David Sinclair is an Australian biologist and professor known for his research on aging and longevity. He is a co-director of the Paul F. Glenn Center for the Biology of Aging at Harvard Medical School. Sinclair's work focuses on understanding the mechanisms of aging and how to potentially slow it down through lifestyle changes and interventions. He is also a co-founder of several biotechnology companies aimed at developing therapies to extend healthy lifespan. Sinclair has authored the book Lifespan: Why We Age—and Why We Don't Have To, which discusses his findings and theories on aging, as well as practical advice for improving health.