I am a Paleoecologist specializing in the impacts of climate change and human activities on ecosystems, in particular the "megafaunal" extinctions that wiped out most of Earth's large mammals between ~10,000 and 50,000 years ago. I co-direct the research and collections department at La Brea Tar Pits, the world's most important Ice Age fossil site, and hold adjunct faculty appointments in the Institute of the Environment and Sustainability at UCLA and the Department of Earth Sciences at the University of Southern California.