Debunking the Stoned Ape Theory

The Dawn of a New Era

"A young Homo habilis ventures warily out of the safe, shaded forest and into the unexplored grassland beyond. From the comfort of the trees, she had watched as juvenile Giraffidae were hunted by lions, and wanted nothing more than to stay away. But desperate times call for desperate measures, and the section of the forest she called home was now too small and over-harvested to host the ever-growing population she was a part of. There wasn’t much food to be found in the grassland, but it would be enough. After finally working up their courage, she and her family were able to scavenge amongst the sparse vegetation and carcasses to supplement what food was left in the jungle. Scattered in the grass are vast quantities of Giraffidae dung, upon which tiny stalks sprout after a rainy day. At first, the Homo habilis and her family ignore them, with other food sources being readily available, but when the herds eventually moved away from the repeated intrusions, the ape’s attention returned to those small stalks -which had grown significantly larger. Apprehensive but with little other choice, they each eat a handful or two of the fungus to reduce the pain of starvation. Half an hour later, they discovered their senses had increased in acuity and a sense of ease and comfort had befallen them. They couldn’t have known it, but these effects were brought on by a substance similar in structure to the compounds that gave them awareness -psilocybin.

Several million years later, one of their descendants creates the “Stoned Ape Theory”, postulating that the rapid doubling of brain matter in early hominids was caused by the advantages provided to those hominids who consistently consumed psilocybin mushrooms... The descendent in question was Terence Mckenna"

-The Book of Psychedelics, page 130

Impossible

The idea that psilocybin mushrooms are responsible for modern human’s incredible level of intelligence is one that psychonauts naturally gravitate towards given the mind-expanding nature of the compound’s experience. The community's struggle to separate psychedelics from the dangerous drugs they have been inaccurately classified is likely an additional motivator to accept it unquestioningly. Recent evidence that the mushrooms stimulate neurogenesis¹ seems to lend the idea some validity, further cementing it in people's minds. However, The Stoned Ape Theory as it is most often understood has fundamental flaws, and future discussions of it must be recontextualized given our current understanding of psilocybin and evolution.

The first of these flaws is in the name: Mckenna’s idea is not -and likely never will be- a theory. In order for an explanation of a natural phenomenon to be considered a theory, there must be substantial evidence in its favor. For example, the theory of evolution as an explanation for the development of modern species is evidenced by the fossil record and bacteria’s rapid development of resistance to medication. Unfortunately for Terence’s idea, there is no such evidence to support his explanation for the doubling of hominid brain size, only evidence of it having occurred. As it is, the idea is no more than a hypothesis, a "supposition or proposed explanation made on the basis of limited evidence as a starting point for further investigation”. This describes the explanation much more accurately, as it is known that hominid brain size rapidly doubled and humans certainly began consuming the mushrooms at some point, leaving the hypothesis to make the link. In Mckenna’s defense, this name was not of his creation -though clarifying this point is still important to understanding the hypothesis.

The second issue is the misconception that consuming psilocybin mushrooms would have a heritable (able to be passed to offspring) effect on those who consumed them. While an increase in an individual’s brainpower by psilocybin would certainly be beneficial, this improvement will remain confined to them. In order for a trait to be passed on, it must be coded for in the DNA of that organism’s sex cells. Even mutations to an organism’s DNA in somatic (body) cells cannot be passed on - luckily, or cancer would have eradicated us all. The improvements in brain function by individuals who consumed psilocybin are analogous to the improvements in musculature brought on by steroid use. Someone can take steroids and become unnaturally lean and strong, but their steroid-derived musculature is not passed on to their children.

Imperfect ≠ Incorrect

Though Mckenna may not have accounted for the difference between adaptational and evolutionary changes when creating his hypothesis, it is not impossible that psilocybin played a significant role in the development of the human brain. However, the means by which this would happen is very different from what people commonly understand the hypothesis to mean. Instead of directly causing a heritable change in the organism, the mushrooms must have provided an artificial advantage to hominids with the traits passed on. When viewed from this angle, the viability of the hypothesis increases drastically.

In humans -and many other animals- there is a positive correlation between intelligence and novelty-seeking behavior. If this correlation is applied to our predecessors, it is likely that more naturally intelligent hominids sought out the altered states of consciousness provided by psilocybin after their effects were accidentally discovered. While a large portion of the population may try the mushrooms once, intelligent individuals will likely consume them with a much greater frequency as they seek new and stimulating experiences. Their regular consumption of the mushrooms could lead to the same neurogenic benefits seen in modern humans, improving their moods and increasing their already elevated level of intelligence. This would grant them an advantage over other hominids as they would have a higher chance of reaching sexual maturity and execute tasks more efficiently than their competitors. The resulting improved health and access to resources would lead to them being more attractive to prospective mates with which to produce offspring. These children would not inherit the increased intelligence gained through the consumption of psilocybin, but the parent’s genetically above-average intelligence. The enhanced intelligence of their parents would allow them to better care for the children and -in combination with the increased empathy psilocybin induces- to better teach them the skills they have learned throughout their lives. Based on the effects they experienced, the parents would also likely facilitate their children’s use of psilocybin, further improving their own intellectual abilities. Repeat this cycle for millions of years and the result is a rapid increase in brain mass and intelligence, as the psilocybin experience continues artificially selecting intelligent individuals and offering them advantages.

To further clarify this, let’s return to the steroid analogy. People who are genetically predisposed to muscularity are more likely to take up an exercise regimen and the use of steroids (or other supplement). Their use of steroids would improve their musculature to levels beyond what they could otherwise attain, allowing them to more easily attract a mate who prefers muscular individuals. Given their interest, the potential mates are also likely to be genetically predisposed to physical fitness. The children of such a pairing will inherit that strength, and their parents will likely facilitate them working out -and perhaps supplementing their exercise- perpetuating the cycle.

Applying this logic to the Stoned Ape Hypothesis: intelligent hominids are naturally more curious and therefore more likely to consume psilocybin mushrooms. The psilocybin makes them smarter and thus more able to maintain their health/acquire more resources than other hominids. This makes them more attractive to females and therefore more likely to reproduce and pass on their initial above-average intellect.

In summary, the Stoned Ape Hypothesis is viable not because the consumption of psilocybin led to an heritable increase in intelligence, but because the psilocybin experience acted as a source of artificial evolutionary pressure. The intelligence required to seek novelty through the use of mushrooms was passed down and compounded over the millennia, leading to the intelligence of modern humans.

As with the previous article -which discussed the evolutionary reason for mushrooms developing psilocybin- the Stoned Ape Hypothesis will likely never be more than speculation given our inability to collect more concrete data.

[1]https://www.frontiersin.org/articles/10.3389/fpsyt.2021.724606/full#:~:text=Psilocybin%2Dtreated%20mice%20exhibited%20increased,dose%20decreasing%20neurogenesis%20(62).