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.

Sexual behavior in our species goes through three characteristic phases: pair formation, precopulatory activity, and copulation, usually but not always in that order. The pair-formation stage, usually referred to as courtship, is remarkably prolonged by animal standards.

...In little more than a single century from 1820 to 19450, no less than fifty-nine million human animals were killed in inter-group clashes of one sort or another.... We describe these killings as men behaving "like animals," but if we could find a wild animal that showed signs of acting this way, it would be more precise to describe it as behaving like men.

Under crowded conditions the friendly social interactions between members of a group become reduced, and the destructive and aggressive patterns show a marked rise in frequency and intensity.

Looking back now on the whole sexual scene we can see that our species has remained much more loyal to its basic biological urges than we might at first imagine. Its primate sexual system with carnivore modifications has survived all the fantastic technological advances remarkably well.

It is interesting that amongst children of preschool age, the more intelligent ones tend to sleep less than the dull ones. After the age of seven this relationship is reversed, the more intelligent schoolchildren sleeping more than the dull ones.

The female covers her breasts, and then proceeds to redefine their shape with a brassiere. This sexual signaling device may be padded or inflatable, so that it not only reinstates the concealed shape, but also enlarges it, imitating in this way the breast swelling that occurs during sexual arousal.