Notes on Michael Ruse: The Darwinian Revolution

Kevin T. Kelly

Department of Philosophy

Carnegie Mellon University

Chapter 7: The Origin of Species

Charles Darwin's chronology:

• 1809 Born
• 1828-31 Cambridge. Biblical fundamentalist.
• 1831-36 Beagle
• 1837 Conversion to evolutionism
• 1838 Natural selection mechanism
• 1842 Sketch of theory
• 1844 Expanded essay; shown to Hooker
• 1845-1855 Tomes on barnacles. Evolution concealed.
• 1855 Began massive work on natural selection and evolution.
• Interrupted by Wallace's essay. Published short tracts.
• 1859 Origin of Species published.

Development of Natural Selection theory

• Grandfather Erasmus Darwin's Zoonomia (late 18th c.)
• Anticipated Lamarck.
• Common ancestor instead of constant spontaneous generation.
• Edinburgh
• Discussed with Lamarckian Robert Grant at Edinburgh.
• Lectures by Robert Jameson, Cuvier's British editor.
• Cambridge:
• Tension over religion vs. science. Pressure on even Sedgwick and Whewell from the right.
• Herschell's philosophy of science.
• Lyell on Beagle Voyage:
• 1831, Read Lyell and converted to uniformitarianism.
• 1832, read volume II on origins debate.
• Lyell on origins:
• Struggle for existence constant.
• Extinction occurs.
• Origins of species dynamic and continuous to maintain steady state.
• Mechanism lawlike: neither creation nor evolution.
• Three Lyellian anomalies observed on Beagle voyage:
• Pampean extinct armadillo resembles extant species.
• Similar organisms replace each other southward in South America.
• Galapagos organisms have similar species of finches and tortoises similar to South American forms.
• 1837 Journal of Beagle Voyage:
• John Gould: Galapagos finches are genuine species.
• Only explanation: lawlike evolution from single parent stock.
• Saltative evolution: follows Lyell's view that intermediate forms would perish.
• 1837: First notebook on speciation.
• Gradual evolution:
• New isolated regions protect intermediate forms.
• Constant geological changes in these isolated regions drive adaptive changes in organisms.
• Extinction is failure to adapt to changing circumstances.
• Branching and extinction causes gaps between current species ("coral of life").
• Evolution must explain fossil record.
• 1838 Second notebook on speciation.
• First notebook didn't explain adaptation of isolated individuals.
• Spring 1838: Lamarckian inheritance of habits.
• But eye doesn't seem to result from habit. Intermediate steps are a great mystery.
• Summer 1838: Reads breeding pamphlets of John Wilkinson and Sir John Sebright to understand variation and inheritance.
• Sebright (1809): "A severe winter... by destroying the weak and the unhealthy, has all the good effects of the most skilful selection".
• According to breeding theory, not all members of a population are the same.
• Darwin still prefers habit-based Lamarckism.
• September 1838: Reads Thomas Malthus: food supply increases arithmetically, population increases geometrically.
• Struggle of existence is mathematically describable force driving natural selection.
• Darwin: "One may say there is a force like a hundred thousand wedges trying to force every kind of adapted structureinto the gaps in the economy of nature. or rather forming gaps by thrusting out weaker ones."
• Evolution through natural selection: Malthusian struggle for existence among members of the same species leads to natural selection of the fittest.
• 1838, Dec. Rereads Herschell's Discourse and Whewell's History.
• Strives to satisfy both concepts of vera causa.
• Herschell's actualist vera causa:
• Change through artificial selection is observed.
• Malthusian struggle is observed.
• Studied more on breeding. Family connections: pigeon breeding in Father's family, sheep breeding in Mother's.
• Development of analogy leads to discovery of sexual selection.
• Whewell's consilience conception of vera causa:
• Special creation explains nothing further, natural selection unifies phenomena in behavior, paleontology, biogeography, anatomy, embryology,....
• Darwin: "Absolute knowledge that species die and other replace them. Two hypotheses: fresh creations is mere assumption, it explailns nothing futher; points gained if any facts are connected."
• 1842 Preliminary sketch, 1844 Expanded essay (230 pgs.)
• Very similar to Origin:
• Domestic selection
• Struggle
• Natural selection.
• Mechanism of selection
• Explanations of phenomena in behavior, paleontology, biogeography, anatomy, embryology.
• Religion (tedious, pedestrian discussion)
• Revealed
• Fundamentalist at Cambridge.
• Miracles crucial (studied Paley at Cambridge).
• Lyell's lawlike geology undermines his faith on Beagle voyage.
• Deist during construction of theory.
• After discovery of natural selection Man is no longer special.
• Fuegians reminded him of orangutans.
• Family ties:
