The standard account of how psychedelics work goes roughly like this: the molecule enters the bloodstream, crosses the blood-brain barrier, binds to serotonin 5-HT2A receptors, and initiates cascading neurological changes — altered connectivity, disrupted default mode network activity, loosened predictive hierarchies. The explanation is accurate as far as it goes. But it begins and ends with the brain. And there is something it cannot account for: the molecule didn't evolve for human brains.

Psilocybin — to take the most studied example — appears to have evolved independently at least twice in distantly related fungal lineages, a striking instance of convergent evolution in natural product biosynthesis (Meyer & Slot, 2023; Reynolds et al., 2018). Convergent evolution of this kind suggests strong ecological selection pressure. The compound was doing something reliably useful long before a human organism ever encountered it — most likely modulating the behavior of insects and decomposers in fungal environments. The fact that it also profoundly reorganizes human consciousness is not incidental, but it does complicate the story. A purely neurocentric account treats the molecule as a key and the brain as its lock. The ecological picture is stranger and, I think, more illuminating.

Communication between organisms is not primarily linguistic. Before language, before nervous systems, before anything recognizable as thought, living systems were already exchanging information. Cells respond to molecular cues that regulate metabolism. Plants detect volatile organic compounds released by stressed neighbors and activate their own defenses via evolved receptor pathways. Mycorrhizal networks mediate chemical exchanges through which trees modulate growth, defense, and resource allocation in response to conditions hundreds of meters away. Bacteria use threshold-sensitive molecules to coordinate collective behavior across entire populations.

This is what biosemiotics describes: semiosis — the production, transmission, and interpretation of meaningful signs — is not a uniquely human achievement. It is a foundational property of living systems. Jørgen Hoffmeyer, one of the field's central theorists, argued that the living world is "perfused with signs." Meaning, in this account, is not something humans project onto a silent nature. It is a mode of organization that nature has been enacting at every scale for billions of years.

The crucial point is that significance arises in the interpretive act, not in the molecule itself. The same chemical compound means something different to a bacterium, an insect, a tree, and a human — because each organism's interpretive apparatus, shaped by its evolutionary history and bodily organization, encounters the molecule differently. Jakob von Uexküll called each organism's perceptual world its Umwelt — the subjective subset of environmental features that are meaningfully registered by that organism. The same garden is a radically different place for the bee navigating by UV patterns invisible to human eyes, the earthworm responding to mineral gradients in the soil, the crow reading social dynamics among its companions. Each inhabits a distinct semiotic world, carved out of the same underlying reality by the particular configuration of its sensing body.

The human Umwelt is not fixed. It is shaped by culture, technology, and the conditions of daily life — and it can narrow. For organisms embedded in industrial-growth societies, surrounded by digital interfaces, artificial environments, and economic logics that organize attention around productivity and consumption, the range of ecological signs actively interpreted tends to contract. What remains perceptually foregrounded is a thin slice of the relational complexity that actually sustains life. The mycorrhizal networks underfoot, the chemical dialogues between species in a hedgerow, the feedback dynamics of the watershed — these are present, continuously, but they are not perceptually available. The semiotic scaffolding that would make them register has atrophied.

This is not merely a poetic observation. Enactive cognition — developed by Varela, Thompson, and Rosch from the earlier biological work of Maturana and Varela — holds that perception is not a passive reception of pre-given data. The organism actively brings forth a meaningful world through its structural coupling with its environment. What registers as significant, what appears salient, what becomes affectively charged: these are not properties of the world itself but achievements of ongoing organism-environment interaction. As Varela and colleagues put it, perception "contributes to the enactment of this surrounding world." Change the organism's mode of coupling, and the world that is enacted changes with it.

Modernity has systematically reorganized that coupling. It has not made ecological reality disappear. It has made it imperceptible.

This is where psychedelics become ecologically interesting. Within the biosemiotic framework, they can be understood as modulators of semiotic scaffolding — compounds that, when introduced into human neurophysiology, temporarily reorganize the interpretive processes through which the organism encounters its environment.

They are not unique in being cross-species chemical signals. Secondary metabolites of this kind pervade ecological networks: compounds that evolved within one set of species relationships and participate, incidentally or consequentially, in others. What makes psychedelics distinctive is the scope and depth of the reorganization they induce. Rather than targeting a single receptor pathway and producing a targeted adjustment, they impact the entire semiotic architecture. Specifically, they target ego-centered control mechanisms — the hierarchical predictive processing structures through which the brain ordinarily filters incoming information in favor of what fits its existing model — and temporarily relax them. What gets suppressed under ordinary conditions begins to flow. The range of environmental features that register as potential signs expands.

The human organism's sensitivity to tryptamine structures like psilocybin reflects embeddedness within a conserved serotonergic neurochemical ecology. The shared molecular affinity is not coincidence or accident; it reflects the deep evolutionary entanglement of animal nervous systems with the chemical environment produced by plants, fungi, and other organisms across deep time. Recent evidence suggests that 5-HT2A agonism shifts cortical processing away from immediate sensory filtering and toward memory-associated networks — which, on the ecological account, may mean activating evolutionarily conserved patterns of relational and ecological sense-making encoded across a very long history of organism-environment coupling (White et al., 2026).

The molecule is not a message. It is a key that temporarily reconfigures the interpretive apparatus through which messages, always already present in the environment, become receivable.

The phenomenological reports from psychedelic experiences are consistent enough to constitute a pattern. People describe the living world as animate, responsive, communicative. They report a felt sense of being in relationship with plants, landscapes, organisms — not as anthropomorphic projection but as direct perceptual encounter. They describe perceiving patterns of interconnection that ordinarily remain invisible. They characterize it as a kind of recognition rather than a revelation: not the arrival of something new, but the recovery of something that was already there.

Within the biosemiotic frame, these reports are intelligible as descriptions of an expanded Umwelt. When the habitual ego-centered filters relax, features of the environment that ordinarily remain perceptually backgrounded — the relational, the alive, the interdependent — come forward. The world does not become more communicative. The organism becomes more capable of receiving what was already being communicated.

This does not require attributing intentional agency to plants or fungi. The interpretive act happens in the organism, not in the molecule. A plant releasing volatile compounds in response to herbivory is not trying to speak to a human. But a human whose semiotic scaffolding has been temporarily reorganized may encounter those same compounds — and the aliveness they signal — in ways that ordinary perception suppresses. The experience of "communication with the forest" is, on this account, a shift in semiosis rather than evidence of anthropomorphic intention. It points toward something real: an expansion of the range of ecological signs that become perceptually and affectively available.

What ecological cognition proposes, then, is not a metaphysical claim but a scientific reorientation. Cognition is not confined to neural processes inside individual skulls. It is distributed across the relational systems within which organisms are embedded — chemical, biological, semiotic. The human mind is a node in a much larger network of sense-making processes. Most of the time, ordinary cognition obscures this embeddedness. The ego-centered predictive architecture does its job too well, filtering the complexity of ecological relations down to what is instrumentally relevant for individual navigation.

Psychedelics temporarily alter the filter. They do not import foreign content into the organism; they shift the conditions under which the organism participates in the relational dynamics that were always already surrounding it. The sense of aliveness, of interconnection, of belonging to something larger — these are not hallucinations. They are what becomes available when the ordinary machinery of disconnection is briefly suspended.

The question this raises is not whether such experiences are meaningful. They clearly are. The question is what happens next — whether the expanded perception gets metabolized into a different way of inhabiting the world, or closes again around the same habits and assumptions it briefly interrupted. That is a question about integration, about community, about what kind of life is being returned to. The molecule opens the perceptual field. Everything else is what you do with the opening.

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