Three Syntheses in Evolutionary Biology. Column in KompyuterraOnline #44
Many components of the Third Synthesis in evolutionary biology have already been developed. What remains is to isolate, from the particulars of circumstance, the primary signal reflecting the mechanism of life's development.
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Dmytro Shabanov
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Surrogates of Conservation Three Syntheses in Evolutionary Biology Difficulties of Career Guidance
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Happy are those who advance science in years when it is not yet complete, but when a decisive turning point has already matured within it. André-Marie Ampère For a long time I have wanted to discuss in this column the problems of evolutionary biology that interest me, but kept putting it off. Columns in Kompyuterra are aimed at the thoughtful and attentive reader who is capable of reading and comprehending a demanding text — not at the specialist biologist. And in evolutionary biology, a peculiar situation has developed: the problems discussed by the general public differ strikingly from those debated among specialists. With non-specialists, the same worn-out topics resurface time and again: Is the human being the product of evolution? Do the intellectual sleights of hand of "scientific" creationists refute evolution? Is there an insurmountable gap separating humans from other apes? Could life have arisen by natural means? And so on. In my own column I have also contributed to the discussion of these "external" topics. But there are also "internal" topics of dispute; they are no less acute, but far more interesting, since they concern the acquisition of new understanding rather than the elucidation of existing knowledge. How do group selection, individual selection, and gene-level selection relate to one another? Do specific mechanisms of macroevolution exist? Can evolution be exhaustively explained at the level of allele selection? Do new traits arise as a consequence of mutational variation, or are they created by natural selection? One of the dangers associated with discussing such problems is that well-meaning outsiders seek in such debates ways to discredit evolutionary biology as such. The moment a contemporary evolutionist draws attention to changes in thinking since Darwin's time, creationists will quote him in support of the theses "Darwin has been refuted" and "evolution never occurred." Normal discussion of questions in evolutionary theory is also impeded by the dogmatism of certain biologists. In early 2009 an open seminar was held among us, dedicated to the 150th anniversary of On the Origin of Species. There were two presentations. My colleague is an ardent adherent of the Synthetic Theory of Evolution (STE), while I criticized that theory for its limitations. Our dispute concerned questions that did not even stand in nineteenth-century science; without familiarity with the newer ideas, Darwin himself would not have understood it at all. This did not prevent my colleague from asserting that, since I disagreed with his viewpoint, I was "objectively against Darwin." In time I learned that some shallow-minded students had come to believe that, since I disputed the STE, I denied evolution itself... Nonetheless, I will take the risk — but I will begin with a disclaimer: evolutionary biology is not equivalent to Darwin's theory; it contains many other theories; contemporary science has no grounds for disputing the fact of evolution, but the mechanisms of evolution have not been fully elucidated; discussions within evolutionary biology demonstrate that this science is alive and has not hardened into dogma.
evolutionary biology is not equivalent to Darwin's theory; it includes many other theories; there are no grounds for modern science to refute the fact of evolution, but the mechanisms of evolution are not fully understood; discussions within evolutionary biology prove that this science is alive and has not turned into a dogma.
