Part 10 (2/2)

But these intrinsic limitations of autocatalysis and self-a.s.sembly processes are also a source of potential synergy. The conditions produced by each of these processes and their limitations together comprise a complementary and reciprocally supportive effect.

Self-a.s.sembly provides the conditions that are most critical for sustaining autocatalysis: the proximity of reciprocally interdependent catalysts. The major consequence of self-a.s.sembling containment is local blockage of molecular diffusion. Spatial proximity of all const.i.tuents of an autocatalytic set is an essential necessary precondition for sustained autocatalysis, but in solution, spontaneous diffusion will undermine this requirement. Containment can, however, maintain proximity irrespective of whether catalysis is or is not taking place, and even in the absence of substrates.

And reciprocally, autocatalysis complements self-a.s.sembly. The major consequence of autocatalysis is the continual production of identical molecules in the same region, whereas self-a.s.sembly is most robust if the concentration of component molecules is maintained despite depletion due to this process. So self-a.s.sembly is most reliable in conditions where there is continual replenishment of component structural molecules up to the point of structural closure, at which point additional components are irrelevant. Thus rapid production of identical molecules at an accelerating pace by autocatalysis is specifically consistent with the conditions promoting self-a.s.sembly.

The reciprocal complementarity of these self-organizing processes means that spontaneous linkage of autocatalysis with self-a.s.sembly containment is a possibility. This would occur in the case that an autocatalytic cycle produced a byproduct molecule that itself was conducive to spontaneous self-a.s.sembly into a shape that could act as a container. In this configuration, each self-organizing process would reciprocally contribute to conditions promoting the stability, persistence, or recurrence of the other. Raw materials would be produced that are conducive to container formation. An enclosing structure would tend to form in the vicinity of the most active autocatalysis and thus would spontaneously tend to enclose autocatalytic set molecules within it. And closure of the container would prevent dissipation of the components of the autocatalytic set. Although this containment would also eventually halt autocatalysis by limiting availability of substrates, it would do so only after closure.

AUTOGENS.

This complementarity of morphodynamic processes can produce far more than merely the creation of a kind of molecular bottle. Their reciprocity produces a special kind of emergent stability, unavailable to either process in isolation. Although continuous catalysis is prevented in the enclosed state, it remains potentiated by the proximity of all the essential molecules of the autocatalytic set. In the event that such a container were to be broken up or breached by agitation or chemical disruption in the vicinity of new substrate molecules, autocatalysis would recommence and new container-forming molecules would be synthesized. This could lead to either re-formation of the original or formation of two or more new containers of catalysts in its place. In other words, the reciprocal complementarity of these two self-organizing processes creates the potential for self-repair, self-reconst.i.tution, and even self-replication in a minimal form.

FIGURE 10.2: Two forms of simple autogenic molecular processes. Left: the formation of polyhedral capsules which contain catalysts that reciprocally catalyze the synthesis of each other and also produce molecules that tend to spontaneously self-a.s.semble into these polyhedral capsules thereby likely to enclose the catalysts that generate them. Right: the formation of a tubular form of encapsulation, which although not fully closed will tend to restrict movement of contained catalysts along its length, but will tend to be increasingly susceptible to partial breakage and release of reciprocal catalysts as it grows longer. Both will tend to re-form or replicate additional copies if disrupted in the presence of appropriate catalytic substrates.

Importantly, this is not a property that is likely restricted to just a tiny set of molecular forms. It is in effect a generic cla.s.s of chemical dynamics that may be achievable in numerous quite diverse ways. In general terms, the key requirements are only a reciprocal coupling of a spontaneous component production process and a spontaneous proximity maintenance process that encompa.s.ses all essential components. Though these reciprocal relations.h.i.+ps are modestly restrictive, they are not extreme, and their spontaneous occurrence is made more probable because they are likely realizable in quite diverse chemical environments.

Candidate molecular conditions will be discussed in a later chapter, but the co-facilitation between two such morphodynamic processes could likely be realized by a wide variety of molecular substrates, and in the laboratory it could probably even be achieved using non-organic materials. Although the stereochemical and energetic requirements for such a system to form spontaneously are nevertheless quite limiting, similar limitations apply to any set of molecular interactions proposed as precursors for living processes. It is the relative simplicity of this system of dynamical relations.h.i.+ps, and the diversity of ways this co-facilitation could be achieved, that makes this type of molecular complex a far more likely candidate for a first spontaneous self-reproducing system. With respect to known processes extracted from life, protein-based autocatalytic sets enclosed by the a.n.a.logues of viral capsules could likely be synthesized in the laboratory. So this is also a realistically testable hypothesis.

