Mirror neurons and the evolution of language.

The mirror system provided a natural platform for the subsequent evolution of language. In nonhuman primates, the system provides for the understanding of biological action, and possibly for imitation, both prerequisites for language. I argue that language evolved from manual gestures, initially as a system of pantomime, but with gestures gradually "conventionalizing" to assume more symbolic form. The evolution of episodic memory and mental time travel, probably beginning with the genus Homo during the Pleistocene, created pressure for the system to "grammaticalize," involving the increased vocabulary necessary to refer to episodes separated in time and place from the present, constructions such as tense to refer to time itself, and the generativity to construct future (and fictional) episodes. In parallel with grammaticalization, the language medium gradually incorporated facial and then vocal elements, culminating in autonomous speech (albeit accompanied still by manual gesture) in our own species, Homo sapiens. 2009 Elsevier Inc. All rights reserved.