In this era of open discussion of sexual violence, testosterone is facing public scrutiny. Hooven's (human evolutionary biology, Harvard Univ.) new book sets out to investigate whether male aggression can be definitively linked to testosterone, or if the social norms of patriarchal societies have more impact than biology. Hoover brings to this discourse her background in natural sciences and her studies in biological anthropology. She has written a thorough and interesting assessment of the science behind testosterone and human behavior; topics include biological determination of sex, effects of testosterone in athletes, and testosterone's use in gender-affirming treatment for some trans people. In addition to the science, Hooven provides cultural context, including personal narratives from people who have transitioned, as well as one person who has detransitioned; she lets people tell their stories in their own words, allowing for a more complete picture. Hooven encourages readers to approach this information through an evidence-based lens and to question their own judgments. Her insight into evolutionary biology and human behavior will be valuable not only to scientists but to anyone interested in social change. VERDICT A provocative, academic, accessible look at the science behind human behavior, suitable for those interested in natural and social sciences.—Cate Triola, Capella Univ., Minneapolis