenon of sexual aversion between close relatives, there is something in the idea that our rejection of parents’ sexuality has a lot to do with their presence in our lives from a young age. But from her evolutionary perspective, the principal cause goes much deeper than that — it’s a yuck factor that was hard-wired into our biology many hundreds of thousands of years ago.
“Humans and many nonhuman animals have mechanisms that prevent individuals from engaging in sexual reproduction with close genetic relatives,” she explains. These mechanisms emerged over countless generations through a logical process of natural selection: Animals that reproduce with close genetic relatives are less likely to have offspring that will survive. Their children “will be more likely to succumb to disease; be more likely to have a genetic mutation that appears that’s lethal. And so, for this reason, it’s expected in humans and in other species that you have some mechanism that prevents individuals from selecting close genetic relatives as sexual partners.” The primary manifestation of that mechanism in our psychology, she says, is the emotion disgust.
“I would claim that other species, especially social primates, have a sense of disgust when it comes to picking sexual partners,” says Lieberman, offering the example of observed avoidance behavior in nonhuman primates: “You might find that mothers tolerate their juvenile sons mounting them. So that might look like, ‘Wait a minute, they don’t have an incest aversion.’ Well, that’s not the case — it’s just that they’re juveniles and their kind of sex play isn’t bothersome. It becomes bothersome when they reach sexual maturity, and then you do find that mothers will scream and go crazy, and rip [their sons] right of off them.” Studies by primatologists — among them Jane Goodall, who spent more than 50 years in the field researching chimpanzees — have shown that inbreeding in species such as chimps and macaques is indeed a rare occurrence.
When it comes to humans, though, we might recognize the instinct to shut down any hint of inbreeding before it gets “bothersome,” but exactly how those aversions are encoded as we’re growing up, and precisely what it is about our family members that triggers our disgust, have proved tricky details to pin down. Among the candidates commonly held to be genetic “kinship cues” — the attributes in others that signal whether we’re related to them — are our ability to pick up on a particular scent, or to recognize subtle family resemblances in facial features. “I don’t think that you can smell relatedness,” says Lieberman. In data she’s collected on scent, she says she “just didn’t find anything preliminarily on things like smell for humans. But that’s not to say that smell doesn’t guide attraction; it’s just that it’s not used as part of the calculus of, ‘Are you my kin?’”
When it comes to facial resemblance, meanwhile, it’s “a big one that people talk about,” but “it’s absolutely not an incest cue!” She explains, “I’m not a believer in facial resemblance, for the following reason: How do you know what you look like in ancestral environments?” Which is to say, all those millennia ago when natural selection was honing our disgust adaptation: No mirrors.
Too Close to Home
So how do we come to know who to be nauseated by when we see them in the nude? Mention incest and the popular imagination will often immediately skip to Sigmund Freud and his Oedipal and Electra urges (the notion that, as children, we forge deep desires to sleep with our opposite-sex parent, and later repress those desires in adulthood to conform to social norms). But many anthropologists, psychologists and sociologists prefer another, simpler theory for incest avoidance, which was proposed by Freud’s contemporary, the Finnish anthropologist Edvard Westermarck in 1891. The “Westermarck Effect” is based on his observance that children raised together developed “a remarkable absence of erotic feelings. Nay more, in this, as in many other cases, sexual aversion when the act is thought of.” Essentially Westermarck was hypothesizing that, in sharing a household during a critical developmental period (often identified as the first six to ten years of life), domestic familiarity breeds sexual contempt.
In the decades since, a number of cases have been seen to have borne out his ideas — notably studies of children raised communally on Israel’s kibbutzim, where youngsters were grouped together by age rather than in biological family units; when they got older, kids who had been brought up in the same peer groups acted like brothers and sisters, and proved highly unlikely to hop into bed together — despite the fact that on paper they were products of a freewheeling hippie commune. Similarly, research on marriage practices in Taiwan, where future husbands and wives often live in the same household from a young age — as well as other cultures in which marriages between cousins are common — have suggested such relationships produce fewer children and are significantly more prone to breakdown than couples who wed as strangers.
The conclusion is that sexual aversion isn’t about genetic traits; instead we infer who’s sexually off limits from the people we spend the most time with. “So how do you know who your mother is?” asks Lieberman. “Well, it’s the woman who breastfed you. How do you know who your sibling is? Well, it’s the other kid who the woman who breastfed you was breastfeeding for a long time as an infant. Who’s my father? Well, this is a good question and one that hasn’t been answered yet. Likely it’s the one sleeping with my mother and investing in me.”
Opposites Repulse
In a study published in 2018 in the journal Evolution and Human Behavior, a research team, which included Lieberman, surveyed 2,499 lucky people on their reactions to imagined scenarios of intergenerational incest, and drew a number of conclusions. First was that the closer the relation, the more intense the average levels of disgust, with suggestions of sexual encounters with uncles and aunts proving not as retch-worthy as moms and dads. In line with previous sibling studies, the researchers also found that “women report stronger incest aversion than men in intergenerational contexts as well.” Lieberman explains that in general, “women tend to find inbreeding far more disgusting and objectionable than men do — because of the higher cost that they bear in terms of reproduction and gestation.”