Very well. Now I wish to explain the scheme of the three syntheses in evolutionary biology. It was proposed by Nikolai Nikolaevich Vorontsov in his book The Development of Evolutionary Ideas in Biology (1999), although similar ideas may have been expressed even earlier. The central problem of biology — the problem of the purposiveness of living organisms — was formulated by Aristotle, and people had begun to perceive it even before him. Socrates had already discussed with his pupils how remarkably the parts of the human body are suited to their purpose. Aristotle sought to understand why the fin of a fish reflects the properties of water, and the wing of a bird those of air. His answer: by virtue of striving toward a certain end — to cleave water, in the case of the fin; to bear upon the air, in the case of the wing. Incidentally, in canvassing various possible explanations, Aristotle also set forth an idea belonging to Empedocles: "Those parts in which everything came together as if they had been formed with a view to some end — having assembled themselves in the appropriate manner — survived. Those in which this did not occur perished and perish, like those bulls with human faces of which Empedocles speaks." Aristotle's explanation sufficed for more than two thousand years of scientific development. The dominant interpretation proved to be that which Paley articulated with such talent: the purposiveness of organisms is a consequence of the wisdom of the Creator. In the eighteenth century, transformism — the view that animals and plants are capable of changing and being transformed into new species under the influence of the conditions of their habitation — became widely disseminated. The nineteenth century demanded a description of the mechanism of such changes. Biology had by that time accumulated a great deal of valuable data. Systematics had distinguished numerous groups of organisms on the basis of their similarities and differences. Comparative anatomy had described the diversity of organismal body plans. Embryology had revealed the gradual appearance of the characteristics of each group in the course of the individual development of any organism. Palaeontology had established the fact of the succession and increasing complexity of faunas and floras, reflected in the geological record of Earth's history. Biogeography had registered the distinctive features of the living world of the studied continents and islands. Do you know what all these data have in common? In modern parlance, behind the noise occasioned by chance circumstances, a phylogenetic signal stands out — a consequence of the fact that different groups of organisms are united by varying degrees of kinship. Modern bioinformatic programs extract the phylogenetic signal by means of formalised algorithms, while nineteenth-century biologists groped for it intuitively. Many sensed it, but were unable to construct a unified and coherent picture. Jean-Baptiste Lamarck advanced furthest, developing what were essentially Aristotelian ideas of striving toward purposiveness. Étienne Geoffroy Saint-Hilaire concentrated on the connections among different body plans and the role of embryonic reorganisations, in many respects anticipating the concept of Evo-Devo that appeared a century and a half after him. These and other ideas each converged on some cluster of facts but encountered difficulties in explaining other observations. The two great evolutionists of the nineteenth century, Charles Darwin and Alfred Russel Wallace, were impelled toward an understanding of the phylogenetic signal by their fieldwork and their acquaintance with the ideas of Thomas Malthus. Field experience testified to the diversity of individuals within any species. Malthus's demographic reasoning demonstrated that any growing population would inevitably encounter the limitation of resources. It remained only to recognise that, depending on their particular characteristics, some individuals have greater chances of success — of survival and reproduction — than others. In place of Empedocles' single test of viability came the continuously acting mechanism of natural selection. Wallace's thinking was the more rapid; Darwin's strength lay in his thoroughness, and moreover he was better acquainted with the practice of selection of agricultural and ornamental organisms. In Darwin's mind the picture of the mechanism of evolution began to take shape earlier, and the final impetus was given by his acquaintance with Wallace's paper. In the end, it was Wallace who proposed the name "Darwinism" for their joint offspring. Thus, Darwinism became the First Synthesis in evolutionary biology. Its power lay not in any single new idea, but precisely in binding together heterogeneous data into a single knot. It was for this reason that Thomas Huxley, one of the foremost zoologists of Victorian England, upon reading Darwin's book exclaimed: "What an ass I have been not to think of that!" The logic of Darwin and the persuasive powers of Huxley contributed to the rapid acceptance of the new synthesis and stimulated progress in nearly all branches of biology at the time. But the new biology was inevitably destined to reach a frontier at which Darwinism — and neo-Darwinism in the version of August Weismann — would no longer suffice. I cannot fit into this column a detailed account of the crisis of the First Synthesis in evolutionary biology, which became manifest at the beginning of the twentieth century; I shall address it another