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From the Biological World to Statistical Theories: Nineteenth-Century Lessons for Twenty-First-Century Philosophy of Biology

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An effort to connect some contributions from W.F.R. Weldon to a contemporary debate over causation in evolution.

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From the Biological World to Statistical Theories: Nineteenth-Century Lessons for Twenty-First-Century Philosophy of Biology

  1. 1. Inference and Statistics in Biometry ISHPSSB 2019, 10.7.2019 Charles H. Pence @pencechp • @pencelab
  2. 2. Outline 1. The structure of evolutionary theory 2. The theory-world relationship, 1890–1930 2.1 Early Weldon 2.2 Late Weldon 2.3 Why the change? 3. How to move forward? The take-home: The contemporary debate over the causal structure of evolution has been with us since the 1890s, and it’s time to approach it from new directions! Charles H. Pence 2 / 28
  3. 3. The Structure of Evolutionary Theory Charles H. Pence The Structure of Evolutionary Theory 3 / 28
  4. 4. trait fitnesses population change predict, explain Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  5. 5. trait fitnesses population change predict, explain individual propensities to survive and reproduce lineage structure change predict, explain Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  6. 6. trait fitnesses population change predict, explain individual propensities to survive and reproduce lineage structure change predict, explain ??? Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  7. 7. trait fitnesses population change predict, explain individual propensities to survive and reproduce lineage structure change predict, explain ??? !!! Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  8. 8. trait fitnesses population change predict, explain individual propensities to survive and reproduce lineage structure change predict, explain ??? !!! ?!? Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  9. 9. trait fitnesses population change predict, explain (how??!) individual propensities to survive and reproduce lineage structure change predict, explain (how??!) ??? !!! ?!? Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  10. 10. trait fitnesses population change predict, explain (analytic) individual propensities to survive and reproduce lineage structure change predict, explain explanatory irrelevance Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  11. 11. trait fitnesses population change predict, explain (causal?) individual propensities to survive and reproduce lineage structure change predict, explain (causal?) causation or supervenience definitional connection Charles H. Pence The Structure of Evolutionary Theory 4 / 28
  12. 12. Statistical Theories and Biological Facts Charles H. Pence Theories and the World 5 / 28
  13. 13. W.F.R. Weldon (1860–1906) Charles H. Pence Theories and the World 6 / 28
  14. 14. Early Weldon: No Connections Required! Charles H. Pence Theories and the World 7 / 28
  15. 15. Charles H. Pence Theories and the World 8 / 28
  16. 16. before we can properly estimate the changes at present going on in a race or species we must know accurately (a) the percentage of animals which exhibit a given amount of abnormality with regard to a particular character; (b) the degree of abnormality of other organs which accompanies a given abnormality of one; (c) the difference between the death rate per cent. in animals of different degrees of abnormality with respect to any organ; (d) the abnormality of offspring in terms of the abnormality of parents, and vice versâ. (Weldon 1893, 329) Charles H. Pence Theories and the World 9 / 28
  17. 17. These are all the data which are necessary, in order to determine the direction and rate of evolution; and they may be obtained without introducing any theory of the physiological function of the organs investigated. The advantage of eliminating from the problem of evolution ideas which must often, from the nature of the case, rest chiefly upon guess-work, need hardly be insisted upon. (Weldon 1895b, 379) Charles H. Pence Theories and the World 10 / 28
  18. 18. Middle Weldon: Connections Important, Not Required Charles H. Pence Theories and the World 11 / 28
  19. 19. A diminution in the frequency of abnormal frontal breadth, with increasing size of crabs, might be due either to a selective destruction of abnormal crabs during growth, or to a modification of these crabs, by which abnormal individuals lose their abnormality as they grow. In order to decided which of these imaginative hypotheses should be adopted, I have spent a great part of the last two years in ascertaining the law of growth of crabs... (Weldon 1896a, 413) Charles H. Pence Theories and the World 12 / 28
  20. 20. Charles H. Pence Theories and the World 13 / 28
  21. 21. A complete knowledge of the processes associated with this relation between frontal breadth and death-rate is a thing of very great interest, and I believe, as firmly as Prof. Lankester, that every effort should be made to attain to it; but, desirable as it is, it is still not necessary in order to know that a crab’s chance of living and breeding may be known by measuring its frontal breadth. It is not necessary in order that the change in mean frontal breadth may be measured from generation to generation, and the direction and rate of evolution by this means ascertained. (Weldon 1896a, 413) Charles H. Pence Theories and the World 14 / 28
  22. 22. Late Weldon: Connections Vital Charles H. Pence Theories and the World 15 / 28
  23. 23. I see no escape from the conclusion that we have here a case of Natural Selection acting with great rapidity because of the rapidity with which the conditions of life are changing. (Weldon 1898, 899-900) Charles H. Pence Theories and the World 16 / 28
  24. 24. These examples, chosen from many others which might have been cited, seem to me to show that it is not possible to regard dominance as a property of any character, from a simple knowledge of its presence in one of two individual parents. The degree to which a parental character affects offspring depends not only upon its development in the individual parent, but on its degree of development in the ancestors of that parent. (Weldon 1902, 244) Charles H. Pence Theories and the World 17 / 28
