Hormones don't make women irrational; they help women choose mates, compete with female rivals, produce healthy offspring, and conquer other biological challenges.

With fresh insight, Martie Haselton explains how the fertility cycle has evolved over millions of years into a fine-tuned signaling system. Among the fascinating findings: During ovulation, women's attractiveness peaks because their "mate search effort" is turned on.

Their walking gait, voice, skin condition, and dance moves are more alluring, and they wear more revealing clothes. They also tend to shop more.

Being on the Pill affects women's preferences in men, and PMS may have evolved to get rid of boyfriends with unfit sperm.

The research is provocative, but Haselton also presents practical advice for women to use their hormonal cycles to their advantage, helping them achieve success in their relationships, careers, and lives. Groundbreaking and counter-intuitive, Hormonal will empower women everywhere to embrace their biology.