See something disgusting? Everyone, everywhere, reacts the same way: We wrinkle our noses and say the international yuck word: "Eugh!"
Some of us, of course, have stronger stomachs than others. But people with the most refined sense of what is yucky are likely to survive longer than their less sensitive brothers and sisters, a new study suggests.
The research, by Val Curtis, Ph.D., and colleagues at the London School of Hygiene & Tropical Medicine, is based on the responses of more than 40,000 people to a BBC Internet survey. The results appear in the online supplement to the Proceedings of the Royal Society of London Series B.
"People with a strong sense of disgust do better in the survival and reproductive stakes than those who don't," Curtis says in a news release. "Disgust arose as a means of warning us of potentially dangerous situations which might put us at risk of disease and death. Ultimately, the disgust response helps to ensure our adaptive advantage."
Caterpillars vs. roundworms
The survey included 20 photographs and a questionnaire. Participants rated the photos on a 1-5 scale, from least to most disgusting. Buried in the photographs were seven pairs of photos -- similar in content, except that one was linked to disease and the other wasn't.
One pair, for example, was a photo of fuzzy caterpillars and a photo of human roundworms. Even though bugs in general are disgusting to a lot of people, the roundworms got considerably higher disgust scores.
Another example: A photo of a towel with a dark blue stain and a photo of the same towel with a dark red stain. Because it looked bloody, the red-stained towel was more disgusting.
But if everybody reacted the same way, where would the survival advantage be? Curtis found that women -- whose evolutionary role as child bearers and protectors of children is crucial to the species -- are more sensitive to disgust than men. Similarly, young people -- who are more likely to reproduce -- are more sensitive than older people. And body fluids from strangers are deemed more disgusting than the body fluids of close relatives.
A final question on the survey asked people to choose the person with whom they'd be least likely to share a toothbrush. The results (drum roll, please):
The most disgusting person, according to nearly 60 percent of respondents, was their postman. Second most disgusting? Nearly 25 percent found the most disgusting person to be their boss at work. The weatherman was most disgusting to nearly 9 percent. Siblings were most disgusting to about 3 percent. A best friend was most disgusting to nearly 2 percent. And, sadly, nearly 2 percent said they would be least likely to share a toothbrush with their spouse or partner.