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A team of researchers from Pennsylvania State University and Universiteit Leuven has found evidence that suggests facial masculinity is not a sexual ornament signaling mate quality in humans. In their paper published in Proceedings of the National Academy of Sciences, the group reports their comparison of facial masculinity with both height and immunocompetence, and what they found.

The masculine facial features have long been considered attractive to females, and thus to be a sexual ornament, akin to peacock tails and deer antlers. But that might not be the case after all. The researchers with this new effort suggest facial masculinity does not pass other tests of ornamentation.

To find out more about the role facial masculinity might play for human males in attracting females, the researchers showed 3-D images of men and women to 1,233 people of European ancestry to judge the level of masculinity in their faces. They then compared the level of masculinity to height and found what they describe as a correlation—taller people appeared to also have more masculine faces. But the correlation applied to both genders, so this finding does not demonstrate that facial masculinity is ornamental for men.

The researchers then turned to immunocompetence as a measure of attractiveness—prior studies have shown that women are more attracted to men that appear to be healthier, and thus more immune to diseases. Historically, it has improved the chances of reproductive success. One way to measure this has been using heterozygosity at the major histocompatibility complex—a marker in the genome that has been identified as a measure of how well a person's immune system works. The team conducted such a test on the people who had appeared in the 3-D images and found that there was no correlation between the degree of masculinity and immunocompetence. They claim these factors taken together suggest that facial masculinity in men is not a sexual ornament. They further note that immunocompetence could be correlated with height, however, offering more evidence that is serves as an attractive feature for women seeking a promising mate.

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More information: Arslan A. Zaidi et al. Facial masculinity does not appear to be a condition-dependent male ornament and does not reflect MHC heterozygosity in humans, Proceedings of the National Academy of Sciences (2019). www.biorxiv.org/content/early/2018/05/17/322255 Journal information: Proceedings of the National Academy of Sciences Arslan A. Zaidi et al. Facial masculinity does not appear to be a condition-dependent male ornament and does not reflect MHC heterozygosity in humans,(2019). DOI: 10.1073/pnas.1808659116

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