Elizabeth Hadly is a professor in the Department of Biology at Stanford University. She has spent more than 25 years studying environmental change, conducting primary research on how living and fossil animals can reveal the ways in which current human impacts are influencing evolutionary and ecological systems. She pioneered the new scientific field of phylochronology, which uses fossil DNA to reveal how animals responded to long-ago perturbations, and the newly emerging field of conservation paleobiology, which uses the natural experiments of Earth’s past to help predict how the biosphere will change in the future. Her work has taken her from iconic Yellowstone National Park to the top of Mt. Kilimanjaro in her efforts to understand how people are changing the planet.