What does evolution explain ? Extending the evolutionary theory .

1. Whatdoesevolutionexplain ?Extendingthe evolutionarytheory. Philippe Huneman IHPST (CNRS/ Université Paris I Sorbonne)

2. EXTENDED evolutionary theory. Dawkins 1982; Turner 2001; Sterelny et al. 1996; Odling-Smee et al. 2003; Pigliucci 2007; Gould 2002 (« expansion ») Extending the explananda ? Extending the explanantia ?

3. I. The explananda – and especiallydiversity

4. Evolutionarytheoryexplains (Lewontin) : Adaptation Diversity Transformations

5. Evolutionarytheoryexplains (Lewontin) : Adaptation -> explained (defined ?) by naturalselection Diversity Adaptive radiation, « principle of divergence » Evolution -> several causes, the major one beingnaturalselection

6. Diversity • Variety, but not muchnovelty (Darwin) -> unitythroughdiversity

7. Finally, then, although in many cases it is most difficult even to conjecture by what transitions organs could have arrived at their present state; yet, considering how small the proportion of living and known forms is to the extinct and unknown, I have been astonished how rarely an organ can be named, towards which no transitional grade is known to lead. It is certainly true, that new organs appearing as if created for some special purpose rarely or never appear in any being; as indeed is shown by that old, but somewhat exaggerated, canon in natural history of "Natura non facitsaltum." We meet with this admission in the writings of almost every experienced naturalist; or, as Milne Edwards has well expressed it, "Nature is prodigal in variety, but niggard in innovation." Why, on the theory of Creation, should there be so much variety and so little real novelty? Why should all the parts and organs of many independent beings, each supposed to have been separately created for its own proper place in nature, be so commonly linked together by graduated steps? Why should not Nature take a sudden leap from structure to structure? On the theory of natural selection, we can clearly understand why she should not; for natural selection acts only by taking advantage of slight successive variations; she can never take a great and sudden leap, but must advance by the short and sure, though slow steps. Origin of species (6th ed.) ch. 6.

8. Similarity, throughdifference : The concept of homology: ‘the same organ in different animals under every variety of form and function’. (Owen 1843) Distinguishing homology and analogy (adaptive convergence)

9. Diversity Idea of a morphospace

11. Diversity Idea of a morphospace Generalisedmorphospace Issue : The clusteringwithin the morphospace The Clustering question : Why?

14. Diversity, 2 The pattern of branching What is the explanans ????

15. 5 Organisms (taxa, specimens) A, B, C, D, E Possible comparisons -> (ab) (cde)), (abc (de)), (a (bcde)) (ab ((cd)e)) etc.

17. (A (B (CD)) • (A (CB) D) • (A (BC) D) • (A (D (BC)) = (A (DBC)) + (A D (BC)) • Suppose you have (A (DB) C) also … : then no possible branching pattern

18. The Branching question • The fact is thatwe have somethinglike a tree ! Why ?? -> Common descent (by anymeans ??).

19. Plant cladogram

20. Vertebratescladogram

21. Partial cladograms

22. Dinosaurs

23. Evolution = two questions about rare facts in spaces of possible spaces • Are thereequal ? Or is an answer to the Clusteringquestion not enough to answer the Branchingquestion ? • Is thereanyprocesslikely to answer the two questions ?

24. II. Darwinianevolutionarytheoryexplainingdiversity

25. Darwin’sview • Unitythroughdiversity ? The Conditions of existence and the Unity of type (E.S. Russell Form and function, 1916; Cuvier vs. Geoffroy St Hilaire 1830)

27. It is generally acknowledged that all organic beings have been formed on two great laws Unity of Type, and the Conditions of Existence. By unity of type is meant that fundamental agreement in structure, which we see in organic beings of the same class, and which is quite independent of their habits of life. On my theory, unity of type is explained by unity of descent. The expression of conditions of existence, so often insisted on by the illustrious Cuvier, is fully embraced by the principle of natural selection. For natural selection acts by either now adapting the varying parts of each being to its organic and inorganic conditions of life; or by having adapted them during long-past periods of time: the adaptations being aided in some cases by use and disuse, being slightly affected by the direct action of the external conditions of life, and being in all cases subjected to the several laws of growth. Hence, in fact, the law of the Conditions of Existence is the higher law; as it includes, through the inheritance of former adaptations, that of Unity of Type. • Chapter VI. Origin of species

28. Darwin’sthesis : « unityof type » is subsumedundernaturalselection • What is « commondescent » for two traits at a samephylogeneticlevel ….resortsto « naturalselection » whenconsidering the first stages (plesiomorphicstates) of the trait…

29. Thus, we can hardly believe that the webbed feet of the upland goose or of the frigate-bird are of special use to these birds; we cannot believe that the same bones in the arm of the monkey, in the fore leg of the horse, in the wing of the bat, and in the flipper of the seal, are of special use to these animals. We may safely attribute these structures to inheritance. But to the progenitor of the upland goose and of the frigate-bird, webbed feet no doubt were as useful as they now are to the most aquatic of existing birds. So we may believe that the progenitor of the seal had not a flipper, but a foot with five toes fitted for walking or grasping; and we may further venture to believe that the several bones in the limbs of the monkey, horse, and bat, which have been inherited from a common progenitor, were formerly of more special use to that progenitor, or its progenitors, than they now are to these animals having such widely diversified habits. Therefore we may infer that these several bones might have been acquired through natural selection, subjected formerly, as now, to the several laws of inheritance, reversion, correlation of growth, &c.

