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Aims & method of this lecture The received view: Aristotle’s biology Evolutionary ideas until Darwin History of evolutionary thought from Darwin to the present Evolution: Theory-structures and concepts Evolution between science and world-view Summary & discussion.
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Aims & method of this lecture The received view: Aristotle’s biology Evolutionary ideas until Darwin History of evolutionary thought from Darwin to the present Evolution: Theory-structures and concepts Evolution between science and world-view Summary & discussion Philosophical presuppositions of evolutionary biologyFFDI Zagreb, 20-25 April 2015 • Prof.Dr.Dr. Winfried Löffler • University of Innsbruck • Department of Christian Philosophy • Karl-Rahner-Platz 1 • A-6020 Innsbruck, Austria • winfried.loeffler@uibk.ac.at • www.uibk.ac.at/philtheol/loeffler
1. Aims and method of this lecture Aims: Some basics about current evolutionary biology Some basics about its historical backgrounds Understand its peculiar theoretical status Distinguish between scientific theory and its ideological interpretations / reductionisms Misunderstandings of anti-evolutionism Method: historical (2-4, partly 6) to understand conceptual backgrounds
2. The received view: Aristotle’s biology 2.1 Life and Works Aristotle (384-322)today usually seen as philosopher, but first big encyclopedist Almost all scientific disciplines: - Physics, biology, physiology, meteorology, psychology, - economics, politology, aesthetics / poetology - ethics, rhetorics, philosophy of language, - philosophy of science - general philosophy (“first philosophy”, metaphysics)
Influential merits in the philosophy of science: - Important basic concepts (substance/accident, potential/actual, matter/form, efficient cause/final cause) - Classification of the scientific disciplines (theoretical/practical/poietical); (episteme / historia / techne) - Structure of scientific arguments (Prior Analytics, syllogism) - Structure of scientific classifications - Structure of an empirical science (empirical “first sentences” & logical derivations from them) – overcoming Platonism Heavy influence on Western thought!!!
2.2 Biological writings • Historia animalium (History of Animals) - see later • De partibus animalium (Parts of Animals) • De generatione animalium (Generation of Animals) • Smaller writings (On movement of animals, sleep and sleeplessness, breathing, life and death etc.) • Biggest part of his work is natural science! • Interestingly: little interest in medicine (son of a healer!) and botany
2.3 Aristotle’s method in biology Empirical (broad sense) with speculative assumptions Classification of phenomena plus question for causes (“4 causes”) Reports of “experts”, own observations Maybe: “experiments”, anatomical sections (stages of fertilized eggs) Only scarcely: quantification (lengths); not weights, food intake etc. Only scarcely: ecological view (what it eats) Aim:Collection/classification of facts (historía)and research forcauses
2.3 Aristotle’s method in biology Teleology without design: Natural things seen as functional units with functional parts Teleological world-picture: Chief pattern of explanation: final explanation, what is it good for? Example: why do animals with a lung also have a neck? De part.An.III,3 (Roughly): Bipartite lungs need some tube to partition the air; that tube needs a certain length, hence the windpipe. Hence also, the oesophagus/jednjak. Hence, the necessity of a neck. (Fish don’t need one). The vicinity of windpipe and oesophagus is technically bad and would cause trouble; hence, nature contrived the epiglottis. Nature as a whole is rational. Natura nihil facit frustra. Form follows function BUT: No external “design plans”.
2.4 Aristotle’s taxonomy • 550 species according to morphological criteria, 300 re-identifiable today • Groups and similarity observations: e.g., “all live-bearing quadrupeds have lungs and windpipes” • Attempts to a classification of the whole range of animals, morphological features; not always consistent and sometimes wrong • Man is included as a sub-class!
