I ate dinner a few months ago with some colleagues and friends, where the subject of dating multiple people at once arose. I joked that dating several men at once was an effective means of cutting down on food expenses in a city with a sometimes prohibitive cost of living. (Crucially, this was a joke. I-N-D-E-P-E-N-D-E-N-T, do you know what that means?!¹)
A male diner at the table turned to me. “You know,” he explained, “men will not find you attractive if you have multiple partners.”
I know what you’re thinking: how lucky that I had a man there to expound on how to attract other men! Though it does seem a bit paradoxical, because if men were not attracted to women who had multiple partners, then presumably those women would not have multiple partners, having been rendered incapable of attracting a mate by their own promiscuity. I was inclined to ask him to draw me a graph, showing the point at which a woman is “too slutty” to attract the attention of any future suitors.² And did it matter whether these relationships were emotional or purely sexual? Did the man have to be cognizant that his lady-friend had other men in her life? What if you were currently in a monogamous relationship, but had had other partners in the past? I had a lot of questions.
The one I asked was, “What about men? Are men unattractive if they have multiple partners?”
“No. Men are supposed to have multiple partners. It’s science,” he said to the biologist.
This is a widely-held belief, perpetuated most famously by the English geneticist, A.J. Bateman, whose namesake describes a crucial tenet of intrasexual competition in evolution. Per Bateman’s Principle, females’ reproductive variance is limited by the number of eggs they can produce, as well as gestation time, whereas males are limited solely on the number of females with whom they can mate, and maybe refractory periods. Therefore, sexual selection arises, where, in order to secure the fitness of her offspring, the female must be choosy; conversely, males should strategize to spread their genetic material widely.
Bateman devised this principle after mating Drosophila melanogaster (fruit flies are pretty spectacular animal models because they don’t require a lot of upkeep and they reproduce quickly), counting the offspring, and using their phenotypes to assign parental line. As predicted, he found that male reproductive success was directly proportional with number of mates, whereas female reproductive success was not related to number of mates in any statistically significant way.
This theory is consistent across many species, and it laid the foundation for the development of parental investment theory, vis-a-vis Robert Trivers, which basically says that it is typically good evolutionary strategy for females to invest more in their offspring, from choosing mates to gestating to contributing to raising them to adulthood or thereabouts.³
With the explosion of sociobiology, Bateman and Trivers went from being cited a handful of times to being cited thousands of times. Then, the so-called “Men’s Rights Movement” appropriated it, using it as pseudo-scientific justification for their demeaning attitudes toward women. On the blog of one of these Men’s Rights proponents, to which I won’t link, so as not to direct any more internet traffic to his hateful nonsense, the man outlines rules for his “community.” Here are rules number 1, 2, and 6:
1. Men and women are genetically different, both physically and mentally. Sex roles evolved in all mammals. Humans are not exempt.
2. Women are sluts if they sleep around, but men are not. This fact is due to the biological differences between men and women.
6. A woman’s value is mainly determined by her fertility and beauty. A man’s value is mainly determined by his resources, intellect, and character.
These are some of the ideas that influenced the writings of mass-murderer, coward, and woman-hater, Elliot Rodger, to which he alluded in his rambling manifesto before killing six people in Isla Vista, California.
The problem is that they are not founded in scientific evidence.
The Limitations of the Scientific Method
Irrespective of scientific veracity, it is always dangerous to apply the conclusions of controlled experiments in other animals to humanity. For one, our mating patterns usually do not occur in captivity, and are influenced by a wide variety of factors that have nothing to do with instinct or genetics. We also do not exist in single-family or single-tribe units anymore, and our survival now depends on a communal network. I think it would be extremely difficult to determine–with any certainty–the influence of multiple partners on fecundity in humans, male or female, due to the immense number of confounding variables for which a researcher would have to control.
