The research, led by Takuya Okabe of Shizuoka University, Japan, used mathematical models that took that messy reality into account; by including random demographic fluctuations, mortality rates, sex ratios, and the likelihood that some adults never have children, researchers landed on the 2.7 the figure. The study also found that a female-biased birth ratio, with more girls than boys born, reduces the risk of extinction as it increases the population of would-be mothers. As for where things stand now, Earth.com reports two-thirds of the global population live in countries where the fertility rate is below the 2.1 mark; in the US, it's around 1.6.
Author: Kate Seamons with Newser.AI
Published at: 2025-05-03 22:45:00
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