2.4 Aristotle’s taxonomy An example from HA IV 1, 524a3-20: “The octopus uses its tentacles both as feet and as hands; it draws in its food with the two that are placed over its mouth. The last of them, which is very sharp and is the only one which is whitish in colour and bifurcated at the tip—it is made so as to uncoil on the rhachis side (the rhachis being the smooth surface of the tentacle away from the suckers)—this one it uses in the act of copulation. In front of the sac and above the tentacles they have a hollow tube, by means of which they discharge from the sac any sea-water which may have come in while taking food into the mouth. The animal can move this tube to right and to left; it also discharges its “ink” through it. It swims obliquely in the direction of the so-called head, stretching out its feet; and by swimming in this way it can see forwards (since its eyes are on top), while its mouth is at the rear. So long as the animal is alive, the head is hard and as it were inflated. It takes hold of things and retains them with the underside of its tentacles, and the membrane between its feet is kept extended in its entirety. If it gets on to the sand, it can no longer retain its hold. […]”
Aristotle’s taxonomy (roughly): Animals with blood: (today: vertebrates) Live-bearing quadrupeds Egg-laying Quadrupeds Birds Fish Cetacea (sea mammals) Egg-laying footless (snakes) Live-bearing footless (vipers) Man Animals without blood: Cephalopods Molluscs Insects Crustaceans
2.5 The stability of species Fundamental for 2300 years. Minimal traces of evolutionary ideas? (1) “Libya always produces something new” (De gen.an. II,7): crossing of animal species at waterholes; reflection about the infertility of hybrids (2) Reflection about Empedocles’ (5.century BC) mythical explanation of the origin of life: plants first, then parts of animals, then animals, only the useful ones survived Aristotle: random combinations would not have survived (Phys. II, 8) (3) Knowledge about variation: not all animals conform to species, monstrosities, freak animals etc. (Not worrifying, just “freaks of nature”)
2.6 Astonishing pioneerhoods and errors Pioneerhoods: Sexual life of octopus Opposition to preformation theory / homunculus theory of the sperm (until 19th century!). “Epigenetic”, step by step, formation of organs – the important ones for the genus-membership first. Errors: Bison throws feces 7m for defense Women have less teeth Dayfly has only 4 legs Speculations: Parthenogenesis and other forms of reproduction Procreation (in mud etc.) – until Pasteur, 19th century! Brains serve to cool blood Women are incomplete men (more influence of katameria than of sperm) Women get soul later, birth rates m/f have to do with winds
3. Evolutionary ideas until Darwin • 3.1 Some aspects of biology after the middle ages • Renaissance: • Excursions, geograph. discoveries, herbaria, museums • flourishing of anatomy (Andreas Vesalius, Fabrica(1543; De humani corporis fabrica libri VIII); public section of corpses; previously unknown exactness; descent-line: apes – “pygmies” (Plinius!) – man) • 17th cent.: • new science of nature (Bacon, Galilei)Experiments (planned variation of conditions, protocols) • New tools of observation: microscope, telescope; discovery of micro-organisms, fine structures, insect development • “Physico-theology” & speculative preformationism (1695)(hot discussions 18th cent. (Spallanzani), end 1830!)
3.2 Carl von Linné’s taxonomy • Various attempts to classifications, morphology comes in focus (microscopes!) • Tension: Theory still Aristotelian (tree / pyramid), experienceshows multiplicity and similarities across branches • “Natural history” becomes a discipline of its own Carl von Linné (Linnaeus), 1707-1778; Swedish medic and botanist Reform of taxonomy, 3 merits: • Newsystem of plants, with classification method (according to number and structure of reproduction organs; “sexual system”)Systema naturae 1735; Genera plantarum 1737 etc. • Binary nomenclature (instead of descriptions), e.g. Sambucus nigra (sambucus = genus, sambucus nigra = species) • Terminology for the parts of plants
3.2 Carl von Linné’s taxonomy Backgrounds of Linné’s thought: Objective structures in nature, ideas of the divine creator. Not Aristotelian essentialism, but rather Enlightenment’s ideal of ordering Does classificatory relatedness imply anything about historical relatedness? Does the Systema point to a relation? - Linné understood it as an artificial system with the task of ordering/quick finding; “natural system” as final project at horizon. Growing discontent about Linné´s artificiality. - Some unclear remarks about an origin of plants - Controversial how firmly he believed in the stability of species
3.3 Early French speculations about evolution Georges Buffon (Histoire Naturelle, 36 vols., 1753-1788): • Complexity and similarities in nature make a Linnéan classification impossible. And: “species” is an abstractum; there are individuals • Procreation and change, by climate etc. Related species might have common ancestors, maybe one. Earth out of a collision sun-comet. • Evolutionary scale/ladder instead of Linné´s hierarchical classification • Evidence: similar anatomy across many species (donkey/horse, man/ape, man’s foot / horse’s foot etc.); rudimentary, useless organs • Indirect message: EITHER God made the species by variation of few plans (great!), OR they have a common history. (Officially, the first…)
3.3 Early French speculations about evolution Georges Cuvier (1769-1832), Étienne Geoffroy Saint-Hilaire (1772-1844) and the Paris Academy Dispute 1831: Idealist versus evolutionary morphology? Cuvier: “King of functional anatomy”, fine drawings, function determines structure, structure allows conjecture to function. “Reconstruction of died-out animals out of a few bones.” Four basic construction plans of animals Yet firm opposition to any evolutionary change (cats from Egypt, …) Fossils are just extinct species, in global/regional catastrophes. No “intermediate forms” in fossils Geoffroy St.Hilaire: Research in homologies (e.g. gill bones in fish – ear bones in humans; vertebrate is similar to inverted worm (nerves at back, intestinal at front). Hence, change of species, common ancestry. Political relevance: (1) not ideas of God (2) ...if not even nature is stable?
