The evolution of the vocabulary of a language is characterized by two different random processes, abrupt lexical replacements, when a complete new word emerges to represent a given concept (which is at the basis of the Swadesh foundation of glottochronology in the 1950s) and gradual lexical modifications that progressively alter words over the centuries, considered here in detail for the first time. The main discriminant between these two processes is their impact on cognacy within a family of languages or dialects, since the former modifies the subsets of cognate terms and the latter does not. The automated cognate detection, which is here performed following a new approach inspired by graph theory, is a key preliminary step that allows us to later measure the effects of the slow modification process. We test our dual approach on the family of Malagasy dialects using a cladistic analysis, which provides a strong evidence that lexical replacements and gradual lexical modifications are two random processes that separately drive the evolution of languages.

This content is only available as a PDF.

Author notes

Action Editor: Minlie Huang

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits you to copy and redistribute in any medium or format, for non-commercial use only, provided that the original work is not remixed, transformed, or built upon, and that appropriate credit to the original source is given. For a full description of the license, please visit