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Just when I thought I had my subject figured out, I came across another researcher whose work has shaken my perspective on several points I thought were settled. Shaken, but not destroyed; rather, Michael Levin’s insights cast light into some of the murkier corners, and offer support where support was needed. Since I am presently twelve chapters in to a book on personal identity and the human experience of self, it is unsettling to realize that I will need to go back and revise biggish parts of it—but it is reassuring that these changes point in the direction of a stronger theoretical foundation for conclusions I had already reached.
Levin is a thinker who makes my head explode. He offers a fundamental paradigm shift in thinking about the units of life. The defining principle of a living entity is its orientation to the homeostatic goal of maintaining its own living conditions: self-regulating its temperature, its oxygenation, its nutrition, its safety, etc., within the range optimal for growth and reproduction. Significant deviations from these homeostatic norms are stressors; the entity seeks to reduce stress.
The Russian Dolls of Life
When we define living individuals that way, we find them at several levels of organization. A cell is such an individual; but Levin says that “biochemical networks” at the sub-cellular level also exhibit self-regulatory characteristics. As do the tissues to which the cells of multi-celled organisms belong; the organs composed of those tissues; and the whole organisms (plant, animal, or fungus) which we are accustomed to thinking of as the units of biological life. But Levin does not stop at the organism. Groups of organisms—colonies of social insects, for example—also have self-regulating, homeostasis-seeking systems. As do wolf packs and flocks of birds. And human groups: families, bands of hunter-gatherers, communities, corporations, nation-states. The biosphere, says Russia-born Levin, is “a set of nesting dolls.”
Levin’s theoretical framework changes our understanding of cognition, consciousness, embryonic development, what it is to be an individual, what it is to be a group. One of his starting points is “a commitment to evolution: every capacity has a natural history and emerged from simpler variants.” [Levin, 2019]This led him to identify functional aspects of cognition in non-neural tissue, and to the hypothesis of “Scale-Free Cognition.” This includes the idea that cognition is manifested not only in the brain, but in other organs and tissues. More broadly, it is the view “that most biological systems consist of multiple, nested selves.” (Levin uses the terms ‘self’ and ‘individual’ nearly interchangeably.)
Levin describes the goal of his research program as showing:
…how complex agency and goal-directedness evolves naturally from ancient mechanisms. The evolutionary pressure to survive in a challenging world leads (in order) from simple homeostasis to infotaxis, memory, anticipation, spatio-temporal scale-up of measurement and prediction, and large-scale global goals (system-level agency). [Levin, 2019]
Bioelectricity and the Goals of Cells
A fertilized egg divides and becomes a blastocyst. As cells continue to divide, they differentiate, forming precursors of arms, legs, stomach, head, brain. When a developing arm is long enough, the cells at its extremity shape themselves into fingers. As the fingers form, fingernails appear. Hair follicles appear on the scalp—not on the tongue. Teeth grow from the jawbone, not from the pelvis. How does this happen? All somatic cells contain the same DNA information, which somehow works as a blueprint for the entire body. But what mechanism guides a cell in one part of the body to become a neuron, and a cell somewhere else to form lung tissue?
Levin’s work points to bioelectricity as an important factor in making this self-assembly happen. Somatic cells are not isolated; they communicate with neighboring cells through “intracellular electrical synapses known as gap junctions.”
Individual cells will all measure local conditions at their cell surface. When coupled into networks via gap junctions however, the whole collective can measure and act upon the same sensory data – the Umwelt expands to create a larger individual in which the comprising cells share a unifying picture of the world. [Levin, 2019]
Levin emphasizes that this intracellular communication through synapses is not an exclusive talent of neurons; all somatic cells do it. Neurons, with their long wire-like axons and intricately branching dendrites, are adapted to forming much more sophisticated communication networks than are liver cells or skin cells. But the liver and skin cells exchange information too, communication that is needed for them to form healthy, well-behaved tissues.
Bioelectrical communication keeps our cells in line. When it is interrupted chaos ensues, in interesting ways. The goal-directed, homeostasis-seeking activity of a muscle cell supports the health and normal function of the muscle tissue it belongs to. But if a physical barrier of inert plastic isolates the cell from its neighbours, its goals change. Instead of aligning its activities with the rest of the muscle, it starts to behave like a one-celled organism, avidly absorbing all the nutrients it can to maximize its growth and reproduction. When it divides, it no longer does so following the pattern of the tissue it was part of; it forms a tumor instead. Pursuing its “cell-level goals of individual survival,” the cell becomes cancerous.
