What Is the Stoned Ape Theory and Why Is It So Controversial?

What Is the Stoned Ape Theory and Why Is It So Controversial?

Brandon Rich
Brandon Rich
September 11, 2023
5 min

It’s tempting to imagine that ever since humans developed consciousness, we’ve been pondering how it happened. Truthfully, it probably took millennia for us to begin asking that question. While many have wagered their own fair guess since then, few ideas have been as bold as the stoned ape theory.

Research into psychedelics is heating up, and you only have to look as far as the potential of psilocybin to treat depression to understand that the hallucinogenic compound can have remarkable properties to alter our minds.

In addition to the compelling scientific evidence, a previously disregarded theory about the link between magic mushrooms and human evolution is regaining relevancy and reentering discussions. This speculative thesis was once pushed to the sidelines but is now making a return to the conversation.

But what is the stoned ape hypothesis, and who made it?

The origin of the Stoned Ape Theory

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The stoned ape theory is a relatively controversial hypothesis. It suggests that early hominids’ consumption of Psilocybe cubensis (magic mushrooms) was a major turning point in human consciousness and cultural development.

This theory, posited by ethnobotanist Terrence McKenna, asserts that the ingestion of psychoactive shrooms by early humans was a catalyst for psychological development — one that gradually guided primates into the state of consciousness that defines our modern human brains.

McKenna’s hypothesis doesn’t claim that early hominids were like your festival buddy Justin, walking around on a dedicated hunt for their next trip.

Instead, his thought process follows a more natural path: As nomads, early humans (Homo erectus) followed migrating fauna across savannahs and consumed psilocybin mushrooms that grew from animal droppings along the way.

Once these wild cattle were domesticated, people came in closer contact with these substances, psychedelic experiences became more common, and the art, culture, language, and religious practices that define homo sapiens proliferated rapidly.

As Terrance McKenna’s brother Dennis McKenna said in the documentary Fantastic Fungi, “It was like a software to program this neurologically modern hardware to think, to have cognition, to have language…”

The early history of McKenna’s idea

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Terence McKenna first posited his theory in the 1992 book, Food of the Gods.

The stoned ape theory was built on studies conducted and published in the 1960s and 70s by pharmacologist Roland L. Fischer. Fischer’s studies compared the hallucinogenic effects of LSD to psychosis found in people with schizophrenia.

Using Fischer’s research, McKenna put forward the idea that the consumption of psilocybin by early humans led to improved visual acuity – the ability to distinguish the details of objects from a distance. This would, in turn, result in higher capabilities in hunting, eventually leading to increased food resources that could support larger populations.

According to the theory, continued ingestion of what we now regard as psychedelic drugs would go on to activate the regions of the brain responsible for language formation.

Subsequently, cultural bridge points like music, art, and religion developed with increased communication. Humans propagated greater genetic diversity, tightened tribal bonds, and reduced their internal egos through psilocybin.

When Terence McKenna proposed his theory, the scientific community considered it too speculative. They argued that the theory oversimplified the nature of human evolution. Many believed the ethnobotanist’s ideas misrepresented the results of Fischer’s studies.

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The psychedelic theory gains traction

Although McKenna passed in 2000, his theory has resurfaced recently. Mycologist Paul Stamets revived the idea at the 2017 Psychedelic Science Conference. According to Stamets,

“What is really important for you to understand is that there was a sudden doubling of the human brain 200,000 years ago. From an evolutionary point of view, that’s an extraordinary expansion. And there is no explanation for this sudden increase in the human brain.”

And Stamets isn’t the only modern proponent linking this jump to hallucinogenic shrooms.

As scientists continue to study the relationship and impact between psychedelic drug use and neuroscience, other theorists are digging into the potential links between evolved cognition and psilocybin.

Backing up McKenna’s claims

For many people, the stoned ape hypothesis makes sense as a theory. After all, Stamets has a point in his claim that human brains grew incredibly quickly in the span of 200,000 years.

Nevertheless, no clear-cut proof supports the idea that early humans ingested psychoactive substances and that this consumption led to the evolution of human consciousness.

It’s not as simple as “psilocybin exists, hominids eat it, hominids trip, psychedelics foster human conscience.” Regarding scientific acceptance, hard evidence is needed to confirm bold conclusions.

