Abstract: This paper defends the theory that the human language faculty is a biological adaptation and, like other examples of complex adaptive design in the natural world, it is a product of natural selection. Language is designed to code propositional information for the purpose of sharing it with others, and thus fits with other features of the distinctive human "cognitive niche” including cause-and-effect thinking and hypersociality. Finally, the paper demonstrates that these and other evolutionary hypotheses about language as an adaptation have been supported by two new areas of research: evolutionary game theory, and tests for selection in molecular evolution

Key words: language evolution, adaptation, natural selection, evolutionary game theory, molecular evolution