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Two kinds of evolutionary thinking


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Two kinds of evolutionary thinking

  1. 1. Two kinds of evolutionarythinkingDarwinism and Lamarckism
  2. 2. John WilkinsMay 22, 2013Some quotes“Evolution is so simple, almost anyonecan misunderstand it” – David Hull“Natural Selection is not Evolution ” –Ronald A Fisher“Nothing in biology makes senseexcept in the light of evolution” –Theodosius Dobzhansky
  3. 3. John WilkinsMay 22, 2013Star Trek Evolution Why is it sopopular? Where doesthis idea comefrom? What shouldwe think aboutevolution?
  4. 4. John WilkinsMay 22, 2013The popular version Grades Direction Perfection Steady Humans are the goal
  5. 5. John WilkinsMay 22, 2013The scientific version Branches Randomness + selection Irregular No direction but locally Humans are one animal amongmany
  6. 6. John WilkinsMay 22, 2013Names The popular version is called many things: Great chain of being Ladder of progress Lamarckism The scientific version is also called manythings: Darwinism Neo-Darwinism The Modern Synthesis
  7. 7. John WilkinsMay 22, 2013Progress Depends on the “target” Jacob’s Ladder - God at the top,something ugly at the bottom Evolution has always been thoughtto be progressive Until Darwin (and even then)
  8. 8. John WilkinsMay 22, 2013There are two kinds ofevolution The one Lamarck developed andmade known. The one Charles Darwin developedand made known Only Darwin’s is truly novel, and yetit is the least well known, and so ittakes the longest to really “get”.
  9. 9. John WilkinsMay 22, 2013Before evolution Western thinking was historicalbecause of Christian theology, butchange tended to a goal Everything was ranked from lowestto highest Higher things were “more perfect”than lower things
  10. 10. John WilkinsMay 22, 2013The medieval viewStones … mere beingFire … + motionPlants … + growthAnimals … + senseMan … + reasonHeaven … + incorruptibilityAngels … + knowledge of goodGod … with the lot + perfectionRaymond Lull, 1512
  11. 11. John WilkinsMay 22, 2013The chain was also moralBovillus 1510
  12. 12. John WilkinsMay 22, 2013Great chain of being A view that goes back to the Greeks Everything is lined up along a scale Made into a time series in the 17thand 18th centuries Lamarck one of the firstevolutionists, and followed thisview
  13. 13. John WilkinsMay 22, 2013Three “Lamarckisms” That changes to individualorganisms are likely to be inheritedor will affect the hereditability oftraits. That things evolve on apreprogrammed pathway toperfection That change is predictive of theneeds (or wants) of organisms
  14. 14. John WilkinsMay 22, 2013Lamarck’s scale from lower tohigher At first a single scale Later, two, one for invertebrates,one for vertebrates Each “species” underwent changeup the scale
  15. 15. John WilkinsMay 22, 2013Lamarck’s view of evolution
  16. 16. John WilkinsMay 22, 2013Spontaneous generation Lamarck accepted the constantgeneration of living things in theirsimplest form, from the non-living Each new spontaneous generationstarted a lineage Each lineage would evolve through thesame stages as the earlier ones had Later, he allowed for some branching
  17. 17. John WilkinsMay 22, 2013Lamarck’s view of evolution 2
  18. 18. John WilkinsMay 22, 2013Bees and brains “It is absurd to talk of one animal beinghigher than another – We consider thosewhere the cerebral structures intellectualfaculties most developed, as highest. – Abee doubtless would where the instinctswere.” Charles Darwin, Notebook B “Never say ‘higher’ or ‘lower’” Darwin What about the flowers? What would theysay?
  19. 19. John WilkinsMay 22, 2013Darwin’s view Things get better locally, not globally Being “fitter” is a matter of being able to dowell then and there only Populations, not whole species, evolve Evolution branches all the time Everything has evolved as much aseverything else!
  20. 20. John WilkinsMay 22, 2013Branching evolutionNo real progress here
  21. 21. John WilkinsMay 22, 2013The origin of species
  22. 22. John WilkinsMay 22, 2013The tree of life is a coral tree
  23. 23. John WilkinsMay 22, 2013Darwin used the tree metaphor This, too could be misused Although Darwin’s tree was notdirectional at first, others came tobe
  24. 24. John WilkinsMay 22, 2013Haeckel’smightyoaksCentral trunk leadsdirectly to humans,and everything onthe trunk issomehow“important”
  25. 25. John WilkinsMay 22, 2013IndirectprogressionismPatten (1925) makes adirect line througharthropods (bugs) tovertebrates (non-bugs)
  26. 26. John WilkinsMay 22, 2013Indirect racismNotice how the earlier (and“less evolved”) forms areshown at the left of thediagram. Now notice the“races” of Homo - in order,African (i.e., the “Negro”),Australian (aboriginal),Mongolian (the “Asiatic”),and of course theEuropean.Diagram c1920. There wasno geological evidence atthe time (or now) of any ofthis.
  27. 27. John WilkinsMay 22, 2013Direct racism (1799)
  28. 28. John WilkinsMay 22, 2013Intelligence stillat the top of thechain…Despite the divergence ofevolution until now, Teilhard(1955) still thinks that it willall come together with humansas the final players. At least heisn’t racist about it – all“socialised” humans will evolveto the Omega Point.
  29. 29. John WilkinsMay 22, 2013Missing links and ancestors
  30. 30. John WilkinsMay 22, 2013Missing links and ancestors
  31. 31. John WilkinsMay 22, 2013Any ancestors at all? We cannot be sure that a fossil orliving species is actually anancestor Might be a sibling of the ancestor Might be the ancestor, but how totell? At best, we have likelihoods
  32. 32. John WilkinsMay 22, 2013Populations All evolution happens topopulations Not individuals (that’s “development”) Not entire species (that’s“speciation”) Not larger groups (that’s artificial)
  33. 33. John WilkinsMay 22, 2013Natural selection Does not equal “evolution” Is the process of adaptation (ofpopulations) Is not all that happens in evolution(that’s called “panadaptationism”)
  34. 34. John WilkinsMay 22, 2013SelectionFollows the fitnesspeaks (available ways tomake a living).They have to bereachable, and theyhave to be better thanwhat is already in place.Changes the frequencyof genes in populations.
  35. 35. John WilkinsMay 22, 2013Lessons to be learned Progress is not necessary There is no “next step” Selection is not all there is toevolution Everything is as evolved aseverything else
  36. 36. John WilkinsMay 22, 2013Further reading Bowler, Peter J. Evolution: The History of an Idea. Berkeley:University of California Press, 1984. Dennett, Daniel C. Darwin’s Dangerous Idea: Evolution and theMeanings of Life. New York: Simon and Schuster, 1995. Jordanova, L. J. Lamarck, Past Masters. Oxford; New York:Oxford University Press, 1984. Lovejoy, Arthur O. The Great Chain Chain of Being: A Study ofthe History of an Idea. Cambridge, Mass.: Harvard UniversityPress, 1964 (1936).