3.4 Romanticist Philosophy of Nature and Morphology Johann W. von Goethe (1749-1832): • “morphology” instead of “comparative anatomy”: plants and animals represent certain ideal shapes/forms/con-struction plans (mostly superficial, restricted to outer form) • speculations about construction plan of a “Urpflanze”(ideal plant) which is realized in variants in real plants • Postulates that skull bones are modified rib bones • Discovers the intermaxillary bone in human embryos: since humans represent general mammal plan, and all other mammals have it, it must be somewhere… - in embryonal development! “Göttingen School” (Carl Friedrich Kielmeyer, Johann Friedrich Meckel, Lorenz Oken, influenced by Fichte and Schelling): “Recapitulation”: Development of the embryo recapitulates animals of lower complexity • Partly empirical (embryology, anatomy), partly philosophical: “formative power” of nature etc.; idealist “great chain of beings”
3.4 Romanticist Philosophy of Nature and Morphology Richard Owen (1848): Theory of “archetypes” (ideal design plans). Background: similar organs in very different animals (mole’s hand & dolphin’s fin have same bones!) cannot be due to environment. Archetype of all vertebrates: Terminological proposal, used till today: Homologous organ: same construction, different function (e.g. mole’s hand, dolphin’s fin) Analogous organ: different construction, same function (e.g. bird’s and butterfly’s wing)
3.5 The first “evolutionary theory”: Lamarck 1809 Jean Baptiste de Lamarck (1744-1829): Philosophie zoologique (1809) • “Lamarckism” today: inheritance of individually acquired characteristics, usually seen as overcome since Darwin; partial revival today • First evolutionary theory: a theory that & how species change in the course of time. • Simple forms of life emerge constantly from anorganic matter, procreation; hence, no common ancestry • Inner tendency to higher development, “complexifying force”: le pouvoir de la vie • Organisms adust behaviour to environment and inner state • Use/disuse of organs leads to growth/change of organs (e.g. neck) • … andthat change is inherited! • As with Geoffroy St.Hilaire later: politically dangerous ideas…
3.5 The first “evolutionary theory”: Lamarck 1809 Jean Baptiste de Lamarck (1744-1829): Philosophie zoologique (1809) • “First Law: In every animal which has not passed the limit of its development, a more frequent and continuous use of any organ gradually strengthens, develops and enlarges that organ, and gives it a power proportional to the length of time it has been so used; while the permanent disuse of any organ imperceptibly weakens and deteriorates it, and progressively diminishes its functional capacity, until it finally disappears.” • “Second Law: All the acquisitions or losses wrought by nature on individuals, through the influence of the environment in which their race has long been placed, and hence through the influence of the predominant use or permanent disuse of any organ; all these are preserved by reproduction to the new individuals which arise, provided that the acquired modifications are common to both sexes, or at least to the individuals which produce the young.”
