This book begins the inquiry into the evolution of the collective sensitivities of life. Chapters trace the emergence and evolution of consciousness. Complex behaviors and the social imperatives of bacteria and other life forms during 3,000 million years of Earth history gave rise to mammalian cognition. Awareness and sensation led to astounding activities; millions of species incessantly interacted to form our planet’s complex conscious system. Our planetmates, all of them conscious to some degree, were joined only recently by us, the aggressive modern humans. From social bacteria to urban citizens, all living beings participate in community life. Nested inside families within communities inside ecosystems, each metabolizes, takes in matter, expends energy, and excretes. Each of the members of our own and other species, in groups with incessantly shifting alliances, receives and processes information. Mergers of radically different life forms with myriad purposes—the “chimeras” of the title—underlie dramatic metamorphosis and other positive evolutionary change. Since early bacteria avoided, produced, and eventually used oxygen, Earth’s sensory systems have expanded and complexified. The chapters in this book serve to put sensitive, sensible life in its cosmic context.