Previous studies have found that women's preferences for male physical appearance vary according to their fertility status. During ovulation women tend to find masculine looking men more attractive and prefer their voices and odour. During this fertile phase women are more likely to have an affair with a masculine-looking man, as their features are linked to high testosterone levels, demonstrating good genetic qualities that can be passed on to offspring.
New research at the University has found that men sense this preference shift in their female partners and find masculine men more threatening during their partner's most fertile phase. Rob Burriss and Dr Anthony Little, from the University's School of Biological Sciences, also found that men only behave in this way if their female partner does not use oral contraception ?and is therefore more fertile.
Images of male faces that were either high or low in dominant features, such as a strong jaw lines and thinner lips, were shown to male participants who provided ratings of dominance for each image. A dominant person was defined as someone who looked like they could 'get what they wanted'.
Participants were asked to provide information on whether or not their female partner used oral contraception and the date of her current or previous menses. Male participants whose partners did not use oral contraception and were near ovulation rated masculine faces more dominant than those participants with partners who did use oral contraception and were not near ovulation.
Rob Burriss, from the University's School of Biological Sciences, explains: "'Groups of animals, such as chimpanzees, can live quite happily together, but when a female is ready to mate the two dominant males within the group become rivals and fight for her attention. Simi larly in humans, rated dominance increases when the female is most fertile. What is interesting here is that male behaviour is determined by that of the females; men become more wary of masculine-looking men only when the females facial preferences begin to shift prior to ovulation.
"Face shape and structure are good indicators of dominance. Men with large eyes, rounded chin and full lips, are viewed as more feminine and are chosen as long-term partners. They are not, however, seen as dominant. During the female's most fertile phase, she tends to prefer faces that indicate high testosterone levels, which indicate good genes; masculine faces reflect these qualities."