Because of the familiarity of such component cla.s.ses of molecular processes, and despite the currently hypothetical nature of the process, I think it is justified to a.s.sume that the characteristics I have attributed to these simple molecular systems are realistic extrapolations, which justify considering the implications for emergent dynamic effects. Indeed, I offer this as the potentially simplest cla.s.s of teleodynamic systems. Because of its simplicity and the non-mysterious nature of the properties that such a molecular process would exhibit, if we can demonstrate that its dynamical properties have resulted in a clear, higher-order orthograde dynamic than its component processes with unambiguous ententional properties, even if these are minimal, then we have at our disposal a model system capable of fully demystifying this realm without reducing it to mere thermodynamics or sneaking homuncular properties into the account.

FIGURE 10.3: A cartoon depiction of various stages of polyhedral autogenic structures (as in Figure 10.2) self-a.s.sembling. The final image (e) shows the breakup and rea.s.sembly due to collision.

Elsewhere, I have called this sort of hypothetical molecular system an autocell.5 Unfortunately, I have found this term to be somewhat limiting and misleading, since the components described are not necessarily cellular, and the term is not mnemonically descriptive of its most distinctive properties. For the remainder of the book, I will adopt the more descriptive term autogen for the whole cla.s.s of related minimal teleodynamical systems. This term captures what is perhaps its most distinctive defining feature: being a self-generating system. In this respect, it is closely related to Maturana and Varela's autopoiesis, though referring to a distinct dynamical unit process rather than a process more generally, for which I have reserved the more general term telodynamic. The term autogen is also easily modified to apply to a broader cla.s.s of related forms by describing any form of self-encapsulating, self-repairing, self-replicating system that is const.i.tuted by reciprocal morphodynamic processes as autogenic, and describing the process, appropriately, as autogenesis.

Autogenesis is not, however, meant to be descriptive of just any process of self-generation. It is conceivable that a looser interpretation of this term could refer for example to replication of identical molecules in autocatalytic processes or to the hypothetical self-replication of RNA molecules.6 The term is reserved for simple dynamical systems that accomplish self-generation by virtue of harnessing the co-dependent reciprocity of component morphodynamic processes. Though I am here provisionally a.s.suming that this is only a property exhibited by simple molecular systems, there is no theoretical reason to a.s.sume that it is impossible in radically different forms. Experimentation with simple molecular autogenic systems will ultimately be required to determine the parameters for formation, persistence, and replication of molecular autogens, as well as to determine the supportive properties required of substrate molecules and the surrounding molecular environment. But the logical and theoretical plausibility of this form of dynamical organization provides sufficient justification to consider its implications for the emergence of ententional phenomena. So, in advance of definitive laboratory creation of autogenic molecular processes, and irrespective of whether this property can be realized in other kinds of substrates, many reliable extrapolations concerning the properties of such systems can be explored; and in particular, those that exemplify teleodynamic organization.

Autogenic theory is superficially similar to Manfred Eigen's hypercycle theory to the extent that each of these two self-promoting processes also promotes the other in some way, forming the a.n.a.logue of a causal circle of causal circles, so to speak. But the resemblance to hypercycle architecture stops there, and in other respects autogenic theory is fundamentally different. As we saw above, an autocatalytic cycle is susceptible to self-undermining and self-limiting dynamics, and a hypercycle is doubly (or multiply) susceptible to this (depending on the number of substrate-dependent subcycles that const.i.tute it). Each is a potential weak link that if broken will be catastrophic for the larger synergy. In contrast, the reciprocal linkage of the two complementary morphodynamic processes const.i.tuting an autogen has the opposite effect. Though each component process is self-undermining in isolation and co-dependent, together they are reciprocally self-limiting, so that their self-undermining features are reciprocally counteracted. Thus, whereas substrate exhaustion leads to both autocatalytic and hypercycle cessation and component dispersion, an autogenic system will establish its capacity to re-form before exhausting substrates, so long as closure is completed before this point is reached. Each process contributes essential boundary conditions for the other, providing the equivalent of a continual supportive environment for both processes. One might then describe an autogen as a hierarchic hypercyclic system, with each self-organizing component acting as supporting environment or context for the other.

