"Optimism is expressed by some who feel that since we have evolved a high level of intelligence and a strong inventive urge, we shall be able to twist any situation to our advantage; that we are so flexible that we can re-mould our way of life to fit any of the new demands made by our rapidly rising species-status; that when the time comes, we shall manage to cope with the over-crowding, the stress, the loss of our privacy and independence of action; that we shall re-model our behaviour patterns and live like giant ants; that we shall control our aggressive and territorial feelings, our sexual impulses and our parental tendencies; that if we have to become battery-chicken apes we can do it; that our intelligence can dominate all our basic biological urges. I submit that this is rubbish. Our raw animal nature will never permit it. Of course, we are flexible. Of course, we are behavioural opportunists, but there are severe limits to the form our opportunism can take. By stressing our biological features in this book, I have tried to show the nature of these restrictions. By recognizing them clearly and submitting to them, we shall stand a much better chance of survival. This does not imply a naive ‘return to nature’. It simply means that we should tailor our intelligent opportunist advances to our basic behavioural requirements. We must somehow improve in quality rather than in sheer quantity. If we do this, we can continue to progress technologically in a dramatic and exciting way without denying our evolutionary inheritance. If we do not, then our suppressed biological urges will build up and up until the dam bursts and the whole of our elaborate existence is swept away in the flood."

“Sexual behaviour in our species goes through three characteristic phases: pair-formation, pre-copulatory 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, frequently lasting for weeks or even months. As with many other species it is characterized by tentative, ambivalent behaviour involving conflicts between fear, aggression and sexual attraction. The nervousness and hesitancy is slowly reduced if the mutual sexual signals are strong enough.”

“The idea that it is funny to see wild animals coerced into acting like clumsy humans, or thrilling to see powerful beasts reduced to cringing cowards by a whip-cracking trainer, is primitive and medieval. It stems from the old idea that we are superior to other species and have the right to hold dominion over them.”

“A third solution is to provide and promote harmless, symbolic substitutes for war; but if these really are harmless they will inevitably only go a very small way towards resolving the real problem. It is worth remembering here that this problem, at a biological level, is one of group territorial defense and, in view of the gross overcrowding of our species, also one of group territorial expansion. No amount of boisterous international football is going to solve this.”

“All the higher forms of animal life are aware of at least some of the other species with which they share their environment. They regard them in one of five ways: as prey, symbionts, competitors, parasites, or predators. In the case of our own species, these five categories may be lumped together as the ‘economic’ approach to animals, to which may be added the scientific, aesthetic and symbolic approaches. This wide range of interests has given us an inter-specific involvement unique in the animal world.”

“I discovered long ago that, if you write a book about cats or dogs, everybody loves you, but if you dare to write a book about human beings, all hell breaks loose. It is impossible to write an uncensored, honest book about human behaviour without offending at least part of your audience. If you feel you have a basic truth to tell, then you must tell it and be prepared to suffer the inevitable criticisms.”

“Since none of these gods exist in a tangible form, why have they been invented? To find the answer to this we have to go right back to our ancestral origins. Before we evolved into co-operative hunters, we must have lived in social groups of the type seen today in other species of apes and monkeys. There, in typical cases, each group is dominated by a single male. He is the boss, the overlord, and every member of the group has to appease him or suffer the consequences. He is also most active in protecting the group from outside hazards and in settling squabbles between lesser members. The whole life of a member of such a group revolves around the dominant animal. His all-powerful role gives him a god-like status.”