Claim CB402:

Evolution does not explain the evolution of language ability.

Source:

Response:

1. We do not know the definitive explanation for how language ability arose, but there are plausible hypotheses. Intermediate stages may be reached by gradual changes. For example:
   • The larger brain size of primates arose before language; it may have come from adaptation for functioning in social groups or for finding food.
   • Human brain size has evolved to be unusually large through neoteny; the rapid brain growth of childhood is maintained for a longer time. It may have arisen in conjunction with the evolution of language or before it.
   • Before language, some communication already was done via gestures (which itself probably arose as mimetic imitation) and via vocalizations. Spoken language ability may have built on those vocalizations, or it may have been transferred from gestural language, or both.
   • Once vocal protolanguage began, the vocal tract and neural connections for producing and controlling speech would have begun evolving. Speech probably began in Homo erectus more than a million years ago.
   • Once language becomes a central part of human behavior, language acquisition comes more readily because of the Baldwin effect; the plasticity of learning allows natural selection for language ability to proceed more quickly (Baldwin 1896).
   
   
2. Language is obviously useful, so it is not hard to see how it could have provided selective advantages. In fact, the bigger problem is explaining why chimpanzees did not evolve language. Language was probably primarily an adaptation to a social structure that was (and is) far more complex than that of other primates.

References:

Further Reading:

Deacon, Terence W., 1998. The Symbolic Species: The co-evolution of language and the brain. New York: W.W. Norton.

Johansson, Sverker, 2002. The evolution of human language capacity. Master's Thesis, University of Lund. http://home.hj.se/~lsj/langevod.pdf (esp. pp. 65ff)

Pinker, S., 1994. The Language Instinct. Harmondsworth: Penguin.

Tattersall, Ian, 2001. How we came to be human. Scientific American 285(6) (Dec.): 56-63. Excerpted from The Monkey in the Mirror, Harcourt, 2002.

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