The Human Predilection for Psychedelics May Be an Evolutionary Accident

human predilection for psychedelics could be an evolutionary accident

Because psychedelics can have profoundly positive effects on people, this has led to the narrative that they exist for our consumption. Why else would certain plants and mushrooms have evolved compounds that foster better mental health, induce spiritual and transformative experiences, and lead to enhanced connection to others and nature? However, there is evidence that suggests the opposite (more banal) reality: these compounds have functions that have nothing to do with us.

The Symbiosis/Coevolution Argument

I often come across the explanation that beneficial psychedelic effects have a logical cause: these plants and mushrooms are in a symbiotic relationship with us. They expend energy making psychedelic compounds so that we will consume them, which produce experiences that promote individual, collective, ecological, and planetary health. These effects benefit those same plants and mushrooms as they encourage the environmental conditions that enable their continued survival and reproduction.

Part of this symbiosis argument also involves the suggestion that these plants and mushrooms produce compounds we like because it encourages us to spread their genetic material. Michael Pollan offered this argument for human-plant coevolution in conversation with Jules Evans:

This has been a subject I’ve been writing about since a book I published in 2001 called The Botany of Desire…The idea for the book grew out of a little epiphany I had as a gardener, where a lot of my work originates. I was planting potato seed, and the same week the apple trees in my vegetable garden were just buzzing with activity, they were in full bloom and the honey bees were all over them.

And as I sat there planting, it occurred to me that I was more like the honey bees than I realized or than we generally realize. The honey bee assumes that it is getting the best of its relationship with the apple. It’s breaking in, it’s stealing the nectar… and it has no idea that it’s being manipulated to do that and that the plant is dusting its legs with pollen on its way in and out. The bee is moving the genes of this apple tree around the neighborhood.

And I realized, well, how is that different between, you know, me and the potato? I think I’m getting the benefit of growing potatoes and this wonderful food. But in fact, the potatoes have induced me to order these seeds, have them delivered, plant them, give them new habitat, expand their range.

And so that sent me down this path of looking at the symbiosis of our coevolution. And I give plants a lot more credit I think than some people do for having agency and a point of view. I’m not saying they’re conscious, but they have a set of goals like we do, evolutionary goals. And a certain subset of them have prospered immensely by hitching their wagon to ours. Cannabis figured out, and I used those words advisedly, that by changing human consciousness it could get its genes out of the area in Asia where it originated, into India, China, and get a level of attention and a tailor-made habitat that it never would have.

He goes on to note other examples in nature that he believes support this case for coevolution:

Coffee and tea are also very good examples. By changing our consciousness they benefited enormously and we now give 10s of millions of acres over to coffee and tea, and millions of humans spend their lives tending to the welfare of these plants. Who benefits more? I would say it’s a pretty equal exchange, but I don’t know what the plants would say. I think they’d be laughing.

Evans asked Pollan to comment on whether this line of reasoning applies to natural psychedelics as well, specifically the idea that by making us trip and talk enthusiastically about these experiences, we end up spreading their DNA. Pollan responded:

Well, it may be…Magic mushrooms, the ones that got people high, were the ones that got moved around the world and every time you pick a mushroom, you’re trailing fairy dust of spores and you don’t even know it…And we’ve moved them all over the world, you know. We have been the vector of their spread around the world.

In my forthcoming book, Altered Perspectives, which adopts a sceptical stance towards several common narratives in psychedelic culture, I address the topic of psychedelic-human symbiosis. It is an alternative to a position I call psychedelic teleology, which is thinking that natural psychedelics, because of the intelligence or spirit they contain, have a goal-directed nature. In other words, it is the idea that they have a purpose for us, i.e. delivering messages that enhance community and ecological balance, and which steer us away from the opposite outcomes. 

The symbiosis/coevolution argument is distinct because it is non-teleological. It does not presuppose certain organisms being goal-directed. Instead, it works with the current understanding of evolution, in which certain species cooperate with each other to improve their biological fitness, that is, the likelihood of surviving long enough to pass on their genetic material to offspring. However, I believe both the teleological and symbiotic arguments are flawed. There is no good evidence that some plants and mushrooms evolved to produce psychedelic compounds so that we would consume them.

Some studies have also been published that help to support this case, one related to the origin of these plants and mushrooms, and another that focuses on the functions of psilocybin.

