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Netherlands Graduate School of Linguistics LOT Summer School 2006 Issues in the biology and evolution of language

Netherlands Graduate School of Linguistics LOT Summer School 2006 Issues in the biology and evolution of language. Massimo Piattelli-Palmarini University of Arizona Session 1 (June 12) The birth of a paradigm: Innatism versus selectivism. Plan of this course.

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Netherlands Graduate School of Linguistics LOT Summer School 2006 Issues in the biology and evolution of language

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  1. Netherlands Graduate School of LinguisticsLOT Summer School 2006Issues in the biology and evolution of language Massimo Piattelli-Palmarini University of Arizona Session 1 (June 12) The birth of a paradigm: Innatism versus selectivism

  2. Plan of this course • Today (Monday): The birth of selectivism and the idea of parameters • Tuesday: Towards a genetics of language • Wednesday: Loss of speech • Thursday: The return of the laws of form • Friday: Contemporary biology and the minimalist program Birth of a paradigm

  3. Little guide to the readings • General position papers on biolinguistics: • Chomsky’s Three factors • My paper with Cedric Boeckx • Freidin and Vergnaud • Tutorials • Boeckx Chapter 5 on minimalism • My handout on the Hauser, Chomsky and Fitch versus Pinker and Jackendoff on evolution • Christiansen and Kirby on language evolution • NEW Simon Fisher The tangled web in Cognition June 6, 06 Birth of a paradigm

  4. Little guide to the readings (2) • “Representative” pieces • Turing on morphogenesis • Davidson and Erwin on Gene Networks • Hill and Walsh on brain evolution • Marcus and Fisher (on FOXP2) • Gibbs on epigenetics Punctual papers • Somerville et al. on Williams syndrome • Fisher on genes and language • Scharf and White on Foxp2 in birds • Uriagereka and me on the immune syntax (unreadable) Birth of a paradigm

  5. Some caveats • The biology of language is a huge field • 750 papers just on brain imaging and language • About 150 references (papers and books) on the evolution of language, just in the last 10 years or so • About 25 genes (tentatively) identified already as being language-related • Many other fields are relevant (molecular genetics, evo-devo, neuroscience of cognition, various pathologies, comparative cognitive ethology etc.) • Not to mention, of course, linguistics, language acquisition and psycholinguistics Birth of a paradigm

  6. Some caveats • Our strategy here: • Explore with a critical eye the “possibility” of a biology of language • Its “logic” and its possible import • Privileging what we know (rather than what we would like to know, but we don’t) • Concentrating on the strong points • Singling out the best cases (breakthroughs) • And plausible avenues of future development • With (yes!) some “fine” details that may, at first blush, seem of scant interest to linguists • But they are not (I hope I will persuade you that they are really very interesting) Birth of a paradigm

  7. Three factors in language design • (1) genetic endowment, which sets limits on the attainable languages, thereby making language acquisition possible; • (2) external data, converted to the experience that selects one or another language within a narrow range; • (3) principles not specific to FL. • Some of the third factor principles have the flavor of the constraints that enter into all facets of growth and evolution, and that are now being explored intensively in the “evo-devo” revolution. • There are other third factor elements as well, among them properties of the human brain that determine what cognitive systems can exist. It also might turn out that general cognitive principles that enter into language acquisition pose conditions on FL design. Birth of a paradigm

  8. Two varieties of pessimism • Max Planck: A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grow up that is familiar with it. • Noam Chomsky: New ideas circulate only because, eventually, professors are embarrassed by their students for confessing they do not know about them. Birth of a paradigm

  9. The innatist-selectivist explanatory strategy: • Enters linguistics via the Poverty of the Stimulus (POS) • Explicit references (in earlier work by Chomsky) to Luria and Delbruck, to Hubel and Wiesel and to Monod and Jacob. • In continuity with the powerfully emerging trend in molecular biology • Later reinforced by Fodor’s modularity • By data on language acquisition • And by the principles-and-parameters framework Birth of a paradigm