When a cell goes rogue in this way, its goal-seeking patterns change; they become oriented to the individual cell rather than the tissue it was part of, or the animal the tissue is part of. Such ‘self-serving’ behaviour is not, ultimately, in the ‘interests’ of the cell. Cancer is not usually infectious; if it kills its host, it creates a dead end for itself. When the cell was in communication with other cells, it shared their goals, which promoted healthy tissue and, ultimately, a healthy organism. The homeostatic goals of the individual cell were aligned with those of the animal. Narrowing the focus of its goals to the cell itself is bad for the animal and bad for the cell.
Levin discovered experimentally that it is possible to interfere with bioelectrical communication, re-shaping the goals of growth and development. The patterns of embryogenesis resemble the patterns of regeneration evident in healing. A cut finger will grow new skin, often without leaving a blemish. A scab forms, protecting the site as the three layers of epidermis build up. When the scab comes off, the young, tender skin continues the fingerprint of the skin around it without a break. The orderly process of regeneration is governed by bioelectrical communication. Human beings do not regrow amputated limbs, but some amphibians do. Flatworms are consummate regenerators. Cut up, each piece of a flatworm will regrow into a whole worm, complete with head, tail, and a flatworm’s distinctive, cartoonish eyes.
Levin has found that if he temporarily disrupts the electrical patterns of flatworms before cutting them, their patterns of regeneration change in predictable ways. [Levin et al, 2018] If a population of flatworms are briefly exposed to a gap-junction blocking reagent—a chemical which clears from the body within a few days—they lose the ‘pattern memory’ responsible for their ability to reliably regenerate in the form of a normal flatworm. When these flatworms are divided, 25% of the ‘head ends’ grow another head at the cut end, becoming two-headed.
The genomes of these worms are unaffected by the process, and the chemical exposure is not repeated. When the two-headed worms are divided again, each piece is genetically and morphologically just like the head end of a normal flatworm, and therefore might be expected to grow another tail, as a normal specimen would. But it does not; each ‘head end’ regenerates as a two-headed flatworm! A memory state in the worm’s tissues has been permanently altered so that each piece grows into a two-headed worm.
The 75% of the head ends from the original population that was exposed to the reagent grow tails, and look like normal worms. But they are not normal either; if they are subsequently divided, the head ends continue to produce two-headed regenerants in the same 25% ratio. The 75% are morphologically and genetically normal, but their tissues have been depolarized, altering their ‘pattern memory.’ Levin calls these worms “cryptic.”
Encoded in the tissues of the flatworm, as in the tissues of a human embryo, is a target shape, to which the growing and dividing cells tend to conform. If normal development is disturbed by local damage, the remaining undamaged tissues will correct the process, tending always towards the normal form. This activity is goal-directed, fundamentally teleological, but mindless, independent of intention. It is also fundamentally cooperative.
Boundaries of ‘Selves,’ Cones of Concern
Self-regulating systems are what preserves the order inherent in living things within the order-inimical milieu of the Second Law of Thermodynamics. In Levin’s system, goal orientation is fundamental to the individuation of living things; the units of life are defined by their goals. I am a unit defined by goals; so is my pancreas; so is a single pancreatic cell; but half a cell is not, nor are arbitrary cuts of my body.
Bioelectrical communication, of which neuronal communication is just one, albeit most impressive, example, enables this Matryoshka of nested living entities to work in harmony, aligning the goals of the smallest ‘individual’ (in Levin’s special sense, referring to any living entity organized around homeostatic goals) with those of the whole animal.
An individual, says Levin, is ‘demarcated’ by
…a computational surface – the spatio-temporal boundary of events that it can measure, model, and try to affect. This surface sets a functional boundary – a cognitive “light cone” which defines the scale and limits of its cognition.
[Levin, 2019]
This boundary is extended in time as well as space; Levin represents it as a pair of cones with their bases joined at the present time, one cone tapering into the future and the other into the past.
This boundary of events that an individual can “measure…and try to affect” is not what we would ordinarily understand as the boundary of its body; it is wider than that—more like the extent of its engagement, the arena of its concern. In saying the individual is demarcated by this boundary, Levin seems to downplay the importance of the boundary of the actual body. I am not sure whether he downplays it intentionally. An organism’s interest in its environment may extend far beyond its body. Moreover, its goals, expressed in behaviour, towards its own body often differ pointedly from its goals with respect to what lies outside the boundary of its skin. Organisms almost always strive to nourish and protect their bodies, but often deplenish their environments, displaying attitudes more exploitative than nourishing and protective, even if such exploitation threatens their own future welfare.
