Stephen Stearns, teaching Yale's Evolution and Medicine course, explains parent-offspring conflict as a case study in evolutionary medicine. Drawing on Robert Trivers' theory, he lays out why a parent's optimal investment in a child differs from what the child's own genes favor, since offspring share only half their genome with parents but all of it with themselves. Stearns works through the resulting tug of war over resources such as weaning time and in utero nutrient transfer, and connects the framework to real medical puzzles, including why pregnancy complications like preeclampsia might reflect a fetus pushing for more maternal resources than the mother's body is selected to give. The lecture is a short segment within the larger course built around the Sinauer textbook Evolutionary Medicine, and it stays tightly focused on the mechanics of the conflict rather than surveying the whole field. Dense but clear, it is best watched as part of the fuller course sequence.