A disturbing examination of the diverse and interacting factors that influence the human life span, plus a brief look at some attempts to alter the aging process. Moore, a science writer with a penchant for stirring up controversy (Heart Failure, 1989), argues that risk factors such as obesity, hypertension, and elevated cholesterol levels have been oversold and that individual efforts to control them have little effect on achieving long life. (The exception is smoking, which he acknowledges has a measurable life-shortening effect.) Having long-lived ancestors doesn't help much either. Your best bet, Moore says, is to be a healthy, well-educated, well- adjusted, professionally employed member of a stable, prosperous, democratic society. War, famine, and disease have always been the greatest threats to human life, and it is on infectious diseases that Moore focuses his attention. The relationship between humans and microscopic life-forms is constantly changing, and organisms that are harmless in one environment may become deadly under different circumstances. Moore also warns against overconfidence about our mastery of disease: Influenza, which killed millions earlier in this century, remains a threat, and new viruses such as AIDS could reverse recent gains in human longevity. Theories about why 115 years appears to be the maximum life span and research into how this might be altered are examined in the final chapters, while the author's documentation is tucked away in an end-of-book section. An authoritative, accessible, and lively study that may unsettle those who prefer to feel in firm control of their destiny.