Nature's Nether Regions: What the Sex Lives of Bugs, Birds and Beasts Tell Us about Evolution, Biodiversity, and Ourselves
by Menno Schilthuizen.
Viking, 2014

The science of genitals is a relatively new field for biologists, who have long overlooked the evolutionary importance of species' private parts. Biologist Schilthuizen balances the silly and the serious to describe researchers' latest efforts to understand how “evolution has graced the animal kingdom with such a bewildering diversity of reproductive organs.” Schilthuizen tours some of nature's weirdest inventions, such as the chicken flea penis, which is “actually a profusion of plates, combs, springs, and levers” and looks like “an exploded grandfather clock.”