  10. Charles Darwin Jean-Baptiste de Lamarck (1809 -1882) (1744 - 1829) selectioninstruction Birth of a paradigm

  11. A long-standing debate • Instructive versus selective change and adaptation • Revamped in immunology (around 1890) • Revamped in microbiology (Pasteur and Koch, from 1880 onwards) • Koch’s postulate: one disease = one microbial agent (cholera, typhus, tuberculosis etc.) • Doubts that bacteria could “have a genetics” until about 1935 • Frederick Griffith (1928): the “transforming agent” of pneumococcus from harmless to pathogenic Birth of a paradigm

  12. A long-standing debate (continued) • Avery, McLeod and McCarty (1944): the transforming agent is DNA • Quite a shock to everyone (Nobel Prize 1983) • Further revamped by the discovery of the healing power of antibiotics in the late Thirties and Forties (penicillin, streptomycin, chloramphenicol) • In particular, by the appearance of resistant microbial strains • A debate about what? Birth of a paradigm

  13. Two positions: The first • The “inductivists” (Felix D’Hérelle et al.): Adaptive mutations are induced by the external agent (temperature, antibiotics, viruses, metabolites etc.) • There are “directed adaptive heritable changes” (induced adaptations) • The reference conceptual model: spontaneous radioactive decay • (The probability of decaying is constant across all atoms of a given isotope of that element) • And catalysis (the dominant conceptual model) Birth of a paradigm

  14. Two positions: The second • The “selectivists” (A. Gratia, F. M. Burnet et al.): Mutations are spontaneous, with a stable fixed average probability of occurrence (about 10-8 per locus per generation) • BUT • They occur independently of, in the absence of, and prior to, any exposure to the environmental factor. • No “directionality”. • At the 3rd Congress of Microbiologyin New York, in 1939, Andre’ Gratia declared:"Adaptation by passive selection of pre-existing variants isthe only fact to be proven beyond any doubt" (GRATIA 1939) • Selection acts post hoc and “adaptation” is a result of it Birth of a paradigm

  15. Why do we care? • Reference to these phenomena, and to selectivist explanations, is ubiquitous in Chomsky’s work (see his debate with Piaget) • Luria and Chomsky and Eric Lenneberg at MIT created a bio-linguistics group meeting regularly • The 1974 meeting at Endicott House • Fodor’s innatism and the pre-existence of all concepts • Principles and parameters (ever since the late Seventies) • Parameter-based language acquisition Birth of a paradigm

  16. One language? No learning: • Rather the fixation of a handful of linguistic parameters • Each having only two possible values • + or - • A “cascade” of switches Birth of a paradigm

  17. Birth of a paradigm

  18. Birth of a paradigm

  19. Mark Baker 2001, 2003 Birth of a paradigm

  20. A simple “knockdown” experiment • Salvador E. Luria and Max Delbrück (1943)“Mutation of bacteria from virus sensitivity to virus resistance”,Genetics, Vol. 28, pp 491-511 • Nobel Prize in 1969 with Alfred D. Hershey • Hall of fame of elegant experiments in biology • Inspiration from a slot-machine in a Country Club in Bloomington Indiana • The very idea: Grow different cultures of bacteria sensitive to a virus (a phage) • Make successive dilutions of samples from the various cultures (successive generations) • Add the virus, then see how many resistant colonies you obtain Birth of a paradigm

  21. A simple “knockdown” experiment • If the inductivists are right, then • You get an average constant percentage of resistant mutants at each generation • If and only if, they have been exposed to the virus. • If the selectivists are right, you get “a distribution with an abnormally high variance” • All (or most) of the descendants of a mutant are resistant • All (or most) of the descendants of a sensitive wild type are wiped out • The presence of the virus allows usto make a selection, but it is not the “inducing agent” Birth of a paradigm

  22. A technical challenge: • In order to ascertain the existence of resistant mutants • You have to add the virus to the culture • But then it’s hard to decide whether the mutants pre-existed or are “induced” by the virus • Luria’s and Delbrück’s solution • Fluctuations across generations. Birth of a paradigm