3.6 Erasmus Darwin (1731-1802) and a widely forgotten Anonymous: Robert Chambers (1844) Erasmus Darwin (grandfather of Charles Darwin and Francis Galton) Speculative views about Lamarck-style evolution: “Would it be too bold to imagine, that in the great length of time, since the earth began to exist, perhaps millions of ages before the commencement of the history of mankind, would it be too bold to imagine, that all warm-blooded animals have arisen from one living filament, which the great first cause endued with animality, with the power of acquiring new parts, attended with new propensities, directed by irritations, sensations, volitions, and associations; and thus possessing the faculty of continuing to improve by its own inherent activity, and of delivering down those improvements by generation to its posterity, world without end!” Glimpse of natural selection [R. Chambers] Vestiges of the Natural History of Creation (1844) Popular science book, rather speculative, many errors • Author: Robert Chambers, Scotch writer, anonymous • Variability of species; Man descends from simpler forms of life • Popularity and (slowly starting) excitement
4. History of evolutionary thought from Darwin to the present 4.1 Charles Darwin (1809-1882) – life and works Son of a religion-skeptic physician & unitarian Studies briefly medicine, natural history, theology; future: parson? No professional education as a scientist (biology not yet established!) Invitation to travel on mapping-ship Beagle 1831-36 Collects, studies, draws, sendssamples home Initially only few doubts about stability of species Influences: Charles Lyell (geologist, big changesof the earth surface; but rejectsLamarckism; species are created;they die out due to external change, and suppression by other species) Richard Owen and Romantics Erasmus Darwin Lamarck (via Robert E. Grant!)
Increasing doubts in Lyell’s biology (not in his geology!): • released domestic animals adapt quickly to new environment • two similar ostrich species in overlapping areas (why does the one not repress the other one?) • why do species dies out without change in environment? • why are died-out mammals replaced by other, similar ones? • the finches from the Galapagos islands: - related with each other, related with animals on the continent, - different birds in similar habitats!- No clear-cut line “species” - “variety”
Back in Cambridge • Orders his findings, discusses (with Lyell, Owen, J. Gould (finches!))… • Early speculations about an explanation for relations • 1837: first sketch “I think”, insight that species must be changeable Darwin’s speculations still +/- Lamarckist:- changes/variations are always useful, since- adaptation to environment as an embryo, geograph. isolation may cause new species - changes are inheritable • 1838: reads Thomas Malthus: Essay on the Principle of PopulationPopulations have tendency to grow infinitely, but limited resources cause concurrence and limit growth, • Darwin: Selection not as embryo, but after birth. Theory of natural selection was +/- finished by 1839 (diaries).
The Theory of Natural Selection • Random, undirected, inheritable variations PLUS • natural selection under the pressure of the environment, concurrence for food etc. … • … may in the long run lead to the emergence of adaptive (=useful) change and new species. • I.e., variations need not be perfect anymore. Old idea of perfect adaptation (from natural theology!) abandoned. Variations need just be slightly better. • A manuscript was finished by 1842. Why not published? (1) Fear of scandal (Vestiges 1844!)? (2) Darwin had not yet a good idea for the ramifications / divergences in the changes. • After 1854: Sympatry (different species in same area) is more important than Allopatry (different species in isolated areas). Coherent with the facts. Reason: Big areas have more ecological niches!
The Publication and its effects 1856 Darwin presents his ideas to Lyell etc., friends urge to publish 1858 Alfred Russel Wallace sends a manuscript to Darwin, similar ideas 1858 Common paper by Darwin and Wallace, Wallace admits priority 1859 On the Origin of Species by Means of Natural Selection Public effect: In England dampened by a theol. discussion aboutcorrect Bible interpretation 1860, and Vestiges John Herschel (astronomer, 1792-1871): unscien-tific, since only statistical Thomas Huxley (“Darwin’s Bulldog”) tries to elicitcultural discussion, free universities, no religion Not even whole church opposes. Still: excitement. In France Cuvier dominates, no big interest In Germany: bestseller, quick translation, popularizedby Ernst Haeckel (materialist reading!)
