One thousand million years ago, a huge revolution occurred on Earth - sex happened for the first time. From that moment on, the world became ever more colourful and bizarre, ringing with elaborate songs and dances, epic battles, and rallying cries as the desires of males and females collided, generation after generation, in an unbroken chain of sex going back to the dawn of complex life on Earth. Animal life rings, bleeds, and howls with sex. It's everywhere. Right now warring hordes are locking horns, preening feathers, rampaging lustfully across the savanna, questioning the fidelity of the ones they love. A million females choose; a billion penises ejaculate (or snap off); a trillion sperm battle, block, and tackle. Sex made planet Earth, well, sexy. Writing in a brilliantly engaging style, biologist Jules Howard leads readers on a guided tour of the how and why of sex on Earth, in all its diversity. From sperm wars to cuckoldry, hermaphrodites, virgin births, "exploding" penises, and mallards' "booby-trapped" vaginas, Sex on Earth explores and celebrates the wonders and peculiarities of animal reproduction. "A refreshingly self-aware exploration of the most intimate moments in nature and how the incredible variety of life has led us to frame our own thoughts about this near-ubiquitous biological drive.” —Brian Switek, National Geographic