Ginger is one of seven times spiciness has independently evolved: gingerol, allicin (garlic), capsaicinoids (chili peppers), allyl isothiocyanate (mustard, horseradish, wasabi), piperine (black pepper), eugenol (cloves) and alkylamides (Sichuan peppers, which are distinct from chilis). They’re all functionally pungent, but chemically distinct: meaning no single shared class.