BIOLOGIST Paul Ehrlich wrote in The Population Bomb, published in 1968, that humans were breeding so fast that food would inevitably run out and “hundreds of millions” would soon starve to death. Having toyed with the idea of “interstellar transport for surplus people”, he advocated strict birth control, “by compulsion if voluntary methods fail”.
Many people still worry about overpopulation. But an increasing number, especially in rich countries, fret about the opposite: a population implosion. “Low birth rates will end civilisation,” predicts Elon Musk, a father of many.
Though the number of people is still rising, the fertility rate – the number of babies a woman can expect to have in her lifetime – has been plummeting. And not just in the rich world: Two-thirds of people now live in countries where it is below the “replacement rate” of 2.1 – the standard estimate of what is needed to maintain a stable population. Bogota, Colombia, now has a lower fertility rate (0.91) than Singapore (0.97) and Tokyo (0.99).