Natural Psychedelics Existed Long Before Humans

In a study published this January, a team of researchers at the University of Utah showed that the genus Psilocybe arose much earlier than previously thought. This genus, which includes around 165 known psilocybin-containing mushrooms, originated 65 million years ago. This is around the time that a giant asteroid wiped out the dinosaurs. 

Hominins – our lineage of ancestors that split off from the common ancestor of ourselves and the chimpanzee – first appeared around six million years ago. And Homo sapiens first emerged around 300,000 years ago. So psilocybin-containing mushrooms evolved tens of millions of years before we did, and long before our hominin ancestors existed as well. This challenges the notion that species in the Psilocybe genus started (and continued) to produce psilocybin and psilocin because of human consumption. We simply were not around to eat them, trip, tell others about our experiences, and propagate the mushrooms’ genetic material in the process.

But we have had evidence before this more recent study that indicates natural psychedelics exist for reasons independent of us. For example, the mescaline-containing San Pedro cactus evolved 30 or 40 million years ago in the deserts of South America. Noah Whiteman –  Professor of Integrative Biology and Molecular and Cell Biology at the University of California, Berkeley – notes in an article for TIME:

Although we are still trying to understand the origins and functions of natural psychedelics in the organisms that make them, it is clear that their evolution has nothing to do with us. Given that the ability to produce them evolved millions of years ago when no humans were alive, we would do well to study and scrutinize their natural functions as our society embarks on a rapprochement with these powerful compounds. Basic research into their evolution is as critical as the clinical trials being conducted to assess their potential as drugs. By examining each side of these double-edged swords, we can learn more about how they might work as drugs, and how they might harm us.

Psychedelics May Act as a Defence Against Predators

In a press release for the University of Utah study, Lisa Potter writes, “The authors hoped that psilocybin’s evolutionary history would clarify the most basic question—what does psilocybin do for mushrooms? The psilocybin-producing gene clusters likely have some benefit, but no one knows what it is.”

Nevertheless, the authors suggested some hypotheses related to defence against predation, and they aren’t the first to suggest them. Potters states:

The molecular structure of psilocybin mimics serotonin and binds tightly to serotonin receptors, especially at 5-HT2A, a famous receptor onto which many psychedelic drugs bind. When a chemical binds to these receptors in mammals and similar ones in insects and arachnids, they produce unnatural and altered behaviors. Some have proposed that this altered mental state might be a direct deterrent to predation. It’s also possible that psilocybin functions as a laxative or induces vomiting to spread spores before they are fully digested. However, psilocybin mushrooms often occur infrequently in the wild, making it unlikely that animals could learn to recognize them. An alternative theory is that psilocybin is a chemical defense against insects. However, empirical studies are lacking, and the authors’ observations confirm that psilocybin-containing mushrooms regularly host healthy, thriving insect larvae.

With respect to this last point, a 2018 study found that the larvae of flies can grow inside Psilocybe cyanescens, a potent psilocybin mushroom species. These larvae were successfully reared into adults, indicating they suffered no ill effects as a result of exposure to psilocybin. The authors of the study conclude, “Our results show that psilocybin does not confer complete protection against insect mycophagy, and the hypothesis that it is produced as an adaptive defense compound may need to be reconsidered.” Discussing the University of Utah study, Potters adds:

The authors are preparing experiments to test an alternative theory that they call the Gastropod Hypothesis. The timing and divergence dates of Psilocybe coincide with the KPg boundary, the geological marker of the asteroid that threw Earth into a brutal, prolonged winter and killed 80% of all life. Two lifeforms that thrived during the darkness and decay were fungi and terrestrial gastropods. Evidence, including the fossil record, shows that gastropods had a massive diversification and proliferation just after the asteroid hit, and it’s known that terrestrial slugs are heavy predators of mushrooms. With the study’s molecular dating of Psilocybe to around 65 million years ago, it’s possible that psilocybin evolved as a slug deterrent. They hope that their feeding experiments will shed some light on their hypothesis.

If this hypothesis is correct, it may help explain why psilocybin does not offer complete protection against insects. Certain mushrooms may have evolved the production of psilocybin to protect against certain predatory organisms in an environmental niche, but this doesn’t mean psilocybin will work as a form of defence against all insects. In my book, I note that these potential defence functions of psilocybin were suggested in Kerry Ogame and L.G. Nicholas’ book Psilocybin Mushroom Handbook, published back in 2006. I also covered the topic in a blog post back in 2014. Whiteman observes:

It seems like these chemicals were tailor-made for us. Yet, no humans were around when the organisms producing the chemicals first evolved the ability to make them. A closer look reveals that in many cases we seem to have simply intercepted chemical weapons deployed in what naturalist Charles Darwin called “the war of nature.” Quite simply, many baroque chemicals we use and abuse appeared on the planet because they enhance the survival odds of the organisms that make them or absorb them through their diet or microbiomes.

