Terence Kemp McKenna (November 16, 1946 – April 3, 2000) was an American ethnobotanist, lecturer, and author who advocated for the responsible use of naturally occurring psychedelic plants and mushrooms. He spoke and wrote about a variety of subjects, including psychedelic drugs, plant-based entheogens, shamanism, metaphysics, alchemy, language, philosophy, culture, technology, ethnomycology, environmentalism, and the theoretical origins of human consciousness. He was called the "Timothy Leary of the '90s", "one of the leading authorities on the ontological foundations of shamanism", and the "intellectual voice of rave culture". Critical reception of McKenna's work was deeply polarized, with critics accusing him of promoting dangerous ideas and questioning his sanity, while others praised his writing as groundbreaking, humorous, and intellectually provocative.
Born in Colorado, he developed a fascination with nature, psychology, and visionary experiences at a young age. His travels through Asia and South America in the 1960s and '70s shaped his theories on plant-based psychedelics, particularly psilocybin mushrooms, which he helped popularize through cultivation methods and writings. McKenna became a countercultural icon in the 1980s and '90s, delivering lectures on psychedelics, language, and metaphysics while publishing influential books and co-founding Botanical Dimensions in Hawaii. He died in 2000 from brain cancer.
McKenna was a prominent advocate for the responsible use of natural psychedelics—particularly psilocybin mushrooms, ayahuasca, and DMT—which he believed enabled access to profound visionary experiences, alternate dimensions, and communication with intelligent entities. He opposed synthetic drugs and organized religion, favoring shamanic traditions and direct, plant-based spiritual experiences. He speculated that psilocybin mushrooms might be intelligent extraterrestrial life and proposed the controversial "stoned ape" theory, arguing that psychedelics catalyzed human evolution, language, and culture. His broader philosophy envisioned an "archaic revival" as a healing response to the ills of modern civilization.
McKenna formulated a concept about the nature of time based on fractal patterns he claimed to have discovered in the I Ching, which he called novelty theory, proposing that this predicted the end of time, and a transition of consciousness in the year 2012. His promotion of novelty theory and its connection to the Maya calendar is credited as one of the factors leading to the widespread beliefs about the 2012 phenomenon. Novelty theory is considered pseudoscience.
Terence McKenna was born and raised in Paonia, Colorado,
with Irish ancestry on his father's side of the family.
As a youth, McKenna had a hobby of fossil-hunting from which he acquired a deep scientific appreciation of nature. At the age of 14, he became interested in psychology after reading Carl Jung's book Psychology and Alchemy. At the age of 14, he first became aware of magic mushrooms when he read the article "Seeking the Magic Mushroom" from the May 13, 1957 edition of Life magazine. He began smoking cannabis as a teenager.
At age 16 McKenna moved to Los Altos, California, to live with family friends for a year. He finished high school in Lancaster, California. In 1963, he was introduced to the literary world of psychedelics through The Doors of Perception and Heaven and Hell by Aldous Huxley and certain issues of The Village Voice which published articles on psychedelics.
McKenna said that one of his early psychedelic experiences with morning glory seeds showed him "that there was something there worth pursuing." But it was his experience with DMT in 1967, introduced to him by his best friend Rick Watson, whom Terence described as his "greatest inspiration", that set his "auto compass for life".
In 1965, McKenna enrolled in the University of California, Berkeley and was accepted into the Tussman Experimental College. While in college in 1967 he began studying shamanism through the study of Tibetan folk religion. That year, which he called his "opium and kabbala phase", he traveled to Jerusalem where he met Kathleen Harrison, an ethnobotanist who later became his wife.
In 1969, McKenna traveled to Nepal led by his interest in Tibetan painting and hallucinogenic shamanism. He sought out shamans of the Tibetan Bon tradition, trying to learn more about the shamanic use of visionary plants. During his time there, he also studied the Tibetan language and worked as a hashish smuggler, until "one of his Bombay-to-Aspen shipments fell into the hands of U. S. Customs." He then wandered through southeast Asia viewing ruins, and spent time as a professional butterfly collector in Indonesia.
After his mother's death from cancer in 1970, McKenna, his brother Dennis, and three friends traveled to the Colombian Amazon in search of oo-koo-hé, a plant preparation containing dimethyltryptamine (DMT). Instead of oo-koo-hé they found fields full of gigantic Psilocybe cubensis mushrooms, which became the new focus of the expedition. In La Chorrera, at the urging of his brother, McKenna was the subject of a psychedelic experiment in which the brothers attempted to "bond harmine DNA with their own neural DNA" (harmine is another psychedelic compound they used synergistically with the mushrooms), through the use of a set of specific vocal techniques. They hypothesised this would give them access to the collective memory of the human species, and would manifest the alchemists' philosopher's stone which they viewed as a "hyperdimensional union of spirit and matter". McKenna claimed the experiment put him in contact with "Logos": an informative, divine voice he believed was universal to visionary religious experience. McKenna also often referred to the voice as "the mushroom", and "the teaching voice" amongst other names. The voice's reputed revelations and his brother's simultaneous peculiar psychedelic experience prompted him to explore the structure of an early form of the I Ching, which led to his "Novelty Theory".
During their stay in the Amazon, McKenna also became romantically involved with his interpreter, Ev.
In 1972, McKenna returned to U.C. Berkeley to finish his studies and in 1975, he graduated with a degree in ecology, shamanism, and conservation of natural resources. In the autumn of 1975, after parting with his girlfriend Ev earlier in the year, McKenna began a relationship with his future wife and the mother of his two children, Kathleen Harrison.
Soon after graduating, McKenna and Dennis published a book inspired by their Amazon experiences, The Invisible Landscape: Mind, Hallucinogens and the I Ching. The brothers' experiences in the Amazon were the main focus of McKenna's book True Hallucinations, published in 1993. McKenna also began lecturing locally around Berkeley and started appearing on some underground radio stations.
Psilocybin mushroom cultivation
McKenna, along with his brother Dennis, developed a technique for cultivating psilocybin mushrooms using spores they brought to America from the Amazon. In 1976, the brothers published what they had learned in the book Psilocybin: Magic Mushroom Grower's Guide, under the pseudonyms "O.T. Oss" and "O.N. Oeric". McKenna and his brother were the first to come up with a reliable method for cultivating psilocybin mushrooms at home. As ethnobiologist Jonathan Ott explains, "[the] authors adapted San Antonio's technique (for producing edible mushrooms by casing mycelial cultures on a rye grain substrate; San Antonio 1971) to the production of Psilocybe [Stropharia] cubensis. The new technique involved the use of ordinary kitchen implements, and for the first time the layperson was able to produce a potent entheogen in his [or her] own home, without access to sophisticated technology, equipment, or chemical supplies." When the 1986 revised edition was published, the Magic Mushroom Grower's Guide had sold over 100,000 copies.
In the early 1980s, McKenna began to speak publicly on the topic of psychedelic drugs, becoming one of the pioneers of the psychedelic movement. His main focus was on the naturally occurring psychedelics such as psilocybin mushrooms (which were the catalyst for his career), ayahuasca, cannabis, and the plant derivative DMT. He conducted lecture tours and workshops promoting natural psychedelics as a way to explore universal mysteries, stimulate the imagination, and re-establish a harmonious relationship with nature. Though associated with the New Age and Human Potential Movements, McKenna himself had little patience for New Age sensibilities. He repeatedly stressed the importance and primacy of the "felt presence of direct experience", as opposed to dogma.