How CBD Works: The Endocannabinoid SystemBefore the 1990s, scientists barely understood the effects of cannabis on the human body. When they discovered the endocannabinoid system (ECS) in the 1990s, science health began to change. It was demonstrated that all vertebrates, including mammals, birds, reptiles, and fish, produce endocannabinoids. The primary purpose of the ECS is to make sure the body maintains homeostasis, though it is much more complex than that.