Cannabis works by exciting a variety of receptors in the endocannabinoid system (ECS).  While the ECS was only discovered in humans in the last thirty-five years, it is not a new biological phenomenon. In fact, it is one of the oldest systems in nature. In 2005, neurobiologists found evidence of fully developed endocannabinoid systems in sea squirts which are very tiny, ancient, marine organisms that date back over 600 million years - towards the very origins of life.