When Humans Nearly Vanished: The Catastrophic Explosion of the Toba Volcano

Despite the title, the Toba volcano makes not much more than a cameo appearance in this slim volume. Prothero (The Story of Earth in 25 Rocks), a paleontologist and geologist, describes Toba’s eruption on the island of Sumatra in Indonesia, around 74,000 years ago, as the “largest volcanic eruption in the past 28 million years,” and briefly touches on the theory of how it decimated humanity, leading to a population bottleneck that partly explains the relative lack of genetic diversity in humans today. He also touches on the process by which scientists discovered the eruption had ever occurred, which only became apparent with new findings in 1993. The bulk of this book, however, is a primer for related topics: brief summaries of the geology of volcanism, the structure of DNA, the evolutionary relationship between humans and primates, and the fossil evidence for the evolutionary origins of Homo sapiens. Prothero writes clearly and at a level accessible to the lay reader, but he presents no new material and is unlikely to satisfy anyone looking for more than a precis of the current state of knowledge in these diverse fields. (Oct.)