No doubt about it: Life is truly amazing. I mean, the things it gets up to far exceed our imaginations! (Just watch a few dozen Ze Frank “True Facts” videos to scratch the surface.) It hardly seems necessary to invest in a post to elucidate what constitutes Life, when a small child will correctly identify instances almost every time. Living beings demonstrate awareness about their surroundings, taking actions broadly in service of goals to thrive and reproduce. An amoeba marks itself as alive because we witness its purposeful mobility to secure food and evade danger.

Yet, living beings are undeniably made of atoms—atoms that do not appear in any close investigation to operate outside the usual rules of physics. Our sensation of awareness, experience of color perception, etc. seems so far removed from physics that the intractable connection is obvious to neither child nor adult. How could this awareness (what we label “consciousness”) possibly arise out of inanimate particles obeying physics without some “special sauce” unavailable to mere “machines” like computers or robots? It seems prima facie absurd, so it requires an unusual suspension of disbelief to submit to the baffling prospect.

How is it even possible, though, that inanimate matter can constitute Life? In a word: feedback. Life is feedback. The sun is of huge importance to Life, but we would not say that it is alive itself even though it actively engages with the universe and is a critical contributor to living beings on Earth. It’s continuance as a star is not contingent on these interactions. No feedback loop makes fusion in the core care what happens in Las Vegas. As an aside, I resist dividing lines and include the Sun (and everything else) in a living whole: just try doing without it!

Feedback Makes Things Cool

I often taught a course for physics majors that had them build—in teams of two or three—a working device whose parameters were pretty wide-open. It needed to sense/measure something in the real world, process that information in some way, then act back on the real world in response—usually in a way that altered whatever measurement was being made. This is called feedback: “Hmmm: the signal is stronger in this direction, so I’ll move toward it; even stronger now!” The explosion of creativity that emerged was a delight—and a lesson in itself. Each year, about half the projects reminded me of projects from previous years, but another half would be totally new/original. One recurrent theme was a little motorized wheeled thingy (car) that could roam around and perhaps ignore obstacles, stay within taped lines, navigate a maze, move scattered objects to a collection point, or track down a target—sometimes a combination of these elements. But we also had one-off devices that sorted marbles by color, mixed cocktails perfectly (college kids), threw a ping-pong-ball into a cup (still college kids), tip-tilted a table to navigate a camera-tracked marble through a maze, pulsed and colored a spinning “sphere” of LEDs in response to tones and volume of ambient music, maintained an inverted pendulum via camera feedback—and loads of other fun, creative ideas. [Before my time at UCSD, Mike Judge of Beavis/Butthead fame went through the same class as a physics major.]

As a warm-up exercise, I would have students build a pair of light sensors on a moving wand, the goal being to have the wand point toward light. It also employed a proximity sensor to keep the wand from running into anything. Even in this well-defined domain, I was perpetually surprised by how much behavioral variety emerged. Depending on sensor arrangement, electronic conditioning, and unconstrained choices on how they coded the decision tree, each one had its own personality. You might think I’m being glib about that word, but I swear those things would often make me laugh when I “tested” them out. Sometimes their reaction was super-skittish when I would move my hand close, and it would take a while before they would tentatively creep back toward the light and that big scary obstacle that might still be there. Others seemed aggressive. Some were jittery, while others smooth and relaxed. The odd duck was a bit loopy and hard to characterize. Relatedly, our chickens with walnut-sized-brains had tremendous and distinct personalities: the bar for personality isn’t terribly high.

The projects demonstrated that sensing and feedback is all it takes for a machine to mimic some (tiny sliver) of the behaviors of Life. Yet while important, that’s not the form of feedback of primary concern here.

Awareness and Reaction

Before I get to the feedback that really makes Life incredible, I want to discuss awareness and reaction. The student projects tended to have some form of awareness (sensing) and made decisions (reacted) accordingly—sometimes displaying baffling behaviors that neither I nor the designers/coders could explain. Occasionally unexpected bugs became valuable features that redirected the aims of the project in fun ways.

