The ongoing expansion of interdisciplinary research has been coined a "golden age" in science, yet the replication crisis and difficulties in applying scientific insights have contributed to declining public trust in science. There has been a noticeable lack of focus on theory in advancing scientific practices. Simultaneously, evolutionary social science is proliferating, offering distinct methodological tools that support the development, improvement, and integration of theories across disciplines. In this presentation, I will introduce my integrative research program within evolutionary social science, with a focus on human leadership and conflict resolution. I will demonstrate that through the application of both comparative and ethnographic methods, evolutionary social scientists can make substantial contributions to the development of theoretical models across the social and behavioral sciences.