In 2800, humanity expanded Earth to fifty times its original size to solve an overcrowding crisis, accidentally contaminating the new land with chemical residue that doubled the size of every animal and plant on the planet. A thirty-three hour day, five-month seasons, and megafauna that can look a human in the eye on all fours are now simply facts of life. A century later, the industrial pollution required to colonize all that new land has poisoned the atmosphere over most of the developed world, forcing civilization into sealed dome cities where people breathe filtered air, eat inferior food, and die at forty-five on a good day. The solution governments landed on is brutal and simple: every eighteen-year-old takes a standardized fertility and health exam, and anyone who scores high enough gets sent to live in one of the scattered clean pockets of wilderness that industry never reached. Those who fail stay in the dome. Outside the domes, tribes of exiled humans have built their own culture from scratch — one shaped by the fact that only twenty percent of exam passers are female, which has produced a society where women are precious, men bond with them for life, women choose freely among multiple partners, and everyone bonds at eighteen with a wild predatory animal that becomes their hunting companion for life. The food is extraordinary, the air is clean, and the world is enormous and dangerous and alive in ways the domes never were.