He adds:

Why do some organisms make psychedelic chemicals? Perhaps because what is good for the goose is good for the gander: like botulinum toxin, penicillin, caffeine, Taxol, and ziconotide, natural psychedelics may serve as chemical weapons that plants, fungi, and animals use in defense against enemies.

In my book, I point out (as Whiteman does) that psychoactive drugs like caffeine and cocaine evolved as a form of defence against insects. They act as toxins; they inhibit the hunger of insects, and they cause paralysis and eventually death. Psychedelic exceptionalism may motivate some psychedelic users to concede that many psychoactive compounds exist purely as insecticides, and we just so happen to enjoy their effects, but this cannot possibly apply to psychedelics. The latter are seen as producing effects simply too profound and transformative to be accidental. I understand this line of thought, but it nonetheless requires evidence to support it.

A 2018 study, published in Evolution Letters, also arrives at the conclusion that psilocybin may have been created to ward off insects. While others had suggested this possible function previously, this study – authored by a team of researchers at Ohio State University – helps to support the hypothesis. These researchers compared several species of mushroom containing psilocybin with those that did not. What they discovered was that the psilocybin mushrooms shared a cluster of five genes absent in the non-psychedelic ones. 

The many different species of psilocybin mushrooms may not be closely related, but they nonetheless all like to grow in animal faeces and rotting wood. These are all habitats where you can find many species – of insects and other creatures – that like to feed on mushrooms. While we experience psychedelic effects when we consume these mushrooms, this doesn’t mean that insects and other small animals trip as well. The authors suggest that psilocybin may cause the insects to lose their appetite (the same effect that caffeine and cocaine have on insects). 

Despite being distantly related, various species of mushrooms have been able to share this pest control technique through a process known as ‘horizontal gene transfer’. This involves the movement of genetic material between organisms that are not in a parent-offspring relationship. Bacteria are able to share antibiotic-resistant genes in this way, for instance. This is a tactic commonly employed by single-celled organisms, but it is much rarer to observe it in complex organisms like mushrooms.

The process is typically set in motion by a stressor, such as an attack by a predator. In the case of psilocybin mushrooms, attempts by insects to eat them may have been the catalyst that led the mushrooms to start producing psilocybin. In addition, the insects are not only predators of mushrooms; they also compete with them for food. Termites would be the major fungal competitors inside decaying wood. This would rule out the notion that psilocybin is just a useless waste product of some essential process going on in the mushroom.

Writing on the research for Scientific American, Jennifer Frazer writes (in agreement with what has been said so far about natural psychoactive compounds):

[T]he majority of naturally-produced recreational drugs – caffeine, nicotine, cocaine, morphine, and psilocybin evolved to be, if not quite insecticides, then scramblers of insect brains. The fact that our brains are enjoyably scrambled by them too is sheer coincidence, but also speaks to the uncomfortable truth that your brain is not so different from a cockroach’s as you might like to think.

Psilocybin produces psychedelic effects in us because its metabolite, psilocin, activates the same receptors (5-HT2A) receptors as serotonin. However, we are, of course, not the only creature that produces this neurotransmitter. Insects produce serotonin as well. So psilocybin may also affect the brains of insects, just not in the way we’re familiar with (and in the way we like) when we consume these mushrooms. As Frazer puts it:

Psilocybin may help tilt the playing field in the fungus’s favor by causing insects to, I don’t know, maybe blank on what they went in that log for again? Another serotonin receptor antagonist called 5HT-2A causes Drosophila fruit flies to somehow neglect to eat that fruit they’re sitting on.

This, then, would amount to an eating-inhibiting effect, even if not a hunger-inhibiting one (although perhaps psilocybin and other psychedelics serve that function as well). It is not so hard to imagine psychedelics inducing confusion in insects and other small animals when you consider that tripping can induce similar effects in humans, to the point that one loses the normal sense of what things are. Tripping can involve a loss of interest in – and ability to carry out – normal activities. Hunger tends to be suppressed as well.

