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Written by Ichimoku Sanjin.

Intelligence is one of the most attractive qualities that women look for in a partner. They are drawn to men with a good education, men who think critically, and men who can engage in interesting conversation. The genes for IQ cover a large portion of the genome and intelligence positively correlates with almost everything we consider desirable, from civic engagement to athletic ability. So it makes sense that women would directly select for intelligence. In doing so, they gain not only direct benefits, such as resources and safety, but also a "eugenic premium” in the form of genetically fitter offspring (Miller, 2000). And yet there are many holes in what we shall call the Einstein Sexual Selection Theory ( hereafter: EST).

First, there is the considerable gap between what women (and individuals in general) say they want and what they actually want. This is a well studied phenomenon called social desirability bias. It’s what happens when a research participant skews their answers (consciously or subconsciously) to appease the researcher and/or adhere to social norms, and women do it more often than men. Many of the studies that claim women are attracted to smarter men are self-report surveys (Buss et al., 1990), a method notably prone to this bias. In these surveys, subjects (normally college students) are asked to list the traits they find appealing in hypothetical short or long-term partners. Of course, reality rarely matches hypothetical circumstances, particularly when optimistic thinking and defending one’s social image can contaminate the answers.

One study was conducted in which men and women were asked to rate the significance of physical appearance, personality, and money before a speed date experiment. The researchers then observed the actual significance of these factors based on the results of the participants at the speed date event. Prior to the experiment, women had rated physical appearance as the least important trait. It ended up being their highest priority, even somewhat more important than it was for men, with personality and money coming second and third for both genders. (Eastwick and Finkel, 2008). Of course, these artificial experiments also suffer from a lack of ecological validity. However, they at least allow us to scrutinize the self-report data and EST.

The next problem with EST is the lack of empirical data. Facial attractiveness and intelligence are not correlated either at the phenotypic or the genotypic level. This is contrary to expectations from evolutionary theory because sexually selected traits are usually inter-correlated, either due to pleiotropy (hormonal or genetic) or to cross-trait assortative mating (intelligent people choosing more facially attractive mates, and vice-versa) (Mitchem et al., 2015). Moreover, facial symmetry is a large component of attractiveness and is an indicator of genetic quality. If intelligence was an attractive quality in a mate, more beautiful people would choose the smartest partner, and their offspring would become smarter and more intelligent than average thanks to cross-trait assortative mating. So what do the data on assortative mating show? Here are a few genetic correlations (note that rg stands for genetic correlation and it runs from -1 to +1) (Torvik et al., 2022):

Educational attainment = 0.37

Height = 0.13

Depression = 0.08

Both men and women tend to choose partners with similar social, psychological, and physical traits (height, weight, eye colour, etc.). However, this does not imply that women prefer smarter men. It simply means that women prefer men who are within a certain set of parameters relative to themselves — not too smart, not too dumb.

If sexual selection had been a factor in the rise of intelligence across human evolution, we would expect it to be more prominent in the last century in industrialized societies where individuals, particularly women, have more unrestricted sexual freedom and their choices are less subject to family dynamics and societal coercion. However, the decreasing genetic intelligence trend suggests something is amiss. What’s particularly interesting is that the same is not true for height. Selection for height was not present in the 19th century, but appeared later in the 20th century (Thompson et al., 2022). One study conducted in the Netherlands revealed that taller men had higher fertility than shorter men, which could be a factor in the overall increase in height (Stulp et al., 2015). Women also seem to prefer taller men across a variety of studies, including self-report questionnaires, laboratory, and field settings (Stulp and Barrett, 2016; Courtiol et al., 2010; Stulp et al., 2013). However, there is no such trend for IQ.

If intelligent men were more attractive, women would look for intelligence cues in a potential partner, but this doesn’t appear to be the case. For example, men and women wearing glasses were considered less attractive, despite glasses being associated with higher perceived intelligence (Al Ryalat et al., 2022). Of course, it is possible to assert that the link between wearing glasses and intelligence is an internalized concept that has been developed over time, rather than a biological instinct that influences our sexual desires. Despite this, humans are incredibly social and have the capacity to absorb and combine societal standards with our more primitive inclinations. Money, for instance, is a relatively new concept in comparison to evolutionary time periods, yet it has a strong influence on social behavior and can arguably shape sexual dynamics.

In this regard, an interesting measure is brain size. People with larger brains are, on average, smarter, and people with larger brains tend to have larger heads. However, women aren’t attracted to men with a large head or what is colloquially known as a “fivehead”. Most women would prefer a small-headed basketball player to a big-headed midget alien.