Another finding that seems to support the idea that cohabitation creates an aura of sexual disinterest was the fact that step-parents reported only a slightly weaker aversion to the children in their families than parents who were biologically related, while “daughters reported similar levels of incest aversion to biological fathers and stepfathers.” Here, though, the duration of co-residence didn’t seem to be a factor, and step-parents often aren’t on the scene during a child’s early years in any case, so how this works remains an open question. According to the authors, “It’s possible that actively thinking about a step-child as part of the family activates the same type of aversion that biological fathers experience to their biological daughters.”
How does all this map to more everyday revulsion toward parental sexiness, then? Our incest-quashing mechanism is so powerful it triggers disgust, not only in incestual situations but in any imagined sexual contexts whatsoever. To ensure zero possibility of arousal in ourselves, our brains impose a total no-fly zone that excludes all potential mates from parental airspace.
But according to Lieberman, if we can hold down our breakfasts long enough to examine this, we might find we don’t harbor an equal level of disgust for both parents’ bodies. “If you asked me to imagine my mom having sex with a new boyfriend — not my dad — that’s less disgusting. First it’s my mom, and so, because I’m a heterosexual female, other heterosexual women don’t really enter into my mating psychology — it just doesn’t compute. You’d have to get a little bit more graphic, and then I’d absolutely start getting very nauseated. But the thing is, if you talk about my dad having sex with his girlfriend, now, ‘Eyyy! Eurgh!’ It’s a little more gross. My natural inclination isn’t to focus on the woman but the man. And that’s gross!”
And if you’re gay? “It’s a whole other story,” she says, suggesting “the general rule would be: You’re going to find disgusting individuals who are close genetic relatives who are also of the gender that you tend to find sexually attractive.”
This gendered imbalance is corroborated by observation. In an analysis of telephone habits Lieberman conducted with colleagues in 2010, she found that when women were hitting peak fertility in their monthly cycles, they made markedly fewer calls to their fathers, and spoke with them for shorter periods of time. To put it crudely: Can’t talk Dad, feeling horny. Brown sees the same kind of effect with those parents who tend to be more open about discussing their sex lives with their children (these are usually, he notes, parents who were single and dating during the sexual revolution of the 1960s and early 1970s): “It would be more like-gender to like-gender. So a daughter might be much more comfortable talking to her mother about sexuality as opposed to talking to her father.”
Related Issues
Perhaps unwisely, let’s poke the incest bear (it’s like a Care Bear, but angry and confused, and with an extra tail) a little more. If the anti-arousal we feel toward our parents is asymmetrical according to gender, might there also be a difference in the degree of disgust parents feel when forced to think about their children having sex?
Brown thinks there is. “It may be easier for parents to see their children as sexual beings,” he says. “Young children tend to engage in autoeroticism — they might play with their genitals. It’s a very normal, healthy, developmental stage that young children go through. So parents, assuming that they’re not terribly inhibited, will begin to understand that their children are sexual beings. They will watch their children go through stages of masturbation, or masturbation-like activities, or playing doctor. Then sex education starts coming up — hopefully at home, certainly at school.”
Whereas from the kids’ point-of-view, sharing a domestic environment with their parents might be imprinting an aversion toward them via the Westermarck Effect, for parents, living in close quarters with children might in some ways be working against it. Their ongoing concern and vigilance over their children’s sexual activity might well habituate them to the disgust reaction and help them deal with it better. As Brown characterizes it, a parent’s outlook on their kid’s sexuality might look something like this: “‘Of course my child is a sexual being — even though it makes me somewhat uncomfortable, it’s an absolute reality.’ And there’s none of that feeling of incest. There’s none of that anthropological dynamic that goes along with that in terms of it being a taboo.”
As Lieberman points out, though, there will also be many parents who really do get freaked out by this stuff, and perhaps don’t feel their disgust being eroded by witnessing bathtime erections, mumbling their way through birds-and-bees chats and the like. Which makes future research into this hitherto little-studied aspect of the incest-avoidance mechanism for her a very worthwhile pursuit: “Because if it’s the case that parents are disgusted at the thought of their kids having sex, and we tend to avoid the things that we find disgusting, this is one of the barriers to parents actually communicating sexual practices to their kids.”
Reflecting on her own disgust levels in relation to her young son’s proto-sexuality — she’s a scientist, so she went there — Lieberman says, “It’s not something that grosses me out right now. Now he has no secondary sexual characteristics; he’s still a little boy.” But she continues, “If you were to ask me that question when he’s 14 years old, I might have an extremely different reaction — just like those chimp mothers that I was talking about.”
And as a person whose day job is confronting the things we least like to think about, just how on Earth does she cope with her own yuck factor when wading deep into other people’s? “The type of evolutionary psychology I do really looks at the cognitive science of it,” she says. “So if I were a computer scientist and I had to develop an information-processing schematic to hand off to an engineer at MIT who wanted to program a robot, what kind of information would I tell them they’d have to collect? How would it be integrated in order to produce the behavior I’m interested in? To me, that engineering analysis allows me to geek out and forget about the disgust.”
It surely takes a rare dedication to scientific enquiry, not to mention a firm fix on the long perspective of human evolution, to geek away the gross to this extent and investigate this murkiest corner of the human psyche. As for me, I wouldn’t want to do it. I would rather go dow… Let me try that again: I would just rather not.
Chris Bourn
Chris Bourn is a writer and editor who has writed and edited for many a title, including British Maxim and Time Out. He does stories for MEL covering health, happiness, and how things came to be.
