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Colloque Darwin - Collège de France - 10-12 Juin 2009 Avant l« évo-dévo » : de Bateson à Waddington. Jean Deutsch Université P. et M. Curie.

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Presentation on theme: "Colloque Darwin - Collège de France - 10-12 Juin 2009 Avant l« évo-dévo » : de Bateson à Waddington. Jean Deutsch Université P. et M. Curie."— Presentation transcript:

1 Colloque Darwin - Collège de France - 10-12 Juin 2009 Avant l« évo-dévo » : de Bateson à Waddington. Jean Deutsch Université P. et M. Curie

2 Colloque Darwin - Collège de France - 10-12 Juin 2009 Avant l« évo-dévo » : de Darwin à Gould. Jean Deutsch Université P. et M. Curie

3 Colloque Darwin - Collège de France - 10-12 Juin 2009 C. Darwin 1809-1882 W. Bateson 1861-1926 T.H. Morgan 1866-1945 R. Goldschmidt 1878-1958 G. de Beer 1899-1972 C.H. Waddington 1905-1975 S. J. Gould 1942-2002

4 Colloque Darwin - Collège de France - 10-12 Juin 2009 C. Darwin (1809-1882) Importance des caractères du développement. Le bricolage de lévolution. Le changement de fonction.

5 Colloque Darwin - Collège de France - 10-12 Juin 2009 The Origin of Species, 1 st edition, Chap. XIII, The structure of the embryo is even more important for classification than that of the adult. Community in embryonic structure reveals community of descent. Importance des caractères du développement.

6 Colloque Darwin - Collège de France - 10-12 Juin 2009 Fertilization of Orchids, 1862, Chap. VII, p. 348 Although an organ may not have been originally formed for some special purpose, if it now serves for this end we are justified in saying that it is specially contrived for it. On the same principle, if a man were to make a machine for some special purpose, but were to use old wheels, springs, and pulleys, only slightly altered, the whole machine, with all its parts, might be said to be specially contrived for that purpose. Thus throughout nature almost every part of each living being has probably served, in a slightly modified condition, for diverse purposes, and has acted in the living machinery of many ancient and distinct specific forms. Le bricolage de lévolution.

7 Colloque Darwin - Collège de France - 10-12 Juin 2009 The Origin of Species, 1 st ed., Chap. VI Difficulties on Theory, p. 191 In considering transitions of organs, it is so important to bear in mind the probability of conversion from one function to another. Le changement de fonction.

8 Colloque Darwin - Collège de France - 10-12 Juin 2009 W. Bateson (1861-1926) Lanti-gradualisme Lhoméose La génétique mendélienne

9 Colloque Darwin - Collège de France - 10-12 Juin 2009 W. Bateson (1894) Materials for the study of variation treated with especial regard to DISCONTINUITY in the Origin of Species

10 Colloque Darwin - Collège de France - 10-12 Juin 2009 Homeosis: the essential phenomenon is not that there is merely a change, but that something has been changed into the likeness of something else. W. Bateson (1894) Materials for the study of variation Lhoméose Cimex axillaris Hyménoptère

11 Colloque Darwin - Collège de France - 10-12 Juin 2009 The only way in which we may hope to get at the truth is by the organisation of systematic experiments in breeding. Sooner or later such investigation will be undertaken and then we shall begin to know. W. Bateson (1894) Materials for the study of variation La génétique

12 Colloque Darwin - Collège de France - 10-12 Juin 2009 W. Bateson, 1900 Problems of Heredity as a Subject for Horticultural Investigation. Journal of the Royal Horticultural Society. 25: 54-61. […] a remarkable memoir by Gregor Mendel, giving the results of his experiments in crossing varieties of Pisum sativum. An exact determination of the laws of heredity will probably work more change in mans outlook on the world, and in his power over nature, than in any other advance in natural knowledge that can be foreseen. La génétique

13 Colloque Darwin - Collège de France - 10-12 Juin 2009 T.H. Morgan (1866-1945) Embryologie et génétique

14 Colloque Darwin - Collège de France - 10-12 Juin 2009 T.H. Morgan (1928) The Theory of the Gene, p. 316. …illusion that each mutant character is the effect of only one gene and that each unit character has a single representative in the germ material. On the contrary, the study of embryology shows that every organ of the body is the end-result, the culmination of a long series of processes. If very many steps are involved in the development of a single organ, and if each of these steps is affected by the action of a host of genes, there can be no single representative in the germ-plasm for any organ in the body.