In addition, traits that we assume to be valuable may not be so, after all. On the other hand, genes that we associate with negative features may actually be beneficial. Consider the partial immunity that sickle-cell anemia confers against Malaria. And even if we were able to discern, with absolute certainty, favorable and unfavorable traits, we would not necessarily be able to trace or guarantee their inheritance. For all these reasons, aside from being morally bankrupt and ethically incorrect, the Social Darwinists and Nazi doctors and eugenics proponents were just factually wrong.
The other cool thing about humans is that, in addition to our superior primate genetics–and possibly because of them–we have developed this social infrastructure of “culture” and “morality.” This means that we are equipped with the logic and reasoning faculties to overcome our primal instincts and behave in a way that will promote the survival of the collective.
An Emerging Body of Counter-Evidence
Across species–especially mammals–males do have an interest in female monogamy. After all, a female has a sure-fire way of knowing which offspring are hers: they are typically ejected from her own body. Perhaps at the root of every misunderstanding between the sexes is that males possess none of the machinery involved in gestating progeny. However, the trade-off for escaping the trials of womanhood by one measly chromosome is that males can never know for sure whether they are the fathers of their mates’ babies. Absent a Maury Povich of the animal kingdom, males need a means of enforcing monogamy among females to ensure their parentage.
However, recent studies have offered evidence suggesting that females of some species are able to circumvent this male control, and that it might actually be beneficial to the health of the group as a whole. For example, a 1990 analysis of Fairy Wrens showed that up to 65% of the offspring in any socially monogamous group were not fathered by any of the birds in that group. The community of birds benefits: genetic diversity contributes to decreased in-breeding, while social monogamy confers the protection of group living.
Perhaps at the root of every misunderstanding between the sexes is that males possess none of the machinery involved in gestating progeny.
In humans, one would think that the promise of a man’s contribution to parenting would incentivize women’s monogamy. However, this view comes into conflict with studies that show that, while women want stable partners and doting caretakers for their children, they don’t actually want those people to be their children’s biological fathers. Studies show that women prefer more masculine men–ones with square jaws and more pronounced brow lines–when they are ovulating, and then go back to preferring men with more feminine features when they are not.ª The traits women want to pass to their children are not necessarily the traits that they look for in a long-term partner. This could result in a pattern similar to that in the fairy wrens, where males who are more adept at care-taking unwittingly raise other males’ babies.
Bateman’s principles themselves–that males’ reproductive success depends on number of mates, while females’ reproductive success does not–have come into question as further analysis of his methodology has shown that he may have made errors. For one, replicate studies have suggested that Bateman’s results may have arisen from chance alone. Secondly, when Bateman conducted his experiment in 1948, genetic testing was not as sophisticated as it is today. In the absence of molecular tools, Bateman underestimated his offspring numbers by up to 25%.†
Finally, several examples in the animal kingdom flat-out contradict Bateman’s underlying principles. A 2011 study suggests that female lemurs benefit from mating with multiple partners in a night, as do guppies. One theory to explain these observations posits that females employ post-copulatory selection mechanisms like sperm competition to ensure only the best swimmers reach her egg. Female antelope, who have a very small window of fertility every year, also benefit from multiple mates, sometimes trying to capitalize on this advantage by attacking males in the process of mating with other females. For this reason, Zoologist Jakob Bro-Jorgensen, the lead researcher in the study, said, “We should not regard coyness as the only natural female sex role.”
Even Science–aka Measured, Controlled, and Objective Findings–is Shaped by Contemporary Attitudes and Social Norms
Because humans are imperfect and prone to error, even our noblest attempts at objectivity will fail. Across fields, science is littered with examples of human bias confounding results. Recently, in 2005, researchers at Northwestern University declared bisexuality in men did not exist, because they found that men who self-reported as bi were only physically aroused by images of men. Critics rebuked this conclusion, noting that the standard of self-reporting of bisexuality was too low. When researchers repeated this study using better questionnaires to weed out the “fakers” (like requiring reports of sexual experiences with both sexes rather than just arousal from both sexes), they found that some males did present bisexual arousal patterns. Both studies used significant samples, both studies measured arousal with sophisticated machinery, both employed repeated trials, and both studies published findings in peer-reviewed scientific journals. And yet, the studies starkly contradict each other. It’s interesting to consider that he later study was published in the context of evolved attitudes toward sexuality.