I believe the distinction between body and environment remains important. I have no reason to think that Levin would deny its importance; but his emphasis, here, is on the broader boundary defined by all of an individual’s goals, rather than on the narrower, but keen, interest it displays in the body it nourishes, grooms and defends. This de-emphasis of the body fits with Levin’s broad thesis, which regards the organism as just one member of the hierarchy of living entities that includes subcellular structures, single cells, tissues, organs, organisms, colonies, and other organizations, all of them shaped by their goals.
Cooperation is Baked In
The environment of a cell is the tissue it belongs to. The environment of a tissue is the organ it is part of, and the rest of the organism. The environment of the organism often includes a social milieu of conspecifics, as well as exploitable resources and dangers to be dealt with. If the organism is plant-like, rooted to one spot, its environment includes, usually, a semi-permanent population of neighbours—other immobile organisms with which it coexists. Rooted organisms have a greater stake in sustaining the livability of their environments than do animals that can move on to greener pastures. The evidence of communication and cooperation between neighboring forest trees, documented by Peter Wohlleben [Wollheben, 2015], would fit well into Levin’s framework.
The lives of ‘individuals’ within the confines of an organism’s body—its cells, tissues and organs—typically depend on the continued life of the organism. There are exceptions: infectious bacteria and viruses, parasites within the body that can escape it and move to another host. The health of most ordinary somatic cells depends on the health of the tissues they are part of; the health of the tissue depends on the health of the organism. If the organism is a social animal, its ability to thrive depends on whether groups to which it belongs are thriving. Building this hierarchy of nested life forms of increasing complexity required the evolution of cooperative mechanisms that are not, or not obviously, expressions of the principle of “Survival of the fittest.”
Bioelectrical communication is one such mechanism. Under its influence, the homeostatic drives of a muscle cell are aligned with those of its neighbouring cells, and with those of the encompassing organism. The organism as a whole has its own homeostatic goals, which extend far beyond the goals of any of its cells or organs; its drives are mediated by its nervous system, if it has one; but the principles at work in the nervous system are essentially the same as those at work in the cells of its muscles, skin, and liver. The nervous system is a mechanism enabling the distributed, diverse organs of the body to cooperate, to act as one agent with its own goals. A wolf pack is a larger unit of cooperators, using its own channels of communication—yips, howls, and growls, display behaviour, grooming, fawning, olfactory signals—to establish a safe and productive territory, intimidate competing packs, bring down large prey to feed its members. A human technology company operates in much the same way.
We have long been familiar with the idea that competition drives evolutionary progress through natural selection. Levin’s theory provides balance to that idea. Principles of cooperation are as fundamental to survival as are principles of competition, and affect natural selection in the same way.
Cancerous Selves
A cell’s communications with other cells in the surrounding tissue harmonize its homeostatic goals with those of the entire organism. When the lines of communication are cut, the cell becomes cancerous, an outcome detrimental to the health of its host and, ultimately, itself. Something very similar happens at the top of the hierarchy of living things, when there is interference with the lines of communication that harmonize the goals of a social animal with those of the society it belongs to. The individual can ‘go rogue,’ reverting to a motivational pattern typical of a solitary animal, adopting goals at odds with the goals of the group, to the detriment of the group and, often, itself. Being a ‘lone wolf’ is unhealthy, even for wolves.
Many things can put stress on the social bonds that align an individual with its groups. Physical isolation is one; besides being cruel punishment for human beings, solitary confinement fosters feelings of being ‘one against all.’ As does economic inequality, and the social stratification it engenders. Drug addiction can also shrink the boundaries of an individual’s concern, with results devastating to family life and other cooperations.
Ideas, too, can weaken a person’s social ties. The belief that one always has a reason to favour one’s self-interest, but that helping others is rationally optional, is one such idea. It fosters a sense of isolation from other people, and encourages selfish choices. I have tried to show that there is no scientific basis for that idea. Levin’s work fleshes out a scientific understanding of life and evolution in the context of which such ideas seem less plausible.
And less attractive. ‘Being a cancer’ is not a self-image many people would want to adopt.
References
Levin, Michael (2019), “The Computational Boundary of a ‘Self’: Developmental Bioelectricity Drives Multicellularity and Scale-Free Cognition”, Frontiers in Psychology, 13, December 2019
Levin, Michael, et al. (2018), “Planarian regeneration as a model of anatomical homeostasis: Recent progress in biophysical and computational approaches”, Semin Cell Dev Biol (2018), https://doi.org/10.1016/j.semcdb.2018.04.003
Wohlleben, Peter (2015), The Hidden Life of Trees: What They Feel, How They Communicate – Discoveries from a Secret World, Greystone Books, 2015.
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