"We have sort of a built-in poison detector. You can see this as early as even in newborn infants. If you are willing to do this, you can take a couple of drops of a bitter substance or a sour substance, and you'll see that face, the tongue stick out, the wrinkled nose, as if they're trying to get rid of what's in their mouth.This reaction expands into adulthood and becomes sort of a full-blown disgust response, no longer just about whether or not we're about to be poisoned, but whenever there's a threat of physical contamination from some source. But the face remains strikingly similar. It has expanded more, though, than just keeping us away from physical contaminants, and there's a growing body of evidence to suggest that, in fact, this emotion of disgust now influences our moral beliefs and even our deeply held political intuitions."