This CARTA symposium addresses the question of how human language came to have the kind of structure it has today, focusing on three sources of evidence. One source, which is discussed in these three talks, concerns what contrasts between new and mature languages reveal about how language evolves. Mark Aronoff (Stony Brook Univ) begins with an examination of the Co-emergence of Meaning and Structure in a New Language, followed by David Perlmutter (UC San Diego) on Combinatoriality within the Word: Sign Language Evidence, and Ray Jackendoff (Tufts Univ) on What Can You Say without Syntax? Recorded on 2/20/2015. (#29394)