We seem to find people with a strong immune system more attractive

Men and women are more physically attracted to the faces of people who have higher functioning immune systems that might protect them from diseases over their lifetimes. "There's nothing inherently special or beautiful about a face that we find attractive, so the theoretical rationale is that there must be something over the thousands of years of evolution that has been consistently rewarded in our mate choice, and that we find these specific traits attractive," says Summer Mengelkoch at Texas Christian University in Fort Worth. Scientists had already determined that people are more attracted to the body odours of people of the opposite sex who have better health. However, studies that didn't involve the detection of any bodily chemicals like smells have shown inconsistent links between attractiveness and health or immune function. To investigate further, Mengelkoch and her colleagues asked 159 men and women, averaging 20 years old, to pose for professional headshots in which they had neutral facial expressions and wore no make-up or jewellery.