  25. 25. What Bateson does, and what all Mendelians do, is to take the diagram of frequency and to call a range AB one “character,” and the range BC another “character” of a Mendelian pair. A Mean B C There must be a simple relation between AB, BC, and the S.D. [standard deviation] of the original system, which would make the chance that a grandchild falls within BC = 1 4? (Weldon to Pearson, pearson/11/1/22/40.7.3, 1902-06-23) Charles H. Pence Theories and the World 18 / 28
  26. 26. Good old Galton’s stirp, in which some of the ancestral characters are latent, is still the only “machine” which will work: and the proper line of research is an inquiry into those embryonic stimuli which make a given character evident or latent. That is my fixed belief. (Weldon to Pearson, pearson/11/1/22/40.11.3, 1904-10-??) Charles H. Pence Theories and the World 19 / 28
  27. 27. Why the Change? Charles H. Pence Theories and the World 20 / 28
  28. 28. [On Weldon’s view of inheritance,] you cannot, by any amount of selection, reduce the original variability of a race beyond a certain definite amount. [...] Accordingly, in every generation of [a population under heavy stabilizing selection,] the variability has to be reduced, though the mean is no longer changed, by a selective destruction. (Weldon 1905f, f. 24, 27) Charles H. Pence Theories and the World 21 / 28
  29. 29. [W]hile astronomers, chemists, and physicists have by great and successful efforts reduced the limits of uncertainty concerning the results of their observations until for many purposes they can neglect the discrepancies between the results of individual experiments, and treat their experience as uniform, biologists have not yet gone so far, and they are still forced to base such general statements as they can make on the characters of long series of observations. (Weldon 1906, 96) Charles H. Pence Theories and the World 22 / 28
  30. 30. How to Move Forward? Charles H. Pence Conclusions and Forward Movement 23 / 28
  31. 31. Some biologists: firmly invested in explanatory irrelevance Others: firmly invested in discovering links between levels, causal and definitional relationships between properties Charles H. Pence Conclusions and Forward Movement 24 / 28
  32. 32. An important issue from the very earliest days of “statisticalized” evolution, entirely independent from the classic biometry-Mendelism debate Charles H. Pence Conclusions and Forward Movement 25 / 28
  33. 33. We have over a century of attempts to apply case studies to these questions, with no significant increase in clarity. What to do? Charles H. Pence Conclusions and Forward Movement 26 / 28
  34. 34. We have over a century of attempts to apply case studies to these questions, with no significant increase in clarity. What to do? Stop. Tackle the problem from other directions! (Especially the metaphysics of science and analogies with other sciences.) Charles H. Pence Conclusions and Forward Movement 26 / 28
  35. 35. 1. This is in no way a distinctively biological (or philosophy-of-biological) problem! 2. Attempts to resolve it using biological data or cases date back to the 1890s, and have been generally unfruitful. Charles H. Pence Conclusions and Forward Movement 27 / 28
  36. 36. Questions? charles@charlespence.net https://pencelab.be @pencechp • @pencelab
  37. 37. kinematic properties property changes particular trends entities predict, explain properties of dynamical laws Charles H. Pence Bonus! 1 / 4
  38. 38. macro-kinematic properties macro-level property changes particular macro- level trends predict, explain macro-level dynamical laws micro-kinematic properties micro-level property changes particular micro- level trends predict, explain micro-level dynamical laws Charles H. Pence Bonus! 2 / 4
  39. 39. macro-kinematic properties macro-level property changes particular macro- level trends macro-entities predict, explain properties of macro-level dynamical laws micro-kinematic properties micro-level property changes particular micro- level trends micro-entities predict, explain properties of micro-level dynamical laws Charles H. Pence Bonus! 2 / 4
  40. 40. macro-kinematic properties macro-level property changes particular macro- level trends macro-entities predict, explain properties of macro-level dynamical laws micro-kinematic properties micro-level property changes particular micro- level trends micro-entities predict, explain properties of micro-level dynamical laws compose Charles H. Pence Bonus! 2 / 4
  41. 41. macro-kinematic properties macro-level property changes particular macro- level trends macro-entities predict, explain properties of macro-level dynamical laws micro-kinematic properties micro-level property changes particular micro- level trends micro-entities predict, explain properties of micro-level dynamical laws compose supervenience, relational, or structural properties? Charles H. Pence Bonus! 2 / 4
  42. 42. macro-kinematic properties macro-level property changes particular macro- level trends macro-entities predict, explain properties of macro-level dynamical laws micro-kinematic properties micro-level property changes particular micro- level trends micro-entities predict, explain properties of micro-level dynamical laws compose constraint or supervenience? supervenience, relational, or structural properties? Charles H. Pence Bonus! 2 / 4
  43. 43. macro-kinematic properties macro-level property changes particular macro- level trends macro-entities predict, explain properties of macro-level dynamical laws micro-kinematic properties micro-level property changes particular micro- level trends micro-entities predict, explain properties of micro-level dynamical laws compose constraint or supervenience? supervenience, relational, or structural properties? bidirectional causation, abstraction, constraint? Charles H. Pence Bonus! 2 / 4
  44. 44. R.A. Fisher In these cases [of traits arising from multiple factors] we can confidently fall back upon statistical methods, and recognise that if a complete analysis is unattainable it is also unnecessary to practical progress. [...] A number of points of general interest are shown to flow from purely statistical premises. (Fisher 1922, 415) Charles H. Pence Bonus! 3 / 4
  45. 45. Sewall Wright It should be emphasized, however, that [Fisher’s] conclusion rests to a large extent on the low frequency of even heterozygous mutants, to be expected where mutation is balanced by adverse selection of a higher order. [...] It seems unlikely that similar conditions would occur in nature except in special cases. [...] [In the absence of these,] probably most geneticists would hold that dominance in general has some immediate physiological explanation. (Wright 1929, 277) Charles H. Pence Bonus! 4 / 4

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