To the extent that autogenesis provides the possibility for self-reconst.i.tution after partial disruption, it also provides a potential mechanism for self-reproduction. By the same process that enables an autogen to form in the first place, fractional components of a disrupted autogen-including sh.e.l.l and catalytic molecules in close proximity and new substrate molecules from the surrounding medium-will be able to reconst.i.tute a new complete whole. In other words, a disrupted autogen will be as likely to produce two identical autogens as one. So an autogen can accomplish in molecular terms-and with considerably more compactness than previously envisioned-what von Neumann demanded of self-reproduction: it can reproduce itself as well as its physical capacity to reproduce itself. Remarkably, it can accomplish this without many of the attributes normally a.s.sumed to be essential for life: for example, molecular template-based replication of components and of the template molecules, incessant far-from-equilibrium thermodynamics, semi-permeable membrane containment, and so on.

This self-reconst.i.tuting dynamics provides an active self-similarity-maintaining quality which const.i.tutes a form of individuality, or ”self,” that does not otherwise exist outside of living processes. There is both an individual autogenic ident.i.ty, as a closed, inert, but potentially self-reconst.i.tuting unit, and a self-maintaining lineage ident.i.ty, due to the transmission of relatively invariant intrinsic dynamical constraints and molecular types from generation to generation as a result of replication. Self-reconst.i.tution does not completely maintain material ident.i.ty across time because it allows for molecular replacement, and it does not maintain energetic or dynamical continuity across time either, since it may persist in a static phase for extended periods. But this self-reconst.i.tution capacity does maintain a persistent and distinctive locus of dynamical organization that maintains self-similarity across time and changing conditions. And yet ultimately there is no material continuity, as autogens are disrupted only to be reconst.i.tuted and replicated with newly synthesized components. Only the continuity of the constraints that determine the autogenic causal architecture is maintained across repeated iterations of dissolution and reconst.i.tution.

So an autogen has an ident.i.ty only with respect to this persistent general pattern of constraint maintenance and replication, and irrespective of any particular molecular const.i.tuents. Indeed, it is the continuity of the inheritance of constraints on its molecular dynamics that const.i.tutes this individuality. But ident.i.ty may vary as an autogen lineage evolves variant forms of this defining dynamics (see the section on autogenic evolution below). For all these reasons, an autogen self and autogen lineage ident.i.ty are examples of efficacious general types, in a philosophical sense (see chapter 6). To be more specific, an autogen is an empirical type determined only by the continuity of these dynamical constraints, which are themselves expressions of dynamical limitation-potential modes of change not expressed.

Autogenic organization only exists with respect to a relevant supportive environment. So autogenic individuation is also only defined with respect to a particular type of environment. Ident.i.ty and environment are thus reciprocally defined and determined with respect to each other, because the same molecular configuration in a non-supportive environment lacks any of the defining properties of autogenesis. Indeed, the very possibility for autogen existence can be described as one of the possible micro configurations of a certain cla.s.s of environments with the molecular const.i.tution conducive to autogen formation.

This is the ultimate basis for what Jacob von Uexkull called an Umwelt: the organism-relevant external world.7 This critical autogen-environment relations.h.i.+p is, however, curiously at once a sufficient but not a constant necessary condition for autogenesis to persist. The potential for autogenesis can be maintained even in non-permissive conditions. Although such a molecular configuration is only an autogen with respect to a specifically supportive environment, it can nevertheless persist structurally across diverse and unsupportive environments, to later be reproduced in a supportive one. In this way, autogenic ident.i.ty maintenance transcends any specific context dependence. In its inert closed state, an autogen can maintain this potential across vast epochs of time and through diversely non-supportive contexts. This then provides a degree of autonomy from context that is again a distinctive quality of living but not non-living dynamical systems.

