Since the early 20th century, the statistical human lifespan has doubled—an increase of 20,000 days. This is the largest, most widespread, and most rapid lifespan increase in human history. With this latest work, best-selling author Johnson (Where Good Ideas Come From) attempts to explain the significant factors causing increased life spans and to broaden readers’ understanding of those factors. Johnson looks at seven wide-ranging categories: vaccines and variolation; the use of data; pasteurization and chlorination; testing; antibiotics; safety; and improvements in food availability. In each case, he points out the range of people, events, and seemingly unrelated disciplines that had to collaborate in order for lifespan-increasing innovations to become practical and widely adopted, like Sir Alexander Fleming’s discovery of penicillin. Blending scientific examples with medical discoveries, the narrative remains engaging and accessible from chapter to chapter, especially where Johnson effectively describes how illnesses that were once considered terminal have become manageable conditions. The thoroughly documented book includes numerous charts and an extensive index. VERDICT Johnson, as in his previous works, digs into his subject to highlight new connections and interrelated facts that produce fascinating and sometimes unexpected insights. A smoothly written book of medical wonder that pays specific attention to racial disparities in health care.