Whodunit

1. Whodunit • Population thinking: R. A. Fisher, J.B.S. Haldane, Sewall Wright • The major (or at least best known) ARCHITECTS of Modern Evolutionary Synthesis: • J.S.Huxley, Theodosius Dobzhansky, Ernst Mayr, George Gaylord Simpson, G. Ledyard Stebbins, starting from 1937

2. Evolutionary theory is not born with Darwin but • Natural Selection was the first “scientific” hypothesis for a mechanism within nature itself for explaining adaptation, filling the explanatory gaps of Lamarckism • however • Darwin did not envisage natural selection as the ONLY mechanism for evolution • He kept many lamarckian notions such as heredity of acquired traits, use and disuse etc. • Darwin’s PLURALISM • Darwin’s Theory did not provide: • Neither an adequate theory of heredity • He never read the paper Mendel sent to him… and just shifted from blending inheritance to pangenesis • Nor an explanation of variation, of which he recognized a “deep ignorance” • Nor experimental proofs for natural selection, which was long regarded, even among the fiercest supporters, as speculative

3. Modern Synthesis • “Unification” of biology … under population thinking • An “idealized” summary of its original components: • Neodarwinism (August Weismann’s) • rejection of soft heredity • All-sufficency of natural selection • Mathematical population genetics brought into fieldwork • Statistical methodology, mostly created by Fisher, Haldane and Wright, makes the action of natural selection testable in natural populations (ecological genetics since Ford and Kettlewell) • Chromosomal Theory of Heredity • From Morgan and his school, who revised de Vries’ saltationist notion of mutation, providing evidence of the existence of tiny mutations with no phenotipic effects, and thus reconciling genetics with Darwinian gradualism • Biogeography and systematics • Starting from the populational (biological) notion of species, theories of speciation due to changes in gene frequences in geographically separated populations • Paleontology • the same mechanisms bringing about microevolution are at work in macroevolution and evolutionary innovation (Gould = Extrapolationism) • Rebuttal of orthogenesis – no directed mutations • Fields that DID NOT MERGE • Embryology and morphology

4. General tendency of Synthetic approach • “Modern evolutionary theory can only be understood in the light of population thinking” (Mayr 1959) • “the organic diversity existing in nature, the differences between individuals, races, and species, are experimentally resolvable into genic and chromosomal changes that arise in the laboratory” (Dobzhansky) • Merging of naturalistic and experimentalist tradition • “The proponents of the synthetic theory maintain that all evolution is due to the accumulation of small genetic changes, guided by natural selection, and that transpecific evolution is nothing but an extrapolation and magnification of the events that take place within populations and species." (Mayr 1963) • But adaptation turns into adaptationism: • After World War I, hardening of MS, “increasing emphasis on selection and adaptation” (Gould 1983) • Shifts evident in Dobzhansky (19371947), Simpson (19441953), Wright (19311950s)

6. Adaptationism /panselectionism Natural selection is the ONLY explanation for adaptation Laland et al – ultimate cause of phenotypic characters Role of (structural) genes Gene-centered view of MS Genes are the prime movers of evolution “Genetic program” and “genetic blueprint” Transmission genetics at the core Ultradarwinian selfish genes as leading actors in evolution Redefinition of the role of natural selection in evolution explanatory PLURALISM Neutral evolution and exaptation Self-organisation maybe natural selection is but a form of self-organisation? Gene regulation + universality of a shared genetic toolkit Crucial role of cis-regulatory changes in morphological evolution Genomic itself beyond genetic atomism (Hueng 2009) Systemic and “network” views of gene action Noble 2006: “it might be more helpful to avoid saying that genes do anything at all; it is more that genes are used. They operate under control“ - The “levels of selection” debate (incomplete) summary of issues actually at stake(jumping all that happened meanwhile)

7. Gradualism and extrapolationism Genetic inheritance Passive role of organisms (anti-Lamarckian) Punctuated equilibria Macroevolution and novelty are still unexplained (Erwin) Evo-Devo arguments for role of early developmental variation in major transitions Erwin’s methodological criticism: population genetics is of no use for settling the issue … whether population genetics can account for any of these trends is not at issue. Population genetic models can produce virtually any pattern of morphological evolution and thus provides no clear basis for choosing between opposing models (Since Levins 1966) Increasing role of systems of epigenetic inheritance Niche Construction: organisms make environment more fit and instantiate other systems of inheritance Gilbert’s interspecies epigenesis Issue of horizontal gene transfer

8. (Myth of) genotype – phenotype linear relation “black-boxing” of development Hierarchical structure of evolutionary process (since Gould) Molecular/morphological divide Different rates of evolution Genotype-phenotype (non-linear) mapping Fundamental asimmetry between different levels in biological hierarchy For ex. small steps in genotypic space do not always involve equally small steps in phenotypic space Evo-Devo: reappraisal of morphogenesis and ontogeny and of a view of evolution as a “succession of ontogenies” (Garstang)

9. Variation is pure chance; only natural selection directs evolution selection maintains high polymorphism in natural populations - heterosis Reappraisal of drift and neutral evolution Kimura’s neutral explanation of high variability Variation is not pure chance, and “systemic conditions” of different kinds (internal and external constraints) contribute in directing evolution independently of the action of natural selection Role of chance (crucial against creationism since Darwin)

10. Modern Synthesis is “incomplete” (Gould) – or “unfinished” (Eldredge) • Modern Synthesis needs to be updated to an EES (Extended Evolutionary Synthesis) • Object of 2008 Altenberg Colloquium – the 16) • Regional synthesis still to be done: • http://evodevo.eu/conferences/2010 • The Population Genetics of Development • Integration or overhaul? • In Evo-Devo different stances in this regard • Modern Synthesis as Neurath’s ship • “We are like sailors who have to rebuild their ship on the open sea, without ever being able to dismount it in dry-dock and reconstruct it from the best components”