Still, even current, accepted science is based on hypotheses, which are theories that go on to be tested, then confirmed or denied depending on the evidence.

Regardless, the current proof available allows playful thinkers to haphazard a guess at the connections between evolution and psychedelic mushroom use.

Take recent research published in Frontiers in Psychology as an example. Many widely accept the claim that the diets of early humans were omnivorous, forage-focused, and fungi-inclusive (1). Dually, the authors of this analysis claim that the traits responsible for society building require the development of cooperation and goodwill, which is fueled by serotonin.

And what sort of fungi is known to mimic the flow of serotonin? You guessed it.

The effects of psychedelics on the brain

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It has yet to be seen whether or not psychedelics can be proven as catalysts for brain growth. However, as Emma Beatuel reports for Inverse, these substances significantly impact how the brain operates.

Recent research from 2020 shows that psilocybin affects the way the brain releases neurotransmitters (like serotonin) and the activity of neurons (2). The introduction of the substance destabilizes traditional brain networks while fostering the creation of others. As Beautuel argues:

“That dynamic creates a one-two punch that could allow the brain to tap into otherwise inaccessible states, including the “destabilization” of individual brain networks and the creation of a more “global” network across the brain.”

Sounds like quite a way to jumpstart an early hominid party.

What the research doesn’t confirm, however, is whether a restructuring of the brain’s neural pathways would eventually lead to larger cranial size and increased faculties.

It can be fun to imagine that it might, but as stone ape detractors rightfully remind us, science is about more than speculation.

Criticism of the theory

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At the time of Terence McKenna’s original proposition, the stoned ape theory was regarded as wildly simplistic, with several unexplainable faults.

Critics like Elisa Guerra-Doce have rightly pointed out the lack of material and anthropological evidence supporting McKenna’s theory.

The limited evidence McKenna did provide in terms of psychedelic effects on the mind is frequently disputed as an inaccurate representation of Roland L. Fischer’s cognitive studies.

Research between the brain and hallucinogenic substances was once few and far between. Psychedelic discovery — particularly related to cognition and neuroscience — has come a long way since then. While some of today’s modern studies can be used to back up McKenna’s claims, one counterargument can’t be easily evaded.

In the end, the theory’s simplicity is its greatest limitation.

According to anthropologists, psychologists, and paleontologists alike, the idea that magic mushrooms directly catalyzed human cognition is a reductive approach.

Critics argue that consciousness has developed from a slew of sensory factors, environmental conditions, and the sharpening of survival instincts.

While most of these experts concur that consciousness evolved with our organization into social groups, none are certain that those structures were facilitated by psilocybin.

Instead, it’s likely we first attuned our attention to the survival needs of the outside world and then turned that attention inward.

The unanswered mystery of the Stoned Ape Theory

In the end, the stoned ape theory is just that: a theory. From traditions of ancient shamanism in the North Pole to the DMT-based ayahuasca practices of South America, it is evident that psychedelics have had a pronounced role in human history.

But Western institutions may never concur on the degree to which psilocybin played a part in human evolution — if any at all.

With enough research, we can conclude the effects of magic mushrooms on our development – or the truth may stay locked behind our own cognition.


  1. Rodríguez Arce, José Manuel, and Michael James Winkelman. 2021. “Psychedelics, Sociality, and Human Evolution.” Frontiers in Psychology 12 (September). https://doi.org/10.3389/fpsyg.2021.729425.
  2. Kringelbach, Morten L., Josephine Cruzat, Joana Cabral, Gitte Moos Knudsen, Robin Carhart-Harris, Peter C. Whybrow, Nikos K. Logothetis, and Gustavo Deco. 2020. “Dynamic Coupling of Whole-Brain Neuronal and Neurotransmitter Systems.” Proceedings of the National Academy of Sciences 117 (17): 9566–76. https://doi.org/10.1073/pnas.1921475117.

Fact Checked: Seraiah Alexander


Brandon Rich

Brandon Rich

Content Writer

Table Of Contents

The origin of the Stoned Ape Theory
The early history of McKenna’s idea
The psychedelic theory gains traction
Backing up McKenna’s claims
The effects of psychedelics on the brain
Criticism of the theory
The unanswered mystery of the Stoned Ape Theory

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