The Biology and Evolution of Human Language The human ability to learn and use natural languages is not simply an incidental outgrowth of more general intellectual capacities, but something deeply rooted in the biology of our species. The fact that our “language organ” is not physiologically localized in the fashion of, say, the kidneys, does not alter the conclusion that our capacity for language is biologically determined in the organization of our body, mind, and brain. This symposium will explore several dimensions of that conclusion, surveying communication in other species to demonstrate that the essential properties of human language are quite different from anything found elsewhere. The structural properties of language suggest an origin like that of any biologically determined trait -- evolution through natural selection. We argue that the logical prerequisites for such an account are satisfied in the case of language. Language emerges in the individual as natural growth, not arbitrary learning, and that growth is associated with specific periods in the life of the organism. A nonhuman system showing interesting analogies with important properties of language is birdsong: we present recent work on its neurophysiological bases. The symposium will also survey the brain bases of human language. The signed languages of the deaf have all of the important structural properties of other human languages, and we present evidence that the same neurophysiological and other bases underlie language in both auditory and visual modalities.