15 T.H. Morgan (1934) Embryology and Genetics, p. 16 The question arises as to how the gene produces its effect on the protoplasm of the cells, for it is in the protoplasm that the character is manifest. Colloque Darwin - Collège de France - 10-12 Juin 2009 The answer will have to wait until evidence can be obtained from experimental investigation.

16 Colloque Darwin - Collège de France - 10-12 Juin 2009 R. Goldschmidt (1878-1958) Gènes de contrôle Le monstre prometteur Importance évolutive de lhoméose

17 Colloque Darwin - Collège de France - 10-12 Juin 2009 R. Goldschmidt (1938) Physiological Genetics Gènes de contrôle (rate genes) The mutant gene produces its effect, the difference from the wild-type, by changing the rates of partial processes of development. These might be rates of growth or differentiation, rates of production of stuffs necessary for differentiation, rates of reaction leading to definite physical or chemical situations at definite times of development, rates of those processes which are responsible for segregating the embryonic potencies at definite times.

18 Colloque Darwin - Collège de France - 10-12 Juin 2009 R. Goldschmidt (1933) Some aspects of evolution. Science. 78, 539-547. Le monstre prometteur … the importance of rare but extremely consequential mutations affecting rates of decisive embryonic processes which might give rise to what one might term hopeful monsters, monsters which would start a new evolutionary line if fitting into some empty environmental niche. We must not forget that what appears to-day as a monster will be to-morrow the origin of a line of special adaptations. The dachshund and the bulldog are monsters. But the first reptiles with rudimentary legs or fish species with bulldog- heads were also monsters.

19 Colloque Darwin - Collège de France - 10-12 Juin 2009 R. Goldschmidt (1940) The Material Basis of Evolution Homeosis and segmentation, p. 323-338. We turn now to a group of facts which links genetics, development and evolution. The well-known case of the assumption of snake-like form by saurians through the increase in vertebral number and rudimentation of the extremities. A single genetic change affecting the rate of early embryonic features of segmentation may, therefore, have produced in a single mutational step at least the fundamental elements of the whole group of adaptations to crawling movement.

20 Colloque Darwin - Collège de France - 10-12 Juin 2009 G. de Beer (1899-1972) Homologie. Hétérochronie.

21 Colloque Darwin - Collège de France - 10-12 Juin 2009 It is clear that characters controlled by identical genes are not necessarily homologous. […] It is clear that homologous characters need not to be controlled by identical genes. […] The homology of phenotypes does not imply the homology of genotypes. The analysis of the concept of homology in terms of single genes therefore breaks down. G. de Beer (1938) Embryology and Evolution, p. 66 Homologie.

22 G. de Beer (1940) Embryos and Ancestors, p. 34 Colloque Darwin - Collège de France - 10-12 Juin 2009 The strength of the internal factors of development can vary and exert their effects at different rates, with the result that the time of appearance of a structure can be altered. To this shifting along the time-scale the term of heterochrony is applied. It is thus possible for two organs to reverse their appearance in successive ontogenies, and, by varying the rates at which animals become mature, adult structures can be reduced to a vestige and discarded, or youthful structures can become adult. Hétérochronie.

23 Colloque Darwin - Collège de France - 10-12 Juin 2009 C.H. Waddington (1905-1975) Paysage épigénétique. Canalisation. Assimilation génétique.