Later Publications 1871 The Descent of Man (no big scandal; evolution of moral behavior) 1872 The Expression of Emotions in Animals and Man Works about coral reefs, plant fertilisation, rainworms, etc. Darwin and religion: 1851 Death of his daughter, loss of religious faith, respectful agnostic 1882 Tomb in Westminster Abbey
4.2 The Five Basic Tenets of Darwin’s Darwinism (E. Mayr) • Evolution: species come and go through time, and while they exist they change. (But: the real bearer of evolution is the individual, not the species!) • Common descent • Species multiply: the diversification of life involves populations of one species diverging until they become separate species • Gradualism: evolutionary change occurs through incremental small steps; new species are not created suddenly. • Natural selection: some variants change individual’s survival & reproduction probability. • Against Lyell: species are not stable; not perfectly adapted to environment; species are not created quickly (Lyell was a theory of species sequence, not of species evolution!) • Against Lamarck: individual changes are not inherited; common descent
4.3 Darwin’s Speculations about the biological fundament • Notabene: Darwin had no idea about the place and nature of genetic information, laws of inheritance (Mendel’s rules etc.) • Theory of Pangenesis: all cells produce little “gemmulae” (little buds), they gather in reproduction organs. In the young they mix • = a Lamarckist remainder in Darwin! • Still even in 1868 (book on selective breeding of animals and plants). Soft inheritance, acquired traits are passed on.
4.4 Some open questions in Darwin • Small steps or jumps? (Is mutation or selection the more important driving force of evolution?) • Why sudden speeding up of evolutionary change, rapid growth of species numbers in certain stages of earth history (“Cambrian explosion” etc.) • No real theory about inheritance, similarity and variability • Why is there life at all? No procreation (no conflict with Pasteur 1859); maybe 4 or 5 original forms of life. Reference to creator more courtesy? • Speculation about the warm little pond (letter to Hooker 1871): “But if (and Oh! What a big if!) we could conceive in some warm little pond, with all sorts of ammonia and phosphoric salts, light, heat, electricity etc, present, that a protein compound was chemically formed ready to undergo still more complex changes...” • Similarity to Miller-Urey experiment 1953, “primordial soup” …
4.5 Ernst Haeckel (1834-1919): Materialism with idealist traces • Great graphic illustrator, popularizer in Germany • Materialist (Darwinism as anti-religious and anti-conservative program!) • Yet: some idealist remainders, idea of dynamics of growing complexity: • takes on recapitulation-idea of Kielmeyer • Creates terms, and “biogenetic fundamental law”: “ontogeny” repeats “phylogeny” • Evolutionary morphology: similarity of gastrula stage; speculation to a “Gastrea” as common ancestor “tree of life” suggests height of development, dynamics to complexity. (false: successful simple organisms, backward-developments)
4.6 Francis Galton (1822-1911): Evolution becomes statistical • Cousin of Darwin, multidisciplinary scientist: statistics, fingerprints, efficacy of prayer, questionnaire, blood-transfusion, eugenics • Experiments against Darwin’s “gemmulae” • semi-lamarckian speculative theory of inheritance • Important: Separation Organism – genetic information (“stirp”). Organism is just a representative selection from stirp, like a parliament • Inheritance becomes statistical matter, every parent contributes ½ • Variation is now a matter of the population (not the organism, not the species!). New subject of evolution. Farewell to Aristotelian ideas. • Beginning of theoretical biology as a mathematicised discipline!
4.7 August Weismann (1834-1914): The organism as mere vehicle of genetic information • Radical materialist • Similar to Galton, but with more empirical justification: experiments with sea urchins (ježinac): germ cells are separated from the rest of the organism in very early stage • Separation germ cells – somatic cells • Half-speculative theory of “immortal germ plasm”. • Revolutionary: genetic info isthe bearer of variation, notthe organism; only “vehicle” • Separation: growth/reproduct. • “Lamarck finally dead” • Cf. Dawkins’ Selfish Gene !!
4.8 Gregor Mendel (1822-1884) The first robust theory of inheritance OSA monk and abbot in Brno (CZ). Experiments with peas etc., publication 1865 in Austrian Journal, no reception. Only from 1900! Question in those times: Does evolution go uniformly or in jumps? Darwin: (Newton’s ideal! Natura non facit saltus!): uniformly Huxley, Galton: undirected, small mutations / variations BUT: such undirected small changes can cause no big changes, since statistics equalizes their effect. Statistical samples tend to average. Hence, there must be other factors, Mutation must be more important. Mendel’s method: reduction to only few (Y/N, not gradual) features, quantification (counting) Experiments with crossing of peas and beans; features: white/lilac flowers; white/red/pink flowers, smooth/wrinkled seed. Result: Mendel’s rules
4.8 Gregor Mendel (1822-1884) The first robust theory of inheritance Mendel’s first law (+ some more) Presumptions: unmixable, discrete factors of inheritance mutation more important than selection, bigger jumps are possible But: biometry, statistics show continuous slow change. How can this possibly be harmonized? “Great crisis of Darwinism” in early 20th century!
