Evolution of the Organism

Part of a series that started with my evolution of the cell post. However, this one is likely easier to grok.

Before there were multicellular organisms, there were single cells. As the name implies, the multicellular organism can be best understood as a collection of single-celled organisms. How did we get here?

Communities and Films

In the evolution of the cell essay, I talk about the origin of the cell wall, and how it both improved catalytic efficiency and changed the evolutionary dynamics by creating separate heritable parcels. Essentially separating self from other. The key to moving on to larger organisms is here– this self other distinction is fundamentally illusory, there are still autopoietic traces leaking between the cell and its environment. Communities are a way to improve efficiency again as a way for autopoietic structures to emerge and eventually become codified at the next scale.

Imagine a collection of cells. This collection has no metastructure, but there are various chemical pathways that run through the community. The community is stable, but not reproducible. Now imagine the same community, but over time the genetic code of all the cells that leak chemical traces that run through the community start to encode those traces The genetic code starts to encode the community, and the community starts to encode the genetic code.

These traces are often referred to as ‘cell signaling pathways’. Once the cellular information starts to encode the community, the community can start to co-evolve. Soon, faster and more efficient pathways start to emerge, such as gap junctions. Gap junctions allow for two cells to become electrically coupled and to communicate by electrical impulses, which increases their communication time by orders of magnitude. Cellular collectives start to form. The gap junction also serves to mechanically couple cells to one another. This increases the co-evolutionary pressure, and acts as another mode of communication.

At this point we have mechanically, electrically and chemically coupled cells. These form biofilms and the first microbial mats.

Tissues, Blood and Nerves

Once the genome of a community is co-evolving, the community can start to specialize. The community starts to form into specialized regions with different autopoietic traces and functions. These are the first tissues. Tissues can take advantage of a high degree of local homeostasis, as their local environment is maintained at equilibrium by other tissues (eventually the cell wall and the blood system). This means they can optimize ruthlessly for a single task. This optimization brings significant constraints and opportunities. For example, nerve cells evolve to communicate messages over long distances very quickly, but lose the ability to differentiate, reproduce or divide. The muscles in the heart have, individually, incredibly motility– but this motility is driven constantly by the demands of the heart.

At the point where a significant number of different tissues have evolved, there is an opportunity to illustrate what we were referring to earlier by autopoietic traces leaking between the cell and its environment. At some point, the tissues of the organism start to organize fluid flows through its structure, both to bring in material from the environment and to pass matter more quickly between its parts. These fluid flows act as rapid chemical signalling pathways between regions. This is the prototype for the blood system– the blood system illustrates clearly the autopoietic traces that remain between cells in the community. It is the physical instantiation of the autopoietic traces between tissues.

The cells locally maintain rapid communication of material and information by means of strong coupling via gap junctions. Longer distance communication of material happens via the blood and other fluid networks, and long distance communication of information happens via the evolving nervous tissues.

Gross Morphology

With the blood and nervous systems affording long distance communication of large amounts of material and information, the scale of the organism can increase further, the scale of the tissues can increase, and the degree of specialization can intensify. The nervous system can now rapidly respond to sensory information by choosing between different morphologies. This implies a stored repertoire of morphologies that the nervous system selects from. Here we have the origins of memory.

It is worth pointing out at this point that the terminology is loaded. Perhaps a better way to describe the relationship between the body and the nervous system is to say that the nervous system is where the body stores its own morphologies, in the same way as the cell stores its patterns of activity in the nucleus. We can then use the terms ‘morpho-instant’ to refer to a pattern of morphology stored in the nervous system, and ‘morpho-instance’ as that same pattern instantiated in the structure of the organism. In organisms such as ourselves, it is clear that there is a two-way relationship between morpho-instances and morpho-instants– we learn a new skill by putting our body into a particular morphology ‘manually’, and then recording that morphology with the nervous system.

Again, the orders grow. The nervous system can now store and recall morphologies. The nervous system becomes more and more specialized in compressing and decompressing morphologies. Sensory modalities multiply and draw more and more information from a larger space in the environment. The range of the environment that the organism can sense determines the range that it can influence, they are coupled. And as the distances that it enfolds grow, the morphologies that it contains become more dense and coupled into higher and higher order algorithms. The organism starts to enfold large parts of its environment into itself, make them part of its morphology– ideas that will eventually become ‘home’ or specific destinations for foraging or mating are enfolded into its nervous system.

