This book is a history of how life has responded to toxic chemicals, from cells' response to UV radiation more than 3 billion years ago to people's response to the chemicals in plastics today. Emily Monosson argues that in an age when we are constantly bombarded by new synthetic chemicals, it is critical to understand the 'defense mechanisms' humans have developed over millennium to deal with toxics. She writes, 'by considering the evolution of a body's response to harmful amounts and combinations of chemicals, toxicologists might better predict, and possibly prevent harm caused by today's novel challenges.'