Psychologists have found that adult females who have prominent chins are more sexually active than those with softer features, yet are less attractive to men looking for a long-term partner.
Larger chins on women are often caused by a high level of the male growth hormone testosterone, present in all women in various amounts.
The hormone also increases sexual assertiveness in a woman, a tendency more commonly attributed to males.
The researchers, from four universities across the US and Canada, took a group of young women and questioned them on their sexual histories and fantasies.
These women were then rated by a group of men on their desirability as a life partner.
It was concluded that men will shun women with such masculine features when looking for a long-term partner because they fear being cuckolded.
Psychologists believe it is linked to their evolutionary desire to have a partner who will produce children for only one man.
Authors of the study, published in the journal Personality And Individual Differences, said: "The findings are important in demonstrating that perceptions of women as desirable and trustworthy long-term mates can be reliably gleaned by men from viewing only the women's facial features.
"Results suggest that information about women's sexual unrestrictedness, which is related to their risk of infidelity, can potentially be conveyed by the masculinity of women's faces."
The theory has many examples in the celebrity world.
Actress Meg Ryan, 47, who has a strong chin, famously cheated on her husband Dennis Quaid with her co-star Russell Crowe.
However, the actress Joanne Woodward, who has a dainty jawline, was happily married for 50 years to Hollywood icon Paul Newman until his death in September.
Dr Lorne Campbell, a psychologist from Western Ontario University, who took part in the project, wrote: "It is difficult to conceal physical features, such as facial characteristics, that are partly governed by testosterone and reliably correlate with one's sexual history and attitudes.
The research is the first to our knowledge to suggest that a more masculine facial appearance in women might convey their sexual unrestrictedness and perhaps their long-term mate quality."Original here