The reason why so many women are attracted to 'masculine' men may have less to do with their rugged good looks and more to do with their powerful immune systems, a study has found.
An ability to stave off man-flu might not sound like the hottest trait in a man but in evolutionary terms it does make sense, as women are inherently attracted to men who could provide their children with the strongest possible immune system.
The researchers at Abertay University studied 74 Latvian men in their early twenties, measuring their immune response to a hepatitis vaccine as well as the concentration of testosterone and cortisol in their blood.
Latvian women, also in their twenties, were asked to rate the facial attractiveness of the subjects using a 10-point scale.
Men with high levels of testosterone had a strong immune system and were ranked as more attractive.
Men with low levels of testosterone had weaker immune systems and higher concentrations of the stress hormone, cortisol, which may have inhibited their immune responses.
This also suggests that stressed-out men may be less attractive to women.
Researcher Dr Fhionna R Moore, Ph.D. said: "It's always been an assumption that the healthier you are, the more attractive you are but it has never really been proved before.
"We found there was a really strong connection between how well these men reacted to the jab, and how attractive women thought they were.
"We believe it's because inherently women seek for their offspring to inherit the healthiest immune systems."
Like a red rag to a bull it would seem the colour red also fires up the passion in women. A study at the University of Rochester asked 288 female and 25 male undergraduates to look at photos of a man in which his shirt was digitally coloured either red or another colour. Women in a variety of countries agree that the red shirt made the man appear "more powerful, attractive and sexually desirable."
Women can subconsciously sense if a man is attracted to her by the smell of his sweat, according to a study at Rice University in Texas. A group of 19 women in their twenties were exposed to two types of male sweat - one labelled 'normal' and the other 'sexual'. The normal sweat was obtained from the men while they were watching educational videos while the 'sexual' sweat was gathered while they were watching an erotic video. The women's brains were monitored while they were exposed to the sweat. The brain activity showed that they recognised and responded to the sexual sweat.
Anthropologists in New Zealand carried out studies to find the precise waist to hip ratio that drives men wild. Volunteers were asked to rate the attractiveness of images of women that had their bust, hip and waist sizes digitally altered. The eye movements of the participants were tracked using infra-red cameras. Most men were drawn to the breasts but hips and waists were also important. The most attractive ratio was the waist measuring 70% of the hips. Not surprisingly, Marilyn Monroe, Kate Moss and Jessica Alba all share this ratio.
Men with high levels of testosterone are attracted to women with highly feminine faces, a study at Aberdeen University found. A group of 70 women and 30 men underwent a series of tests to examine the role of testosterone in attraction between the sexes. It was found that attitudes towards the opposite sex changed depending on their fluctuating testosterone levels throughout the day. Researcher Dr Ben Jones, said "When men's testosterone levels were high, they were more attracted to feminine women. When women's testosterone levels were high they were more attracted to masculine men."
According to a study by Florida State University men are unconsciously attracted to a woman's scent when she is ovulating. Four female volunteers - two who were ovulating and two who were not - were asked to wear a plain white T-shirt for three consecutive nights. Male volunteers were asked to smell the T-shirts. Those who smelled the T-shirts of the ovulating women had testosterone levels 37% higher than those who smelled the T-shirts of the women who were not ovulating.
It's a long-held belief that we are naturally attracted to people that resemble ourselves. In an experiment conducted by the University of Illinois, volunteers were shown pictures of of two faces morphed together. One group was shown images of faces of strangers morphed together while the other group was shown faces that were a composite of a stranger's face and up to 45% their own face. The subjects shown images containing their own face found the picture more sexually attractive.
Contrary to the theory that we choose partners similar to ourselves and backing up the old adage 'opposites attract', scientists have found an evolutionary reason why we may be attracted to those who are genetically most different to us. A Brazilian study found tthat people are more likely to choose someone with differences in the DNA region that governs the immune system as parents with dissimilar genetic regions could provide their offspring with a better chance to ward infections off because their immune system genes are more diverse.