  23. The Luria-Delbrück dilution experiment Bacteria sensitive to the virus (a bacteriophage) in black. Resistant mutants in red. Culture 1 harbors a 3rd generation mutant. Culture 3 harbors a 1st generation mutant. The probability of observing mutants varies very strongly. In fact, it is 1 or 0, depending on whether the ancestor is or is not a mutant. Birth of a paradigm

  24. The Luria-Delbrück dilution experiment Had the mutation been “induced” by the exposure, we would Expect a uniform probability of finding mutant colonies (an average constant fraction of all later cultures would be mutants) Birth of a paradigm

  25. Conclusion: • “We consider the above results as proof that in our case the resistance to virus is due to a heritable change of the bacterial cell which occurs independently of the action of the virus.” (emphasis added) • Do we need successive dilutions? • Not necessarily • Same results with a different technique: Replica Plating Birth of a paradigm

  26. Replica plating (Joshua and Esther Lederberg 1952) Birth of a paradigm

  27. Birth of a paradigm

  28. “The procedure at no time exposes the indirectly selected populations to the specific agent [streptomycin]. These observations, therefore, are cited as confirmation of previous evidence for the participation of spontaneous mutationand population selectionin the heritable adaptation of bacteria to new agents.”(emphasis added) Joshua and Esther Lederberg (then at Madison Wisconsin) Journal of Bacteriology, 1952 Joshua Lederberg, Nobel Prize 1959 “for studies on genetic recombination and organization of the genetic material in bacteria” Birth of a paradigm

  29. 1st important lesson: • The selective agent does not induce the mutation • It selects pre-existing mutants • Specific mutants pre-exist, regardless of all encounters with the selective agent Birth of a paradigm

  30. Next classic experiment • Preceded, over many years, by a puzzle (enzymatic adaptation) • Something you expected to happen but doesn’t. • Imagine the following cases: • (1) A new kind of combustion engine • Outputs 200 HPs when burning fuel A • Outputs 300 HPs when burning fuel B • What do you expect with a mixture of the two fuels? • (2) Most patients recover in 30 days under treatment with antibiotic A • Most patients recover in 60 days under treatment with antibiotic B • What do you expect with a mixed treatment? Birth of a paradigm

  31. Log n Log n Jacques Monod and the “double growth” (diauxia) (1940) 2 Glucose 1 1 Xylose t t Log n Glucose + Xylose Expected t Birth of a paradigm

  32. Log n Log n Jacques Monod and the “double growth” (diauxia) (1940) 2 Glucose 1 1 Xylose t t Log n Glucose + Xylose Actually observed t Birth of a paradigm

  33. Monod’s original (non-logarithmic) graphs Birth of a paradigm

  34. In Monod’s doctoral dissertation (1940) • “Microbiology will not make much progress until we have solved this puzzle”. • It took 20 years to solve it: • Genetic regulation as a switching process • (not a “catalytic” one) • There are DNA sequences (genes) whose exclusive function is the activation-inactivation of adjacent genes. • Nobel Prize with François Jacob and André Lwoff in 1965 Birth of a paradigm

  35. Monod’s and Jacob’s explanation • The regulating mechanism and the final result have been associated and fine-tuned by natural selection • (the “inductor” is the very metabolite that the enzyme - expressed by the activated gene - “digests”) • But the process is totally “mechanical” • The regulator and “its” gene can be separately disassembled and re-assembled at leisure Birth of a paradigm

  36. Birth of a paradigm

  37. In the absence of lactose repressor blocks promoter Birth of a paradigm

  38. In the presence of lactose repressor cannot bind Birth of a paradigm

  39. Central points: • Seeing clearly that a puzzle in a class of phenomena stonewalls the discipline as a whole • Even in the absence of the faintest idea on how to solve the puzzle • Seeing clearly that the extant conceptualizations (catalysis) cannot begin to solve the puzzle • An educated guess that the solution of the puzzle will reverberate much beyond that class of phenomena Birth of a paradigm

  40. The case of antibodies • Selectivism, then 50 years of instructivism • Then, finally, selectivism Birth of a paradigm

