Hadza Cooperation (VIDEO) University of Pennsylvania This video is under embargo. Please login to access this video. Caption Why do humans cooperate? For six years, Coren Apicella and doctoral candidate Kristopher Smith of the University of Pennsylvania have worked to answer this great puzzle, focusing on the Hadza, a nomadic hunter-gatherer population in Tanzania. New findings, which included work from doctoral candidate Tomás Larroucau, suggest that cooperation is flexible, not fixed. Credit SciAni Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.