In the late 1860s, Charles Darwin proposed that being grossed out could have an evolutionary purpose. Disgust, he wrote, was inborn and involuntary, and it evolved to prevent our ancestors from eating spoiled food that might kill them. Darwin hypothesized that the early humans most prone to revulsion survived to pass on their genes, while the more nutritionally daring died off.

For many years afterward, though, scientists didn’t pay much attention to disgust. It wasn’t until the early 1990s, a decade when gameshows eagerly slimed contestants, that disgust garnered more attention in psychological and behavioral research. Since then, scientists have identified different types of disgust and have explored how they affect the way we behave.

The research shows that Darwin was basically right: Disgust is a major facet of the behavioral immune system, a collection of actions influenced by some of the most primal instincts that keep our bodies in prime condition.

“In terms of keeping us healthy, disgust is associated with fewer infections, so it is a helpful emotion in disease-relevant contexts,” says Joshua Ackerman, an associate professor of psychology at the University of Michigan. In January, for instance, researchers reported that people more innately prone to disgust have indeed fared better during the COVID-19 pandemic, probably because they are inclined to engage in more hygienic actions like hand-washing.

Read the full article at National Geographic.