An eye-opening look into why our bodies work--or don't--the way they do. From blurry vision to crooked teeth, ACLs (anterior cruciate ligaments) that tear at alarming rates and spines that seem to spend a lifetime falling apart, it's surprising that human beings have beaten the odds as a species. After all, we're the only survivors on our branch of the tree of life. Why do human mothers have such a life-endangering experience giving birth? And why are there entire medical specialties for teeth and feet? In this funny, wide-ranging and often surprising book, biologist Alex Bezzerides tells us from where we inherited our adaptable, achy, brilliant bodies in the process of evolution. The book traces the delightfully unexpected answers to these questions and many more: · Why do we blink? · Why don't our teeth regularly fit in our mouths? · Why do women menstruate when so many other mammals don't? · Why did humans stand up on two legs in the first place?