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TOM KEANE

Are we overpopulating?

Fiction and doomsayers notwithstanding, maybe not

andrew saeger for the boston globe

The premise of Dan Brown’s bestseller “The Da Vinci Code’’ was that Jesus Christ and Mary Magdalene, presumably bored of miracles and sermons, married and had kids. His newest novel, “Inferno,’’ is kind of the same except that this time (spoiler alert!) it’s the rest of us having kids — and far, far too many. The shocking solution: Wipe out almost half the human race. Many finished Brown’s earlier book believing descendants of God literally walk among us. So before they treat his latest offering as gospel, so to speak, a word of caution: Brown is flat-out wrong.

Brown draws from the work of political scientist Robert Malthus, who in 1798 warned about the dangers of unchecked human reproduction. The collapse of civilization, he feared, was near at hand. The logic of that view led Malthus to oppose the British poor laws — which gave aid to the destitute — for the reasons most pithily expressed by Ebenezer Scrooge: “If they would rather die they had better do it, and decrease the surplus population.”

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Other have taken up Malthus’s crusade, notably Paul Ehrlich, whose 1968 book, “The Population Bomb,’’ predicted a near cataclysm in the 1970s. Oops. Malthus, Ehrlich, and their followers aren’t wrong on their math, however. The earth’s population has grown, and that growth has been rapid. In 1800 there were just 1 billion. Last year, according to the US Census Bureau, we hit 7 billion.

Population notwithstanding, however, humanity is better off than it ever was. What the doomsayers didn’t anticipate is that human ingenuity would be able to keep pace, and more so. Food production per acre climbed. We found new sources of energy. Modern, free-market economies created wealth where once there was only misery. Indeed, over the last 20 years the global poverty rate has been cut in half, and it is realistic to expect that dire poverty could well be eliminated in the next 20.

Still, at some point you’d think, Malthus and Ehrlich have to be right. The earth may be able to tolerate 7 billion. But double, triple that? There is, after all, only so much room.

Except that the predictions of inexorable population growth are wrong. Our population won’t grow to 21 billion, or even 14 billion. It now looks as if earth will max out at around 10 billion by 2100. And after that, world population might actually fall.

Brown’s fictional hero, Robert Langdon, wanders the hot spots of Europe — Florence, Venice, and Istanbul — observing how crowded those cities are. But that’s because they’re tourist traps. Europe, in fact, is shrinking. The so-called replacement level — the number of children a woman must have to keep population stable — is 2.1 (the fraction accounts for childhood death or infertility). Europe is an amazingly low 1.51 (and Italy, the country that seems especially crowded to Langdon, a mere 1.41). Other developed nations follow suit: Japan is 1.39, Canada 1.59, Australia 1.77. The United States is somewhat of an outlier, at 2.06 (in large part because, as former Florida governor Jeb Bush recently and clumsily put it, new immigrants are “more fertile”). Still, we’re lower than the replacement rate.

Yes, poorer parts of the world continue to have high growth. Sub-Sahara Africa is 4.66, for instance, but demographers see that declining to 2.1 by 2070. In fact, by 2027 the entire world will likely fall below the replacement rate.

And why? Population experts call it the “demographic transition.” As countries develop — as they modernize, grow their economies, improve health care, decrease mortality, and educate more of their population (especially girls) — a remarkable thing happens: birthrates fall. The effect of education is particularly profound. Educated girls grow to be women who have more choices in life than merely being pregnant. Educated girls are as well a proxy for how societies are evolving in terms of their economies, their attitudes toward their citizens, and their regard for women’s rights.

One of the principal characters in Brown’s book initially dedicates her life toward social work but, seeing the teeming slums of Manila, she despairs, turning instead toward a manufactured plague as the solution. She should have stuck it out. The Three Rs, it turns out, are more powerful than any germ.

Tom Keane can be reached at tomkeane@tomkeane.com.
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