Arguably the best evidence against EST comes from a recent study (Driebe et al., 2021) where measured intelligence did not predict increased mate appeal in either speed dating or video clip experiments. The study even found a very small but significant effect in the opposite direction! Instead, men who were funnier were deemed more attractive, but having a sense of humor was not correlated to g (general intelligence). Physical attractiveness was the most influential factor in determining a man's sexual appeal (b= 1.15, meaning that for each unit increase in physical attractiveness, sexual mate appeal increased by 1.15 units). Interestingly, the slight negative effect of intelligence was not caused by women being unable to assess men's intellect, because more intelligent people were indeed seen as smarter! Incorporating cues (such as reading newspaper headlines) only improved the appeal of more attractive men, not more intelligent ones (Driebe et al., 2021). Remarkably, this effect persisted even after accounting for facial attractiveness.

A more speculative problem for EST would be the differences in intelligence between men and women shown by Richard Lynn (2017). Lynn showed that males gain approximately a 4 IQ point advantage over females during late adolescence and into adulthood. Sexual dimorphism is typically a trait that is sexually selected, meaning it is a physical characteristic that is different in males and females of the same species. This can include features like size, fur color, and facial structure. However, sexual selection can be driven by female choice or by intra-sexual dynamics. Intrasexual competition among humans typically occurs within social settings, such as vying for wealth and status, rather than involving physical violence. If Lynn is correct, men may have evolved superior cognitive abilities in order to gain access to more influential positions and, in turn, better access to the most desirable women. In this instance, intelligence would not have been selected for directly as an attractive quality, but only indirectly as a result of its correlation to wealth and social status.

Consider these guys:

How many are objectively above a 7/10? Probably one of them…and not for his looks.

However, does the lower attractiveness of smart guys in experimental settings translate to a real-world lack of mating success? In 2000, a depressingly titled study was published: “Smart teens don’t have sex (or kiss much either)” (Halpern et al., 2000). The most sexually active individuals were in the 75-90 IQ range for males, with these males being found to be the least likely to be virgins as adolescents. (Halpern et al., 2000). Controlling for age, physical maturity, mother’s education, and race, adolescents with an IQ of 130 were 3 to 5 times less likely to have had intercourse than those with average IQ. Interestingly, a curvilinear relationship was observed, with both very low and high IQ boys being more likely to be virgins than those with an average IQ! Even more intriguingly, boys with a level of IQ that would qualify for intellectual disability (60) were still more likely to have had sex than those with a very high IQ (130). Conversely, for girls, the odds of being a virgin at both ends of the IQ distribution were about the same.

Relationship between IQ (measured by the Add Health Picture Vocabulary Test (AHPVT)) and odds of ever having had intercourse (i.e. lower values on the Y-axis means higher likelihood of being virgin) (Halpern et al., 2000)

With all this in mind, it is not difficult to comprehend why females swoon over attractive athletes, actors, or musicians, yet they tend to be conspicuously absent from the Nobel Prize presentation. But what are the long-term consequences if EST is indeed wrong?

Industrialization has led to dramatic changes in sexual morality, with women gaining more control in mate selection. If a woman lives in a city with a smart phone, she effectively has an infinite supply of men to select from. Of course, there is no reason to suppose that the aggregate of these choices is positive for humanity, quite the opposite in fact. Studies have shown that women are more attracted to men who have traits associated with the Dark Triad personality cluster: narcissism, Machiavellianism, and psychopathy — traits that evolved to facilitate men’s short-term mating strategies (Carter et al., 2014). This also explains why certain women are drawn to serial killers, gangsters, or psychopaths.

Darwin taught us that any deviation from the optimum phenotype is weeded out by natural selection, including the traits that are attractive to a partner but too costly for the survival of the individual. However, in modern populations this evolutionary trade-off has disappeared and sexual selection proceeds unfettered. It is possible that if the significance of sexual selection is heightened, a group of humans may eventually come to resemble Thor or a Greek goddess, since physical traits are undeniably the primary elements in mate selection. This could also lead to a caste-like situation in which individuals have genetically diverse predispositions for academic success, political affiliations, and personality. This is due to the fact that assortative mating widens the gap between people with different attributes, while keeping the average steady.

If there is no conscious effort to improve humans through embryo selection or genetic engineering, the modern selection process may not counteract the dysgenics trend. In all likelihood, it will worsen it.

Ichimoku Sanjin is an evolutionary anthropologist. He has worked in population genetics for the last ten years and has carried out research in chronobiology, evolutionary psychology, creativity, and behavioural genetics. He has published in peer-reviewed journals such as Intelligence, Creativity Research Journal, and Thinking Skills and Creativity. He once published poetry but now prefers the language of R.

References:

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