A brief history of the female body An evolutionary look at how and why the female form came to be

Biologist Emera's enlightening debut traces the evolutionary history of women's bodies. Mammary glands, Emera explains, likely developed from sweat glands in humans' amphibian-like distant ancestors more than 350 million years ago. Nipples formed later, providing offspring with a more sanitary alternative to licking milk droplets mothers "sweat out" on their skin, where the milk would have risked spoiling and mingled with bacteria. Exploring the science of why women menstruate, Emera suggests it's likely a form of "quality control... screening for the best eggs, sperm, and embryos." Another theory illuminates how the interests of a mother and child sometimes conflict: the endometrium that builds up in the uterus during the menstrual cycle is possibly a precaution to make it harder for a yet-to-be-formed embryo to sap more nutrients from its mother than she can afford to lose. Emera also discusses research into the mechanics of mate selection, including one study in which women reported finding the scents of men who were genetically dissimilar from them more attractive than the scents of men who were more similar. Thought-provoking and accessibly written, this fascinates. (Aug.)