This book provides a detailed comparison of nonhuman primates and human infants with regard to key abilities that provide the foundation for language. It makes the case for phylogenetic continuity across species and ontogenetic continuity from infancy to childhood. Examined here are behaviors fundamental to language acquisition, such as vocalizations, mapping of meaning onto sound, use of gestures to communicate and to symbolize, tool use, object concept, and memory. The author provides evidence linking these abilities with language acquisition. Similarities and differences across species in these precursors are analyzed and how these may have influenced the evolution of language. Hypotheses about the origins of language are described.