This book shows how to combine grammaticalization theory with the comparative method to reconstruct the grammar of Proto-Languages. To showcase the methodology, seven morphosyntactically distinct verbal systems in the Cariban family--three ergative, three nominative, and one inverse--are reconstructed. Spike Gildea presents detailed data in his reconstruction of Proto-Carib verbal and nominal morphologies. The inverse verbal system reconstructs to Proto-Carib; the other six are innovative, and reconstruct to Proto-Carib nonfinite source-constructions.