On the parallel evolution of syntax and lexicon: A Merge-only view

- Neither syntax nor the lexicon came first. Both evolved in parallel on the basis of Merge.
- Merge evolved as an exaptation of object combination.
- The two hypotheses on the origins of Merge and pre-linguistic symbols should be integrated into one evolutionary scenario.
- Transitivity alternation of verbs can be accounted for by Merge and Label.

It is a generally accepted view that syntax and the lexicon are two separate modules of human language and therefore that their evolution must be studied independently of each other. In this brief article I challenge this traditional view and argue, in light of the recent development in the minimalist program of generative grammar, that both syntax and the lexicon evolved from the single capacity of the elementary combinatorial operation Merge: neither syntax nor the lexicon came first but both evolved in parallel on the basis of this uniquely human innovation. I argue that the so-called lexical items are complex objects composed of pre-linguistic symbols and that this composition is made possible by Merge. For the evolution of Merge and these pre-linguistic symbols, I introduce the hypotheses of the motor control origin of Merge (Fujita, 2014) and the string-context mutual segmentation (Okanoya & Merker, 2007), respectively, and propose to integrate these two hypotheses for the purpose of studying language evolution in a wider perspective. I also illustrate the syntactic nature of word formation by providing a new Merge/Label-based account of the transitivity alternation of verbs.