Human language is unique within the animal kingdom. However, the study of communicative behavior in extant nonhuman primates - particularly great apes - is critical for understanding the evolutionary origins of this uniqueness. Specifically, to determine why and how such a sophisticated communication system has evolved in humans, one must distinguish those characteristics that are derived in the human lineage and those that are ancestral. However, human language does not leave direct indelible marks in the fossil record. Therefore, to decipher the evolutionary origins of human language, one must identify similarities, as well as differences, between the communicative behavior of humans and their closest phylogenetic relatives, chimpanzees and bonobos. In this talk, I will review a number of studies from my lab that collectively support the broad hypotheses that 1) the most-recent common ancestor of humans, chimpanzees, and bonobos possessed critical pre-requisites for language, and 2) over the course of hominin evolution, increasing group size may have driven the emergence of increasingly complex communication systems eventually culminating in human language.