"Lifespan: Why We Age—and Why We Don't Have To" is a book by David Sinclair, a renowned biologist, that explores the biological mechanisms of aging. Sinclair discusses how aging is not an inevitable process but rather a condition that can be influenced by various factors, including genetics and lifestyle choices. The book presents scientific research on potential interventions, such as resveratrol and NAD+ boosters, that may help extend lifespan and improve health during aging. Sinclair emphasizes the importance of understanding the aging process to develop strategies that could lead to longer, healthier lives.