Deconstructing Darwin: Evolutionary theory in context

The topic of this paper is external versus internal explanations, first, of the genesis of evolutionary theory and, second, its reception. Victorian England was highly competitive and individualistic. So was the view of society promulgated by Malthus and the theory of evolution set out by Charles Darwin and A.R. Wallace. The fact that Darwin and Wallace independently produced a theory of evolution that was just as competitive and individualistic as the society in which they lived is taken as evidence for the impact that society has on science. The same conclusion is reached with respect to the reception of evolutionary theory. Because Darwins contemporaries lived in such a competitive and individualistic society, they were prone to accept a theory that exhibited these same characteristics. The trouble is that Darwin and Wallace did not live in anything like the same society and did not formulate the same theory. Although the character of Victorian society may have influenced the acceptance of evolutionary theory, it was not the competitive, individualistic theory that Darwin and Wallace set out but a warmer, more comforting theory.     

Charles Darwin and the mutation theory

Ohne Zusammenfassung

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Charles Darwin and the mutation theory

     

Darwin and sexual selection: One hundred years of misunderstanding

Darwin's book on the Descent of Man and Selection in Relation to Sex (1871) is often viewed as the continuation of TheOrigin of Species published 12 years earlier (1859), both because of the implicit parallelism between natural selection and sexual selection, and because Darwin himself presents the book as developing a subject (man) which he intentionally omitted in the Origin. But the Descent can also be viewed as the continuation of his book on Variation published three years earlier (1868). Firstly because Darwin's hypothesis of pangenesis links the selection process to the origin of variation through use and disuse, an idea underlying his speculations on the origin of moral sense in humans. Second because like the action of the horticulturist on his domestic crops, sexual selection exerted by one sex on the other sex can develop fancy traits that are not easily accounted for by their utility to the selected organism itself, such as artistic taste, pride, courage, and the morphological differences between human populations. These traits are difficult to reconcile with pangenesis. They add up to other contradictions of the book possibly resulting from Darwin's erroneous inference about the mechanism of inheritance, like those on the determination of sex-ratio, or the confusion between individual adaptation and the advantage to the species. These inconsistencies inaugurate a weakening of the Darwinian message, which will last 50 years after his death. They contributed to the neglect of sexual selection for a century. Darwin however maintained a logical distinction between evolutionary mechanisms and hereditary mechanisms, and an epistemological distinction between evolutionary theory and Pangenesis hypothesis. In the modern context of Mendelian genetics, Darwin's sexual selection retrospectively appears as luminous an idea in its pure principle as natural selection, even though the mechanisms governing the evolution of sexual choice in animals remain largely unresolved.     

Darwin after 100 years. 1983.]

The triumph of Darwinism, together with the rise of Genetics, produced the virtual abandonment of the problem of form in Biology. The statement that any adaptive theory is tautological is however poor, the adaptation concept having an evident intuitive content. As in Geometrical Optics, a ray of light is, among the crowd of continuous curves uniting two points, the one requiring the minimum time for the light to go from one point to the other, so actual evolution, among the crowd of virtual evolutions between two forms, is the one best fitted to face 'selective pressure' in a given environment. The effect of selective pressure on the genome is unfortunately a merely theoretical not quantifiable concept. Most biological forms are forced by their internal stability to an essential fixity, so that the leap from one type-form to another should be abrupt-catastrophic. A good theory of evolution depends on a proper understanding of specific form stability. Biology must eventually return to the concept of ideal structure, the Goethian 'Urbild'.     

Why Darwin would have loved evolutionary game theory

Humans have marvelled at the fit of form and function, the way organisms'' traits seem remarkably suited to their lifestyles and ecologies. While natural selection provides the scientific basis for the fit of form and function, Darwin found certain adaptations vexing or particularly intriguing: sex ratios, sexual selection and altruism. The logic behind these adaptations resides in frequency-dependent selection where the value of a given heritable phenotype (i.e. strategy) to an individual depends upon the strategies of others. Game theory is a branch of mathematics that is uniquely suited to solving such puzzles. While game theoretic thinking enters into Darwin''s arguments and those of evolutionists through much of the twentieth century, the tools of evolutionary game theory were not available to Darwin or most evolutionists until the 1970s, and its full scope has only unfolded in the last three decades. As a consequence, game theory is applied and appreciated rather spottily. Game theory not only applies to matrix games and social games, it also applies to speciation, macroevolution and perhaps even to cancer. I assert that life and natural selection are a game, and that game theory is the appropriate logic for framing and understanding adaptations. Its scope can include behaviours within species, state-dependent strategies (such as male, female and so much more), speciation and coevolution, and expands beyond microevolution to macroevolution. Game theory clarifies aspects of ecological and evolutionary stability in ways useful to understanding eco-evolutionary dynamics, niche construction and ecosystem engineering. In short, I would like to think that Darwin would have found game theory uniquely useful for his theory of natural selection. Let us see why this is so.     

Darwin and divergence: The Wallace connection

Concluding statement Wallace's contributions to biological thought tend to be overlooked or overly praised, neither of which produces a satisfactory assessment. Examples of the latter tendency are the recent expositions by Brackman and Brooks; although both books contain much worthwhile material, both are flawed. At critical points their theories fail to measure up, Brackman's because of his misinterpretations of events in the month of June 1858, and Brooks's Darwin's September 5 letter to Gray could, and probably did, represent an ordering of his ideas in response to a felt challenge.A fruitful way to characterize the relationship between Darwin and Wallace may be found in terms of game theory. Most scholars look upon the relationship as a zero-sum game, with a winner and a loser, the matter of priority being considered as a single event. Another approach would be to look upon it as a non-zero-sum game with each man influencing the other. In this case, the productivity of one is stimulated by the contributions of the other, resulting in a net gain in knowledge overall, and both men become winners, or codiscoverers. This approach is possible if Wallace's contributions to the theory of evolution by means of natural selection are recognized.     

The clonal theory of parasitic protozoa: 12 years on

The question of population structure in parasitic protozoa has recently gained a renewed topicality with significant contributions on medically important pathogens, such as Plasmodium falciparum, Toxoplasma gondii and Cryptosporidium parvum. The proposals that initiated this debate are reviewed here and the subsequent developments of the clonal theory, in light of recent contributions, are examined.     

Darwin would have loved DNA: celebrating Darwin 200

Analysis of DNA sequences now plays a key role in evolutionary biology research. If Darwin were to come back today, I think he would be absolutely delighted with molecular evolutionary genetics, for three reasons. First, it solved one of the greatest problems for his theory of evolution by natural selection. Second, it gives us a tool that can be used to investigate many of the questions he found the most fascinating. And third, DNA data confirm Darwin''s grand view of evolution.     

The Darwin of pangenesis

The Darwin of pangenesis is very much another Darwin. Pangenesis is Darwin's comprehensive theory of generation, his theory about all sexual and asexual modes of reproduction and growth. He never explicitly integrated pangenesis with his theory of natural selection. He first formulated pangenesis in the 1840s and integrated it with the physiology, including the cytology, of that era. It was, therefore, not consilient with the newer cytology of the 1860s when he published it in 1868. By reflecting on the role of pangenesis in Darwin's life and work, we can learn to take a wider view of his most general theorising about animal and plant life.