1 Introduction
There has been growing interest in language evolution among non-linguists as
well as linguists. Even in the dawn of evolutionary theory, Darwin (1859, 1871)
himself mentioned the adaptive emergence of language as the extension of natural
selection on biological evolution, but the dispute about it has neither reached
nor gotten close to a valid conclusion until recently. Pinker and Bloom (1990)
posit that the human language faculty is a complex biological adaptation that
evolved by natural selection for communication. On the contrary, Chomsky refuses
their claim and strongly insists that language is not the production of natural
selection and did not evolve adaptively solely for communication. Although both
points of view seem to be quite contrary, their proposals are not incompatible if
viewed from a different angle. It can be thought that they see opposite sides of
the same coin. This chapter proposes that there are both adaptive and non-adaptive
aspects in the evolutionary process of language. Specifically, on the basis of empiri-
cal evidence of case phenomena attested in Icelandic and the historical change of
the English language, it is argued that language should be divided into Language
of Thought (LoT) and Language of Communication (LoC) on the basis of the
assumption that case plays an important role in identifying thematic roles of nouns
exclusively at LoC. Then it will be proved that the former has a non-adaptive
process of evolution, whereas the latter is vulnerable to selection pressure.
2 Issues concerning case/Case
Within the standard framework of GB theory, NP lacking case must move to
a position where it is assigned case because of the Case Filter in (1).
(1) *NP if NP has phonetic content but no Case.
For example, as illustrated by (2b), the book, which does not receive case in
its base position, must move to Spec, IP in order to receive nominative case.
(2) a. The book was bought by John.
b. [IP the booki [Iā was+I [VP [VP bought ti ] by John]]]
Two aspects of syntactic
evolution
1