ABSTRACT
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 empirical 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.
