““Good looks, for example, are denoted by symmetrical features—a sign that early life development was not disrupted by infection—and skin that shows no trace of pockmarks, sores, or other blemishes. With that in mind, you’d expect beauty to be more valued by those more susceptible to germs—a theory that evolutionary biologists put to the test in a survey of over seventy-one hundred people on six continents. In keeping with their prediction, those who lived in countries where parasites were leading causes of death and disability—in Nigeria and Brazil, for example—deemed good looks much more important in a mate than did inhabitants of nations like Finland and the Netherlands, which have among the lowest incidences of infection. In a British study, merely prompting people to think of germs—by, for example, showing them photos of a festering skin sore or a white cloth with a dark stain resembling a fecal smear—boosted how much they preferred symmetrical faces in the opposite sex.””
