Every woman must have more than two children to prevent human extinction, study warns

A new study says the global fertility rate needs to be 2.7 children per woman—higher than the previously believed 2.1—to ensure long-term human survival, challenging assumptions about population sustainability and collapse.

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For years, scientists and policymakers have believed that a woman must have an average of 2.1 children for a population to replace itself without shrinking. This number, known as the ‘replacement fertility rate,’ has shaped global policies and economic forecasts.

However, a new study published in the journal PLOS One argues that the long-accepted figure of 2.1 may no longer be sufficient to prevent a future decline—or even extinction—of the human population, reports Daily Mail.

Why 2.1 Was the Magic Number

The 2.1 fertility rate is slightly above two to account for child mortality and the fact that not every woman has children. For decades, demographers used this number to estimate the population's ability to replace itself. If a country’s average fertility rate dropped below this threshold, it signaled eventual population decline.

Why That Number May Be Too Low

The latest research, led by scientists studying long-term demographic trends, suggests that this target doesn't fully account for several important variables. These include:

• Deaths before reproductive age
• Sex imbalances at birth
• Adults who choose not to or cannot have children
• Random fluctuations in family sizes

Taking all these into account, the researchers now estimate the real replacement rate should be closer to 2.7 children per woman, not 2.1.

Elon Musk’s Warning and the Baby Bust

Tech billionaire Elon Musk, who has 14 children himself, has repeatedly warned that declining birth rates are “the biggest risk to civilization.” He believes that prosperity, modern values, and changing lifestyles are leading to a “baby bust” in developed countries—and this new study backs his concerns, at least in part.

Musk argues that shrinking populations will mean fewer workers to support the elderly, growing debt, and eventual economic and societal breakdown.

Global Fertility in Freefall

Fertility rates are falling around the world. In 1960, the global average was about 5.3 children per woman. By 2023, it had dropped to 2.3—and it's still declining:

• South Korea has the lowest fertility rate globally, at just 0.87.
• England and Wales have seen a 60% decline in childbirths in some regions over the last decade.
• China’s population shrank by over a million in 2024 alone.
• Even in the United States, the fertility rate is now around 1.62—far below both the traditional 2.1 and the newly proposed 2.7 threshold.

Why Women Are Having Fewer Children

There are several reasons behind this global trend:

1. Higher Education and Career Focus:

More women than ever are attending college and entering the workforce. They’re delaying childbirth to pursue careers, and many are choosing to have fewer children.

2. Cost of Raising Children:

In many countries, the cost of housing, childcare, and education has skyrocketed. For working parents, having more than one or two children is often financially unfeasible.

3. Access to Contraception:

Improved access to birth control and reproductive health education has given women greater control over their fertility.

4. Climate Anxiety:

A growing number of people say they’re choosing not to have children due to fears about climate change and the state of the world their children would inherit.

5. Declining Sperm Counts:

Some scientists point to falling sperm quality in men due to environmental chemicals, poor diet, and pollution as a possible contributor. However, others believe lifestyle choices and family planning decisions play a much bigger role.

Not Everyone Agrees

Despite these alarming numbers, some experts believe the concern about human extinction is exaggerated. Demographers like Joseph Chamie, former director of the UN Population Division, argue that the global population will keep growing until the 2080s, peaking at around 10.3 billion before slowly declining.

In his view, the focus should be on adapting to smaller populations—not reversing the trend. “People are choosing to have fewer children, and that change is likely permanent,” says Dr. Jennifer Sciubba, a population expert and author.

What the Future Holds

While the new study doesn’t suggest humans are on the brink of immediate extinction, it does warn of long-term instability. Fewer births mean fewer people to work, pay taxes, and care for the elderly, especially in aging nations.

The study concludes that to truly ensure the future of humanity—not just in numbers, but in preserving cultures and communities—we may need to reassess what replacement fertility really looks like.

In short, to avoid an irreversible decline, the average number of children per woman may need to be 2.7—a figure many modern societies are currently far from reaching.