Unveiling the Power: How Sexual Behavior Shapes Strength in Both Women and Men

Although numerous studies have examined the potential evolutionary connections between male strength and sexual behavior, a study from Washington State University incorporated data from women yielding an unexpected finding. Women, like men, exhibiting increased upper body strength showed a tendency toward having more lifetime sexual partners compared to their counterparts.

The research, published in the journal Evolution and Human Behavior, aimed to explore evolutionary theories regarding human sexual dimorphism—specifically, that in early human history, men’s enhanced upper body strength may have offered a reproductive advantage.

Another observation from this research indicated a possible explanation for that physical disparity: males with greater upper body strength were also more inclined to engage in long-term partnerships.

“Society holds certain beliefs about men’s sexual conduct and its links to evolution. In addition to acquiring more sexual partners, forming long-term partnerships likely held significance for men throughout evolutionary history,” remarked lead author Caroline Smith, a recent WSU Ph.D. graduate in anthropology.

For this investigation, Smith and her supervising professor, WSU evolutionary anthropologist Ed Hagen, examined data from 4,316 U.S. adults gathered between 2013 and 2014 from the National Health and Nutrition Examination Survey conducted by the Centers for Disease Control and Prevention. They primarily utilized grip strength, a common metric for estimating upper body strength, and correlated it with participants’ survey feedback regarding their sexual behavior.

The results offer a nuanced perspective, noted the authors.

Several theories exist regarding why men exhibit greater upper body strength. One prevalent concept, termed the sexual selection hypothesis, revolves around competition: similar to other primates, human males competed with one another for access to mates and thus needed to be physically imposing to propagate their genes. This hypothesis suggests minimal correlation between women’s strength and their mating success.

“While men are generally stronger than women and report more lifetime partners than women, both genders align on the same regression line,” explained Hagen. “No matter their gender, individuals with greater strength tend to have more lifetime sexual partners. This was an unexpected discovery and somewhat contradicts the sexual selection hypothesis.”

Conversely, the findings regarding long-term partners may align with another theory based on “provisioning.” As infants demand extensive care and resources, particularly from women during pregnancy and breastfeeding, men become more appealing as partners when they can supply meat through hunting, which, for millennia prior to modernity, necessitated upper body strength. Stronger human males, who also remained available to provide additional food for their growing children, would enhance their survival chances.

While theories concerning men’s strength and reproductive success are abundant, there are fewer regarding women’s strength, partly due to their limited inclusion in such studies.

The study did not provide a clear rationale within its data for why women with enhanced upper body strength also had a higher number of lifetime partners. The researchers considered various factors, including overall health and testosterone levels, yet the correlation persisted. They proposed several hypotheses, including “assortative mating,” which suggests that physically formidable individuals tend to partner with one another more frequently. It may also be possible that women who possess greater physical strength require less investment from males or feel more empowered to take risks.

Ultimately, additional research including women would be necessary to unearth further evidence supporting the reasons behind this link, as well as to attain a deeper understanding of human evolution as a whole.

“It is crucial to continuously challenge our theories, particularly by broadening our research inquiries to encompass women,” Smith concluded.