An autogen's individuality is strangely diaphanous in one interesting sense. When closed and complete, an autogen is inert and yet when broken open and actively forming new const.i.tuents, it is merely a collection of molecules dispersed into a larger molecular milieu. In other words, it is a bounded individual only when inert, and actively self-generating only when it is no longer a discretely bounded material unit. This further demonstrates that what const.i.tutes an autogenic ”self” cannot then be identified with any particular substrate, bounded structure, or energetic process. Indeed, in an important sense, the self that is created by the teleodynamics of autogens is only a virtual self, and yet is at the same time the locus of real physical and chemical influences. This was also a feature recognized by Francisco Varela in his conception of an autopoietic system, even though he did not recognize how synergistic reciprocity of self-organizing processes could produce this. He describes this virtual self as follows: What is particularly important is that we can admit that (i) a system can have separate local components [for] which (ii) there is no center or localized self, and yet the whole behaves as a unit and for the observer it is as if there was a coordinating agent ”virtually” present at the center.8 The generic, autonomous, and diaphanous character of autogenic systems makes this a functional property, not a material, chemical, or energetic property. An autogen is a precisely identifiable source of causal influence because it generates and preserved dynamical constraints-the basis for thermodynamic work. But, as we've seen, constraint is the exemplification of something that does not occur. So, in this sense, an autogenic system confronts us finally with an unambiguous absential quality. This is the essence of teleodynamical causality. By examining this model system more closely, we will be able to demonstrate how ententional processes acquire this seemingly paradoxical character of efficacious absence.

AUTOGENIC EVOLUTION.

Because autogens are capable of self-replication, they are also potential progenitors of autogen lineages. An autogen lineage will increase in numbers so long as there are sufficient substrate molecules in the surrounding environment, along with sufficient molecular agitation to periodically disrupt autogen integrity, but not so much agitation as to disperse their contents more rapidly than they can rea.s.semble. This is the first condition for natural selection.

The second condition is compet.i.tion among these lineages. This will occur spontaneously as well because the multiplication of each lineage is dependent on the same (or catalytically similar) molecules in the surrounding environment. Different lineages are therefore in compet.i.tion for these substrates, as well as for persistence against the relative disruptive influences potentially present in the environment-and to an extent necessary for lineage growth.

The third condition is variation among these lineages. Let's begin with the simplest case: a single type of autogen. Although autogens tend to self-reconst.i.tute and thus reestablish the molecular structures predisposed by the catalysts and sh.e.l.l molecules that produced their progenitor, because this must occur via partial breakup and reclosure of the sh.e.l.l, it is likely that each new sh.e.l.l will additionally incorporate other molecules present in the local environment, some of which may continue to be pa.s.sed on via future divisions. For the most part, these will tend to be innocuous inclusions that might only decrease the relative concentrations of active catalysts. Higher or lower concentrations of these relatively neutral molecules will tend to produce slight differences in rates of reconst.i.tution or sensitivity to dissociation between lineages. If, however, incidentally included molecules are uncorrelated with any allosteric specificity of autogen functions, their addition to or loss from a lineage will be a matter of chance. Some fraction of incidentally incorporated molecules will have allosteric similarities with functional catalysts, their products, or their substrates. These will have a tendency to interact directly with them and will affect functional attributes of autogen chemistry. Their possible effects include directly interfering with or augmenting the rate of catalysis, affecting container formation, altering container stability, influencing molecular diffusion during disruption, providing linked parallel catalytic steps in the cycle that enables utilization of alternate or slightly variant molecular substrates, and so on.

Incorporation of functionally interactive molecules will make a given lineage relatively more or less successful in propagation. Autogen lineages containing different types of molecules that augment function in any of these ways will tend to out-reproduce others. This will only have a permanent selective effect on a lineage when another condition is met. Persistent inclusion of these divergent molecular types within a lineage will depend on being synthesized as part of an extended or parallel autocatalytic cycle. By these means, increased complexity and reliability of autocatalysis, improved containment, and utilization of special structural and energetic features of other molecular types (e.g., metals) could evolve by differential lineage propagation.

Together, these considerations show that although autogens are incredibly simple molecular systems, their self-reconst.i.tution properties in favorable environments spontaneously bring into being the systemic conditions that are sufficient to initiate a persistent, if weak, form of natural selection. So, in an environment where autogen reproduction is likely, autogen evolution is also likely. In molecularly complex environments, autogen lineage compet.i.tion for resources will tend to lead to the evolution of variant lineages differentially ”fitted” to their local environments. This satisfies all necessary and sufficient material and logical conditions for natural selection, despite occurring in a system lacking many core attributes of life, including genetic inheritance in the biological sense.

Having established the logic of autogen evolvability, we can briefly consider certain special cases and features of this process that diverge from the norm of natural selection among organisms.

