The purposes underlying this writing are twofold: Explain in layman's terms the true development of human existence and behavior; and encourage readers to think about their existence. Because behavior is a product of genetic and environmental influences, it involves the same evolutionary processes that have shaped our physical structure over the preceding seven million years. Over the course of this book, readers will be presented with three sections that cover the greatest influences in shaping humanity - Sex, Survival, and Salvation. Although this writing contains some information about our physical evolution, it is primarily about the evolution of our behavior. It is behavior, that of others and of ourselves, which is most important in determining how we get through life, whether we are happy, or unhappy. It looks at the most important aspects of human existence through the lens of evolution, principally the evolution of behavior, and the historical development of that behavior. Hopefully, this book will help the reader to make rational life decisions knowing that reality is quite simple.