Bryan Levman argues that the Buddha spoke not Pāli as we know it, but an earlier, related vernacular or *koine* that differed in word form, morphology, and sometimes meaning. Evidence for this earlier linguistic layer is uncovered by applying comparative historical linguistics to the various Pāli recensions and parallel transmissions in other Prakrits, such as Gāndhārī. This method reveals that many variant readings and semantic ambiguities in the canon can be traced back to a common ancestral form in the *koine* which had undergone significant phonetic simplification, such as the weakening of intervocalic consonants into glides or the reduction of various aspirated stops to a simple aspirate. Later redactors, transmitting the teachings into their own dialects, reinterpreted these simplified sounds, resulting in the multiple cognate forms found today, a process further complicated by influences from prestigious northwestern dialects and the assimilation of non-Aryan words. Levman concludes that this linguistic evolution is consistent with the Buddhist doctrine of impermanence and supports the Buddha's historicity.
