Lecture Notes: Language and Evolution Edward Stabler January 11, 2007 The study of evolution and language provides a unique opportunity for carefully examining basic questions about evolution, language, and the kinds of explanations available for sources of order in physical, biological, cognitive and cultural domains. Spring 2006 Syllabus The study of evolution and language provides a unique opportunity for carefully examining ba- sic and important questions about evolution, language, and the kinds of explanations available for sources of order in physical, biological, cognitive and cultural domains. Human languages provide a kind of mirror on human thought, and so we want to under- stand the forces that have shaped the structures we see there. Evolution provides a source of structure at two levels. First, the human organism has evolved, with linguistic abilities of certain kinds, by genetic transmission and natural selection. And second, each particular lan- guage is a cultural artifact, transmitted by learning and selected by various cultural and natural forces. In each case, we can ask: what aspects of language structure can be explained by evo- lutionary forces? And what other forces are shaping human languages? These are fundamental questions that every thinking person is likely to be curious about, and so it is no surprise that there is a wealth of popular and scientific work addressing them. Readings will be drawn from classic and contemporary research, supplemented with lecture notes each week. 0.1 Some things you will know at the end of the class the fundamental axioms of Darwin’s theory of evolution • Mendel’s argument for genetic “atoms” – “genes” • Hardy’s theorem about conditions under which a genetic population is stable • some of the clues that led Watson and Crick to the discovery of DNA • some idea of how DNA controls protein synthesis from amino acids • how many basic elements are in the “language” of DNA (here’s the answer now: 4) • how many of these occur in the human genome (here’s the answer now: 3,164,700,000) • ≈ how many Mendelian atoms occur in the human genome (here’s the answer now: 35,000) • ≈ why AZT is ineffective against HIV (the terrible answer: HIV evolves rapidly) • some critiques of the “neo-Darwinian” research program • Frege’s argument for “semantic atoms” and “compositionality” in human language • how many basic gestures in each human language (here’s the answer now: 11-160) • i Stabler - Language and Evolution, Spring 2006 how many Fregean atoms in each human language (here’s the answer now: >10,000) • what is the “Chomsky hierarchy,” and where in it are DNA and human languages • what do English, Quechua,1 and American Sign Language (ASL) have in common • how human language is “structure-dependent,” unlike any other animal language • how a language learner can be regarded as a mathematical function • some critiques of the “neo-Lockeian” empiricist research program • how nothing in the universe is really like Locke’s “blank slate” • ⋆ whether human language abilities emerged by selection: why the experts disagree how all these things relate to each other (!) • These are things everyone should know. Can we fit all this in? We’ll try. 1Quechua is the language of the Incas, now spoken by approximately 7 million people in South America. The lecture notes have a glossary and index for less common names and terms like this one. ii Contents Spring 2006 Syllabus i 0.1 Some things you will know at the end of the class . ................. i 0 Evolution and language 1 0.1 Evolution:Firstideas .. .. .. .. ................ 4 0.2 Language:Firstideas ............................. ............... 7 0.3 Cognition:Firstideas .. .. .. .. ................ 9 0.4 Some basic questions: Local and global properties . ..................... 10 0.5 Summaryandpoetry ................................ ............ 16 1 Genetic variation, transmission, selection 19 1.1 The geometric increase in populations . .................. 19 1.2 Twobasiclawsofprobability . ................ 21 1.3 Geneticatomsdonotblend . .............. 23 1.4 The Hardy-Weinberg equilibrium . ................. 27 1.5 Perturbingequilibrium . ................ 30 1.6 Mutationsfornewvariation . ................ 34 1.7 Summary......................................... ........... 38 2 The chemical realization of heredity 43 2.1 Molecularmechanisms . .. .. .. .............. 43 2.2 Molecularchange:mutation . ................ 53 2.3 Molecularphylogeny .............................. .............. 54 2.4 Digression: HIV and why AZT fails . ................ 55 2.5 Threelanguagesoflife . .. .. .. ............... 56 2.6 Summary......................................... ........... 