time. Here I shall say only that, in the conception of biologists at the beginning of that century, the doctrine of selection could not be reconciled with the doctrine of heredity. The great geneticist Wilhelm Johannsen demonstrated in 1903 that selection merely sorts pre-existing hereditary potentials. Johannsen subjected lines of beans to selection. After several generations, when all the plants proved identical in their hereditary properties, selection lost its effectiveness. It followed that selection does not create new qualities. What does, then? An answer was provided by Hugo de Vries, one of the rediscoverers of Mendel's laws. The sudden appearance of a new hereditary property de Vries termed, borrowing a word from palaeontology, a "mutation" — a change. If this were so, mutations direct evolution. It turned out that neither the moment at which a mutation would appear nor the direction in which it would alter the properties of an organism could be predicted. Yet behind the chaos of mutations certain regularities were discernible. Palaeontologists described characteristic evolutionary pathways in which the same patterns recurred. Nikolai Ivanovich Vavilov demonstrated that different species possess identical sets of possible mutations. Lev Semyonovich Berg counterposed to Darwinism — the theory of evolution by undirected, chance changes — nomogenesis, the theory asserting the directive role of law-governed, directed transformations in evolution. The Second Synthesis had many progenitors. Here is an incomplete list of its principal authors with the year of publication of the key work: Sergei Sergeyevich Chetverikov, 1926; Ronald Fisher, 1930; John Haldane, 1932; Theodosius Dobzhansky, 1937; Ernst Mayr, 1942; Julian Huxley, 1942; George Gaylord Simpson, 1944. Finally, in 1949, Simpson proposed calling their joint creation the Synthetic Theory of Evolution (STE), drawing on the title of Huxley's book Evolution: The New Synthesis (1942). The continuity between the First and Second Syntheses was manifested in the fact that Julian Huxley — who gave the new theory the name "synthesis" and who was, among other things, the founder of UNESCO — was the grandson of Thomas Huxley (they share the same surname, Huxley, though the Russian transcription of Thomas's name had acquired an archaic rendering). [IMG_1] Continuity of eras. Thomas Huxley with his grandson, Julian Huxley. Illustration from Wikipedia. And now I will venture an opinion with which not everyone will agree. The classical STE — the Second Synthesis — has become as outdated in the early twenty-first century as Darwinism, the First Synthesis, had become by the beginning of the twentieth. Darwinism, at the time of Johannsen's experiments, was scarcely more than forty years old — the age of maturity; the STE today, given the current pace of scientific development, has long outlived retirement age. At the beginning of the twentieth century there were specialists who asserted that the First Synthesis (in our terminology) faced no threat; the same is observed at the beginning of the twenty-first century with respect to the Second Synthesis. Then as now, the orthodox acknowledge only the need for minor patches and refinements. Then as now, the patches turn out to be more numerous than the underlying fabric they are meant to mend. Of course, Wikipedia blithely refers to the STE as the "modern theory of evolution," but this is merely talking away the problem. Much that is fundamentally new has been added to the picture that Julian Huxley unified into a single knot — new findings that have transformed our current understanding of the mechanisms of evolution. You have already grasped where I am heading. Our time is the time of the crisis of the Second Synthesis. The STE has not been refuted, but it is insufficient to describe everything we know today. I agree with those who await a Third Synthesis in evolutionary biology. I believe that many of its components have already been developed. What remains is to isolate, from the particulars of circumstance, the primary signal reflecting the principal mechanism of life's development. But there is a catch here. "Style is the man" (Georges-Louis Leclerc de Buffon). Today a considerable number of people appear with overvalued ideas who, having seized upon some real or imagined feature of the evolutionary process, attempt to reconstruct all of biology on its basis. Into every university, onto every evolution website, arrive revolutionary manuscripts in which inspired non-specialists sketch, with bold strokes, outlines of an All-Encompassing Theory of Evolution. Alas, their authors differ fundamentally from both Darwin and Huxley. I believe that what we must await is a synthesis, not a revolution, and that such a synthesis can be achieved only by a person or a collective who is genuinely competent in the branches of biology whose achievements need to be synthesised. Do you think the picture I have described speaks to the weakness of evolutionary biology? No — in this its vitality is manifested. We may become witnesses — and some fortunate few, participants — in the formation of a new version of the answer to the question posed by Aristotle. To my mind, this is a remarkable challenge.
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Dmytro Shabanov
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Surrogates of Conservation Three Syntheses in Evolutionary Biology Difficulties of Career Guidance
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