Recent research published in evolutionary psychology Our findings suggest that intelligence in young men is positively related to physical characteristics such as grip strength and masculine body shape. At the same time, this study provides evidence that higher intelligence tends to lead to less sexual activity. These findings support the idea that cognitive ability and physical health may reflect underlying general fitness factors, while also leading smarter men to more monogamous relationship strategies.
This new research was motivated by the idea of a general human fitness factor. There are concepts in evolutionary biology that suggest that overall genetic disposition is expressed through multiple physical and mental traits simultaneously.
This co-expression occurs because a particular gene can influence several seemingly unrelated physical properties or biological systems. This genetic phenomenon is known as pleiotropy. For example, a single gene can affect both a person’s immune system and brain development simultaneously.
Some evolutionary scientists suspect that the total amount of genetic variation in an individual affects the entire body. All people have small genetic variations, and it is generally believed that the lower the total number of these mutations, the better. According to this perspective, people with fewer genetic mutations should naturally have better overall physical and mental functioning.
Previous research has shown evidence that intelligence shares a common genetic background with overall physical health, body symmetry, and even height. However, the relationship between intelligence and evolutionary reproductive success remains complex. Some past research suggests that more intelligent people actually have fewer children, but this seems to contradict the idea that intelligence is an indicator of high evolutionary fitness.
“There is some debate in the existing literature about how intelligence is related to general health and behavioral outcomes. Some studies suggest that intelligence is just one manifestation of overall good genetics. Therefore, high intelligence “People who have “ should also have good physical health, markers of good genetics such as strong grip strength, and success in evolutionarily related life outcomes such as mating,” said study author Tara Dereche, Postdoctoral Fellow and Distinguished Lecturer at the University of Auckland.
“Other research suggests that high intelligence may be correlated with good physical health, but intelligence is most useful for problems that are new to evolution, such as taking an IQ test. Solving problems that were common in our ancestral history, such as finding a mate, should be more difficult with high intelligence. We wanted to uncover the relationship between intelligence, physical health, and mating success.”
This study included a sample of young adult men attending a university in the Midwest. The final analysis included 41 men between the ages of 18 and 33 who completed all parts of the testing procedure. An earlier, broader dataset of 66 men from the same study was also used for some secondary statistical calculations. They decided to focus specifically on men because their reproductive history tends to show physical and behavioral changes from an evolutionary perspective.
To measure cognitive abilities, the scientists used a shortened version of a well-known psychological assessment called the Raven Advanced Progressive Matrices test. This test measures fluid intelligence. This refers to the ability to reason, recognize patterns, and solve new problems regardless of previously learned knowledge. Participants completed a computerized task consisting of 12 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 specifically focused on the behavioral section of the study, looking at how often men had casual, non-committal sex.
In this section, we asked about actual sexual history, not just desires or attitudes. After completing a computer task in a private room, the men provided several body measurements to the experimenter. The experimenter measured each participant’s shoulder and hip circumference using a standard tape measure.
They calculated the shoulder-to-hip ratio by dividing the shoulder measurement by the hip measurement. A higher ratio usually indicates a more V-shaped and muscular torso, which evolutionary biologists often consider as a marker of physical health. The men also measured their physical grip strength using a digital dynamometer.
Participants were instructed to pull the device as hard as possible while sitting. They performed three muscle strength tests on both the left and right hands, and the researchers recorded the average values in kilograms. Finally, the researchers used a digital medical scale to record each participant’s height and weight and calculate their BMI.
After analyzing the data, scientists found a clear link between fluid intelligence and physical measurements. Specifically, in the main sample of 41 men, they found that higher intelligence scores were associated with stronger left hand grip strength and a higher shoulder-to-hip ratio. When the researchers expanded their analysis to a larger group of 66 men, they found that both left and right hand grip strength were positively related to intelligence.
On the other hand, this study revealed a negative relationship between intelligence and casual sexual behavior. Men with higher cognitive test scores reported less promiscuous sexual activity. This suggests that while intelligence may indicate good physical fitness, it does not necessarily lead to seeking more casual sexual partners.
The researchers ran an additional statistical model that took BMI into account to ensure that simple body size did not skew the results. Even when controlling for overall body weight, shoulder-to-hip ratio remained a marginally significant predictor of higher intelligence. Scientists have noted that these physical and mental traits tend to be grouped together as one package.
Scientists used statistical methods to group all these characteristics and uncover hidden underlying patterns in the data. This mathematical analysis suggests the existence of two main groups, one reflecting complete physical muscle mass and the other reflecting overall fitness factors. This overall fitness factor is associated with higher intelligence, a more V-shaped torso, and a lower propensity for casual sex.
Although these findings provide evidence for general fitness factors, the average person should avoid making absolute conclusions about intelligence and dating success. Some might think that fewer reports of promiscuity means that smart men have a harder time finding willing sexual partners.
However, scientists suggest that this pattern actually indicates that highly intelligent men are more successful in monogamous, long-term relationships than in casual sexual encounters. The evolution toward sexual exclusivity may be a more modern human strategy, and it requires advanced intelligence to navigate it successfully.
“Our findings are more consistent with the idea that, at least among men, intelligence is associated with physical health and good genes, but inversely with promiscuous sexual behavior,” Deretsche told SciPost. “Some may interpret this as increased difficulty in mating success. However, it may also suggest that males with higher intelligence are more likely to succeed in monogamous mating environments.”
This study has several limitations that need to be considered. The most important limitation is the small sample size of only 41 men in the main analysis. With such a small group, the findings may not accurately represent the general population. Additionally, the sample consisted mostly of college students from a single region, which limits the applicability of the results to different age groups and cultures.
“These results should be interpreted with caution until they are replicated more widely,” Dereche said.
In the future, scientists hope to investigate how intelligence relates to specific dating situations, rather than just casual sex. Future research could test these physical and mental connections in larger and more diverse groups of people. Investigating how different mating environments interact with physical markers of genetic disposition can help clarify the evolutionary role of human intelligence.
The study, “The Association between Intelligence and Anthropometric Characteristics: Evidence from a Sample of U.S. Youth,” was authored by Tara Deretsche, Gavin S. Vance, Bernhard Fink, and Todd K. Shackelford.