4.9 The Molecular Revolution in Evolutionary Biology End of 19th century: discovery of chromosomes in cell nucleus 1903/04 Sutton/Boveri: genetic info stored in chromosomes 1910 Johannsen: Terminology “Genotype” (inner constitution, info) “Phenotype” (appearance); Genotype Phenotype! The genotype is inherited, not directly the features!! After 1909 Drosophila experiments (quick reproduction, only 4x2 chromos.) Beginning of localisation of genetic info on chromosomes (chemistry still unknown till 1953!) Insights: - some features controlled by more than one gene - there are interactions between genes - one gene can influence more than one feature HENCE: 1:1-matching “genes features” false since early 20th century! “genetic blueprint” metaphor likewise wrong (still it is around…)
4.9 The Molecular Revolution in Evolutionary Biology 1953 Watson/Crick: Discovery of double-helix structure of desoxyribonucleic acid (DNA) Since mid-1960: Mechanisms of gene expression (DNA – RNA – proteine synthesis) begin to be clarified “Human genome project” 1990-2003 Mind the correct way of speaking: “Sequencing the genome”. (Not: “decoding the genetic code” – fallback to blueprint model!)
4.10 The “Modern Synthesis” (1920s, 1930s onwards) Darwinism had no undisturbed victorious career; no uniform development of post-Darwinist biology. Especially Mendel’s genetic discoveries caused worries: quick changes, “either/or” are possible. Mutation is more important! Darwin’s intuition: small, incremental steps, selection is more important “The great crisis of Darwinism” / “Eclipse of Darwinism” (J.Huxley 1942) Late 19th/ early 20th century: all 5 tenets of Darwin come under doubt, many biologists step back to older theories, partly speculative. Extension of population genetics (Ronald Fisher, Sewall Wright, John B. S. Haldane): Complex mathematical models to combine Mendel & Darwin Some ideas from population genetics: • On genotype level Mendelian jumps, on phenotype level only small Darwinian changes: since features often depend on many genes! • Population (not individuals) as the unit of evolution, statistics equalize: in some individuals Mendelian jumps, in population slow Darwinian shift • The smaller a population, the easier are big jumps possible.
4.10 The “Modern Synthesis” % Theodosius Dobzhansky, Ernst Mayr and others: “The Modern Synthesis”, “Synthetic Biology of Evolution”… …connects: Darwinian core idea (stepwise evolution, selection) Mendelian genetics Population genetics Biometry Microbiology Biochemistry Behavioral science Paleontology Geology etc.
4.11 Some special ingredients of the Modern Synthesis Genetic drift / bottleneck / founder effect (A non-adaptive effect, against pan-selectionism!) Punctuated equilibrium (Eldredge/Gould) Various explanations of stages of stasis and rapid evolutionary change; allopatric origin of species (related with genetic drift) Neutralism (Kimura):many big changes in DNA come and go, without being tested by selection, neutral changes possible %
4.11 Some special ingredients of the Modern Synthesis % Cooperation between genes; “Regulator genes”, governing the expression of other genes, “genetic switches”. E.g. Hox genes, regulate development of legs, antennas etc. mutations in such genes may have big effects! “Evo-Devo” (Evolutionary developmental biology): • similarities in the genotype are astonishingly high across species, but • phenotypes differ dramatically! • Hence: genes in themselves are not so important • Hence: difference must lie in the expression of the genes, development of the organism, regulator genes etc. • Evolutionary biology in the past took adult organism (and populations out of them) as subject to natural selection, • EvoDevo takes the whole process/cycle of development of an organism as the subject of natural selection.
5. Evolution: Theory-structures and concepts 5.1 Theory-structure of EB Physics, chemistry etc.: law-like explanations, able to prediction false predictions a part of falsification Evolutionary biology admits of (almost) no interesting predictions Herschel: “un-scientific”, mere statistical relations (young) Popper: unfalsifiable tenets like “the survival of the fittest”, circular. Partial answer: (1) Parts of explanations admit of predictions (cell level etc.) Some few experiments with bacteria admit of prediction even of “direction of evolution” on macro-level: in lactose solution, bacteria with mutation develop genes to process lactose (2) Why decreeing that all “scientific” explanation must resemble physics?
