As far as we can tell, only one species has a communicative system of the complexity of human language, and that is humans. By comparing full-blown human language with other systems, we can learn something about how human language arose in prehistory. Recent advances in primate cognition and social behavior, infant cognition and social behavior, archeology, genetics, and other fields allow us to adduce various sorts of evidence, of various degrees of directness, to make hypotheses about the origin and development of human language. In doing so, we can also learn more about human language itself and the nature of the human species.