SOCIETY

The Great Fertility Decline

~1970 CE

History · Contemporary · Holocene · Meghalayan

Quietly, in two generations, humanity halved its fertility: from almost five children per woman in 1950 to just over two in 2021, below replacement level in more than half the world's countries. It falls where girls go to school and contraception spreads, where child mortality drops and where life becomes urban, and its momentum is such that annual births already peaked in 2016. The argument now is less about whether world population will crest this century than about when, and how steep the far side will be.

Why it matters

After two centuries dominated by the population explosion, the deep story flipped within living memory: the species' problem is becoming contraction and ageing, and it arrives fastest in the richest countries. This transition is voluntary and decentralised, made of billions of private decisions, and as consequential as any conquest on this timeline. The eight-billionth human was born into a world already practising smallness.

Dating & uncertainty

The world's total fertility rate more than halved between 1950 and 2021, from 4.84 to 2.23 children per woman; the anchor sits around 1970, as the decline became global. Annual births peaked in 2016. By 2021, fertility was below replacement in more than half of all countries, and projections put the world average near 1.6 by 2100, with over half of births in sub-Saharan Africa.

Sources

1. Bongaarts (2009), Philosophical Transactions of the Royal Society B · Human population growth and the demographic transitiondoi:10.1098/rstb.2009.0137
2. GBD 2021 Fertility Collaborators (2024), The Lancet · Global fertility in 204 countries and territories, 1950-2021, with forecasts to 2100doi:10.1016/S0140-6736(24)00550-6
3. Barrett, Dasgupta et al. (2020), PNAS · Social dimensions of fertility behavior and consumption patterns in the Anthropocenedoi:10.1073/pnas.1909857117

Our species’ history as one day

23:59:4415.4 s before midnight

if the 315,000 years of Homo sapiens were compressed into a single day