In his book Food of the Gods: the Search for the Original Tree of Knowledge: a Radical History of Plants, Drugs, and Human Evolution, Terence McKenna crafts his carefully thought out theory proposing that our sub-human primate ancestors consumed psilocybin mushrooms for thousands or millions of years, and that this is the primary reason humanity’s evolution rapidly accelerated—launching us forward in the animal kingdom. As one can imagine, this theory is controversial, but when we strip the theory down, what is ultimately being said is that a new psychoactive chemical was introduced to a species, and over millennia, this chemical, that functions as a neurotransmitter, had a drastic effect on the evolutionary trajectory of that species.

The theory Terence McKenna illustrates begins with our primate ancestors in Africa coming down from the trees, roughly four million years ago, and then discovering the psilocybin mushrooms growing on the ground. There are several environmental factors that would have encouraged them to do so: our ancestors came down from the trees at a time when Africa’s climate began to warm, and the forests in Africa began to turn into grasslands. This retreating of the forest and the expansion of drier grasslands would have lead to a scarcity in their normal diet. As McKenna explains, an organism tends to stay within its own diet, because bodies co-evolve in relationship with particular foods and moving beyond the confines of a diet introduces new chemicals in a system, chemicals a body hasn’t developed to digest—and this can be reckless. Given an abundance in their dietary habits, animals tend to stay in their habitual range of food—but fueled by hunger, driven by a sense of survival, most mammals adapt when starving by exploring new sources of food. And to further support the theory, mushrooms, and most of the other psychedelics, have by far the lowest rates of toxicity of any drug; mushrooms and marijuana being the lowest of all. One would have to eat a virtually impossible dose of thousands of mushrooms at once to have a fatal effect.

When considering this theory, a question naturally comes to mind—does a strain of mushroom containing psilocybin even grow in Africa? Out of the over 100 types of mushrooms worldwide that produce psilocybin, in his book Psilocybin Mushrooms of the World: An Identification Guide, mycologist Paul Stamets classifies ten different species of psilocybin mushrooms growing in Africa, while less authoritative and more recent sources claim the number to be sixteen. This makes it a high likelihood that our ancestors would have eventually found the mushrooms. Though there are many scenarios in which our ancestors would have first came in contact with the mushrooms living in their environment, McKenna suggests it would have eventually happened when our ancestors began following the pastoral animals. It is widely known that many psilocybin species are coprophilic, and these dung-loving mushrooms would have sprouted on feces everywhere. At the very least, by the time humans began controlling cattle they would have become aware of the psilocybin mushroom growing in their cow’s feces. As for more concrete and less speculative evidence, the oldest cave paintings we know of depicting shamanic mushroom use date back to 7,000 BCE in Africa.

If we are open to the plausible suggestion that at some point over the last few million years that our primates ancestors would have eventually digested these distinct looking organisms growing on the ground, then, as McKenna states, those primates taking the mushrooms would have had an evolutionary advantage over those that didn’t. An experiment by psychologist Roland Fischer in 1970 shows that at low doses psilocybin intake enhances vision, especially edge detection. As those that have experimented with psilocybin own their own have seen, it appears that a clarity of depth take places, as everything appears more 3D, and colors more vibrant. This enhancement of vision would have helped our ancestors hunt, gather food, and detect predators. At a medium dose, psilocybin creates a sense of restlessness and arousal. This would have encouraged sexual reproduction, a corner stone of evolution. Slowly, these groups of primates holding an evolutionary advantage over other apes would pass the behavior of eating mushrooms to their young, whether by teaching or simply by mirror neuron connections alone.

Eating mushrooms would also serve another function besides survival and reproduction, and that is the boundary dissolution and sheer reverence they create. These experiences would have created a sense of intimacy between the members of the tribe and deepened an overall group cohesion—and this pack bonding would have definitely led to a overall evolutionary advantage over other primates groups. At higher doses, individual and group consciousness would have deepened and expanded, as this would create bizarre, transpersonal, and unitive states of consciousness. One can see that perhaps this is where ritual first developed—bringing logic and imagination together.

As anthropology tells us, shamanism, which uses visionary plants, was humanity’s first form of spirituality, and shamanism went on for tens of thousands of years before widespread organized religion. Because of these intense psychedelic, imaginative experiences, pulling our ancestors outside their visual environment and into lucid dream-like states, they would have had to eventually form transpersonal myths to make sense for their emerging reality.

Though this theory resides outside of the normal bounds of any cultural origin story, when looked scientifically, without the cultural stigmas put on drugs, it seems plausible that our evolution—not only including biological development, but cognition and self-awareness as well—was propelled forward by a change in our diet, one that included the introduction of a psychoactive compound. As for the beginning of religion, when we integrate the scientific evidence gathered on studies of psilocybin, we find the high probability that psilocybin can trigger a religious experience, given the right set and setting—and what can be a better setting than out in nature under the open night skies. This is a natural explanation for religious experiences being provoked in our ancestors—catalyzed by chemicals in their ecosystem.

If this theory is true, then we must reclaim our past. In psychotherapy, part of what creates a trauma is that an intense experience has not been integrated into a person’s life. The patient is then brought into their past to digest the experience—and in doing so finds a sense of wholeness. Until this occurs, there will always be an ache in our psyche. Part of what creates our cultural neurosis and unsustainability is that we have become disconnected from a more intimate relationship with nature—and what is more intimate than inviting nature herself to transform one’s consciousness. For thousands, if not millions, of years, these expanded states of consciousness were a part of our lives, and that needs to be integrated into our cultural memory—changing our identity of humanity from isolated beings to participants in an evolving symbiotic consciousness with the rest of the planet. As we collectively stand at a crossroads—facing an ecological crises, acceleration in technological advancement, and no sense of direction—humanity needs a vision of where to go, and many of us are finding that in the psychedelic experience.

Jahan Khamsehzadeh is a PhD candidate in the Philosophy, Cosmology, Consciousness program at the California Institute of Integral Studies. His dissertation has to do with outlining the emerging paradigm, evolutionary psychology, and the impact psychedelics have played in past and can play in the future evolution of humanity. He received his Masters in Consciousness and Transformative Studies from JFK University, and his Bachelors in Philosophy, with minors in both Psychology and Physics, from the University of Arizona.