Located in the premotor cortex, just in front of the motor cortex, these cells represent, according to Arbib, a mechanism for recognizing the meaning of others' actions. Rizzolatti first noticed mirror cells several years ago in an experiment to determine which neurons fire whenever a monkey grasps an object. Many neurons in the premotor cortex became active when a monkey performed a single task, say tearing or grasping. Arbib calls this mechanism the pre-requisite for speech. For communication to succeed, both the individual sending a message and the individual receiving it must recognize the significance of the sender's signal.
Mirror neurons are thus the missing link in the evolution of language.
They provide a mechanism for the sharing of meaning. These findings support the theory that human speech evolved from an ancient gestural communication system rather than vocal communication evolving directly, as some scientists have speculated. Analysis of fossil skulls suggests that, as the primate brain evolved, it was building a language mechanism even before there was a larynx capable of articulating speech. While monkeys and other non-human primates continue to lack the vocal hardware needed to articulate speech, they do have the brain circuits needed for simple communication.