Evolution of social behavior and its neurobiological basis-where we began, and where we are going.

Understanding how neural systems evolve to coordinate animal social behavior is a longstanding goal of modern biology. Historically, specializations to the brain are thought to underlie the diversification of social phenotypes, whether this entails the emergence of novel circuits or modifications to existing circuits that underlie motivation, arousal, and stimulus saliency. More recent work expands this purview by considering the whole brain and by exploring phenomena like neural coordination between social partners. Meanwhile, new technologies like single-cell spatial transcriptomics and machine learning have upended how we study the brain and its relationship to behavior, creating fresh perspectives on neural system innovation and functional complexity. Future studies will need to incorporate these ideas to craft a more unifying framework that considers how social behavior emerges from distributed neural circuits and how these circuits can be reorganized and repurposed through time to support the diversification of elaborate social forms.