"Despite our grandiose ideas and our lofty self-conceits, we are still humble animals, subject to all the basic laws of animal behaviour. Long before our populations reach the levels envisaged above we shall have broken so many of the rules that govern our biological nature that we shall have collapsed as a dominant species. We tend to suffer from a strange complacency that this can never happen, that there is something special about this, that we are somehow above biological control. But we are not. Many exciting species have become extinct in the past and we are no exception. Sooner or later we shall go, and make way for something else. If it is to be later rather than sooner, then we must take a long, hard look at ourselves as biological specimens and gain some understanding of our limitations."