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?