Relationships between individual development and historical change are understudied, and yet an understanding of these relationships is foundational to understanding human development. The chapter provides a case study model for investigating individual-historical relations that coordinates archival, ethnographic, interview, and experimental methods. The methodological approach is illustrated in studies on numerical cognition conducted in Papua New Guinea. Two generalizable methodological assumptions are articulated: that the emergence of novel representations and ideas is rooted in individuals' activities in collective practices and that the dynamic sociogenetic processes in collective practices provide the context for individual development. The chapter concludes by pointing to extensions of the framework to additional studies conducted in a wide range of communities.