I am a paleoanthropologist engaged in studying early human evolution. I founded and direct the Human Origins Program at the Smithsonian’s National Museum of Natural History, Washington, DC. In partnership with the National Museums of Kenya, I lead ongoing excavations at field sites in southern and western Kenya. After receiving my PhD in biological anthropology at Harvard University in 1982, I taught at Yale before joining the Smithsonian in 1985. Research teams that I organize investigate Earth’s environmental dynamics and the processes that have led to human evolutionary adaptations. Recent contributions focus on how environmental instability has influenced human evolution, an idea that has stimulated new studies in Earth sciences, paleontology, and computational biology. I am also the curator of the Smithsonian’s Hall of Human Origins and of the exhibit “Exploring Human Origins”, which has been traveling across the U.S. since 2015. Among many publications for scientific audiences and educators, I am the author of the exhibit companion book "What Does It Mean To Be Human?"