Introduction

A feature of current computational models of language evolution is that the individuals in later populations are not structurally, ‘physiologically’, different from those in the first. Evolution may be working on the language itself, as learned by agents which do not evolve, or on an innate communication scheme. A number of models specifically demonstrate self-organisation of communication schemes and grammars in populations that are already capable of language.

Such models do not show communities evolving from those capable of some simple protolanguage towards those capable of some fuller language. In contrast, in human evolution, vocalisations and speech provided a selective advantage that led to the exaptation and adaptation of aspects of human physiology to support improved language capacity (Deacon 1992; Lieberman 1992). This led to a process of language-physiology coevolution. From the coevolution of physiology and language, hominids developed differences from other primates, such as increased brain size and a supralaryngeal vocal tract.

The coevolution of speech and physiology in humans was also not without cost. The larger brain costs more energy to maintain, and requires a longer infancy for brain growth to be completed. The dropped epiglottis allows greater clarity and distinctiveness in speech, but increases risk of choking.

While some vocalisations are evolved responses – crying, laughter and so on – speech is learned afresh by every individual. Learning allows quicker adaptation to changes in the environment and faster solutions to environmental problems.