Possible stages in the evolution of the language capacity

Much current discussion of the evolution of language has concerned the emer gence of a stage in which single vocal or gestural signals were used symbol ically. Assuming the existence of such a stage, the present review decompos es the emergence of modern language into nine partially ordered steps, each of which contributes to precision and variety of expression. Bickerton's p roposed 'protolanguage' falls somewhere in the middle of this succession. I n addition to the by-now accepted evidence from language learning, language disorders, and ape language experiments, modern languages evidence of thes e stages of evolution through the presence of detectable 'fossils' in vocab ulary and grammar.