Pronouns form a particularly interesting part-of-speech for evolutionary linguistics because
their development is often lagging behind with respect to other changes in their language. Many
hypotheses on pronoun evolution exist ? both for explaining their initial resilience to change as
well as for why they eventually cave in to evolutionary pressures ? but so far, no one has proposed
a formal model yet that operationalizes these explanations in a unified theory. This paper
therefore presents a computational model of pronoun evolution in a multi-agent population;
and argues that pronoun evolution can best be understood as an interplay between the level
of language strategies, which are the procedures for learning, expanding and aligning particular
features of language, and the level of the specific language systems that instantiate these
strategies in terms of concrete words, morphemes and grammatical structures. This claim is
supported by a case study on Spanish pronouns, which are currently undergoing an evolution
from a case- to a referential-based system, the latter of which there exist multiple variations
(which are called Leísmo, Laísmo and Loísmo depending on the type of change).
