Tech entrepreneur Elon Musk has once again raised concerns about declining birth rates, calling it a significant risk to the future of human civilisation. In a recent post on X (formerly Twitter), Musk responded to a data thread referencing a Fortune report which suggested that the previously accepted replacement fertility rate of 2.1 children per woman is now outdated. The revised figure stands at 2.7, according to scientists cited in the report.

Musk warned that continued declines in fertility rates could lead to long-term population collapse, a view he has repeatedly shared in recent years.

The post, originally shared by user Nawfal, pointed out that 2.1 children per woman may no longer be enough to sustain population levels. He noted that the revised number, 2.7, reflects a more accurate replacement rate because it accounts for those who never have children and existing gender imbalances.

Nawfal also cited data showing that current fertility rates in many developed countries are far below that threshold. For instance, the U.S. stands at 1.66, while Italy and Japan are even lower at 1.29 and 1.30 respectively.

Musk reposted the thread and added, “People who have kids do need to have 3 kids to make up for those who have 0 or 1 kid or population will collapse.”

Musk has previously drawn parallels between falling fertility and the decline of historic empires. He cited Ancient Rome as an example, stating that reduced birth rates were a major factor in its collapse — something he believes is often overlooked.

Elon Musk | Credit: X

He has framed the issue as both demographic and mathematical, warning, “If you don’t believe me now, just wait 20 years.”

Musk is a father to 14 children. His first child, Nevada Alexander, born in 2002 with then-wife Justine Wilson, died at 10 weeks old. The couple later had five more children: twins Vivian and Griffin, followed by triplets Kai, Saxon, and Damian.

The United Nations Population Fund (UNFPA) also addressed the topic in its 2025 State of World Population Report, titled “The Real Fertility Crisis.” According to the agency, fertility rates are dropping globally, with many people having fewer children than they would prefer.

The report identifies the high cost of child-rearing and difficulty in finding suitable partners as key reasons for the decline.

In India, the fertility rate now stands at 1.9 births per woman—below the replacement benchmark of 2.1. UNFPA India Representative Andrea M Wojnar stated that India’s fertility rate has dropped significantly since 1970, thanks to improvements in education and healthcare access.

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