24 Colloque Darwin - Collège de France - 10-12 Juin 2009 C.H. Waddington (1940) Organisers and genes Epigenetic landscape The symbolic representation of developmental processes can be spoken as epigenetic landscape. Epigenesis. The development of the organism by the new appearance of structures and functions, as against the unfolding or growth of entities already present in the egg at the beginning of development (Preformation). (J. Needham)

25 Colloque Darwin - Collège de France - 10-12 Juin 2009 C.H. Waddington (1956) Principles of embryology, p. 329 Developmental pathways and their genetic control (1)The development of an organ or complex substance takes place in a series of steps, each of which is affected by genes. (2)At each step there are several genes acting, and the actual development which occurs is the resultant of the balance between the opposing gene-instigated tendencies.

26 Colloque Darwin - Collège de France - 10-12 Juin 2009 C.H. Waddington (1942) Canalization of development and the inheritance of acquired characters. Nature, 150: 563-565 Developmental reactions, as they occur in organisms submitted to natural selection, are in general canalized. That is to say, they are adjusted so as to bring about one definite end-result regardless of minor variations in conditions during the course of the reaction. The evidence for this comes from two sides, the embryological and the genetical. […] The canalization, or perhaps it would be better to call it the buffering, of the genotype is evidenced most clearly by constancy of the wild type.

27 Colloque Darwin - Collège de France - 10-12 Juin 2009 C.H. Waddington (1953) Genetic assimilation of an acquired character. Evolution, 7: 118-126. (1956) Genetic assimilation of the Bithorax phenotype. Evolution, 10: 1-13. Genetic assimilation is a name which has been proposed for a process by which characters which were originally acquired characters in the conventional sense, may become converted, by process of selection acting for several or many generations on the population concerned into inherited characters. Genetic assimilation is brought about by the operation of orthodox genetic and embryological principles.

28 Colloque Darwin - Collège de France - 10-12 Juin 2009 S. J. Gould (1942-2002) Les contraintes architecturales du développement. Limportance de lhétérochronie de développement. Lexaptation. La nouvelle synthèse.

29 Colloque Darwin - Collège de France - 10-12 Juin 2009 S. J. Gould & R.C. Lewontin (1979) The spandrels of San Marco and the Panglossian paradigm: a critic of the adaptationist program. Proc. Roy. Soc. Lond. B, 205: 581-598. Constraints restrict possible paths and modes of change so strongly that the constraints themselves become much the most interesting aspect of evolution.

30 Colloque Darwin - Collège de France - 10-12 Juin 2009 S. J. Gould & R.C. Lewontin (1979) The spandrels of San Marco and the Panglossian paradigm: a critic of the adaptationist program. Proc. Roy. Soc. Lond. B, 205: 581-598.

31 Colloque Darwin - Collège de France - 10-12 Juin 2009 S. J. Gould (1977) Ontogeny and Phylogeny, p. 246-7. A clock model of heterochrony We want to plot size and shape as two potentially independent vectors operating during the life time of an organism. To do this, we set up a semicircular clock with two hands. One hand represents our best statistic for a measure of size. […] The other hand measures shape, which may be disconnected from its ancestral relationship to size during evolution. […] The clock has three scales corresponding to size, shape and [developmental] age.

32 Colloque Darwin - Collège de France - 10-12 Juin 2009 S. J. Gould & E.S. Vrba (1982) Exaptation, a missing term in the science of form. Paleobiology, 8: 4-15. We suggest that characters, evolved for other usages (or for no function at all) and later co-opted for their current role, be called exaptations.

33 Colloque Darwin - Collège de France - 10-12 Juin 2009 S. J. Gould (1977) Ontogeny and Phylogeny, p. 408. … the evolutionary significance of changes in gene regulation. An understanding of regulation must lie at the center of any rapprochement between molecular and evolutionary biology; for a synthesis of the two biologies will surely take place, if it occurs at all, on the common field of development. La nouvelle synthèse.

34 Colloque Darwin - Collège de France - 10-12 Juin 2009 Je vous remercie de votre attention. jean.deutsch@snv.jussieu.fr


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