I put off publishing my take on semiosis for years because I kept getting better ideas about how to do it. That hasn’t stopped since I published it last month, so I’m redoing it with some major changes. If you read and understood it the first time, you can feel free to skip this, but it should be a better place for newbies to jump on going forward.
Haunted Atoms
There’s a Twitter account called The CryptoNaturalist. The account is popular among people who like nature and weird fiction, but it’s not quite my flavor, and a lot of its tweets get under my skin through a severe case of narcissism of small differences. In most cases I just find his writing a bit mawkish. But the tweets that really bug me are the ones that venerate ignorance as an opportunity for a special kind of secular-spiritual wonder. There’s nothing wrong with that in theory, but when the question is one you have a pretty straightforward answer to, and that answer has been systematically ignored for decades, it’s exasperating to see people treasure their ignorance instead.
And as it happens, one of questions he invites us to marvel at is the big one: what are we, and how did we come to be wondering about it?
Dust, tweeting about dust that tweets. It’s an utterly elegant way to capture the real mystery of our existence. We have scientific theories that can explain, at least to some degree of precision, everything that happened in the Universe from the Big Bang until the formation of life on Earth. We have biochemical models and evolutionary theories that account for how living organisms became the way they are. We have ecological models that show how they fit together into communities.
But there’s still something about life that none of those theories even begin to capture. To not just think, wake up, and tweet, but to notice oneself thinking and waking up and tweeting, is unaccountable. It’s haunting. There must be something else going on, and we still have no idea what it is.
What Living Is
Indulge me in a bit of speculative fiction. Imagine you’re on an alternate Earth, and you step into a physic class and ask, “Professor, what is a star?” They explain that a star is a special kind of gas giant that emits light because it has a high temperature. You might reasonably ask a follow-up question: what causes it to be hot enough that it emits light? If you know anything about physics in our world, you might be shocked to hear the professor reply that the question makes no sense. “Star” is simply a descriptive category used to distinguish astronomical bodies that have the quality of starness, which is associated with traits like heat and light, from those that do not.
Baffled, you dig deeper. You visit the library and look for any mention of fusion in astronomy and physics textbooks. You find only a few passing mentions, but they are dismissive of the theory because it requires the assumption of a whole new physical process. It cannot explain starness in terms of classical mechanics, and therefore it does not meet the requirements of an adequate definition of starness. In this universe, fusion was discovered decades ago and all but ignored by the physics community.
If you replace “star” with “life,” this Twilight Zone world is exactly the one we live in. The definition of life is one of the central questions in the philosophy of biology. But if you ask most philosophers in the field, they’ll echo the CryptoNaturalist. They don’t know what living is. Wikipedia provides a variety of definitions, but all of them are lists of traits. Life is a system that undergoes evolution. It’s a local violation of the trend toward greater entropy. It’s homeostatic, organized, delimited. It grows and senses and reproduces. It’s a star because it’s hot and bright. There isn’t a single mention of the “fusion” that makes all of those things possible: semiosis.
What is semiosis?
There are reasons you know and appreciate the cosmic importance of nuclear fusion but know of semiosis, at best, as an abstruse and perhaps trivial field of study. Its field of study, called semiotics, is one of the worst terminological nightmares I’ve ever encountered. Semiotics has had a few exceptional communicators, but even they have failed to overcome a central problem: showing someone the significance of semiosis is like getting them to appreciate the beauty of their nose without a mirror.
Nuclear fusion is a deeply unintuitive discovery wrested from the unfathomable realm of the atom. Semiosis is our every living breathing feeling moment. To trace it back to its roots, we had to work backwards from our own minds. That left a legacy of terms loaded with connotations that feel fully and uniquely human. It’s tough to convince people that we’re talking about a fundamental natural process, and not a familiar metaphor applied for our analytical convenience.
I don’t want to tell you any of those terms. I want to start from the bottom, with the simplest possible building block. My informal definition of semiosis goes like this: "a physical object that embodies a cause-effect link between two otherwise unrelated processes.”
A single piano key is a familiar example. A force is exerted to pivot the key. A string vibrates at a certain frequency. In the absence of the piano these are not cause and effect. Only the mechanism that connects the two makes one ensue predictably, inevitably from the other. A piano key creates a new law of physics, conditional on its presence and condition.
Because the cause and effect thus linked are otherwise unrelated—the length and color and composition of the key has no connection to the pitch of the string, eg—the connections formed by semiosis are arbitrary. They are just one of many possibilities within the universal laws of physics, but once they exist, their new linkage of cause and effect becomes lawlike where they are present. They are local, conditional addenda to the laws of physics, which can be endlessly modified and combined.
