Study Suggests Women Prefer Men With Larger Genital Size

A new study published in PLOS Biology finds that, contrary to the saying, size does matter when it comes to sexual attraction. Researchers report that women generally rate men with larger genitalia as more attractive, while men interpret the same trait as a sign of strength and competitive ability.

The Study and Its Findings

Lead author Dr. Upama Aich of the University of Western Australia wrote in a Conversation piece that the team confirmed earlier findings: “We confirmed our earlier finding that women find a larger penis more attractive.”

The study set out to explore why the human penis is disproportionately large relative to body size compared with other great apes, despite its primary biological function of transferring sperm. Researchers concluded that larger size serves dual purposes: attracting mates and signaling dominance to rivals, similar to how deer use antlers or lions display their manes.

How the Research Was Conducted

The study involved over 600 male and 200 female participants, who were asked to rate computer-generated male figures varying in height, body shape, and penis size. Female participants assessed sexual attractiveness, while men evaluated perceived threat levels — both as fighters and sexual competitors.

The results showed that women preferred taller men with V-shaped upper bodies and larger penises, although there was a point of diminishing returns where further increases in size offered little additional attractiveness. Men, meanwhile, perceived well-endowed figures as more intimidating and competitive.

Evolutionary Implications

From these findings, researchers suggest that the unusually large human penis evolved partly as a sexual ornament to appeal to females, and partly as a signal of combative ability to rival males. Humans’ upright posture, long before clothing, meant the penis was always visible, broadcasting status and reproductive potential.

Professor Michael D. Jennions, co-author and Emeritus Professor of Evolutionary Biology at Australian National University, explained: “While the human penis functions primarily to transfer sperm, our result suggests its unusually large size evolved as a sexual ornament to attract females rather than purely as a badge of status to scare males, although it does both.”

Caveats and Considerations

The researchers noted several limitations: participants evaluated only penis size, height, and body shape, without accounting for other traits such as personality or facial features. Cultural standards of masculinity also vary globally and over time, which could influence perceptions.