The themes discussed in this book, translated to English by Australian Kieran Tapsell, form part of a revolutionary discipline known under the name of evolutionary psychology, a discipline that has become the most powerful tool discovered to date for man to understand himself. Much of the knowledge revealed by human science is explained as a result of the evolutionary process, using as a premise the theory that the majority of modern man?s desires, impulses, interests and inclinations, and mental faculties were designed by the evolutionary process of the species. This new focus allows us to synthesize a group of already established findings, coming from such diverse disciplines as genetics, evolution, ethology, anthropology, psychology, neurology and epistemology. In this way, it is possible to explain an important part of complex human behavior under one sole, unifying principle: the direct or indirect search for a greater reproductive efficacy. With this work, easily readable by the general public, the author completes a cycle of subjects that he had begun with From the Big Bang to Homo Sapiens (2004), a book published in Spanish by Villegas Editores.