The origin of the Indo-European simple thematic presents

It is now generally agreed upon that the Indo-European simple thematic presents are a post-Anatolian innovation. The origin of this formation, however, remains unclear. In this paper it is argued that the initial core of simple thematic presents was of denominative origin. They go back to an early Core PIE class of denominatives derived from e-grade thematic adjectives through conversion, e.g., adj. *léu̯k-o- ‘clear’ (Gk. λευκός ‘white’) → vb. *léu̯k-e/o- ‘be/make clear’ (Ved. rócate ‘shines’, TB lyuśtär ‘will light up’). This derivational pattern became obsolete already within Core PIE and a number of original denominatives like *léu̯k-e/o- were reinterpreted as primary present stems.