A study by University of Glasgow psychologists finds no evidence in favor of the controversial hypothesis that women’s preference in a male partner appearance fluctuates in accordance with their hormonal cycle.

Past research has both supported and countered this supposition, as well as the claim that taking hormonal contraceptives that interfere with the cycle will thus alter their perception of what facial features are appealing. The basis for these studies is a social-evolutionary theory that exaggerated male characteristics are indicators of high testosterone and a strong immune system, and thus, selecting a mate with this appearance will lead to the fittest (in all senses of the word) offspring. In contrast, more feminine features on men are believed to be indicators of a mate that would provide better care during the long period of child development.

Accordingly, many have postulated that women at their most fertile phase (ovulation) are more attracted to masculine men, and more open to men with feminine faces during the rest of the cycle.

However, as the authors of the current study, published in Psychological Science, point out, these investigations relied on women to self-report where they are in their cycle, only tested one time each at opposite points in the cycle, and only showed women one type of face.

To finally address this scientific question with a more robust experimental design, the team recruited 584 heterosexual women and asked them to pick which version of a male face they found attractive for a one-night stand/casual relationship. Then, during a separate round, the women were asked which they would pick for a committed partnership. Saliva samples were taken at each session to objectively measure hormone levels. In order to account for long-term hormone fluctuations, this test was performed once a week for 5 weeks. About seven months and 24 months later, second and third 5-week testing blocks were performed, though only 18 participants showed up for the third.

Though the women were, overall, more attracted to men with more masculine faces when selecting short-term relationships, the authors conclude: “Collectively, our analyses showed no compelling evidence that changes in women’s salivary hormone levels are associated with their facial-masculinity preferences or that the combined oral contraceptive pill decreases women’s masculinity preferences.”

When considering the implications of their discovery and other similar, recent findings, they believe that the hypothesis that masculine features evolved as an indicator of strong immune system-related genetics needs to be rethought, stating, “Rather than functioning as a cue of men’s immunocompetence, men’s facial masculinity may primarily function as a cue of their intrasexual competitiveness.”

In summary, the ancestors of ruggedly handsome men may have been more likely to throw rocks at other dudes interested in their mate, but there was nothing special about their ability to fight off infections.

Interestingly, the team did find that women with increased levels of the stress hormone cortisol were more less likely to be attracted to male faces with a high degree of symmetry – a major factor in so-called good looks. They suggest this revelation should be followed up with future studies.