Strength linked to the sexual behavior of both women and men

While many studies have examined possible evolutionary links between men’s strength and sexual behavior, a Washington State University study included data on women with a surprising result. Women, as well as men, who had greater upper body strength tended to have more lifetime sexual partners than their peers.

The study, published in the journal Evolution and human behaviorwas designed to test evolutionary theories of human sexual dimorphism, namely that early in human history there likely existed a reproductive advantage by selecting for greater upper body strength in males.

Another finding from this study hints at a reason for this physical difference: Men with greater upper body strength were also more likely to be in long-term relationships.

“People have assumptions about men’s sexual behavior and how it relates to evolution. In addition to acquiring more sexual partners, establishing long-term relationships was probably also important for men in evolutionary history,” said lead author Caroline Smith, a recent doctoral student at WSU. degree in anthropology.

For this study, Smith and his faculty advisor, WSU evolutionary anthropologist Ed Hagen, analyzed data on 4,316 U.S. adults from 2013 to 2014 from the National Health and Nutrition Examination Survey. Centers for Disease Control and Prevention. They primarily used grip strength, a common measure for assessing upper body strength, and compared it to survey participants’ responses about their sexual behavior.

The results present a mixed picture, according to the authors.

There are several hypotheses as to why men have greater upper body strength. One popular theory, known as the sexual selection hypothesis, is based on competition: like other primates, human males competed with each other for access to mates and therefore had to be physically formidable to pass on their genes. This theory predicts little relationship between women’s strength and their sexual success.

“On average, men are stronger than women and men report having more life partners than women, but men and women are on the same regression line,” Hagen said. “Regardless of whether they are male or female, stronger individuals have more lifetime sexual partners. This was a surprising finding and somewhat contrary to the sexual selection hypothesis.”

On the other hand, the findings of this study on long-term partners seem to support another theory based on “provisioning.” Since human babies require a lot of care and resources, especially from females during pregnancy and breastfeeding, males were more sought after as partners when they could provide meat through hunting, which , for hundreds of thousands of years before the modern era, required upper body strength. Stronger human males, who also stuck around and helped provide more food resources to these children as they grew, would also better ensure their survival.

While there are theories about male strength in relation to reproductive success, there aren’t many about female strength, in part because women are not often included in these types of studies.

There was no obvious explanation in this study’s data for why women with greater upper body strength also had a greater number of lifetime partners. Researchers controlled for many variables, including general health and testosterone levels, but the link still held. They cited a few potential theories, including that it’s due to “assortative mating,” meaning that physically stronger people tend to pair up more frequently. It could also be that physically stronger women require less male investment or feel they can take more risks.

Ultimately, more studies involving women would be needed to uncover more evidence for the reasons for this connection as well as a better understanding of human evolution in general.

“I believe it is important to continually test our theories, including expanding our research questions to include women,” Smith said.