Self and Other

At some point, the organism can move so far and so effectively that its environment is many times larger than itself. It grows to contain other organisms completely, and whole ecosystems and groups of organisms. It has created a repertoire of forms that it can choose from so large and dense that it starts to model its entire body and the bodies of those around it. It learns to predict and control its own behaviour and the behaviour of others. It develops new means of communication– via light it communicates its identity with patterns and shapes. By using mechanical coupling via air molecules it communicates complex rapidly changing messages over time. Its time-horizon grows, and its mind starts to maintain a continuous present alongside its asynchronous knowledge of the world and the ways it can move through it.

It is worth noting at this point how the genome has experienced all this. When communities started co-evolving, some part of their collective dynamics were encoded in the genome of each individual. When tissues started specializing, this specialization was encoded in particular subsets of the cellular morphologies that the genome encodes. And as the nervous system started to store large repertoire of morphologies, abstract commonalities between them started to be encoded in the genome. The genome evolves much more slowly than the nervous system, which can learn new patterns and morphologies and deploy them almost instantly. But inasmuch as there are deep structures underlying the highest levels of behaviour, we must expect them to be encoded in the genome over evolutionary time. Exactly how much neural architecture and behavioural architecture the genome can encode is an open question.

We have arrived at the complete multicellular organism with a complex relationship with itself and its environment. Ecosystems are coupled and co-evolving across and between species1. The organism perceives, enfolds, manipulates and understands its environment and has a nervous system complex enough to maintain a present moment and the beginnings of a past and a future.


  1. For a beautiful illustration of this, read about the co-evolution of warm-blooded creatures and flowering angiosperms, here is an excerpt from The Immense Journey by Loren Eisely: “Somewhere, just a short time before the close of the Age of Reptiles, there occurred a soundless, violent explosion. It lasted millions of years, but it was an explosion, nevertheless. It marked the emergence of the angiosperms—the flowering plants. Even the great evolutionist, Charles Darwin, called them “an abominable mystery,” because they appeared so suddenly and spread so fast.Flowers changed the face of the planet. Without them, the world we know—even man himself—would never have existed. Francis Thompson, the English poet, once wrote that one could not pluck a flower without troubling a star. Intuitively he had sensed like a naturalist the enormous interlinked complexity of life. Today we know that the appearance of the flowers contained also the equally mystifying emergence of man.If we were to go back into the Age of Reptiles, its drowned swamps and birdless forests would reveal to us a warmer but, on the whole, a sleepier world than that of today. Here and there, it is true, the serpent heads of bottom-feeding dinosaurs might be upreared in suspicion of their huge flesh-eating compatriots. Tyrannosaurs, enormous bipedal caricatures of men, would stalk mindlessly across the sites of future cities and go their slow way down into the dark of geologic time.In all that world of living things nothing saw save with the intense concentration of the hunt, nothing moved except with the grave sleepwalking intentness of the instinct-driven brain. Judged by modern standards, it was a world in slow motion, a cold-blooded world whose occupants were most active at noonday but torpid on chill nights, their brains damped by a slower metabolism than any known to even the most primitive of warm-blooded animals today.A high metabolic rate and the maintenance of a constant body temperature are supreme achievements in the evolution of life. They enable an animal to escape, within broad limits, from the overheating or the chilling of its immediate surroundings, and at the same time to maintain a peak mental efficiency. Creatures without a high metabolic rate are slaves to weather. Insects in the first frosts of autumn all run down like little clocks. Yet if you pick one up and breathe warmly upon it, it will begin to move about once more.In a sheltered spot such creatures may sleep away the winter, but they are hopelessly immobilized. Though a few warm-blooded mammals, such as the woodchuck of our day, have evolved a way of reducing their metabolic rate in order to undergo winter hibernation, it is a survival mechanism with drawbacks, for it leaves the animal helplessly exposed if enemies discover him during his period of suspended animation. Thus bear or woodchuck, big animal or small, must seek, in this time of descending sleep, a safe refuge in some hidden den or burrow. Hibernation is, therefore, primarily a winter refuge of small, easily concealed animals rather than of large ones.A high metabolic rate, however, means a heavy intake of energy in order to sustain body warmth and efficiency. It is for this reason that even some of these later warm-blooded mammals existing in our day have learned to descend into a slower, unconscious rate of living during the winter months when food may be difficult to obtain. On a slightly higher plane they are following the procedure of the cold-blooded frog sleeping in the mud at the bottom of a frozen pond.The agile brain of the warm-blooded birds and mammals demands a high oxygen consumption and food in concentrated forms, or the creatures cannot long sustain themselves. It was the rise of the flowering plants that provided that energy and changed the nature of the living world. Their appearance parallels in a quite surprising manner the rise of the birds and mammals.”↩︎