&i;`When we grasp fully that the best expressions of our humanity were not invented by civilization but by cultures that preceded it, that the natural world is not only a set of constraints but of contexts within which we can more fully realize our dreams, we will be on the way to a long overdue reconciliation between opposites which are of our own making.'&o; - from Coming Home to the Pleistocene. Throughout his long and distinguished career, Shepard returned repeatedly to this guiding theme, the central tenet of his thought: that our essential human nature is a product of our genetic heritage, formed through thousands of years of evolution during the Pleistocene epoch, and that the current subversion of that Pleistocene heritage lies at the heart of today's ecological and social ills. This book provides the fullest explanation of that theme. Completed just before his death in 1996, it represents the culmination of Paul Shepard's life work and constitutes the clearest, most accessible expression of his ideas.