And yet, as evinced in the discussion of Bateman above, bias doesn’t have to manifest itself in obvious ways, like cherry-picking test subjects or excluding females entirely from a study. Perhaps because his findings supported the 1950s-era mentality toward female promiscuity, Bateman was satisfied enough not to delve into mating patterns of other animals. Maybe Trivers, later on, got subconscious inspiration for his work on parent-offspring conflict from the social atmosphere of the 70s. Maybe I am giving too much credence to critiques of principles that are generally accepted as mostly true because I’m influenced by my own feminist leanings. Regardless, the fact remains: objective science is influenced by subjective human opinion, which is formed by the times. This can also be taken as a lesson in intellectual humility: if even the smartest, most logical and calculated people on the planet can overlook a variable and be wrong about something, doesn’t it stand to reason that you could be missing something, too?
In Conclusion, Nobody’s Listening
If I revisited the dinner table referenced at the beginning of this piece and read the entire thing aloud, I would probably change nobody’s mind. I would convince no one who believed otherwise that my reproductive success probably has nothing to do with the number of partners I have (or could be improved by finding more partners). Incidentally, a recent study in pediatrics showed that anti-vaxxer parents, when presented with clear evidence that vaccines are completely safe, have virtually no side-effects (especially not autism), served to eradicate deadly diseases from the planet, and save hundreds of thousands of lives every year, still refused to vaccinate their children. In fact, some parents steeled against vaccines further, reporting that they felt even more inclined not to vaccinate their kids after they were presented with the findings. In other words, humans ignore cold, hard, facts when they conflict with their most sincerely-held beliefs. Thus, the likelihood of someone who doesn’t already agree with me reading this article and changing his or her mind is slim.
After all, I’m just a silly girl, and my brain is smaller than a man’s.
1. But if you insist, I’ll stop pretending to rifle through my purse. (Pro tip: this is the real reason women’s pursues are so big.)
2. I am somewhat notorious for bar napkin graphs and drawings. I hope to give new meaning to the phrase “bar graph.”
3. However, this is sometimes at the expense of the mothers’ fitness, leading to parent-offspring conflict. Another really fascinating phenomenon that Trivers and Dan Willard discovered was that females could adjust the sex ratio of their offspring dependent on their maternal “condition.” For example, in red deer, mothers in better “conditions” will produce more sons, and mothers in poorer “conditions” will produce more daughters. Really, really cool stuff.
a. And hairy dudes. Bring me the hairy dudes.
† As mentioned, molecular biology was unavailable to Bateman and his colleagues in 1948. Therefore, instead of sequencing genes of flies to determine their parental lineage, he crossed flies he knew to be carrying a specific mutation, and counted the number of resulting offspring based on the traits they displayed. This method would not account for number of mates if certain gene combinations were deadly.
So, let’s say that a particularly sexy male fly was sporting a spotted wing mutation. If Bateman observed a bunch of flies with spotted wings the next day, he could say that the studly fly with spotted wings got around. However, a later study found that up to 25% of flies in a repeated experiment inherited a double-mutation that resulted in their inviability–meaning Bateman would never have counted them, because they died before they were born. So, using the same analogy, let’s say that the sexy spotty-winged fly met an equally sexy lady fly with white eyes. However, perhaps the spotty-wing-and-white-eye combination is deadly. So, despite adding to their number of fertilizations, the copulations of the star-crossed sexy fly lovers would go uncounted. (The Eagles’ “Life in the Fast Lane” comes to mind.) Losing a quarter of offspring to double mutations could skew the results, and may explain why some scientists have not been able to replicate Bateman’s numbers.