Testosterone is the most mythologized and misunderstood hormone, but Harvard evolutionary biologist Carole Hooven offers riveting human stories and cutting-edge research to reveal the far-reaching effects of testosterone on our brains, bodies, and behavior. The biological source of virility and masculinity has inspired fascination, investigation, and controversy since antiquity. From the eunuchs in the royal courts of ancient China to the booming market for "elixirs" of youth in nineteenth-century Europe, humans have been obsessed with identifying and manipulating what we now know as testosterone. And the trends show no signs of slowing down-the modern market for testosterone supplements is booming. Thanks to this history and the methods of modern science, today we have a rich body of research about testosterone's effects in both men and women. The science is clear: testosterone is a major, invisible player in our relationships, sex lives, athletic...