Psilocybin, IQ, and the Stoned Ape Hypothesis

A while back, I wrote a post discussing the potential for psychedelics to increase intelligence. There are many reasons this is of particular interest. For one, we have been looking for an “IQ pill” for a long time now with no luck. The main choices are nootropics like modafinil, Adderall, etc. Unfortunately, these don’t seem to work too well. Second, there are obvious benefits to a higher IQ, particularly in the labor market (Gwern, 2016; Strenze, 2015; Salgado and Moscoso, 2019). Third, as I will talk about shortly, even a very small, but significant increase in intelligence due to psilocybin may have some interesting implications for the so-called Stoned Ape hypothesis.

Why might psilocybin increase IQ scores? Well, the main driver of these effects would be through neurogenesis. Many studies so far have found psychedelics play a large role in increasing cognitive functioning, such as through depression, fixing minor debilitative disorders, and abolition of the conditioned fear response in the brain. Catlow et al. (2013) injected one group of mice with a low dose of psilocybin and another group of mice with saline. They found the psilocybin injected group gained new neurons in the hippocampus. Before the mice were given psilocybin, they were placed in a freeze monitor box where they were conditioned into a fear response. This conditioned fear response was significant reduced in the psilocybin treated group. In rats, other tryptamines were associated with increase in dendritic arbor complexity and dendritic spine growth and synapse formation (Ly et al., 2018).

We can rationally expect these effects would translate to humans due to the success in treating depression with psilocybin in humans. A clinical study gave 12 patients with treatment-resistant depression psilocybin. The participants received two total doses, each of a very low to moderate size and 7 days apart, and they found that even after 3 months, there were significant reductions in depression (Carhart-Harris et al., 2016 [generally anyone interested in psychedelics should read all of this guys studies]). Unfortunately, there was no control or placebo group, so proving the causality is difficult. But, when the treatment group has treatment-resistant major depressive disorder and faces substantial effects over a long period of time, it is unlikely this was due to a placebo effect or a random happening. Carhart-Harris et al. (2017) found similar results in strong effectiveness of treating depression with psychedelics and also found these were related to changes in the amygdala. Griffiths et al. (2016) used a random, double blind cross-over trial to find if psilocybin was useful for treating depression and anxiety in cancer patients. They found after moderate-large doses of psilocybin, the treatment group faced large decreases in death anxiety, and depression and increases in quality of life, meaning, and optimism in comparison to the placebo group. Community observers also observed these changes in the participants.

So, from what we can tell, psilocybin is an interesting drug in treating major disorders and probably causes neurogenesis in the brain. If one is interested in an incredibly interesting anecdotal experience attributed to neurogenesis, I strongly recommend watching the story in this clip:

Anyways, what does this mean in the long run?

Stoned Ape Hypothesis

The following hypothesis has been heavily mocked or ignored by the scientific community. And it’s understandable why. It sounds crazy. But I ask the reader to suspend their disbelief for just a moment and consider the possibility. One major mystery in modern evolutionary biology is the happening of a doubling in brain size over a span of some two million to two hundred thousand years. Thus far, little plausible explanation has been given for why this occurred. In 1994, Terence McKenna proposed the Stoned Ape hypothesis to argue the brain size increase was due to epigenetic neurogenesis which occurred through the casual consumption of Psilocybe cubensis. Regarding the brain size increase, McKenna (1994) wrote,

With Homo habilis began a sudden and mysterious expansion of brain size. Homo habilis’s brain weighed an average 770 grams (27. 5 ounces), compared with 530 grams (19 ounces) for competing hominids. The next two and a quarter million years brought an unusually rapid evolution in brain size and complexity. By 750,000 to 1.1 million years ago a new hominid type, Homo erectus, was widespread. The brain size of this new hominid was 900 to 1100 grams (2 to 2.4 pounds). Evidence is good that Homo erectus used tools and possessed some sort of rudimentary culture. At Choukoutien Cave in South Africa, there is good evidence of fire use along with burnt bones indicating the cooking of meat. These are attributed to Homo erectus, which was the earliest hominid to leave Africa, a million or so years ago.

Why does McKenna’s view even make sense? As our primate ancestors left the jungles and traveled the desert areas, they needed to look for food. When you look for food, you’re typically looking for things like footprints and dung as they are telling as to where animals have been. The most prevalent fleshy mushroom found within animal dung, like that in hippopotami, cows, etc. is Psilocybe cubensis. We now know that 22 primate species consume mushrooms in general, and that multiple primates even consume psilocybin mushrooms which does give this theory some more credence (eg. sex differences in toy choice are visible in monkeys who have never even been shown to recognize gender therefore we can argue sex differences have an evolutionary basis).

