London School of Hygiene & Tropical Medicine

The emotion of disgust evolved to protect humans from the risk of infectious disease and ensure our adaptive advantage, according to a survey of over 40,000 people published today in the Royal Society's 'Biology Letters'.

Our reactions to things which make us go 'yuck', such as bodily fluids, lesions and faeces has long been the source of speculation, with some claiming that disgust reactions help to distinguish humans from animals, and others that they protect us from hazards such as poisoning.

Dr Val Curtis, Dr Robert Aunger and Dr Tamer Rabie from the London School of Hygiene & Tropical Medicine carried out a web-based survey which examined people's responses to a series of pictures on a BBC website, which included images of body lesions, parasites, rotting meat and faeces.

Objects which appeared to have a link with disease, such as a towel apparently stained with bodily fluids, provoked a greater disgust reaction than those with no obvious disease link, such as a towel with a blue stain, as did pictures of creepy-crawly type insects linked with disease, compared with those insects which were not, such as caterpillars or wasps.

Women, who in evolution shoulder the greatest responsibility for carrying on their genes because of their role in reproduction and caring for children, were found to be more squeamish than men. Younger people, most likely in evolutionary terms to reproduce, were found to be more prone to disgust reactions than older people past their child-bearing years. All of this makes perfect evolutionary sense.

Dr Curtis says: 'People with a strong sense of disgust do better in the survival and reproductive stakes than those who don't. Today's survey provides the first quantitative evidence that disgust arose as a means of warning us of potentially dangerous situations which might put us at risk of disease and death and that, ultimately, the disgust response helps to ensure our adaptive advantage'.

'Disgust is a very sticky emotion', she adds. 'If you label something as disgusting it tends to stick and, in evolutionary terms, that is for a very good reason'.

To interview Drs Curtis, Aunger or Rabie please contact the London School of Hygiene & Tropical Medicine's Press Office on 020 7927 2073.

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