Scientists using hi-tech body scanners have discovered that people with more symmetrical bodies are more attractive to the opposite sex.

The research backs up previous findings that symmetrically proportioned faces are more attractive and suggests that our brains are hard-wired to find symmetry sexy in a potential partner. In our evolutionary past, symmetry may have been an honest signal of flawless development and health.

“It is widely believed that human beings are attracted to one another as a result of genotype and phenotype quality – in other words, their prospect as a mate who will yield higher quality offspring for the chooser,” said Dr William Brown, an evolutionary psychologist at Brunel University who led the study.

“Your body proportions, shape and stature are signals that conspicuously advertise your good development or health and therefore the degree to which you are a desirable reproductive partner. In many species fewer departures from perfect symmetry are associated with good development, health and reproductive success.”

The theory is that disturbances in the womb, infections, poor nutrition and genetic flaws all increase your degree of asymmetry and so good proportions are an honest indication of healthy development and hence a partner’s ability to produce healthy children.

Brown’s team asked 40 men and 37 women to strip down to their underwear and enter a 24-camera body scanner. The device rapidly takes hundreds of measurements of the subject’s body allowing the researchers to build up a 3D image. They also calculated a composite measure of symmetry from the hundreds of minute symmetry differences recorded by the cameras.

The team showed each of these images to 87 evaluators who rated them for attractiveness. The researchers were particularly interested in how body asymmetry would affect the ratings, so to avoid adding another factor to the evaluators’ decision, the team presented each image with the head of the subject removed.

The evaluators preferred more symmetrical body shapes in both men and women. “They are choosing individuals who would have evidence for good development which means that maybe their offspring would be more healthy and have good development as well,” said Brown.

The results are reported in the Proceedings of the National Academy of Sciences.