Evolution of Evolution: From Genetic Inheritance to Intratechnical Replication of T-Memes. Column for Computerra #102
An attempt to classify the stages of the evolution of evolution and the inheritance mechanisms underlying them: – biological inheritance (based on genetic, epigenetic, and possibly other mechanisms); – cultural inheritance (inheritance through learning); – extrasomatc...
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Dmytro Shabanov
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← Dmytro Shabanov → Toad venom, an unsuccessful venture into business, and doubts about the innovative prospects of university science Evolution of Evolution: From Genetic Inheritance to Intratechnical Replication of T-Memes A multilateral conflict: individuals, genes, and memes; individuals and groups; proximate goals and distant prospects...
Column for Computerra #101 Column for Computerra #102 Column for Computerra #103 Man is not the static center of the world, as he has long believed, but rather the axis and apex of evolution, which is far more beautiful. Pierre Teilhard de Chardin In this column I will attempt to systematize my thinking on a question for which, as far as I am aware, established terminology and a classification of stages have not yet been developed. The words encountered will be formidable (as in the title), but I will do my utmost to explain everything clearly. The central idea is that within the evolving biosphere, an advantage accrues to those branches of the tree of life that prove capable of developing the necessary adaptations more rapidly than others — that is, they outcompete their rivals by virtue of a capacity for faster evolution. This acceleration is achieved through the mastery of ever-new mechanisms of inheritance. Some of these are known to us; some, perhaps, are not yet. The specific character of our species' evolution fits within the general picture of the evolution of evolution, and in full accord with Teilhard, we find ourselves at the very cutting edge of this process. I was persuaded by Blackmore's idea (described in the column before last) of distinguishing typical memes, as units of cultural inheritance transmitted from one mind to another, and t-memes, replicators of a higher level that employ other means of transmission. I began to think about how to describe these replicators from the perspective of organisms (recall the grid in the figure in the penultimate column) and concluded that we are dealing with several stages of evolution and several mechanisms of inheritance. Allow me to explain in more detail. Here is a diagram showing the principal pathways of information transmission typical of members of highly organized groups of living beings. I once drew something similar, but now, it seems, I have shown the necessary things somewhat less confusingly. [IMG_1] Pathways of information transmission underlying biological evolution. The phenotype+, the result of individual development, is repeatedly tested for correspondence with the environment The diagram shows two generations (and the transmission of heritable information to a third). The yellow rectangles represent organismal development, depicted by the violet arrow. One can say that the genotype (the totality of genetic information, i.e., information encoded in the sequence of monomers in the polymer chains of nucleic acids) influences the formation of the phenotype (the totality of an organism's traits) during ontogenesis (individual development). With your permission, I will write of "genotype+", "ontogenesis+", and "phenotype+" to indicate that I interpret these concepts in a broad sense. For example, although the spatial organization of the egg cell does not constitute part of the genotype in the strict sense, it nonetheless belongs among the important heritable (transmitted to subsequent generations) determinants. Under a strict interpretation of "ontogenesis", it probably should not include the formation of conditioned reflexes, and when speaking of the phenotype, life experience is not usually included. I wish to use these concepts as broadly as possible. As you will have understood, I treat behavioral traits here as just as much a part of phenotype+ as traits related to morphology (structure) or physiology (function). Yes, but the phenotype+ is of course also influenced by the environment. The red arrow in the diagram shows a specific action of the environment to which the phenotype+ responds in a regular manner, while the grey dashed lines represent noise, the source of randomness. Noise has both external and internal origins with respect to the organism. Each of the depicted pathways of information transmission is the result of a prolonged preceding evolution, a consequence of the selection of one or another replicator (structures that are copied, altered, and selected: autocatalytic reactions, genes, organisms...). The mechanisms governing development in accordance with heritable determinants (the violet arrow) are the result of selection for increased fidelity in the transmission of innate adaptive traits. The more robustly (despite informational noise) the norm selected across prior generations is reproduced, the greater the organism's chances of transmitting its heritable determinants to offspring. Once the task of noise-tolerant development is solved, an organism's chances of survival and reproduction may be enhanced by its capacity to adjust to the specific environmental conditions in which it happens to develop. A classic example is the difference between a pine that grew in an open location and one that developed in a dense forest. And do you know what happens when we (members of the European race) sunbathe? Our skin can realize different variants of dark pigment — melanin — synthesis, depending on the quantity of incoming ultraviolet radiation. If UV rays are scarce, the skin must be made transparent to them in order to ensure vitamin D synthesis; if they are in excess, protection is needed to reduce the likelihood of skin cancer developing. The examples given are but a small part of the information that a developing organism receives from its environment (the red arrow). We develop under specific conditions, under specific gravity, in an environment with the requisite chemistry, entering into interactions (including social ones) necessary for our development. One must not underestimate the pathway of information transmission indicated by the red arrow! At one time it seemed that heritable information was entirely independent of the outcomes of development. It has now become clear that highly developed organisms have acquired a feedback loop (that brownish one) which modifies the character of heritable determinants in dependence on the phenotype+. Under conditions in which generation after generation must realize a specific developmental variant from among several possible ones, success is enhanced by taking into account information about which of the alternatives was favored by the ancestors of each individual. I am fully aware that for discussing such information channels, some readers will attempt to affix to me the label of "Lamarckist." Well, what can one do! Epigenetic inheritance is established quite reliably, although the specific mechanisms underlying this pathway of information transmission are insufficiently studied. The mechanisms of epigenetic inheritance currently known are associated with chemical modification of individual monomers