The Biology and Evolution of Human Language The study of how sentence structure changes over time -- historical syntax -- is being transformed by new connections to other sciences (e.g., cognitive science and complexity science) and new tools, especially the creation of large datasets. This symposium will consider how changes in syntax can be understood in light of two such innovations: on the one hand, advances in our understanding of first- and second- language acquisition and, on the other, advances in corpus development and the statistical analysis of such data. Core syntactic change takes place during transmission of language from one generation to another. Recent work on phase transitions in language acquisition sheds light on how large syntactic changes take place. The creation of new languages, or creolization, provides unique perspectives on the interplay of first- and second-language acquisition as a new grammar is built from complex and variable input. A full picture of changes large and small over a broader span of time requires corpora of a size unimaginable only a few years ago. Corpus work allows us to see fine-grained conditioning of change and establish tipping points for larger changes. The focus will be on how these approaches complement one another and how a new synthesis can emerge for the study of syntactic change as a window on human cognition and how the treatment of phase transitions in syntax relate to phase transitions in other areas of science (e.g., evolutionary changes in biology).