Evolutionary theory and behavioral biology suggest that kinship is an organizing principle of social behavior. The ability to recognize kin and the adjustment of behavior based on kin preference is key to altruism, attachment theory and mate selection. Despite the fundamental importance of kinship, the underlying neural mechanisms are not understood. I have developed a research avenue for investigating the mechanisms of kinship in the brain, with an initial focus on the lateral septum. I will follow this line of research in the Grass Fellowship with novel technical approaches including large-scale neural recordings in socially interacting rats. I will focus on the stages of social-sensory processing beginning with recognition and ending with social attachment. In between, I hope to disentangle both innate and learned aspects of kinship behavior. Two specific behaviors which I will observe in the fellowship project are familial huddling and inbreeding avoidance behavior.