1. Department of Anthropology, New York University , New York City, 10003 , USA
2. Department of Biological Science, Vanderbilt University , Nashville, 37232 , USA
3. Department of Psychology, University of Exeter , Exeter, EX4 4QG , United Kingdom
4. School of Life Sciences, Center for Evolution and Medicine, and School of Human Evolution and Social Change, Arizona State University , Tempe, 85281 , USA
5. Child and Brain Development Program, Canadian Institute for Advanced Study , Toronto, M5G 1M1 , Canada