72 iii Stabler - Language and Evolution, Spring 2006 3 The neo-Darwinian synthesis 79 3.1 Modeling populations: from complexity to chaos . .................... 79 3.2 Wrinkles in classical Mendelian genetics . .................... 86 3.3 The missing interpretation: proteomics and beyond . ..................... 87 3.4 Self-organization............................... ................ 89 3.5 Whatisselected?................................. .............. 93 3.6 Another challenge: Phenotypic plasticity . ..................... 94 3.7 Atthelimits,briefly.............................. ............... 97 4 What is a language? First ideas 111 4.1 Communication as information transmission . ................... 112 4.2 Molecularcommunication . ............... 114 4.3 Non-humananimalcommunication . ............... 115 5 What is a human language? 123 5.1 Firstobservations ............................... ............... 123 5.2 Languagestructure:English . ................. 127 5.3 Languagestructure:Quechua . ................ 153 5.4 Languagetypology................................ .............. 157 5.5 Universals:firstideas. ................ 160 6 Origins of human linguistic ability: Selection, exaptation, self-organization 165 6.1 Innateness...................................... ............. 165 6.2 An argument for emergence by selection . ................. 167 6.3 Another argument for emergence by selection . .................. 169 6.4 Anargumentforemergencebyexaptation . ................. 171 6.5 The ability to produce, recognize, and represent recursivestructure. 173 6.6 Structure-dependence and language complexity . .................... 176 6.7 Self-organization of language abilities? . ...................... 179 7 Origins of particular languages and structures: Selection, exaptation, self-organization 185 7.1 Language transmission: learning . .................. 187 7.2 Languagevariation............................... ............... 189 7.3 Selection, exaptation, or self-organization? . ....................... 191 7.4 Strange conclusions, and some related issues . .................... 199 iv Lecture 0 Evolution and language The main goal of the class will be to develop a clear conception of the fundamentals of evo- lution and of language, so that we can consider two questions: to what extent has the nature of human linguistic ability been shaped by natural selection, and to what extent can the devel- opment of particular languages, as cultural artifacts, be regarded as an evolutionary process of a similar kind. The class will be designed to foster clear, critical thinking about these mat- ters, and to incite an interest in pursuing them further. With these goals, it is natural to focus on clear cases of evolution and on well-understood properties of language. Surprisingly, this makes the content of the class rather unusual, because it has been common to use evolutionary analogies as the basis for speculations about things that are not well-understood, and not in the mainstream of research in either evolutionary or linguistic theory: things like the extent to which Neanderthals might have had speech and communicative abilities, the relationship be- tween brain size and “intelligence” (whatever that is), the nature of the neural structures that implement linguistic abilities, and how you should revise your religious beliefs in the light of all this. These matters are of great interest, of course, and so in some popular literature these are often the main thing (Deacon, 1997; Loritz, 1999; Lieberman, 2000; Calvin and Bickerton, 2000, …), but our concern here is the real thing, what is really known, and how. This is the secure foundation upon which the study of the more obscure topics must rest. A long-standing and still essential component of linguistic study focuses on the descrip- tion of particular languages, the origins of words, the variations in pronunciation, the shifts in meaning over time and across populations. But Chomsky and others in the 1950’s and 1960’s drew attention to some new kinds of questions: are there properties that all languages have in common, properties that must be due to something other than the particular characteristics of a common ancestral language? There are, and among those properties, some are apparently fundamental to our ability to acquire and use our language as we do. Of course, interests of the former kind continue, but this class will introduce questions of the latter kind, and con- sider some preliminary discussions of the clearest and most substantial results that have been obtained there. Very roughly, in all human languages, we find roughly similar kinds of pieces forming tightly interlocked structures, which over an infinite range can be “compositionally” interpreted by speakers of the language. 1 Stabler - Language and Evolution, Spring 2006 A similar