Why (some) mushrooms are "magic"

Ed Yong has an interesting article at the Atlantic, explaining a theory that some mushrooms make hallucinogens to ward off insects:

These genes seem to have originated in fungi that specialize in breaking down decaying wood or animal dung. Both materials are rich in hungry insects that compete with fungi, either by eating them directly or by going after the same nutrients. So perhaps, Slot suggests, fungi first evolved psilocybin to drug these competitors.

His idea makes sense. Psilocybin affects us humans because it fits into receptor molecules that typically respond to serotonin—a brain-signaling chemical. Those receptors are ancient ones that insects also share, so it’s likely that psilocybin interferes with their nervous system, too. “We don’t have a way to know the subjective experience of an insect,” says Slot, and it’s hard to say if they trip. But one thing is clear from past experiments: Psilocybin reduces insect appetites.