30. Consequences : micro and macroevolution • Darwin’sgradualism • The scale-free diagram – zoom in (processes) and zoom out (branching pattern, homologies)

32. The Modern Synthesisview Change in allelicfrequencies as the core of evolution « Population thinking» (Mayr) and population genetics: genes and (alleles) populations are the two main explanatorylevels. Irrelevance of development to evolution (whatcounts is the phenotype’seffect on the replication rates of the genotypes) Natural selection is the main cause of the departuresfromgenefrequenciesequilibria

33. About processes: macroevolution as extrapolation frommicroevolution (Mayr, Simpson) About patterns : Gradualism

34. III. Whatwouldbe an alternative view ?

35. Population thinking and typology • Amundson’sclassification («Homology and homoplasy : a philosophical perspective » 2004): typology = homology more important thannaturalselection « Typologistswereunitednot by metaphysical or anti-evolutionary commitments, but by a belief in the importance of homology over adaptations” • Micro vs macro evolution = is adaptation differentthan« novelty »? (Muller and Newman 2003) Shouldnoveltyneedanother explanans ?

37. MS : explainsdiversitythrough adaptation (radiations…) • Explainsunity by commondescent (and in fine naturalselection…) • Typologist : explainsunity (in diversity) by commonalities of structure (developmental)

38. The role of development • MS view : naturalselectionexplains the branching (throughcommondescent) and (throughboth homologies and analogies) the clustering • (Developmental) typologistview : Common developmentalprocessesunderpin homologies (hence the branching) and clustering

40. 4. Whatis empirical and What is « purely » conceptual in those challenges to the modern synthesis?

41. Extending vs rebuildingevolutionarytheory? Integrating : • Development (Gilbert, Opitz & Raff 1996) • Ecology (Odling Smee et al. 2003; Hubbell 2001) • Both(Eco evodevo, Gilbert 2008)

42. Severalcleavages • Genes / epigenetics (Gilbert; Kirschner & Gerhardt 2005) • Genes / developmentalsystems (DST) • Genes / Genomics (Fox Keller 2000, Stolz, etc.): what if « genes » don’texistany more in moleculargenetics ? • Genes / organisms (West Eberhardt 2003; Walsh 2008; Odling Smee et al. (2003)) (Gould & Lewontin 1979) • Forms / Genes (Pigliucci 2007) • Structure/ Function (adaptation) (Amundson 2005) or Externalism vs. Internalism (Godfrey Smith 1996)

43. The problem Are all those « challenges » to the modern synthesislikely to besynthesised ? Whathangsuponempiricalfindings in those question ?

44. A common thread: Against « genecentrism » 1. In defining evolution • Evolution is not « change in allelicfrequencies » (i) (a definitionalreadycontroversialamong MS writers: “Evolution is not a change in gene frequencies, as is claimed so often, but the maintenance (or improvement) of adaptedness and the origin of diversity. Changes in gene frequency are a result of such evolution, not its cause.” (Mayr 1998, 2093)). But • Change in developmentalpathways (Caroll 2005) (ii) • Change in bodyplans (iii) Etc. (No more assumingthat i entails ii and iii)

45. A consequence : • Macro evolution is not immediatelyderivedfrommicroevolution (vs. Mayr, Simpson, Dobzhanski) • The challenges are in the same time about the patterns of evolution (here, emphasis on the processes; see Gayon 2008)

46. Againstgenecentrism 2. In explaining evolution • Developmentis as important as genotypes • (Evolution is not led by genes) • Organismis a fundamentallevel of evolution; About c. : Darwin vs. Neodarwinism (Ariew 2008; Pigliucci 2007) d.Evolutionarygenesdon’t match genesfromgenomics/moleculargenetics (pb. for a theory of variation and inheritance ?)

47. Two options: • explainother explananda (e. g. 1.a Form, the unity of forms; or a synthesis of allelic evolution and form, or adaptation and form) (e.g. Amundson 2005; Pigliucci 2007; 1.b, novelty (Newman and Muller 2003; Watson 2005)) 2) explaindifferently (some of) the same explananda • 2a. Another explanans thannatural selection (Kauffmann; walsh; odlingsmee et al. ?; Gould ?; Jablonka & Lamb ?; • 2b. Natural selection differentlyunderstoodis an explanans (DST; Caroll 2005; West Eberhardt ?)

48. (1) calls for a synthesis of MS and somethingelse in order to build a generalevolutionarybiology • (2a) needs to extend MS • (2b) means a re-writing of MS

49. What may be the targets of criticism ? The 2 controversialgene-relatedtheses in the Modern Synthesis : Darwinism (natural selection as a major cause of evolution, adaptation and diversity) Mendelism (Particularinheritance) -> genes are the substrate of inheritance (p) Weissmanism (germen soma distinction) -> developmentdoes not impinge on evolution (q)

50. The typologicaldevelopmentalistattacks q. But : Possibly: verysophisticateddevelopmentalphenomena (involvinggenes, epigenetics etc.) withoutmakingdevelopment relevant for evolution -> the argument from genotypephenotypemaps