It must be stressed that there is nothing insulting about looking at people as animals. We are animals, after all. Homo sapiens is a species of primate, a biological phenomenon dominated by biological rules, like any other species. Human nature is no more than one particular kind of animal nature. Agreed, the human species is an extraordinary animal; but all other species are also extraordinary animals, each in their own way, and the scientific man-watcher can bring many fresh insights to the study of human affairs if he can retain this basic attitude of evolutionary humility.
