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Language Evolution: BBS Call for Commentators

S. R. Harnad harnad at phoenix.Princeton.EDU
Thu Feb 8 19:49:44 EST 1990

Below is the abstract of a forthcoming target article to appear in
Behavioral and Brain Sciences (BBS), an international, interdisciplinary
journal that invites Open Peer Commentary on important and
controversial current research in the biobehavioral and cognitive
sciences. Commentators must be current BBS Associates or nominated by a
current BBS Associate. To be considered as a commentator on this
article, to suggest other appropriate commentators, or for information
about how to become a BBS Associate, please send email to:

harnad at clarity.princeton.edu  or harnad at pucc.bitnet        or write to:
BBS, 20 Nassau Street, #240, Princeton NJ 08542  [tel: 609-921-7771]
            Natural Language and Natural Selection

                    Steven Pinker
                    Paul Bloom
           Department of Brain and Cognitive Sciences
           Massachusetts Institute of Technology


Many have argued that the evolution of the human language faculty
cannot be explained by Darwinian natural selection. Chomsky and Gould
have suggested that language may have evolved as the byproduct of
selection for other abilities or as a consequence of unknown laws of
growth and form. Others have argued that a biological specialization
for grammar is incompatible with Darwinian theory: Grammar shows no
genetic variation, could not exist in any intermediate forms, confers
no selective advantage, and would require more time and genomic space
to evolve than is available. We show that these arguments depend on
inaccurate assumptions about biology or language or both. Evolutionary
theory offers a clear criterion for attributing a trait to natural
selection: complex design for a function with no alternative processes
to explain the complexity. Human language meets this criterion: Grammar
is a complex mechanism tailored to the transmission of propositional
structures through a serial interface. Autonomous and arbitrary
grammatical phenomena have been offered as counterexamples to the claim
that language is an adaptation, but this reasoning is unsound:
Communication protocols depend on arbitrary conventions that are
adaptive as long as they are shared. Consequently, the child's
acquisition of language should differ systematically from language
evolution in the species; attempts to make analogies between them are
misleading. Reviewing other arguments and data, we conclude that there
is every reason to believe that a specialization for grammar evolved by
a conventional neo-Darwinian process.

Keywords: Language, Evolution, Language Acquisition, Natural Selection,
Grammatical Theory, Biology of Language, Language Universals,
Psycholinguistics, Origin of Language

                               Table of Contents
1. Introduction                                                               2
2. The Role of Natural Selection in Evolutionary Theory                       5
     2.1. Nonselectionist Mechanisms of Evolutionary Change                   6
     2.2. Limitations on Nonselectionist Explanations                         7
     2.3. Two Issues that are Independent of Selectionism                    13
          2.3.1. Gradualism                                                  13
          2.3.2. Exaptation                                                  14
3. Design in Language                                                        16
     3.1. An Argument for Design in Language                                 16
     3.2. Is the Argument for Language Design a Just-So Story?               21
     3.3. Language Design and Language Diversity                             25
     3.4. Language Design and Arbitrariness                                  28
          3.4.1. Inherent Tradeoffs                                          29
          3.4.2. Parity in Communications Protocols                          31
          3.4.3. Arbitrariness and the Relation Between Language Evolution   34
                 and Language Acquisition
4. Arguments for Language Being a Spandrel                                   37
     4.1. The Mind as a Multipurpose Learning Device                         37
     4.2. Constraints on Possible Forms                                      38
5. The Process of Language Evolution                                         41
     5.1. Genetic Variation                                                  41
     5.2. Intermediate Steps                                                 43
          5.2.1. Nonshared Innovations.                                      43
          5.2.2. Categorical Rules.                                          45
          5.2.3. Perturbations of Formal Grammars.                           46
     5.3. Reproductive Advantages of Better Grammars                         48
          5.3.1. Effects of small selective advantages.                      49
          5.3.2. Grammatical complexity and technology.                      50
          5.3.3. Grammatical complexity and social interactions.             51
          5.3.4. Social use of language and evolutionary acceleration.       52
     5.4. Phyletic Continuity                                                54
6. Conclusion                                                                56

Stevan Harnad  Department of Psychology  Princeton University
harnad at clarity.princeton.edu       srh at flash.bellcore.com
harnad at elbereth.rutgers.edu    harnad at pucc.bitnet    (609)-921-7771

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