Some 4,000 million years ago, life appeared on Earth. What is the history of its evolution? Was life inevitable? And what about the human race? Would there have been any other intelligent being if there had not been humans? What patterns does the evolutionary mechanism use? Does evolution advance like an arrow, always forward? Starting from questions such as these, and with a solid review of the scientific answers they have been given over the years, the author traces an authentic history of life that culminates in the question of the meaning of humanity: Why are we here? The next great book by Juan Luis Arsuaga after "The Chosen Species". The most ambitious book on evolutionary theory by the most prestigious scientific expert on the subject, both in Spain and internationally.