These messages mediate satisfaction, happiness, and optimism. Serotonin levels are reduced in depression, and most modern anti-depressant drugs, known as serotonin reuptake inhibitors (SSRIs), act by increasing the amount of serotonin available to brain cells.

Many indigenous cultures are led by a shaman, a person who serves both as a doctor and spiritual leader of the community. In South America, the curandero is a traditional native healer, who carries forth the collective wisdom of the tribal history, sharing stories, and presiding over rituals, using psychedelic plants as a channel and guide.

In 1970, Roland Fischer demonstrated that low doses of psilocybin improve cognitive health. His research claims that the incorporation of small doses of psychoactive mushrooms, and cannabis plants into the diet of early humans likely enabled them to live more consciously, increase their knowledge, and advance their culture. This might just prove to be the beginning of the symbiotic relationship between psychoactive plants, mushrooms, and human beings.