LING001

1. LING001 Evolution and Language 4-27-2009

2. Evolution and Language • “Nothing in biology makes sense except in the light of evolution”. Theodosius Dobzhansky (1973) • The uniqueness of human language in the biological world has driven people to “make sense” of it in the light of evolution. • But it is important to distinguish mere “stories” from testable scientific theories • Today: • basic structure of Natural Selection and the difficulties with which it is applied to language and cognition (Lewontin) • some suggestions about the evolution of language

3. Angry Dick • Richard Lewontin (b. 1929): perhaps the greatest living evolutionary biologist, also prominent social commentator • Outlines the structure of the argument for Natural Selection and dismisses existing accounts of evolution of language as story telling

4. Three Components of Natural Selection • Variation: individuals must be different (no variation, no evolution) • Heredity: differences must be passed down to descendants • Selection: differential reproduction and survival due to variation • The fallacy of the role of skin cancer in the evolution of skin colors • Fitness is not constant: Bad eyesight is a good reason to avoid the draft

5. Natural Selection in Real World • Natural Selection only increases the probabilityof passing down the gene but doesn’t guarantee it: like a coin toss • N.S. can boost the chance of getting tails from 0.5 to 0.51 (0.01 advantage is considered large in nature) • If the population is very large, tails will make up close to 51% of the population in one generation, and more next, and will gradually take over • But if the population is small, you may not have get more tails in next generation even if it’s more likely to draw tails • Draw 10 balls: 60% of drawing red, 40% of drawing green • we may end up with a 6-4 split, but also 5-5, 2-8, even 0-10

6. Natural Selection in Real World http://news.nationalgeographic.com/news/2008/04/080424-humans-extinct.html • For human evolution, it is generally held that while in Africa, and when our ancestors marched out of Africa, the population size was quite small • this makes the effect of sampling a lot more dramatic • as a result of this and other factors, in human evolutionary genetics, the default hypothesis of observing change is to assume that it is NOT caused by Natural Selection • Which is why no serious biologists participate in the story telling of the evolution of language and cognition: it’s almost exclusively the game of psychologists, philosophers, ... and linguists!

7. Stories • It’s possible to simply tell plausible stories about biological properties of organisms. • In the case of language, there are many such stories; language is required for communication, hunting, evolved because of gossip • : This ‘story-telling’ can involve more or less plausible parts; but ultimately we’re interested in theories that can be tested, and that’s where most of Lewontin’s critique is directed. No one doubts language did evolve by biological mechanisms

8. A “just so” story • Pinker & Bloom (1990: cited in Lewontin article) • Because language is complex (any questions?), it must be the product of Natural Selection • Because Natural Selection has produced many complex things though complexity is also the argument used by creationists as evidence of a Designer • Much of evolutionary psychology has held Natural Selection to be the force that created cognitive systems • “God gene”, “cheater detector gene”, etc., each with a Natural Selection story that “makes sense” • But gene-trait mapping is not unique

9. Difficulties with Evolution of Language • Language doesn’t leave fossils • We have no “close” relatives: chimps diverged from us about 5-7 million years ago • no time to evolve every component of language individually, contrary to Pinker & Bloom • The measurement of cognitive abilities is itself very challenging • the Bell curve and the IQ test controversy • Not clear where to find genetically based variation • Not clear how variation translates into selectional advantage • the first caveman who started talking might have been killed instantly

10. Homology vs. Analogy • Homology: similarity by common descent • Analogy: similarity via independent evolutionary pathways • When a monkey is doing X, which bears some rudimentary aspect of language, it’s difficult to know X is homology or analogy to infer about the evolutionary history • With this in mind, we turn to a few cases that have surfaced in language and evolution in recent years that compare the cognitive abilities of humans and other species homology

11. Speech Perception • Categorical perception: bah~pah • once held to be uniquely human and uniquely linguistic • this has been disconfirmed: recall that chinchillas, monkeys etc. can do CP as well • Tracking prosody to identify speech in language learning • rodents and monkeys can do that too • But none of these touches on the core element of language: the combinatorial infinity of phonology, morphology, and syntax

12. Starling Syntax (NY Times)

13. Monkey Business • Fitch & Hauser (2004, Science): cotton-top tamarin • A={ba, di, yo, tu, la, mi, no, wu}: female voice • B={pa, li, mo, ku, ka, bi, do, gu}: male voice • matched for duration, loudness • Are monkeys good at pattern matching? 13

14. Monkey Syntax? • Played a sequence of syllable, of the following patterns • (AB)n = AB, ABAB, ABABAB ... • nolibapa, lapawumonoli • AnBn = AB, AABB, AAABBB • yo lapa do, ba la tu li pa ka • “Training” by exposure to a pattern • “Test” by playing a sequence than violates the training pattern

15. Monkey Syntax?

16. Monkey Syntax? • Such experiments are often difficult to interpret: • There could be other cognitive or processing mechanisms that affect the ability to learn these patterns • But one possibility is that monkeys do not have language: they really don’t • They lack the cognitive/computational capacity to process AnBn patterns, which are the minimum requirement for the design of human language • This may be the right kind of research question to pursue

17. Morphology • All languages have morphology • We create morphological classes from data with remarkable accuracy • In languages like Italian or Spanish, children produce correct agreement in over 98% of the contexts from the beginning of speech • They seem to place words into their appropriate classes very accurately • In English past tense, children over-regularize (about 10% of the time) but they do not over-irregularize (about 0.2%) • i.e. they say “bring-bringed”, and do not say “bring-brang” • Categories are discrete rather than based overall similarity (which would have produced think-thunk, flow-flew)

18. Categorization (Medin et al. 1987)

19. One dimensional sort

20. Learning in a maze • Many species learn to match the probabilities of events/rewards/etc. in the environment when they make choices • They do not, for instance, go for the most prominent/frequent choice

21. Learning both languages • In “bilingual” environments, children acquire both options, closely matching the frequencies of their usage • Here “bilingual” could mean two alternative choices in phonology, morphology, or syntax, like some of the sociolinguistic variation to be discussed on Wednesday • In monolingual environments, children go through a period of time trying both the target and the non-target forms, which are given by Universal Grammar, before settling on the target • These strongly suggest that at some level, the mechanisms of language learning are the same as those used in running the maze, and evolutionarily ancient • These mechanisms in turn pose constraintson, or explain, the properties of human language

22. Conclusion • To understand language evolution, we need to partition the properties of languages into distinct components and hope to find them in other cognitive/perceptual systems and in other species (Hauser, Chomsky & Fitch 2002) • The irreducible components must be uniquely human and evolved recently (but don’t expect to trace them to a single gene) • Of course, that begs the question of how the shared components evolved, which may be cognitive and leave little trace behind, and we are back to Lewontin.

23. Into the wild • There are many other linguistics courses that deal with various subfields in depth: feel free to explore them. • The field of linguistics is becoming increasingly inter-disciplinary