Before Malthus appeared on the scene, William Godwin recognized that the expanding population might ultimately produce an unfavorable ratio of population to resources which could create a problem. Five years later Malthus viewed this problem as an inevitable result of human nature reacting to a world of limits. Godwin, however (in the passage previously quoted at the end of Box 3-1) had proposed to solve the population by changing human nature. He suggested that some day our species might "cease to propagate." Since this was written in England two hundred years ago, in the absence of contradictory evidence we can only assume that Godwin was postulating an end to human sexual activity. He no doubt thought the sacrifice would be worthwhile because, in his Utopia, there would be "no war, no crimes, no administration of justice, as it is called, and no government. Besides this, there will be neither disease, anguish, melancholy, nor resentment." Most of Godwin's suppositions are too ridiculous to linger over, but one of them deserves an extended analysis because it touches on a general principle that will be called upon repeatedly as we continue to look for ways to avoid overpopulation. There is not the ghost of a chance that the human species will ever "cease to propagate." The reason is found in the great discovery made by Charles Darwin sixty years later: selection. Suppose, following Godwin, that the natural fertility of our species evolves almost all the way to zero. Then what? Initially, fertile individuals might be but a tiny minority of the whole; but, over time, selection would ensure the dominance of the fertile fraction. If there were even the slightest genetic basis for fecundity in human beings (as indeed there is in other animals) then fertile human beings would in time replace the infertile. To postulate a selection for universal sterility (as Godwin's scheme would require) is to perpetrate an oxymoron. Nature does not work with oxymorons. We who are alive now are the descendents of an unbroken line of fertile ancestors. This line extends back millions of years to the first humanoids—indeed, billions of years to the beginning of sexual life of any kind. Powerful though she is, Nature cannot create a self-sustaining, totally infertile, sexual species.
XIX.—On a Mode of Taking the Density of Vapour of Volatile Liquids, at Temperatures below the Boiling Point