A recent study published in Evolutionary Psychological Science suggests that intelligence in young men is positively linked to physical traits like grip strength and a masculine body shape. At the same time, the research provides evidence that higher intelligence tends to be associated with less promiscuous sexual behavior. These findings support the idea that cognitive ability and physical health may reflect an underlying general fitness factor, while also steering smarter men toward more monogamous relationship strategies.
The new study was motivated by the idea of a general fitness factor in humans. In evolutionary biology, there is a concept suggesting that overall genetic quality is expressed through multiple physical and mental traits at the exact same time.
This concurrent expression happens because certain genes can influence several seemingly unrelated physical characteristics or biological systems. This genetic phenomenon is known as pleiotropy. For example, a single gene might affect both a person’s immune system and their brain development simultaneously.
Some evolutionary scientists suspect that an individual’s total load of genetic mutations affects their entire body. Every person carries small genetic mutations, but having a lower total number of these mutations is generally considered advantageous. According to this perspective, people with fewer genetic mutations should naturally display better physical and mental functioning across the board.
Previous studies have provided evidence that intelligence shares a common genetic background with overall physical health, body symmetry, and even body height. Yet, the relationship between intelligence and evolutionary reproductive success remains complicated. Some past research suggests that highly intelligent people actually produce fewer children, which seems to contradict the idea that intelligence is a marker of high evolutionary fitness.
“There is a bit of a debate in the existing literature about how intelligence relates to general health as well as behavioral outcomes. Some research suggests that intelligence is just one manifestation of overall good genetic quality, so if someone has high intelligence they should also have good physical health, markers of good genetic quality such as having strong grip strength, and success in evolutionarily relevant life outcomes like mating,” said study author Tara DeLecce, a postdoctoral Researcher and special lecturer at Oakland University.
“Other research suggests that high intelligence may correlate with good physical health, but it is most useful for evolutionarily new problems, like taking IQ tests. Solving problems that have been common over ancestral human history, like finding a mate, should be more difficult with high intelligence. We wanted to clarify the relationships between intelligence, physical health condition, and mating success.”
The study involved a sample of young adult men attending a university in the American Midwest. The final analysis included 41 men, ranging in age from 18 to 33, who completed all parts of the laboratory procedures. An initial, broader dataset of 66 men from the same study was also used for some secondary statistical calculations. They chose to focus specifically on men because male reproductive history tends to show more physical and behavioral variation in evolutionary terms.
To measure cognitive ability, the scientists used a short form of a well-known psychological assessment called the Raven Advanced Progressive Matrices test. This test measures fluid intelligence, which refers to the ability to reason, recognize patterns, and solve new problems independently of prior learned knowledge. Participants completed a computerized task consisting of twelve visual pattern problems.
For each cognitive problem, the men had to select the correct missing piece to complete a complex geometric design. The researchers also assessed the participants’ sexual habits using a standardized questionnaire. They focused specifically on the behavioral section of this survey to determine how frequently the men engaged in casual, uncommitted sex.
This section asked questions about their actual sexual history rather than just their desires or attitudes. After completing the computer tasks in a private room, the men provided several physical measurements to an experimenter. An experimenter measured the circumference of each participant’s shoulders and hips using a standard tape measure.
They calculated the shoulder-to-hip ratio by dividing the shoulder measurement by the hip measurement. A higher ratio typically indicates a more V-shaped, muscular torso, which evolutionary biologists often view as a marker of physical health. The men also used a digital hand dynamometer to measure their physical grip strength.
The participants were instructed to pull back on the device as hard as they could while seated. They performed three strength tests for both their left and right hands, and the researchers recorded the average values in kilograms. Finally, the researchers recorded each participant’s height and weight using a digital medical scale to calculate their body mass index.
When analyzing the data, the scientists found positive associations between fluid intelligence and the physical measurements. Specifically, higher intelligence scores were linked to greater left-hand grip strength and a higher shoulder-to-hip ratio in the main sample of 41 men. When the researchers expanded their analysis to the larger group of 66 men, they found that both right and left grip strength were positively related to intelligence.
On the other hand, the study revealed a negative relationship between intelligence and casual sexual behavior. Men who scored higher on the cognitive test reported engaging in fewer promiscuous sexual acts. This suggests that while intelligence may signal physical fitness, it does not necessarily translate to seeking out a high number of casual sexual partners.
The researchers ran additional statistical models accounting for body mass index, ensuring that simple body size was not skewing the results. Even when controlling for overall body mass, the shoulder-to-hip ratio remained a marginally significant predictor of higher intelligence. The scientists noted that these physical and mental traits tend to group together as a single package.
The scientists grouped all these traits together using a statistical technique to uncover hidden underlying patterns in the data. This mathematical analysis suggested the presence of two main groupings, with one reflecting sheer physical muscularity and another reflecting an overall fitness factor. This overall fitness factor connected higher intelligence, a more V-shaped torso, and a lower tendency for casual sex.
While these findings provide evidence for a general fitness factor, the average person should avoid drawing absolute conclusions about intelligence and dating success. One might assume that reporting less promiscuity means smarter men struggle to find willing sexual partners.
However, the scientists suggest this pattern actually points to highly intelligent men succeeding more in monogamous, long-term relationships rather than casual sexual encounters. Evolving toward sexual exclusivity may be a more modern human strategy that requires higher intelligence to navigate successfully.
“Our findings more align with the idea that, at least among men, intelligence is related to physical health and/or good genes but is inversely related to promiscuous sexual behavior,” DeLecce told PsyPost. “Some may interpret this as increased difficulty with mating success. However, this might also suggest that men of higher intelligence are more likely to succeed in monogamous mating contexts.”
The study has a few limitations that require consideration. The most significant limitation is the small sample size of only 41 men in the main analysis. With such a small group, the findings might not represent the general population accurately. The sample was also mostly made up of college students from a single region, which limits how broadly the results can be applied to different age groups or cultures.
“These results should be interpreted with caution until they are replicated more widely,” DeLecce said.
Moving forward, scientists hope to explore how intelligence relates to specific dating contexts rather than just casual sex. Future research will likely test these physical and mental connections in larger, more diverse groups of people. Investigating how different mating environments interact with physical markers of genetic quality will help clarify the evolutionary role of human intelligence.
The study, “Associations Between Intelligence and Anthropometric Traits: Evidence from a U.S. Sample of Young Men,” was authored by Tara DeLecce, Gavin S. Vance, Bernhard Fink, and Todd K. Shackelford.