Awareness is at the core of what we call consciousness. I’m often “on about” consciousness because of our culture’s tendency to elevate it to a grand, transcendent state in classic human-supremacist (and dualist) fashion—set apart from the mundane elements of the universe. Having such sophisticated cranial hardware—a prefrontal cortex and all—gives us more of this neural connectedness and awareness (of our brian’s workings—or thoughts—for instance) than is the case for most creatures. It is, therefore, this particular quality we select as a definition of superiority: we pretend it’s a game/competition then write the rules to ensure we “win.”

I dismiss the notion of any “quantum” leap in awareness, putting humans on one side of a sharp line. The property appears to track cranial complexity, but even exists to some degree in the absence of brains or neurons. Most of the many-millions of species on Earth don’t bother with neurons, yet still require awareness and reactivity to operate, learn, and survive. Microbes sense food gradients, toxicity gradients, light gradients, etc. and move according to their changing needs. Plants sense water, nutrients, light, and configure accordingly. They also sense infestation and warn others nearby to ready defenses.

Thus, if we must use the word “consciousness,” then extending the privilege to any form of Life, however brainless, seems the least we could do. It’s a continuum of complexity, all apparently rooted in material interactions. Anyone who disagrees can try thinking their objection without complete dependence on matter and energy (arranged appropriately). No one has yet succeeded in that challenge.

Transition States

In another important waypoint en route to the main point, let’s look at seeds and spores. As discussed in a closely parallel post called Decisions, Decisions, seeds can remain dormant and viable for tens of thousands of years and spores for hundreds of millions of years! All that time, they maintain a sort of vigilant awareness of their environment. Yet, they do so without a nanojoule of metabolic expenditure, without neurons, without tiring. (I would venture that what ultimately disables them is a random high-energy particle—from cosmic rays or terrestrial radioactivity—destroying a critical atomic arrangement; more likely to occur for larger, more complex seeds than tiny-target spores.) The patient “awareness” of seeds and spores is more easily traced to a “mechanistic” origin of receptors essentially spring-loaded to effect a change when ambient conditions and resources warrant (opening channels for ion flow). Seeds and spores unable to make “good” decisions in this sense never get folded into successful lineages.

All the Way Down

As a final illustrative example, we’ll consider the electron—as a familiar example of a fundamental particle. An electron is “aware”—to varying intensities—of every other charge in the universe (in its causal “light cone“), constantly reacting. Similar to how a microbe might move in reaction to a sensed food gradient, an electron moves according to the gradient of electric potential. The fact that it obeys strict rules every single time does not in any way preclude complex behavior that is effectively unpredictable and “sensitive” (try the most difficult level of the electric field hockey game; I’ve managed legitimate navigation using 6 placed charges—or 3 in a “loophole” cheat).

So, being aware of its surroundings and reacting accordingly, would we say that electrons are conscious? I suppose I can’t stop anyone from doing so, but it seems inappropriate in the usual sense of the word. The electron is just doing as it must in reaction to its surroundings—in complete, constrained compliance with the laws of physics.

Ah: but if I yank the privileged term from electrons, then surely spores deserve the same revocation: they “just” have some physics-based receptor that will trigger when the appropriate molecules come in contact. Well, then, the microbe is decked with sensors and structured in such a way that signals on this particular channel stimulate this kind of response. It’s still using the same rules of physics (elaborated to the level of chemistry and biology), just in a far more sophisticated way that quickly/easily exceeds our limited comprehension. By the time we have the full self-replicating microbe, we are FAR beyond the level of sophistication achievable by our engineering efforts.

So it goes with plants, fungi, mollusks, worms, frogs, hawks, skunks, and humans. Increasing layers of complexity—conspicuously expressed in hardware (!!)—permit increasing levels of awareness and complex reaction. By the time we get to human-like brains, the prefrontal cortex is wired in contact with many other parts of the brain explicitly to exercise some balancing/management of potentially competing impulses. Thus part of our organism becomes “aware” of (some subset of) our internal processes…and we call this “magic” (transcendence) in the absence of complete understanding—which I’d bet we never acquire.

All this to say: if one wants apply the term “consciousness” to humans, then be prepared to extend the courtesy all the way to elementary particles—which by definition lack constituent parts such as neurons. If no sharp distinctions exist on the continuum, then either all individual particles and collection of particles have (transcendent) consciousness, or none do at all. I prefer the latter, as the original intent of the word obviously becomes stretched to the absurd at the electron level (also fruitful to muse about the free will of an electron, which is so well-behaved as to require no transcendent qualities). I don’t at all mean to imply that because no dividing line exists on the continuum from electrons to humans, both have the same level of awareness: that would be absurd and not at all consistent with material complexity. I just suggest that the spectrum is one of vast differences in complexity, lacking an ontological gap.

