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Lecture 3 1. 2. 3. Kinds of evidence and reasoning at work in evolutionary theorizing. Anticipating next readings (by A.J. Ayer and Karl Popper) and topic. Introduction to “The Mind’s Big Bang” The Likelihood Principle O: an observation or set of observations H: a hypothesis proposed as an explanation of O The likelihood principle asks “What is the likelihood of O (observations) given H (hypothesis)?” P(O/H) NOT “What is the probability of H given O? P(H/O) The Likelihood Principle O: There is noise in the attic. H: Gremlins are bowling in the attic. “What is the likelihood of O given H?” P(O/H) VERY HIGH! “What is the probability of H given O? P(H/O) VERY LOW (if probable at all)! Paley’s argument from design O: Organisms are perfectly fit to their environments and their parts (e.g., eyes) are perfectly designed for their functions. H1: Organisms and their parts were produced by a Designer. H2: Organisms and their parts are the result of random, physical processes. “Obviously”, Paley concluded, P(O/H1) >> P(O/H2) The likelihood of O is much higher if H1 than if H 2. Paley’s reasoning updated… O: Organisms are perfectly fit to their environments and their parts (e.g., eyes) are perfect designed for their functions. Turns out there are many imperfections, and a change in environment can easily wipe out a population or species… H1: All was produced by a Designer H2: All are the results of random, physical changes Paley could only think of two possibilities but now we have: H3: Natural selection, which doesn’t require supernatural intervention and is also not random. The Panda’s Thumb O: the panda’s “thumb” (TPT) and what it actually is (an enlarged wrist bone) H1: TPT came about through natural selection: the (blind) tinkering with available parts that gave those ancestors with it an advantage and, thus, the trait spread. H2: TPT was designed by perfect engineer. Gould: P(O/H1) >> P(O/H2) The Panda’s Thumb Gould: P(O/H1) >> P(O/H2) What is the evidence? Comparative anatomy: Both the radial sesamoid, which in its elongated form constitutes this false “digit”, and the relevant musculature that gives the digit its relative rigidness and relative flexibility, are common to other species, including other bears. The (perhaps single) genetic change producing a larger radial sesamoid, would given their spatial locations, force the change in the musculature. The Panda’s Thumb Gould: P(O/H1) >> P(O/H2) What is the evidence? Comparative anatomy: In many other bears, the radial sesamoid is also somewhat enlarged. This is by no means a “perfect” thumb (it is neither opposable nor able to manipulate objects by itself). It is, rather, the result of tinkering with parts available to the panda’s ancestors. Darwin’s orchids Non-sexual reproduction is cheaper, but sexual reproduction insures that an organism’s progeny are varied (and thus will have a better chance of survival if conditions change). From the same relatively primitive petal of its ancestor, varieties of orchids have different “contraptions” for insuring cross-pollination (insuring that insects lured by their nectar are also coated in pollen that they will in turn pass on to the next female orchid they visit…) QWERTY PHENOMENA Like the arrangements of the keys on a keyboard, QWERTY phenomena are phenomena that show signs of history: a history of R&D (research and development) using what’s available, and limited or directed by contingencies and constraints… Francis Crick called them “frozen accidents” QWERTY phenomena abound in the organic world. QWERTY PHENOMENA In our case: wisdom teeth, the blank spot in the center of each of our eyes, the possibility of retinal detachment, our “tail bone”, our back problems, (perhaps) our appendix, relatively short gestational period, male nipples…. Other cases: blind fish in dark caves, with eyes that don’t function, but whose ancestors had functioning eyes blind fish in dark caves, without eyes, whose ancestors did have eyes “toothless” species of whales in which embryos have teeth and lose them during natal development What distinguishes science from pseudo-science? And why care? The emergence of the philosophy of science in the 1920s in Europe The Vienna Circle Logical Positivism (aka Positivism or Logical Empiricism) Reacting to 2 significant developments: The eclipsing of Newtonian physics by Special and General Relativity The growing menace of Fascism, anti-Semitism, and the so-called scientific theories put forward by Nazis What distinguishes science from pseudo-science? Logical Positivism: Science should and must be a positive force for human wellbeing Logical Empiricism (same movement): Working to identify the role of logic and that of experience in the workings of genuine science. Both emphases underlie the work to identify the criterion (or criteria) that demarcate science (i.e., distinguish it from) “pseudo-science” and “nonscience”. What distinguishes science from pseudo-science? A.J. Ayer (first reading) A Logical Positivist (aka Logical Empiricist) His target as “pseudo-science” (“nonsense” or without meaning): statements that cannot be verified by experience. He terms them ‘metaphysical’ but as he uses it, the term has a different sense than that we discussed as “philosophical metaphysics or ontology” It concerns efforts to identify a reality that allegedly “transcends” our experiences. His criterion: verifiability What distinguishes science from pseudo-science? Sir Karl Popper (second reading) Rejects “Verifiabiliity” (too many pseudoscientific theories be claimed to “fit” the evidence) Offers “Falsifiability” as an alternative criterion Simply put: a statement, hypothesis, or theory is scientific only if it is, in principle, falsifiable There are things it prohibits, which if they were to occur or be observed, would show the hypothesis or theory in question to be false. The Mind’s “Big Bang” When and how did the human brain emerge? A single mutation? Gradually? What kinds of evidence do scientists appeal to in “reconstructing” the event? The method of “reverse engineering” Drawing inferences based on what we can observe (by way of traits and artifacts) to historical episodes DNA analysis, paleontology, anthropology, archaeology The Mind’s “Big Bang” When and how did the human brain emerge? What kinds of evidence do scientists appeal to in “reconstructing” the event? Consider the evidence discussed in the film. Do you find some inferences more compelling than others? If so, why… Cave paintings Tools Beads Graves…