Book excerpt: The hidden intelligence of hormones and their role in empowering women to succeed sexually, reproductively, and socially. Did you know women walk more, eat less, socialize more, meet more men, dance more, and flirt more when they're ovulating? Or that PMS may have evolved to get rid of boyfriends with unfit sperm? Behind the "fickle" differences in what women find sexy about men, or what they like to wear, there's a hidden adaptive intelligence that has been shaped over eons. In this provocative and paradigm-shattering book, Martie Haselton, the world's leading researcher on sexuality and the ovulation cycle, takes a deep, revealing look at the biological processes that so profoundly influence our behavior and sets forth a radical new understanding of women's bodies, minds, and sexual relationships, one that embraces hormonal cycles as adaptive solutions to genuine biological challenges. At the core of Hasleton's new Darwinian feminism is her remarkable discovery that humans, like our animal cousins, possess a special phase of sexuality, called estrus, which comes with a host of physiological and behavioral changes. Rigorously researched, entertaining, and empowering, Hormonal offers women deep new insights into their bodies, brains, relationships, and affairs, allowing them to make better-informed choices about sex, marriage, friendship, contraception, and more. Above all, Hormonal is a clarion call to appreciate and embrace the genius of female biology.