Stephen Stearns, teaching Yale's Evolution and Medicine course, examines the shift from foraging to agriculture as a turning point in human biology. Drawing on the textbook Evolutionary Medicine, he traces how the change in diet, population density, and lifestyle that came with farming altered patterns of disease and reshaped the selective pressures acting on human populations. The lecture connects the archaeological and demographic record of this transition to specific health consequences, including shifts in infectious disease exposure and nutrition-related conditions, framing them as evolutionary responses rather than isolated medical events. As part of a numbered lecture series, this segment builds on earlier material regarding evolutionary theory and sets up later discussion of how ancient adaptations affect modern health. The presentation is spoken lecture format, aimed at students already following the course's evolutionary medicine framework.