and this, too, shall pass

In order to fully replace a generation, technically, every female must have two of her newborns survive into adulthood. Throughout history, given the high frequency of death, meeting this target often required from four to eight deliveries per lifetime. Thanks to medical and nutritional advances, two grown-up children demand as few as 2.1 births per woman today. As of 2005, however, birthrates in more than 90 countries are below this replacement threshold of 2.1. In the most developed regions of the world, sub-replacement fertility has been the rule for decades. 

The baby drought doesn’t stop there. It is spreading across the globe, touching societies as far apart as Confucian Korea, Catholic Brazil, Orthodox Russia, Muslim Turkey… The phenomenon may be rooted in humanity, that common ground below national cultures, religious traditions and skin tones. Modernity appears to be at play: the higher a country ranks in development tables, the lower its fertility. If having few kids is what people everywhere - black, white, yellow, red, green, purple… - do when raised in a modern setting, the prospect of a global demographic decline is not a joke. Counting in centuries, as westerners were still enjoying third-world living standard not long ago, even today’s poorest will be living in modern consumer paradises in no time at all. 

By making every succeeding generation slightly smaller than the last, sustained low fertility can bring radical long-term consequences. While the species’ quantitative rise has been extremely slow, as high mortality offset high fertility, the fall could be brutal. At a global birthrate of 1.85 per female, the level of America’s non-Hispanic whites, France or Ireland (two best European performances), humanity would drop to 2.3 billion by 2300. If low fertility is indeed an active choice driven by human nature, there may be no limit as to how low world population can fall.