Chapter 2 y though we are not exactly descended from present-day apes we do share common ancestors with them. And evolution from other animals has become the central theory in biology y as has often been remarked, darwin (1859) dethroned human beings from their place as unique creations in the image of god. A piece of darwin s evidence was the similarity of human emotional expressions to those of lower animals. Elements of an evolutionary approach to emotions y the engine that drives evolution has three parts. The first of these darwin called superabundance: animals and plants produce more offspring than necessary merely to reproduce themselves. The second is variation; each offspring is somewhat different than others, and differences are passed on by heredity. The third is natural selection: characteristics that allow the individual to be adapted to the environment are selected for; disadvantageous characteristics are selected against. Selection pressures y at the core of natural selection are selection pressures.