Men who sport chiselled jaws and classic "masculine" facial features are actually healthier than their less manly peers, researchers suggest.
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And women who choose them may do so because they are instinctively looking for a healthier mate, they say.
However, Australian researchers found that although adolescent males with more masculine faces had better health, they were not necessarily seen as more attractive.
So it may be that women are, deep down, aiming to attract the healthiest, rather than the most attractive, father for their children.
Femininity in teenage girls' faces is perceived as a sign of being healthy and attractive, but there was no link with how healthy they actually were.
The theory that masculine faces in men may be seen as "healthier" is connected to the effect of testosterone on the immune system.
People correctly interpret masculine traits as signs of health
Dr Gillian Rhodes, University of Western Australia
The hormone suppresses the body's defence system, so the theory is that those men who have strong masculine characteristics must be in good health in order to withstand testosterone's effect on their immune system.
Women could therefore improve the chances of children being healthy by choosing a more masculine "healthy" mate.
The relationship between female hormones and health is less clear, so men may not use female facial appearance as a sign of health.
Researchers from the University of Western Australia showed 37 students over 300 photos of male and female faces, taken in the US between 1920 and 1929.
Hairstyles were blocked out so students could concentrate on facial characteristics.
They were asked to rate the male faces for masculinity and female faces for femininity.
The researchers then used data on the photographic subjects' actual health in adolescence.
Writing in Biological Sciences, a journal of the Royal Society, the research team led by Dr Gillian Rhodes, said: "Masculinity correlated modestly, but significantly, with actual health during adolescence.
"Masculinity was also perceived as healthy, suggesting that people correctly interpret masculine traits as signs of health."