The author argues that there are specific turning points in evolution. Structures and behavioral patterns that evolved in the service of discrete functions sometimes allow for unforeseen new developments as a side effect. In retrospect, they have proven to be pre-adaptations, and serve as raw material for natural selection to work upon. Love and Hate was intended to complement Konrad Lorenz's book, On Aggression, by pointing out our motivations to provide nurturing, and thus to counteract and correct the widespread but one-sided opinion that biologists always present nature as bloody in tooth...

With the discovery of conditioned reflexes by I. P. Pavlov, the possibilities for experimenting, following the example set by the classical, exact sciences, were made available to the behavioral sciences. Many psychologists hoped that the component parts of behavior had also been found from which the entire, multifaceted cosmos of behavior could then be constructed. An experimentally oriented psychology subsequently developed including the influential school of behaviorism. This first text on human ethology presents itself as a unified work, even though not every area could be treated with...