McKenna is sure to steer clear of Lamarckianism, as he wrote in his book:

The short answer to this objection, one that requires no defense of Lamarck’s ideas, is that the presence of psilocybin in the hominid diet changed the parameters of the process of natural selection by changing the behavioral patterns upon which that selection was operating. Experimentation with many types of foods was causing a general increase in the numbers of random mutations being offered up to the process of natural selection, while the augmentation of visual acuity, language use, and ritual activity through the use of psilocybin represented new behaviors. One of these new behaviors, language use, previously only a marginally important trait, was suddenly very useful in the context of new hunting and gathering lifestyles. Hence psilocybin inclusion in the diet shifted the parameters of human behavior in favor of patterns of activity that promoted increased language; acquisition of language led to more vocabulary and an expanded memory capacity. The psilocybin-using individuals evolved epigenetic rules or cultural forms that enabled them to survive and reproduce better than other individuals. Eventually the more successful epigenetically based styles of behavior spread through the populations along with the genes that reinforce them. In this fashion the population would evolve genetically and culturally.

McKenna’s hypothesis can thus be roughly stated as so: psilocybin consumption was evolutionarily beneficial because it caused neurogenesis and allowed for a brain size increase, the development of language, and the creation of basic civilization. The issue is proving psilocybin usage as evolutionarily beneficial or that it even increased intelligence in some way. That is where the theory of psychedelics and IQ comes in.

Do Psychedelics Increase Intelligence?

Not too long ago, I wrote a moderately sized blog post reviewing all of the data I could find on this topic. Few of the studies are actually on psilocybin usage; this was just psychedelics in general. Even then, the amount of studies is very small. It took a while and there is no conclusive evidence so far. All of the studies have been shoddy and non-representative. That said, most indicate a potential increase, albeit a probably small one. Here is a table summarizing the research I found:

I should note that any increase at all is potentially useful. When discussing the brain size increase, we are talking 200,000 years to 2 million years. If our primate ancestors were consuming these drugs every day, perhaps multiple times a day even, then the effects of one dose being small is radically multiplied in significance. Since psychedelics may very well increase intelligence, there is certainly a stronger argument for the Stoned Ape hypothesis.

Modern Implications

If the Stoned Ape hypothesis is correct, then there are other things which must be true about psilocybin usage. We would have to somehow show that high doses of psilocybin are associated with language making abilities (the best way I could think of testing this is with a group of either very low IQ people or perhaps hunter-gatherers), as well as increases in sexual behavior. This latter one is expected to be true, because psychedelics are associated with greater tactile response and overall a greater love for your surroundings, finding beauty in more things and getting a larger response when touching, seeing, or listening to various things. Once again, I ask the reader to suspend their disbelief for a moment. Say one of our ancient ancestors is looking through the desert for food and comes across Psilocybe cubensis. If it is responsible for extinguishing the conditioned fear response, we know he could certainly hunt better. The same goes for visual and audio perception. Additionally, the group may take these and experience greater empathy which is shown across many studies so far. This is of particular interest in the creation of civilization. Bravery and altruism are great things to have in coordinating a group.

And so, if this is true, perhaps we ought to change the way we view these drugs. We see their benefits and if we could somehow give more credence to the Stoned Ape hypothesis, we would understand that we are forever indebted to them for allowing Homo sapiens to arise and create modern civilization. Indeed, it would almost create cause for mass participation in psilocybin usage (not that I advocate this). A study done by Hendricks et al. (2017) found that psilocybin usage decreased criminal behavior by ~20 percent. Imagine the consequences if everyone took these drugs. A 20 percent drop in crime would be extraordinary.

But, maybe for more conservative readers, this is extreme, this is ludicrous, etc. Fine. Say psychedelics have some effect on intelligence. What could you do to make this beneficial to you? Well, I can hardly advocate we treat these breathtaking experiences which can be very anxiolytic for many people as an automatic IQ increase. But, more and more evidence is increasing towards the benefits of microdosing. This is essentially taking a non-active dose of psilocybin or LSD maybe 5 days a week. It can also be combined with Lion’s Mane which is a legal medical mushroom which encourages neurogenesis, and with niacin which spreads the effects around the brain, allowing greater coverage of regeneration of neurons. Microdosing is known to be used by coders and businessmen in Silicon Valley. And if it really is all that helpful for things like creativity and cognitive functioning in general, then it will automatically put these people at an advantage. A non-active dose will not bring about any visuals, at least after the first day of microdosing and so it will not have the same anxiolytic effect large doses of psilocybin might have.

In conclusion, I think the Stoned Ape hypothesis is certainly plausible especially with some, however non-conclusive, evidence that psychedelics may increase intelligence. If this is true, we may consider rethinking how we view our relation to psilocybin and mushrooms in general, perhaps. We still can’t really prove the Stoned Ape hypothesis, but we could prove that psychedelics have an effect on intelligence. All it requires is a proper study, maybe two which look at the effects of one or more large doses in the first one and the effects of microdosing in the second one. One may bring up the Algernon argument when discussing lasting effects of psilocybin microdosing on IQ, but this is not all that important if one just decides to continue dosing, especially with next to zero risk (aside from law enforcement as of writing this). Indeed, in a study using Lion’s Mane to help cognitively disabled people, there were substantial, positive effects on IQ, but if the user stopped dosing then it went away. Overall, this whole thing needs more research and in respect of free inquiry and the desire for scientific improvement, I think it should be done.

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