There are one hundred and ninety-three living species of monkeys and apes. One hundred and ninety-two of them are covered with hair. The exception is… - Desmond Morris

She only ovulates at one point during the cycle, so that mating at all other times can have no procreative function. The vast bulk of copulation in our species is obviously concerned, not with producing offspring, but with cementing the pair-bond by providing mutual rewards for the sexual partners. The repeated attainment of sexual consummation for a mated pair is clearly, then, not some kind of sophisticated, decadent outgrowth of modern civilization, but a deep-rooted, biologically based, and evolutionarily sound tendency of our species.

The most successful behaviour-liars are those who, instead of consciously concentrating on modifying specific signals, think themselves into the basic mood they wish to convey and then let the small details take care of themselves. This method is frequently used with great success by professional liars, such as actors and actresses. Their entire working lives are spent performing behavioural lies, a process which can sometimes be extremely damaging to their private lives. Politicians and diplomats are also required to perform an undue amount of behavioural lying, but unlike the actors they are not socially ‘licensed to lie’, and the resultant guilt feelings tend to interfere with their performances. Also, unlike the actors, they do not undergo prolonged training courses.

Having said all this, I must now point out that there is an important exception to the rule. The biological morality that I have outlined above ceases to apply under conditions of population over-crowding. When this occurs the rules become reversed. We know from studies of other species in experimentally over-crowded conditions that there comes a moment when the increasing population density reaches such such a pitch that it destroys the whole social structure. The animals developed diseases, they kill their young, they fight viciously and they mutilate themselves. No behaviour sequence can run through properly. Everything is fragmented. Eventually there are so many deaths that the population is cut back to a lower density and can start to breed again, but not before there has been a catastrophic upheaval. If, in such a situation, some controlled anti-reproductive device could have been introduced into the population when the first signs of over-crowding were apparent then the chaos could have been averted. Under such conditions (serious over-crowding with no signs of any easing up in the immediate future), anti-reproductive sexual patterns must obviously be considered in a new light.
Our own species is rapidly heading towards just such a situation.