I spend probably too much of my time (and now yours) trying to work out the apparent differences between animate and inanimate arrangements of atoms. In practice it’s not at all hard to tell one from the other, even if a mass spectrometer would confirm that all the same atoms comprise the collections. Children easily differentiate one from the other. Isn’t that definitive?

In a similar vein, it’s not hard to tell a star from a brown dwarf, even though they have essentially identical compositions. The one having more than 8% the mass of our sun will ignite fusion and light up, while the one not “tall enough to go on the ride” will continue sulking as a dim, warm lump.

It’s not hard to tell the difference in behavior between a piece of paper fluttering to the floor and the exact same piece wadded tightly and dropping straight down. A clear sheet of glass or ice becomes an opaque white powder simply by crushing it thoroughly. A log looks and acts much differently before and after burning, even though no atoms were created or destroyed—most are dispersed as invisible gas. Arrangement matters.

But I want to poke a little deeper and identify an arrangement that we would never call animate, yet displays many of the hallmarks of Life. This is my clumsy attempt at doing so. The purpose is not to find an exact match in this example, because that’s impossible: identifying flaws is easy sport. Rather, this exercise provides a window that might allow our crippled imaginations to dimly grasp how Life might develop behaviors that appear purposeful in the context of evolutionary feedback. So, instead of focusing on imperfections, the challenge is: are you able to make out the shape beyond the distracting foreground fog? What new insights does this perspective offer? How might you build upon it and make it even better?

This is the first in a two-part series on what constitutes Life, as far as I can gather.

Traits of Life

Every living being comes from beings able to reproduce/replicate. Not all life can itself reproduce (ask a mule), but most can. Life adapts by genetic mixing and random mutation in feedback relation to demonstrated success (i.e., life evolves under selective influences). Life enacts proactive decisions that impact how it fares in the world. These decisions, too, are part of the great feedback mechanism called evolution that shapes not only morphologies, metabolism, mobility, dexterity, etc. but also decisions to be successful in an adaptive sense. Life collects resources from its environment in order to secure the atoms it needs to live and pass along its pattern. Life tends to be robust enough to mitigate a number of adverse circumstances: tolerating extremes in temperature, moisture, food availability, dangers, and damages.

The paragraph above lists an impressive set of capabilities, right? Clearly we won’t find rocks engaged in any of these activities. By no coincidence, internal structures of a rock are not even remotely as complex as those in living tissue. As I said, arrangement matters!

Land of Eternal Rain

I remember as a kid growing up in the 70s spending seemingly-interminable periods in the car while it rained and my mom did important things like shopping and putting items in lay-away. I would watch rivulets on the window, mesmerized by their antics: watching patterns emerge out of the pitter-patter. It’s a lot like being entranced by fire, which also seems to have a life of its own.

Earth is a land of eternal sunshine. By that, I do not mean that it is sunny at every moment in every location. But the sun has steadily shone on Earth for billions of years without even a single nanosecond of vacation. It’s a dependable, essentially eternal source of energy that powers Life.

For our thought experiment, we’ll imagine a land of eternal, steady rain. This rain will fall on a sloped piece of glass like a windshield. Rain is the resource, which accumulates. Beyond a threshold, globs migrate down the surface, snow-balling as they gather more “resource” in a sort of avalanche process. By having established a route, the next gathering is likely to execute the same path, or at least much of it. Depending on surface properties, slope, and rate of rainfall, rivulets may become essentially permanent, like little river-lets (ohhh…) sweeping water off the glass.

Self-Replication

I already hinted at one critical piece. Once a path has been forged through the randomness, that path is likely to be followed again. It may even become a semi-permanent structure. Think of the path as a blueprint, and the drops that race along as individual lives (moving from birth to death). The pattern is a standing pattern like a particular species—following a DNA blueprint—while individuals are expressed in that mold, flowing through the pattern.

Anyway, the essential feature is that a rivulet establishes conditions that make repetition of that particular pattern far more likely than a fresh start from scratch.

Measure of Success

If a rivulet (or more realistically, a set or network of rivulets) is not clearing the entire windshield, water will accumulate in neglected areas and something else will spring up to fill that niche. It will have to navigate the existing space, either replacing/disrupting other rivulets, merging with them, or failing to establish as a repeating phenomenon: a one-off trial.

Success is assessed by how effectively the windshield is cleared by the set of rivulets. The patterns will keep changing until well-matched to the steady input. A successful rivulet—or ecology of rivulets—will have established an efficient and essentially complete assimilation of the resource flow.

Decisions

As we watch a fresh start on a blank slate (with tiny beads of water beginning to accumulate), the path of the upstart is only predictable in the widest sense: it will flow sort-of downhill. Life is similarly predictable in broad-brush: flowing from birth to death, accumulating resources, reproducing: all the things it must do to remain a part of Life. But rivulets on windshields express jigs and jags; pauses and sprints. Likewise, (most forms of) lightning will predictably reach from cloud to ground, but by creative, jagged paths—consisting of many branch points (decisions).

As the rivulet forms, it sometimes takes unexpected turns by happening to glance a droplet, encounter a defect on the substrate, or perhaps get nudged by an incoming rain drop or gust of wind. It’s got some randomness to it: not strictly predictable. What makes it decide to go left or right—or to pause or race—can’t be foreseen by us, even if we can work backwards and make sense of the influences that played a role in shaping its particular behavior.

Like fire, lightning, or a leaf in the wind, the rivulet can appear to have a mind of its own, executing “interesting” behaviors.

