Terrance McKenna, 53, died of brain cancer On April 3 at the home of a friend in San Rafael, CA. McKenna, a native of Paonia, Colorado, gained notoriety as an advocate for the use of the hallucinogens, including mushrooms in the Psilocybe genus.

McKenna studied Shamanism and Conservation of Natural Resources at Berkeley before traveling extensively around the world. At this time he became exposed to the use of hallucinogenic drugs as a part of primitive rituals. After experiencing foreign cultures and the powers of mind-altering drugs, he developed a theory describing the physical and social evolution of humans dependent upon the use of psychoactive drugs.

McKenna proposed that as primitive man scavenged for food, they inevitably ate hallucinogens. At moderate dosages, these drugs heighten visual and auditory acuity, giving them an edge over non-imbibing populations. During times of plenty, the idea goes, these populations could easily gather enough food to allow time for development of culture, tool-making and farming. During the lean years, their use of hallucinogenic drugs would give them the advantage in hunting because of enhanced senses.

McKenna goes on to say that climate change caused many hallucinogenic plants and fungi to become scarce, leading to conflict between groups, including man's first battles between one another. McKenna advanced his ideas through several books, including The Invisible Landscape and True Hallucinations.