One potential source of lineage difference is independent emergence. It is possible that entirely independent and distinct types of autogens could arise in slightly differing environments, each giving rise to lineages that eventually overlap in their environments. Such independently arising lineages need not have overlapping substrate needs, and so would not necessarily be in compet.i.tion. Multiple parallel threads of autogen evolution are possible, and perhaps likely, since a molecular context that is sufficiently rich to give rise to one type probably has the potential to give rise to other variants as well. This would not necessarily produce a natural selection dynamic, except to the extent that there was chance overlap of some substrate. Even so, their independent effects on other aspects of the environment might eventually lead to indirect effects that influence relative propagation rates in some more generic way (e.g., by effects on molecular diffusion).

This is crudely a.n.a.logous to the way different species in an ecosystem affect each other's evolution, even if not directly interacting. But the pa.s.sive and partially destructive nature of autogen propagation, which is quite unlike most living cellular reproduction, also introduces other potential avenues of evolutionary interaction. The most direct form of interaction could arise by mixing, as a result of inclusion of the components of one type of autogen within another. Since containment and co-localization of essential catalysts are somewhat generic features of autogen dynamics, there are many opportunities for linkages to develop between lineages with very different origins, and even for inclusion of the entire catalyst set of one autogen type within another. This is like endosymbiosis, now recognized as an important, if perhaps rare, source of novel synergistic functions in evolution, or lateral gene exchange, which is common in bacterial and viral evolution. The incorporation of complementary self-reconst.i.tuting systems within other self-reconst.i.tuting systems with somewhat different substrate requirements, catalytic dynamics, and structural self-a.s.sembly conditions could be a significant source of complexification and adaptation. The somewhat unregulated cycles of breakup and re-enclosure that autogen propagation depends on are in this way more a.n.a.logous to virus reproduction than to cellular reproduction, and so may share other characteristics with virus evolution as well.

Natural selection is the aggregate dynamic that arises out of the interactions of large numbers of unit systems with these properties. Different lineages of autogens each maintain a thread of mnemonic continuity and ident.i.ty, even when mixture occurs. Irrespective of such lineage convergence effects, when they are separated in different lineages, variant autogenic mechanisms will be in compet.i.tion with respect to resources available in surrounding conditions. This makes each individual autogenic mechanism also a representative of a specific correlation between its intrinsic dynamic topology and features of the larger environment.

So, with autogens, there are multiple interlocking units of evolutionary individuation: the lineage, the autogen as autonomous system, and the reciprocally self-maintaining dynamical synergy, though the latter will likely grade into an autogenic unity once independent reciprocal dynamics intertwine into a single integrated system. Living organisms derive their peculiar causal dynamics-their seeming end-directedness, functional logic, superficial reversal of the second law of thermodynamics, and adaptability-from this upward s.h.i.+ft in what const.i.tutes a unit of reproductive and evolutionary individuation.

The foregoing a.n.a.lysis has shown that natural selection emerges from the dynamics of reciprocally reinforcing self-organizing processes. This self-reconst.i.tutive dynamical synergy is the essential ingredient that precedes and underlies life. This in turn suggests that natural selection is ultimately an operation that differentially preserves certain alternative forms of morphodynamic processes compared to others, with respect to their synergy with one another, and with respect to the boundary conditions that enable them. Selection is not then fully defined only with respect to replication of genetic information. As Kant recognized, a self-maintaining ”formative power” is critical. And this requires processes that generate, preserve, and propagate constraints. Morphodynamic processes are the only spontaneous processes that generate and propagate constraints, and autogens demonstrate that reciprocity between morphodynamic processes can preserve and replicate constraints.

THE RATCHET OF LIFE.

Autogens may be subject to natural selection and evolution but they are not alive in most senses. They lack the majority of attributes a.s.sociated with living organisms today. Most significantly, they are effectively pa.s.sive-though not inert-structures, because they do not actively acc.u.mulate and mobilize energy within themselves that can be used for self-repair and reproduction. The energy driving their self-perpetuating dynamics may derive from an environmental source (such as the heat of volcanic vents), or it may be obtained by breaking the molecular bonds of large substrate molecules. In any case, autogens are parasitic on their environment, even for the initiation of replication, in much the same ways that viruses are. Unlike viruses, however, autogens reproduce without the help of other organisms.

In this respect, autogens are not quite ”autonomous agents,” in Stuart Kauffman's sense. For Kauffman, the most basic characteristic of living systems is their ability to ”act on their own behalf.” Although an autogen does not ”act” in a self-animated sense, it nevertheless fulfills the two criteria that Kauffman uses to define what he means by autonomous agency-criteria that he argues are the basis for this self-directed activity. It ha

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