An exploration of aging that answers all readers’ questions except how they might reverse it. Innumerable enthusiastic authors have revealed how to achieve vast longevity, but British science writer Armstrong (P53: The Gene that Cracked the Cancer Code, 2015) confines herself to genuine aging research, the scientists who engage in it, and the problems they face. It turns out that the news is not all bad. Early theorists pointed out that germ cells (ova and sperm) are immortal; every other body cell (the soma) supports them. Once the organism has reproduced, somatic cells have served their purpose, so evolution removes them to make room for a new generation. “Just because aging is a natural process that happens to us all inexorably…it doesn’t mean that it is either healthy or intractable,” writes Armstrong, who emphasizes that aging seems wasteful. After all, evolution designed a complex process to build an adult from a tiny embryo, but then it falls apart. Wouldn’t it be easier to keep it working than to build it in the first place? Scientists have discovered many mechanisms of aging whose fashions wax and wane. Perhaps harmful genetic mutations gradually accumulate. Perhaps free radicals, chemical products of metabolism, slowly oxidize our defenses. This remains debatable among scientists, but “antioxidants” have become a bestselling health product. Another preoccupation is the telomere, a cap on every chromosome that shortens with each cell division. Once the telomere becomes too short, the cell stops dividing and enters senescence. Keeping it long may be the solution—or maybe not. Stopping the immune system’s steady decline with age seems a possibility. Other researchers hope to tap our body’s immature stem cells. These retain the ability to mature into every kind of tissue, so this would permit creation of fresh young replacement organs. Armstrong’s sensible review of anti-aging science concludes that its goal is achievable—but not yet.