This work aims to show that, contrary to the received wisdom, the ideas of the two most influential thinkers of the modern age were not by definition antagonistic or antithetical, but are in fact part of a neglected whole only now being unearthed by a new breed of scientist. This book proves how Freud was right and Darwin was right - sex is the motor of human behaviour. The author shows why: we have evolved to love our children while neglecting ourselves; you fight hardest, and squabble most fiercely with those least dissimilar to you, for example, your (nearly) close relations; a woman will always invest more in her child than her man (be he a new man or an old one), and she will typically favour a male child over a female; marrying your first cousin might not be such a bad idea; the likelihood of any murder being committed by a step-parent is staggeringly high; homosexuals behave, in a way, like cryptic heterosexuals; we are very ambivalent about incest - we are repelled by it, and we are attracted to it, at the same time.