There’s a fish that makes its home in the butt of a sea cucumber. Why? Because it worked for one crazy ancestor, and winning strategies, however unseemly, get perpetu­ated by natural selection. (That goes for humans too: Our mating rituals seem normal to us, but they must be hilarious to our pets.) Ultimately, life is pretty simple: Eat, don’t get eaten, and perpetuate the species—all the rest is optional. While researching my new book, The Wasp That Brainwashed the Caterpillar (out October 25), I got familiar with a wild assortment of evolution-approved survival tactics. Here are some of my favorites.