ONE of the most significant phenomena of modern history is the demographic transition: as people get richer, they have smaller families. This slowing of reproduction with economic development is the reason why Thomas Malthus’s prediction of disaster, caused by the human population outstripping its supply of food, is unlikely ever to come true. In the short term, Malthusian doom has been evaded by innovations that increased the food supply. But in the long term it is likely to be a ceiling on demand that helps to save humanity. The world’s population, now some 7 billion, is expected to level out at a little over 10 billion towards the end of the century.
Why the demographic transition happens, though, is obscure—for this reaction by Homo sapiens to abundance looks biologically bonkers. Other species, when their circumstances improve, react by raising their reproductive rate, not curtailing it. And work just published by Anna Goodman of the London School of Hygiene and Tropical Medicine and her colleagues, in the Proceedings of the Royal Society, suggests what humans do is indeed bananas. Dr Goodman has shown that the leading explanation advanced by biologists for the transition does not, in the context of the modern world, actually deliver the goods.
Read more at The Economist.