By this definition, the most basic but overlooked category of semiosis is the humble catalyst. A chemical reaction that is slow, improbable, or even nearly impossible under normal circumstances becomes fast and inevitable simply due to the presence of a molecule that links the beginning to the end. If catalysts are familiar to you, think of semiosis as “catalysis for everything.”
The Origin of Life
Of course, the “causal duct tape” I’m calling semiosis is ubiquitous in the universe. The formation of any molecule changes the reactions and interactions its component atoms are likely to experience. Fusion yields new elements that can fuse to form heavier elements. To define life, we need to be a bit more specific. Just as the fusion of two hydrogen nuclei does not constitute a star, the occurrence of semiosis doesn’t constitute life. In both cases, the threshold to qualify is a self-perpetuating chain reaction. The dawn of life on Earth was the moment when the causal duct taping of semiosis formed a closed-loop cycle.
Conditions on Earth just before that moment were cosmically unusual. Large, complex molecules found rarely if ever elsewhere in the universe were coming into existence all the time. Most of them were unstable and quickly broke down. Due to their size and complexity, the array of possible cause-effect links these molecules could embody was much wider than chemical soups on other bodies.
As long as those conditions persisted, the chemical soup kept trying out different combinations of semiosis. Among those possible links was a set of molecules that happened to form a loop. Each molecule catalyzed the creation of the next. That combination was extremely unlikely in the random soup of molecules, but as soon as it came into existence, it became inevitable. As soon as each link in the cycle was present, all would remain present.
The molecules that compose that cycle have since covered the surface of the Earth, extending themselves into environments completely unlike the ones that first brought them into being. They did so by exploiting the two unique possibilities offered by semiosis, which we’ll call coding and nesting.
Codes, Genetic and Otherwise
With that groundwork firmly established, we can safely introduce a single term from biosemiotics (the study of semiosis within the domain of biology). A code is “a set of rules that establish a correspondence, or a mapping, between the objects of two independent worlds” (Barbieri 2003).
A single piano key sounds only one note. To play a song, you need a full keyboard. Likewise, a single catalyst is just a catalyst. A full suite of catalysts is a code.
Evolution doesn’t require the existence of a code. The first code itself was the product of the Darwinian differential-persistence of molecule combinations in the chemical soup. But in the presence of a code, evolution is hypercharged. The set of possible cause-effect links grows exponentially. If each molecule needs to be the catalyst for the next link in the chain on its own, the size and complexity of each molecule is limited by size and complexity of the catalyst that creates it. With a code, complex molecules can be built step by step by a sequence of unrelated catalysts. And unlike the structure of a catalyst, the sequence of those steps is unconstrained by physical law. As soon as the piano is built, any combination of notes can be played.
The first code, built from that first self-perpetuating loop of semiosis, was the genetic code. The “independent worlds” it relates are nucleotides and amino acids, linked by the quite of transfer RNA catalysts that translate sequences of one into the other.
Biologists are of course well aware of the genetic code. What they generally fail to appreciate is that the genetic code was only the first, foundational code. Every subsequent leap in the complexity of life was also enabled by the emergence of a code. Each new code enables evolution to elegantly sort through increasingly complex arrangements of matter.
Nesting
In a piano key, the causal link between the pivot of the lever and the sounding of the string isn’t direct. It’s intermediated by a Rube Goldberg cascade of internal parts.
This is typical. Beyond the simplest chemical catalysts, every semiotic cause-effect link is really a sequence of intermediate steps. This makes these internal mechanisms modular and interchangeable. If they are replaced by functionally identical parts, they can yield the same results through a different path. Of course, some changes aren’t functionally identical, and in those cases the overall semiosis is also altered. Nor is there anything special about what we call the “cause” or “effect.” More steps can be chained to the front or back of the chain indefinitely.
The result is that semiosis is an infinitely nestable process. It builds on its own previous products. And unlike fusion, which is bounded by the instability of heavy elements, semiosis has no apparent natural limit short of the maximum information density of spacetime. The evolutionary history of life is the story of cumulative causal duct-taping, acting iteratively on the increasingly intricate physical laws created by the last round.
This is “what living is.” The same process that brought about the genetic code from the molecular soup makes us stop for red lights and write tweets about dust that tweets. Granted, that elides every interesting detail, including many important mysteries. The sense that thinking is a kind of haunting has less to do with molecular soups than the miracle of consciousness. But the CryptoNaturalist has the right question. Consciousness is far downstream of the real miracle, the process that gave life to dust. And it’s all the more miraculous that that miracle is not a distant mystery. It’s intimately familiar to all of us. It’s meaning itself.