of the genetic text. This modification is reflected in the mode of spatial folding of the DNA molecule, and hence in its activity. I assume that other mechanisms of information transmission in the same direction — from phenotype+ to genotype+ — also exist. Possibly, certain additional mechanisms of DNA editing (for instance, involving information transfer from RNA molecules) also act in this direction. However, this topic requires a separate discussion... The phenotype+ interacts with the environment. If the environment "approves" the result of development (it proves sufficiently adapted and simply has luck on its side), its heritable information will be passed to the next generation. In organisms with sexual reproduction, each individual receives heritable information from two parents; this is not shown in my diagram (it was already sufficiently complex). Note the two feedback loops. Heritable determinants influence development and are themselves corrected (epigenetically, and possibly otherwise) by its outcomes. The environment approves or rejects the result of development, which is itself dependent upon it. These feedback loops are highly important for accelerating the development of necessary adaptations. As I have had occasion to write when discussing epigenetic evolutionary theory, for an organism's success in survival and reproduction, it is immaterial on what basis its adaptive traits developed. However, if the environment repeatedly preserves the bearers of certain traits, this will lead to an increase in the robustness of their development. Incidentally, do not be confused: epigenetic inheritance (EI) is not "related to" epigenetic evolutionary theory (EET). In the case of EI, the word "epigenetic" (i.e., situated above the genes) is used to denote the marking of the genetic text, while EET examines the system of developmental regulation of an organism situated "above" the genetic level. The mechanism of information transmission depicted in the figure under discussion is itself a masterpiece of evolution. But there is no limit to perfection, and multilevel selection will nonetheless confer an advantage upon that group of organisms which finds a way to improve it and intensify the development of adaptations. Over time, some species succeed others, and the group that ensures faster development of adaptations will, in time, occupy a more prominent place in the biosphere. One of the ways to intensify the development and transmission of beneficial behavioral traits was cultural inheritance. Initially it was confined to parents teaching children, and the bandwidth of this channel was quite small. Our genus staked its future on this mode of evolution; in us it has achieved unprecedented effectiveness. [IMG_2] To the pathways of information transmission shown in the previous diagram, mechanisms of cultural inheritance have been added: the transmission of behavioral traits through learning As you can see, cultural inheritance is shown in the diagram by orange arrows. Note: the cultural (learning-mediated) transmission of information can flow from parents to children, but may also proceed in other directions; it can connect organisms that are not related to one another. Is it legitimate in this case to use the word "inheritance", comparing learning with the operation of the genetic mechanism? Yes. Despite all its specificity, cultural inheritance arises as an improved pathway for the transmission of behavioral traits from individual to individual. I will not elaborate here at length: I examined this topic in the column "Evolution: Biological and Social". Examples of cultural inheritance (of relatively modest capacity in terms of the quantity of transmitted information) have been described in several groups of mammals, birds, and insects. In our species, the capacity of this information transmission channel has grown incomparably. And the next pathway of information transmission is altogether a prerogative of our species. [IMG_3] Our current civilization was shaped by extrasomatic inheritance. Information is carried from individual to individual by means of writing, electromagnetic and optical recording You can see: a new mode of information transmission has appeared in the diagram — via external media (rock engravings, writing, photo- and film stock, electromagnetic and optical devices, etc.). You too are currently interacting with me through the mediation of external media. What shall we call this information channel? Extrasomatic (extrabodily) inheritance. It is precisely extrasomatic inheritance that has made humanity a global species. Cultural and extrasomatic inheritance ensure the transmission of memes — copyable blocks of information. Although memes can be stored and reproduced outside of us (in our printed materials or in our computers, for instance), their existence is inevitably bound up with us as their consumers. We have identified two different mechanisms of inheritance: cultural and extrasomatic. Do two distinct categories of memes correspond to them? Probably not. The same memes can spread utilizing both pathways. Of course, different memes may specialize in different modes of propagation. As Blackmore quite rightly argues, there exists yet another category of replicators — t-memes — which multiply and are selected in the technical environment, bypassing our psyches. The most obvious example of such replicators are computer viruses. This is yet another stage in the evolution of evolution, and so I draw a fourth and final diagram. [IMG_4] The emergence of intratechnical replication. Now the transmission and evolution of informational replicators is tied not only to biological beings, but also to devices that are relatively independent of them The development of external media leads to yet another stage of evolution. Devices emerge that exchange information with one another autonomously. Human interaction with them is not fundamentally different from interaction with traditional media, but for the replicating units of information themselves, the situation changes radically. The environment that determines their fate is no longer the psyche of biological beings. T-memes spread, multiply, and evolve in a new, technogenic environment. We, the creators of this environment, may console ourselves that we control its principal operating parameters. Alas, one must not forget that once such an environment becomes self-complicating and self-evolving, control over it becomes severely limited. To call this mode of information transmission "inheritance" is most likely no longer appropriate — for here we are not speaking of the traits of any organisms. Very well, let us speak instead of intratechnical replication. Intratechnical replication remains, for the present, a terra incognita. We can observe only its first steps. About the comparison of biological, cultural, and extrasomatic inheritance, much more can be said. I hope it will prove possible in the not-too-distant future.
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Dmytro Shabanov
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Toad venom, an unsuccessful venture into business, and doubts about the innovative prospects of university science Evolution of Evolution: From Genetic Inheritance to Intratechnical Replication of T-Memes A multilateral conflict: individuals, genes, and memes; individuals and groups; proximate goals and distant prospects...
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