AbstractIt is an old and widespread assumption in historical linguistics that hypotactic structures evolved out from paratactic structures. In more recent times, the parataxis-to-hypotaxis hypothesis was associated with the assumption that syntactic structures are discourse-based. This means that hypotactic structures evolved via syntacticization, i.e., via “a process by which flat, paratactic discourse-pragmatic structures transform over time into tight, hierarchic syntactic structures” (Givón 1979: 82f.). One special aspect of this assumption is that complementizers are held to have grammaticalized from nouns, verbs, prepositions, or pronouns in bi-sentential, paratactic source structures. In this paper, I will re-evaluate the existing evidence for the parataxis-to-hypotaxis hypothesis with special focus on the emergence of complementizers. The result of the re-evaluation is that in all cases, where we have enough historical data to reconstruct the development in detail, we have to assume a source structure that already displays subordination. In most cases, the subordinate clause is a relative clause suggesting that relativization is probably the oldest form of subordination. The over-all result of the re-evaluation is that there is no reliable evidence at all for the parataxis-to-hypotaxis hypothesis in its current form.