Human evolution is marked by two important locomotor transitions. A shift to bipedal walking and increased aerobic activity levels that likely evolved with the adoption of a hunting and gathering lifestyle. How did these changes influence human anatomy, physiology, neurobiology, and life history and how and why will our current, more sedentary lifestyle impact our physical and mental health? In this Episode: Renu Malhotra, Ph.D. Professor, Planetary Sciences, Chair of the Theoretical Astrophysics Program, University of Arizona, Member, National Academy of Sciences and of the American Academy of Arts and Sciences; Leslie Tolbert, Ph.D, Regents' Professor in the University of Arizona's Department of Neuroscience