What is it that’s so scary about recognizing what we call consciousness as the experience facilitated by a remarkably sophisticated arrangement of matter operating by nothing other than physics? Why not marvel? I’ll tell you this right now: no one has a shred of evidence contradicting this unified description of how everything—including Life—works, while corresponding physical structures are ubiquitously found as compelling circumstantial/forensic evidence.

Back to Feedback

I previously dangled the notion that some aspect of feedback separates Life from inanimate matter. So which is it: all the same stuff, or something transcendent?

Yes to both, in a mundane sort of way. I would put forth that it’s all the same matter obeying all the same rules of interaction (in fact, no choice otherwise—raising the spectre of determinism that some constitutions cannot mentally abide). What makes Life unique is feedback on performance. It’s the painfully simple but unimaginably powerful concept behind evolution. Viable organisms propagate their genetic instructions to future organisms. Non-viable organisms don’t stick around.

What this means is that the amoeba whose reaction to a food gradient is to move in the direction of higher food concentration fares better, so whatever trial coding told it to do that is passed down. That’s the basic story, repeated and amplified and honed in billions of different ways. The fly that lifts off before the horse tail slaps down will remain a fly and make other flies with the correct decision-wiring to automatically evade a fatal slap. Life exhibits proactive, purposeful action because it could not exist any other way. The idea that it manages to do so within a material context is all the more impressive to me.

Practically speaking, Life boils down to electromagnetic interactions (gravity and nuclear forces hardly shaped the origins of Life) executing a stupendously rich dance according to molecular structures and vanilla physics. It would appear to have no other choice: no violations have ever been noted.

The “magic” happens precisely because of this selection feedback. An electron responds to a defined gradient in potential in a fully predictable manner. Life, however, can surprise us (our stripped-down mental models) purely based on the complexity of relevant interactions.

The light-seeking, collision-avoiding wands students built in my class might execute surprising behaviors, but lacked an essential ingredient: the ones I saw were not proven to be reproductively viable in a tangled ecological context. Nothing we build is. No computer, AI platform, helicopter, etc. has the staggering burden of making decisions impacting its viability to remain in the world, and thus come off as empty executors of deliberately de-complexified (debugged, “lobotomized”) code. The quirks of the wands were effectively random, based on arbitrary component properties, physical arrangements, and coding decisions made by the students. When it comes to Life, every quirk has consequences and thus a deep story: a reason it serves the being well (enough), in its context.

The post on rivulets offers a case of inanimate but adaptive, reinforcing decision-making. Rivulets are an example of success-based feedback for self-replicating structures whose initial “random” decisions are selected for fitness so that surviving rivulets appear to have the magic sauce to make “smart” decisions. Though brain-busting complexity sits between mature rivulets and penguins, the fundamentals are not wholly unbridgeable: both are selected to make the kinds of decisions that allow them to survive. That doesn’t diminish the penguin’s amazingness in any way. For me, it serves to inspire even greater awe at the outcome.

What is Life?

Our universe may be one of a multitude—as experimentally-motivated cosmologies and landscape string theories promote. Whether or not this is true, our particular universe has a particular (very small) set of fundamental particles and a rich set of interactions between them (the primary story is interactions, not the bit-player particles). Arbitrary combinations of mass ratios, relative strengths of the fundamental forces, vacuum energy, symmetries, etc. are exceedingly unlikely to produce even atoms or complex chemistry, let alone galaxies, stars, and planets. We’re in the lucky sort of universe that can make stars and truck on for billions of years. Belief in luck isn’t actually required, as our being in the “right” sort of universe represents an unavoidable and major selection effect.

So, what is Life? To me, it’s a staggeringly impressive trick that the universe can perform, playing by the normal rules utilizing the normal material. Wow. Lucky us! When something can happen, we ought not be too surprised when it does somewhere in a vast and ancient universe—especially when that surprise traces to a lack of our own capacity to pin down how it happens.

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