  41. How everything began: Paul Ehrlich • The hypothesis Ehrlich developed to explain immunological phenomena was the side-chain theory, which described how antibodies - the protective proteins produced by the immune system - are formed and how they react with other substances. • This theory was based on an understanding of the way in which a cell was thought to absorb and assimilate nutrients. Birth of a paradigm

  42. Ehrlich’s side-chain theory ofantibody production • Each cell has on its surface a series of side chains, or receptors, that function by attaching to certain food molecules. • While each side chain interacts with a specific nutrient - in the same manner as a key fits into a lock - it can also interact with disease-causing toxins produced by an infectious agent. • When a toxin binds to a side chain, the interaction is irreversible and blocks subsequent binding and uptake of nutrients. • The body then tries to overwhelm the obstruction by producing a great number of replacement side chains — so many that they cannot fit on the surface of the cell and instead are secreted into the circulation. Birth of a paradigm

  43. Ehrlich’s side-chain theory ofantibody production • According to Ehrlich's theory, the circulating side chains are the antibodies, which are all gauged to and able to neutralize the disease-causing toxin and then remain in the circulation, thus immunizing the individual against subsequent invasions by the infectious agent. • Antibodies pre-exist. Birth of a paradigm

  44. Karl Landsteiner and the dawn of biochemistry • Small organic molecules of simple structure, such as phenyl arsonates and nitrophenyls, are not natural danger signals, and do not provoke antibodies when injected by themselves. • However, antibodies can be raised against them if the molecule is attached covalently, by simple chemical reactions, to a protein carrier. • Such small molecules were termed haptens (from the Greek haptein, to fasten) by the immunologist Karl Landsteiner, who first studied them in the early 1900s. Birth of a paradigm

  45. Karl Landsteiner and the dawn of biochemistry • Landsteiner found that animals immunized with a hapten-carrier conjugate respond by producing distinct sets of antibodies. • No lock-and-key, but a more or less good fit. • Antibodies drape themselves over the charge outline of their target antigen (instructivist model). Birth of a paradigm

  46. Felix Haurowitz and the Template Theory of Antibody Formation.Selectivism is unvorstellbar • Haurowitz and Landsteiner collaborated to define the chemical nature of antibodies. • "I concluded that the antibody must be serum globulin and suggested therefore that the antigen interferes with the process of globulin biosynthesis in such a way that globulins complementarily adjusted to the antigen are formed." • Antibody formation takes place by the assembly of the antibody molecule on the antigen (instructivist model). Birth of a paradigm

  47. The 1984 Nobel Prize in Physiology or Medicine: Niels Jerne • Niels Jerne’s natural selection theory for the immune system was published in 1955 (!). • Lederberg and Nossall: one lymphocyte clone = one antibody • Jerne proposed that the capacity of the immune system to recognize millions of foreign molecules was predetermined, already existing in the body when the very first contact with a foreign structure was made. What then happened was merely a selection amongst the naturally occurring antibody population resulting in an increase in production of exactly those antibodies which happened to have a good fit for the structure. Birth of a paradigm

  48. The 1984 Nobel Prize in Physiology or Medicine: Niels Jerne • Jerne's theory stood in great contrast to prevailing theories at that time (the unimaginable wastefulness of selection), but was rapidly confirmed and extended. • Natural selection applies to the cells of the immune system. Those cells which happen to have received the property to produce a wanted antibody type will upon vaccination be rewarded with proliferative capacity and survival. Birth of a paradigm

  49. The adaptive immune response The molecules of adaptive immunity (e.g., antibodies): • Are generated by random DNA rearrangements • Pre-exist to the encounter with danger signals (innate) • Are selected by specific stimuli • Repertoire is virtually unlimited (3D recognition of molecular shapes) Birth of a paradigm

  50. Grammar is a science that is more than 2000 years old, whereas immunology has become a respectable part of biology only during the past hundred years. Though both sciences still face exasperating problems, this lecture attempts to establish an analogy between linguistics and immunology, between the descriptions of language and of the immune system. Birth of a paradigm

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