The story of evolution as you've never heard it before What's the easiest way to tell species apart? Check their genitals. Researching private parts was long considered taboo, but scientists are now beginning to understand that the wild diversity of sex organs across species can tell us a lot about evolution. Menno Schilthuizen invites readers to join him as he uncovers the ways the shapes and functions of genitalia have been molded by complex Darwinian struggles: penises that have lost their spines but evolved appendages to displace sperm; female orgasms that select or reject semen from males, in turn subtly modifying the females' genital shape. We learn why spiders masturbate into miniature webs, discover she dungflies that store sperm from attractive males in their bellies, and see how, when it comes to outlandish appendages and bizarre behaviors, humans are downright boring. Nature's Nether Regions joyfully demonstrates that the more we learn about the multiform private parts of animals, the more we understand our own unique place in the great diversity of life.