Evolution has primed us to avoid anything icky to ward off disease. But science also shows that disgust can be a double-edged sword.While disgust mostly protects people from getting sick, getting a little dirty can have its advantages. Studies show that kids under age one who physically interact with a dog will have a 13 percent reduction in the likelihood of developing asthma.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
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