BEWARE of people preaching that we live in special times. People have preached that message before, and those who listened sold their furniture and climbed up on rooftops to await ascension, or built boats to float out the coming flood, or laced up their Nikes and poisoned themselves in some California subdivision. These prophets are the ones with visions of the seven-headed beast, with a taste for the hair shirt and the scourge, with twirling eyes. No, better by far to listen to Ecclesiastes, the original wise preacher, jaded after a thousand messiahs and a thousand revivals.
One generation passes away, and another generation comes; but the earth abides forever.... That which has been is what will be, that which is done is what will be done, and there is nothing new under the sun. Is there anything of which it may be said, "See, this is new"? It has already been in ancient times before us.
And yet, for all that, we may live in a special time. We may live in the strangest, most thoroughly different moment since human beings took up farming, 10,000 years ago, and time more or less commenced. Since then time has flowed in one direction -- toward more, which we have taken to be progress. At first the momentum was gradual, almost imperceptible, checked by wars and the Dark Ages and plagues and taboos; but in recent centuries it has accelerated, the curve of every graph steepening like the Himalayas rising from the Asian steppe. We have climbed quite high. Of course, fifty years ago one could have said the same thing, and fifty years before that, and fifty years before that. But in each case it would have been premature. We've increased the population fourfold in that 150 years; the amount of food we grow has gone up faster still; the size of our economy has quite simply exploded.
But now -- now may be the special time. So special that in the Western world we might each of us consider, among many other things, having only one child -- that is, reproducing at a rate as low as that at which human beings have ever voluntarily reproduced. Is this really necessary? Are we finally running up against some limits?
To try to answer this question, we need to ask another: How many of us will there be in the near future? Here is a piece of news that may alter the way we see the planet -- an indication that we live at a special moment. At least at first blush the news is hopeful. New demographic evidence shows that it is at least possible that a child born today will live long enough to see the peak of human population.
Around the world people are choosing to have fewer and fewer children -- not just in China, where the government forces it on them, but in almost every nation outside the poorest parts of Africa. Population growth rates are lower than they have been at any time since the Second World War. In the past three decades the average woman in the developing world, excluding China, has gone from bearing six children to bearing four. Even in Bangladesh the average has fallen from six to fewer than four; even in the mullahs' Iran it has dropped by four children. If this keeps up, the population of the world will not quite double again; United Nations analysts offer as their mid-range projection that it will top out at 10 to 11 billion, up from just under six billion at the moment. The world is still growing, at nearly a record pace -- we add a New York City every month, almost a Mexico every year, almost an India every decade. But the rate of growth is slowing; it is no longer "exponential," "unstoppable," "inexorable," "unchecked," "cancerous." If current trends hold, the world's population will all but stop growing before the twenty-first century is out.
And that will be none too soon. There is no way we could keep going as we have been. The increase in human population in the 1990s has exceeded the total population in 1600. The population has grown more since 1950 than it did during the previous four million years. The reasons for our recent rapid growth are pretty clear. Although the Industrial Revolution speeded historical growth rates considerably, it was really the public-health revolution, and its spread to the Third World at the end of the Second World War, that set us galloping. Vaccines and antibiotics came all at once, and right behind came population. In Sri Lanka in the late 1940s life expectancy was rising at least a year every twelve months. How much difference did this make? Consider the United States: if people died throughout this century at the same rate as they did at its beginning, America's population would be 140 million, not 270 million.
If it is relatively easy to explain why populations grew so fast after the Second World War, it is much harder to explain why the growth is now slowing. Experts confidently supply answers, some of them contradictory: "Development is the best contraceptive" -- or education, or the empowerment of women, or hard times that force families to postpone having children. For each example there is a counterexample. Ninety-seven percent of women in the Arab sheikhdom of Oman know about contraception, and yet they average more than six children apiece. Turks have used contraception at about the same rate as the Japanese, but their birth rate is twice as high. And so on. It is not AIDS that will slow population growth, except in a few African countries. It is not horrors like the civil war in Rwanda, which claimed half a million lives -- a loss the planet can make up for in two days. All that matters is how often individual men and women decide that they want to reproduce.
Will the drop continue? It had better. UN mid-range projections assume that women in the developing world will soon average two children apiece -- the rate at which population growth stabilizes. If fertility remained at current levels, the population would reach the absurd figure of 296 billion in just 150 years. Even if it dropped to 2.5 children per woman and then stopped falling, the population would still reach 28 billion.
But let's trust that this time the demographers have got it right. Let's trust that we have rounded the turn and we're in the home stretch. Let's trust that the planet's population really will double only one more time. Even so, this is a case of good news, bad news. The good news is that we won't grow forever. The bad news is that there are six billion of us already, a number the world strains to support. One more near-doubling -- four or five billion more people -- will nearly double that strain. Will these be the five billion straws that break the camel's back?
WE'VE answered the question How many of us will there be? But to figure out how near we are to any limits, we need to ask something else: How big are we? This is not so simple. Not only do we vary greatly in how much food and energy and water and minerals we consume, but each of us varies over time. William Catton, who was a sociologist at Washington State University before his retirement, once tried to calculate the amount of energy human beings use each day. In hunter-gatherer times it was about 2,500 calories, all of it food. That is the daily energy intake of a common dolphin. A modern human being uses 31,000 calories a day, most of it in the form of fossil fuel. That is the intake of a pilot whale. And the average American uses six times that -- as much as a sperm whale. We have become, in other words, different from the people we used to be. Not kinder or unkinder, not deeper or stupider -- our natures seem to have changed little since Homer. We've just gotten bigger. We appear to be the same species, with stomachs of the same size, but we aren't. It's as if each of us were trailing a big Macy's-parade balloon around, feeding it constantly.