• Grandfather Erasmus was weak deist and evolutionist.
• Father was atheist.
• Uncle Wedgwood was Unitarian.
• Older brother Erasmus was atheist by Darwin's return from Beagle.
• Professional friends:
• Babbage: rule of law.
• Carlyle (friend of Erasmus): natural supernaturalism, all nature is equally exalted
• Natural:
• Studied Paley at Cambridge.
• 1830's adaptation produced by law.
• God as farmer
• Adaptation not perfect
• No adaptation of one species for another.
• Finally, natural selection makes God's design irrelevant.
• Mystery: non-publication of Essay.
• Huxley's story:
• Darwin showed Essay to Hooker.
• Hooker not convinced.
• Hooker recommends studies inbiology.
• Darwin studied barnacles to deepen understanding of natual selection.
• Unlikely.
• Little change between Essay and Origin.
• Darwin hungry to publish everything.
• More likely: concern with professional reception of evolutionism.
• Reception of Vestiges in same year Essay was finished.
• Told Hooker admitting evolutionism was like admitting murder.
• First had to assemble a new scientific community around himself.
• Barnacle study took longer than expected.
• 1845-1855 Barnacle work:
• Beautiful adaptation of shell and feeding organs.
• Wide variation of each character.
• Difficult to discern boundaries of species.
• Emphasis on embryological form in classification (contra Owen). For Darwin, barnacles were crustaceans, since they are mobile prior to metamorphosis.
• Study of archetype (a.k.a. common ancestor).
• Critique of serial homology.
• Two phenomena suggesting evolution:
• Stalk is modified ovarian tube and cement is modified ova.
• Sexual variations: hermaphrodites, tiny males, two sexes. Darwin suspected hermaphrodites were earliest and two sexes result from disuse of organs. Truth is reverse.
• Assumed on evolutionary grounds that little males could not be parasites because there are places for the males and no species accommodates parasites in the struggle for existence.
• 1856-1858: Begins colossal opus on evolution.
• 1858: interrupted by Wallace's paper. Origin written in one year.
• 1859: Origin of Species
• Variation under Domestication: domestic varieties arise from selection and use/disuse.
• Variation under Nature: argues with confidence for individual variations in nature, partly based on barnacle work.
• Struggle for Existence: High birth rate produces struggle for existence.
• Natural Selection: Struggle leads to retention of favorable variations.
• Sexual selection (female preference, male combat).
• Geographical isolation nolonger crucial: isolated populations might be too small to contain sufficient variation.
• Principle of divergence: occupying a new places in nature aids survival, providing a cause for branching of the "tree of life".
• Laws of Variation:
• Blind: physical causes operating on reproductive system.
• Use/disuse (wingless birds).
• Difficulties:
• Absence of transitional forms:
• Transitional form is wedged between niches of main forms.
• Can't compete, so numbers remain small.
• Small group likely to go extinct because it has insufficient variability to meet new challenges.
• Eye: articulata have simple and complex eyes. Focus not perfect in even the best eyes.
• Instinct: Instincts are adaptive and subject to natural selection.
• Hybridism: slippery slope between fertility and sterility, so species/variety distinction is unsound. Sterility is incidental; not fashioned by natural selection.
• On the Imperfection of the Geological Record: Prima facie problems.
• Inadequate time: Is too! Denudation of the Sussex Weald: 300 millioin years for sea to wear down a cliff.
• Gaps:
• Record incomplete.
• Speciation occurs most rapidly during epochs of elevation (new islands). But then fossils are not being deposited.
• Emergence of life fully developed in early Silurian: Pre-Silurian life was on continents that are now under the seas and the pressure of the sea metamorphosed all the fossils.
• On the Geological Succession of Organic Beings: Parallel developments, progress only along branches.
• Geographical Distribution: Strongest cards.
• Parallel climates in old and new worlds have different animals.
• In South America, similar animals up and down.
• Different forms across barriers. Similar forms with no barriers.
• Galapagos species more similar than any are to mainland species.
• All explained by evolution of species and mechanisms of distribution.
• Morphology, Embryology, Rudimentary Organs:
• Taxonomy and homologies: due to common descent.
• Embryology: Less selective pressure on immature forms in womb, so they resemble ancestral type more.
• Rudimentary organs: retained by descent; probably due to disuse rather than to natural selection.
• Recapitulation and Conclusion: Theory applies to man.
• Darwin's theory arose from Lyellian paradigm, not earlier evolutionism.