It is also possible that in larger (but non-human) animals, psychedelics have different psychoactive effects, but these are still felt to be unpleasant. It is true that many animal species enjoy getting high, but this does not mean every animal would experience the consumption of psychedelic plants and mushrooms as pleasant. They may feel disoriented and in a fear-ridden state, which we can see in a 1960 film showing a cat on LSD. Moreover, animals in this altered state of mind would be more vulnerable to attack, which adds a further reason for them to avoid consuming psychedelic plants and mushrooms.

Bitter Taste and Nausea Can Act as Further Defence Mechanisms

Psychedelic compounds may help plants and mushrooms defend themselves against animals larger than insects and slugs. As Whiteman notes:

5-Meo-DMT, DMT, psilocybin, mescaline, and ergot alkaloids are extremely bitter, so most animals probably avoid them in nature, which can serve as a defense in itself. Among the plants that make 5-Meo-DMT and DMT, grasses in the genus Phalaris are protected from grazing mammalian herbivores like sheep, who find these and related but non-psychedelic chemicals like gramine, unpalatable. If they are eaten, a condition known as the “phalaris staggers” has been reported, reflecting the potentially neurotoxic effects of these alkaloids in the grasses.

Similarly, one clue to why magic mushrooms evolved to produce high levels of psilocybin comes from the fact that these fungi turn blue when injured. In that case, two enzymes chemically transform psilocybin into a chain of psilocin molecules that become linked to one another. These chains act much like indigo or some tannins, which also turn blue when oxidized, and may disrupt the digestive tract. Although psilocin is what causes psychedelic experiences after it is converted from psilocybin, those experiences may be unintended consequences of its ultimate function for mushrooms.

As I highlight in my book, the bitter taste and nausea caused by many psychedelic compounds indicate that they were not meant for us to consume. To me, it seems more likely that these effects are a form of defence against consumption rather than an unpleasant barrier we have to push through in order to gain access to the wisdom and messages of the plant or fungal intelligence.

On the other hand, as the psychedelic researcher David Luke points out, “the principle of exaptation means that while psilocybin (for example) may have evolved in one species for one purpose (and it co-evolved numerous times seemingly) it can shift its function to a different purpose evolutionarily.” So perhaps psilocybin and other psychedelics originally functioned as deterrents against predatory organisms but later served as a chemical means of enhancing human consciousness. As the mycologist Paul Stamets claims, the message from psilocybin mushrooms is “always that we are part of an ‘ecology of consciousness’, that the Earth is in peril, that time is short, and that we’re part of a huge, universal bio-system.”

One may wonder why naturally-occurring psychedelics would still produce nausea and stomach upset if they seek to deliver a pro-environmental message to humans. We should keep in mind, however, that evolution is not a perfect system. In the case of exaptation, the fact that a trait shifts its function over time doesn’t mean it can eradicate every aspect of that trait. Natural selection can only build on what currently exists. It cannot start from scratch and produce a perfect solution. Hence, even if natural psychedelics cause us to experience nausea, this doesn’t rule out the possibility that they’re still meant to alter our consciousness in environmentally positive ways. Nausea could be one of the indications that psychedelics served a different function in the past.

Gratitude for the Existence of Psychedelics

Even if it is accidental that psychedelics are psychoactive for us in a way that we value, or deeply value, this does not mean we can no longer feel grateful that they exist. In fact, the kind of gratitude we feel will be different. The sense of being lucky truly becomes magnified once we consider how compounds that arose as a form of defence can serve to improve our lives in a myriad of ways. For example, I like to think of psychedelics as syndeogens, or connection-generating agents – they enhance connection at the smallest level (the level of neurons) and at larger scales, where we can feel more connected to ourselves, other people, other creatures, the natural world, the universe, and ultimate reality.

For some, it may not only be more banal to think of psychedelics as originating in the warfare between competing organisms; this might also seem like a sad state of affairs. Nonetheless, there may be reasons to be cheerful. Defensive compounds in nature may offer us benefits yet to be discovered. As Frazer states:

As a result of the chemical warfare going on between fungi and insects in dung and dead logs, these results also suggest decay mushrooms may be a good place to search for new neuro-active drugs. Fungi in such haunts may be veritable factories of neurotransmitter-targeting drugs. Though originally intended to throw insects off their game, there is no telling what unintentional, valuable – and interesting – effects they may have on us.

Fungal and botanical gifts exist all around us, but they weren’t gifted to us by any being or with a purpose for us in mind. By using them wisely – with our own ethically driven, constructed purposes – we can turn a creation of blind evolution into a tool for human flourishing.

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