5.2 Is EB a “science”? Not a science like physics; combination of natural & historical disc. Rather: a scientific research program, uniting many disciplines Criteria by Philip Kitcher (The Advancement of Science, 1993) A scientific practice… • Investigates an accepted domain of objects • Investigates accepted problems and questions • Has a non-natural technical terminology • Has commonly shared convictions at its basis • Applies accepted means and methods • Has accepted standards on aim and success of the investigations • Has accepted standards how to accepts results from other sciences • Is part of a social network Evolution biology scores excellently under most criteria!
5.3 The bearers / objects of evolution Individuals / organisms? Species? Populations? Genetic information? Life-cycles? …different metaphysical views on objects of biology! 5.4 What are the traits / characteristics / features tested by evolution? a) only bodily features (shape, food tolerances, …) or also behavior? Dawkins: “the extended phenotype” (including behavior) is being tested! b) “Adaptive” traits (with a success story) – “maladaptive” traits – “by-products” c) Is every feature adaptive? Panselectionism. (But: what is a feature??) d) Beware of a frequent misunderstanding concerning “success story of trait”: - not the trait makes its success story (the trait is not there from beginning!) - rather: ex post, we see a success story of the trait and its previous traits (evolution does “bricolage” with available traits!). No “trait essentialism”
5.5 Misunderstandings “Survival of the fittest”: - Can be incremental; need not be perfect - need not be “the strongest/biggest/…” “Struggle for life”: - is not intra-population struggle - need not be fight with similar species - just general struggle with the ecological conditions: food, climate, safety, nesting-places… 5.6 “Genes” (… an unsettled debate! “by the genes” is no explanation!) “place on the chromosome”? – surely to imprecise “sequence on the DNA” (concrete gene)? – things are more complicated: are “regulated /switched-on” genes really genes? Coding/non-coding DNA? Some DNA sequences are “read” more than once, some corres-pond to more than one proteine? Beginning/end sometimes unclear, … “whatever makes a difference in fitness” (abstract, functional gene)? – may come close to antirealism concerning gene & genetic info.
6. “Evolution” between science and world-view 6.1 Overview SCIENCE: Darwin’s (historical) Darwinism “Darwinism” Synthetic theory of Evolution (1940 onwards) Current EB (“New synthesis”, “EvoDevo”, …) CONTROVERSIAL: Pan-Selectionism Sociobiology “Cultural Evolution”, “Memetics” NON-SCIENCE: Social Darwinism Pop-Darwinist Slogans
6.2 Pan-Selectionism Sometimes also: “strict neo-Darwinism”, “Darwinist orthodoxy” (Terminology seems not to be entirely fixed) • Thesis: natural selection is the driving force of evolution; every feature has an “evolutionary success story” behind it • Tendency to a deterministic account of the world and the human being: evolutionary successful features are +/- “hard-wired”, that includes also our mind, our reactions, etc. • Critical evaluation: empirically unplausible in the light of modern genetics • Ironically: a remainder of old “perfect adaptation” ideas (natural theology)
6.3 Sociobiology • Extension of evolutionary explanations also to our behavior, moral beliefs etc. • First visions already in Darwin: “moral tribes” might be more successful • Example1: why is altruism evolutionary successful? • At first glimpse: not at all. Risk your life, lose eating-time etc. • Example “whistle-blowing” birds • But kin-selection /group-selection (E.O. Wilson, Sociobiology 1975): brothers/sisters have 50% same genetic info, cousins 25%, … saving the life of, e.g., 5 cousins by whistle-blowing (and sacrifying own life!) increases the survival of own genetic info! 125 - 100= +25% • Example 2: why are moral norms evolutionary useful?An economic way to secure cooperation of group members, internal/mental control instead of expensive external forces • Critical evaluation: Empirically: unclear evidence • Manifold cultural shapings of behavior, limit natural/cultural unclear • Sociobiol. is no exclusive explanation (“altruism is nothing butxy…”)
