THE DEMOGRAPHIC FATE OF intelligent SPECIES: 2/7. Below 2.1 births/woman makes societies smaller and older : it's not just white folks, it's 80+ countries from all continents.

2/7. Below 2.1 births/woman makes societies smaller and older : it's not just white folks, it's 80+ countries from all continents.

To fully replace a generation and keep a population constant, every female of our species must have two of her newborns survive to the end of their reproductive life. Without immigration from outer space, world population rises/falls when, on average, more/fewer than two make it to and through that window. Although the typical pre-industrial woman had between 4 and 8 deliveries in her lifetime, as just a fraction more than two survived in those brutish days, human population grew anemically for most of history. Everyone back then wanted to have as many toddlers as possible to improve the chance of having enough offspring around for old age support. Thanks to medical progress, things began to change radically in the 19th century, when parents, still prudent in late life planning, started to see most of their 5/6/7 children survive. World population, consequently, rockets from 1 billion to 7 billion in the last 200 years. So much progress has happened that even in the lowest income countries, it now takes only between 2.5 and 3.3 births to get two surviving adults, depending on the specific country's mortality rate. In richer societies, two grown-up children today necessitate as few as 2.1 childbirths per woman.
As of 2011, however, birthrates in more than 80 countries have dropped below this modern replacement threshold of 2.1. In the most developed regions of the world, sub-replacement fertility has been the rule for decades. Without immigration, this will, overtime, translate into a smaller and older population, with a higher median age. With median ages above 46, Germany and Japan are now the two oldest countries in the world, with Italy in third place at 44.5. The baby drought doesn't just confine itself to Earth's most advanced societies. As archaic as it may seem to some western eyes, birthrate is now lower in deeply religious Iran than in the UK (1.6 vs. 1.9), having fallen dramatically from 6.5 in 1970. Alarmed by this epic collapse, Iran's supreme leader felt compelled to issue an Islamic fatwa in May 2014 prodding for more little Iranians. Not far behind Iran or Turkey, many demographic giants are quickly approaching the 2.1 threshold: India (1.2-billion population, world's 2nd largest, birthrate dropped from 5.5 in 1970 to 2.6 in 2011), Indonesia (250 million, world's 4th, from 5.5 to 2.1), Mexico (120 million, from 6.7 to 2.3)... It looks like sub-replacement fertility, having already dominated the top half of the development league table, is now spreading to countries increasingly lower in the bottom half.
Catholic Brazil, Orthodox Russia, Buddhist Thailand, Muslim Turkey, godless Germany, Confucian Korea, high-welfare Denmark, free-capitalist America… have very different histories, religious backgrounds, cultural heritages... yet their birthrates are all below 2.1, which shows how low fertility may be an universal phenomenon, not particular to some cultures or religions. The modern living conditions these nations share might matter much more than where they came from. When the same reproductive pattern appears in so many different human societies, isn’t it likely to stem from human nature, that common ground below national cultures, spiritual faiths, linguistic barriers, or skin tones? If that is the case, humans everywhere will act the same when exposed to similar conditions, no matter how local they look on the outside. For those geographically dispersed populations to experience the same shift in procreative behavior, there must be similar changes they have all undergone in recent decades.
Modernization appears to be the culprit here: the higher a country ranks in development tables, the lower its fertility. Apart from a few oil-rich Arab countries, human societies with annual per-capita income above $20,000 all have below-replacement fertility rates. The correlation is even stronger when you pair a society's birthrate with its women's education level, which seems to matter even more than financial income. If having fewer than 2.1 descendants is what people of all shades - white, black, yellow, red, green, purple… - do when their society modernizes, a global demographic bust is entirely possible in the next 100 years as all remaining high-fertility nations are racing towards modernity. Across the backwaters of the world, it's now cool and hip to be modern. Most young people want the enchanting life they see in Hollywood movies, much to the dismay of the old and religious. As Germany was third-worldly poor, autocratic and full of shoeshine boys a short century ago, it's conceivable that a hundred years from now most Africans will be living in sophisticated consumer paradises. And having fewer than 2.1 babies. If modernity is a human thing, not some hopelessly western idiosyncrasy, then so is low fertility.
By making every succeeding generation smaller than the last, sustained low fertility can bring radical long-term consequences. While our species’ quantitative rise has been very slow historically, with high mortality offsetting high fertility most of the time, the fall could be sharp. At a global birthrate just shy of 2,1, like that of generous Scandinavia or dog-eat-dog America, humanity would simply lose more than half of its 21st-century peak population come the year 2500. Continue that rate for another 200,000 years, the current age of our East-Africa-born species, and there might be no more mankind to talk about. As for humanity's median age, can you imagine it above 65 in 2500? While individual countries can attract immigrants to keep their median ages in check, this won’t work on a planetary scale, unless mass immigration from other stars occurs. To save mankind, should those highly fertile sub-Saharan populations be forever barred from modern progress? Such absurd proposals underscore the seriousness of global aging.
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. And a high median age humanity will become reality much sooner than you think possible.

(Next) 3/7. From survival necessity to just another demanding hobby: how babies encounter serious competition in modern life

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