Upper Body Strength Linked to Mating Success in Both Genders
Greater upper body strength correlates with more lifetime sexual partners for both men and women.

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A study from Washington State University, published in Evolution and Human Behavior, explored the connections between upper body strength and sexual behavior in humans. Traditionally, such research has focused on men, but this study included women and found unexpected results: individuals with greater upper body strength, regardless of gender, reported more lifetime sexual partners.
“People have assumptions about men’s sexual behavior and how that’s related to evolution. Besides acquiring more sexual partners, establishing long-term relationships was likely also important for men in evolutionary history,”
Dr. Caroline Smith.
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Subscribe for FREEEvolutionary hypotheses tested
The researchers examined two prominent theories explaining human sexual dimorphism – physical differences between males and females. One is the sexual selection hypothesis, which suggests that in early human history, male physical strength was advantageous for competing for mates. The other, known as the provisioning hypothesis, posits that stronger males who could gather resources, such as through hunting, were better partners and providers, enhancing reproductive success.
Sexual dimorphism
Refers to physical differences between males and females of the same species, such as size, coloration, or body structure, often driven by evolutionary pressures.Sexual selection hypothesis
A theory in evolutionary biology suggesting that traits enhancing an individual’s ability to compete for or attract mates are passed on to future generations.Provisioning hypothesis
An evolutionary theory proposing that males who contribute resources, such as food, increase offspring survival and reproductive success.Key findings
- Both men and women with greater upper body strength had more lifetime sexual partners. This finding diverges from predictions of the sexual selection hypothesis, which typically associates male strength with mating success but not female strength.
- Men with greater upper body strength were more likely to be in long-term relationships, aligning with the provisioning hypothesis.
“Men are stronger than women, on average, and men report more lifetime partners than women, but men and women are on the same regression line. Regardless of whether they’re males or females, stronger individuals have more lifetime sexual partners. That was a surprising finding and somewhat contrary to the sexual selection hypothesis.”
Dr. Ed Hagen.
Methods and data sources
The study analyzed data from 4,316 U.S. adults collected in the 2013–2014 National Health and Nutrition Examination Survey. Upper body strength was measured using grip strength, a standard proxy. This was then compared with survey responses about sexual behavior. The analysis controlled for variables such as general health and testosterone levels.
Implications and unanswered questions
The connection between upper body strength and mating success in women is less clear. Researchers hypothesize that assortative mating, where individuals with similar traits pair together, might play a role. Alternatively, stronger women might be more willing to take risks or require less male investment. These explanations remain speculative, highlighting a gap in research on women’s evolutionary traits.
Limitations and future directions
This study underscores the need to test evolutionary theories across genders to gain a more complete understanding of human sexual behavior. Future research could explore why strength correlates with reproductive success in women and investigate other potential factors influencing these dynamics.
“I believe it’s important to continually test our theories, especially by expanding our research questions to include women,”
Dr. Caroline Smith
Reference: Smith CB, Hagen EH. Strength, mating success, and immune and nutritional costs in a population sample of US women and men: A registered report. Evolution Human Behav. 2025;46(1):106647. doi: 10.1016/j.evolhumbehav.2024.106647
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