Enlightenment Now: The Case for Reason, Science, Humanism, and Progress

None of this was supposed to happen. In 1798 Thomas Malthus explained that the frequent famines of his era were unavoidable and would only get worse, because “population, when unchecked, increases in a geometrical ratio. Subsistence increases only in an arithmetic ratio. A slight acquaintance with numbers will show the immensity of the first power in comparison with the second.” The implication was that efforts to feed the hungry would only lead to more misery, because they would breed more children who were doomed to hunger in their turn.

Not long ago, Malthusian thinking was revived with a vengeance. In 1967 William and Paul Paddock wrote Famine 1975!, and in 1968 the biologist Paul R. Ehrlich wrote The Population Bomb, in which he proclaimed that “the battle to feed all of humanity is over” and predicted that by the 1980s sixty-five million Americans and four billion other people would starve to death. New York Times Magazine readers were introduced to the battlefield term triage (the emergency practice of separating wounded soldiers into the savable and the doomed) and to philosophy-seminar arguments about whether it is morally permissible to throw someone overboard from a crowded lifeboat to prevent it from capsizing and drowning everyone.¹⁰ Ehrlich and other environmentalists argued for cutting off food aid to countries they deemed basket cases.¹¹ Robert McNamara, president of the World Bank from 1968 to 1981, discouraged financing of health care “unless it was very strictly related to population control, because usually health facilities contributed to the decline of the death rate, and thereby to the population explosion.” Population-control programs in India and China (especially under China’s one-child policy) coerced women into sterilizations, abortions, and being implanted with painful and septic IUDs.¹²

Where did Malthus’s math go wrong? Looking at the first of his curves, we already saw that population growth needn’t increase in a geometric ratio indefinitely, because when people get richer and more of their babies survive, they have fewer babies (see also figure 10-1). Conversely, famines don’t reduce population growth for long. They disproportionately kill children and the elderly, and when conditions improve, the survivors quickly replenish the population.¹³ As Hans Rosling put it, “You can’t stop population growth by letting poor children die.”¹⁴

Looking at the second curve, we discover that the food supply can grow geometrically when knowledge is applied to increase the amount of food that can be coaxed out of a patch of land. Since the birth of agriculture ten thousand years ago, humans have been genetically engineering plants and animals by selectively breeding the ones that had the most calories and fewest toxins and that were the easiest to plant and harvest. The wild ancestor of corn was a grass with a few tough seeds; the ancestor of carrots looked and tasted like a dandelion root; the ancestors of many wild fruits were bitter, astringent, and more stone than flesh. Clever farmers also tinkered with irrigation, plows, and organic fertilizers, but Malthus always had the last word.

It was only at the time of the Enlightenment and the Industrial Revolution that people figured out how to bend the curve upward.¹⁵ In Jonathan Swift’s 1726 novel, the moral imperative was explained to Gulliver by the King of Brobdingnag: “Whoever makes two ears of corn, or two blades of grass to grow where only one grew before, deserves better of humanity, and does more essential service to his country than the whole race of politicians put together.” Soon after that, as figure 7-1 shows, more ears of corn were indeed made to grow, in what has been called the British Agricultural Revolution.¹⁶ Crop rotation and improvements to plows and seed drills were followed by mechanization, with fossil fuels replacing human and animal muscle. In the mid-19th century it took twenty-five men a full day to harvest and thresh a ton of grain; today one person operating a combine harvester can do it in six minutes.¹⁷