Penis size may matter more to men than women

Human history is full of juvenile jokes, bizarre stereotypes and downright harmful misinformation about the size of a man’s penis. But the real science behind size suggests that men themselves are more likely than women to get upset about the subject. According to a study published today in the journal Biology PLOSmen routinely feel more physically and sexually threatened by well-endowed rivals, regardless of how women feel about these matters.

For years, evolutionary biologists have been confused by one particular aspect of human anatomy. Relative to overall body size, the human penis is generally larger than that of most other primates. The reasons remain unclear, although there are many theories related to attracting mates, repelling opponents, and even improving reproductive success.

To better understand the psychological influences on humanity’s sexual history, researchers at the University of Western Australia asked more than 600 men and 200 women to examine computer-generated male bodies with varying penis shapes, heights and sizes. The men then rated each example based on the degree of physical and sexual intimidation they felt. During this time, the women rated each character’s hypothetical sexual attractiveness. Each participant saw either a full-size image or a full-scale alternative.

Women most often rated male bodies as more attractive when they had a higher shoulder-to-hip ratio (i.e., V-shape) and a larger penis. That said, these attributes had their limits. There came a time when overall body and penis size offered diminishing returns.

Men, if you can believe it, were often a little more sensitive about potential rivals. Unlike the other volunteers in the study, the men constantly rated their same-sex opponents as more intimidating as body and penis size increased, with no cap on the measurements. At the same time, they also viewed men with greater attributes as a greater sexual threat. Compared to women’s responses, it seems that many men truly believe that size matters more than often.

The team says their work offers the first such experimental evidence that men assess penis size to judge an opponent’s fighting and sexual prowess. The overlapping responses from both sexes also suggest that increased human penis size is an evolutionary adjustment aimed at attracting mates.

“While the human penis functions primarily to transfer sperm, our results suggest that its unusually large size evolved as a sexual ornament to attract women rather than simply a badge of status to scare away men,” Michael Jennions, study co-author and evolutionary biologist from the University of Western Australia, said in a statement. “Even if it does both,” he added.

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