Feedback

Here’s where the rubber meets the road. A rivulet that has made “good” decisions…so that it:

1. is effective at clearing a region of the windshield;
2. “plays well” with the other rivulets in place;
3. and leaves a path that encourages future generations to follow…

will be the rivulet that persists. Rivulets that make “poor” decisions will fail to establish any sort of permanence, for any number of retrospectively-obvious reasons. Evolutionary feedback operates on what initially might be random decisions, but patterns of decisions become selected based on their demonstrated ability to contribute to success.

That an amoeba appears to execute sensible reactions to a food gradient—navigating itself to a meal—is a similar selection effect. The degree of complexity compared to a rivulet is already stupendous in this case, but not obviously operating on an entirely different plane. What would be truly remarkable is an amoeba that systematically fled food, ran toward danger, and refused to reproduce. Such decision patterns obviously perish from Earth. One may imagine (even if actually cognitively incapable of the feat) elaborating from the rivulet to the amoeba and then toward more complex organisms, following the same principles. That the squirrel dithers in the road in reaction to an oncoming car points to competing processes in an exceedingly complex decision-tree juggling a swarm of stimuli all at once.

An Ecology

One rivulet does not clear the entire windshield efficiently. There’s only so much it can do. Others necessarily crop up and interact. Some interfere, and others reinforce. One can imagine a late-stage equilibrium of sorts where the self-preserving (replicating) rivulets are as a whole clearing the rainfall in a mature, stable pattern. These are the results of an evolutionary process, sensitive to the many random-but-effective—and interacting—decisions that contributed to each rivulet’s path. In hindsight, they look like genius decisions—simultaneously weighing many factors and relationships. But, that’s just what worked, in the full context. Surviving decisions have to be good ones by this measure.

Evolution

Real ecologies are always on the move as continents shift, climate changes, volcanoes erupt, Life evolves/migrates, and any number of other disturbances manifest. To better approximate the real deal, we’re going to need a bigger windshield! The rain rate won’t be the same everywhere, and can also slowly vary.

Rivulets well-adapted to a particular static condition will begin to fail in the same configuration under changed conditions. But if the changes are slow enough, some rivulets will be able to adapt by their own random set of “good” decisions (mutations), while others will perish and be replaced by new structures that may compete for a while before establishing something new that works in relation to the rest.

And, of course, our windshield is a much simpler “parameter space” than a real, complex ecosystem. Instead of rainfall rate, slope, and surface properties, we have a rich set of interacting ingredients relevant to how Life forms and maintains itself.

Also important is timescale. Life had billions of years to establish. Even though waiting in the car for my mom might have seemed like a billion years, my attention span was likely insufficient to witness the establishment of a mature state (and variable rainfall conditions probably precluded such an emergence anyway).

Taking Stock

The rivulet analogy, like any, will be imperfect. But it does illustrate the principle of how inanimate systems possessing some self-replication capability under a metric of success in feedback can utilize standard physics and randomness to try configurations and persist when hitting on the right, lucky mix of decisions. Just give it time.

Few upstarts will have what it takes to satisfactorily match the resource provision and work in concert with the others, thus will be forgotten. Likewise, any lifeform that can’t incorporate the physics at hand to achieve a “golden” state simply won’t hang around to be admired.

We have in the rivulets, then, self-replicating structures that appear to make decisions, operating under an evolutionary pressure so that survivors are the ones who made “correct” decisions in relation to the other happenings around it—and continue to execute those genius decisions by dint of the blueprints in place. The entire windshield shapes each mature rivulet via many interdependencies and resource-matching conditions in a pass/fail feedback arrangement. Evolution is also possible, as the ecology of rivulets adjusts to slow changes.

The Hard Part

Even a meat-brain like mine can guide the assembly of atoms (designing and building technological devices) in ways that perform sensing and decision-making. But nothing I ever built came anywhere close to being able to self-replicate, secure necessary resources and fashion them into the desired configurations, operating within an interactive ecology of similar creations. Sensing and deciding are actually the easy parts, and are quickly shaped by selective criteria once the barrier of a self-replicating capability is achieved. Having secured this feat, natural variations and selective pressure can generate all manner of impressive (progressively more elaborate) decision-making processes that bear on survival. Feedback makes it look magical.

Note also that unlike real Life, rivulets starting from scratch are far more likely to fail in establishing permanence, having no benefit of evolutionary heritage in having an instinct for the right decisions. Conversely, each species in the Community of Life inherited a successful set of vetted decisions, and thus starts from a position of (proven) success, not (presumed) failure.

The Vast Gulf

I am not claiming that we need to consider rivulets or fire or lightning as animate forms of Life. The difference in complexity is truly staggering. Yet, the comparison offers a mottled window—especially into decision-making processes that appear (via feedback/success) to be directed, or purposeful. Their self-defining or reinforcing purpose is to promote continuation, in aggregate.

When we witness a family of adult quail with lots of babies (fuzzy walnuts) zipping into the bushes in reaction to an overhead hawk, we call that a good decision. So does evolution. If the quail’s “internal rivulets” were not formed in such a way as to produce suitable reactions, then we would not enjoy their company today. What looks like magic in the form of a proactive decision is in some sense the only way things can go. Or, at least, it’s a way that has been proven to work well enough in a complex and variable context, and that’s all it takes.

Does this perspective make Life any less amazing, magnificent, splendid, extraordinary? It needn’t. One might even say that this viewpoint makes Life all the more remarkable—for being able to craft a viable living out of the basic physics at hand. Human brains are woefully incapable of conjuring—or even fully grasping—any such amazingness.

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