If people stopped having babies, how long would it be before humans were all gone?

San Francisco Chronicle​

5 hours ago

(The Conversation is an independent and nonprofit source of news, analysis and commentary from academic experts.)
If people stopped having babies, how long would it be before humans were all gone? – Jeffrey
Very few people live beyond a century. So, if no one had babies anymore, there would probably be no humans left on Earth within 100 years. But first, the population would shrink as older folks died and no one was being born.
Even if all births were to suddenly cease, this decline would start slowly.
Eventually there would not be enough young people coming of age to do essential work, causing societies throughout the world to quickly fall apart. Some of these breakdowns would be in humanity's ability to produce food, provide health care and do everything else we all rely on.
Food would become scarce even though there would be fewer people to feed.
As an anthropology professor who has spent his career studying human behavior, biology and cultures, I readily admit that this would not be a pretty picture. Eventually, civilization would crumble. It's likely that there would not be many people left within 70 or 80 years, rather than 100, due to shortages of food, clean water, prescription drugs and everything else that you can easily buy today and need to survive.
Sudden change could follow a catastrophe
To be sure, an abrupt halt in births is highly unlikely unless there's a global catastrophe. Here's one potential scenario, which writer Kurt Vonnegut explored in his novel 'Galapagos ': A highly contagious disease could render all people of reproductive age infertile – meaning that no one would be capable of having babies anymore.
Another possibility might be a nuclear war that no one survives – a topic that's been explored in many scary movies and books.
A lot of these works are science fiction involving a lot of space travel. Others seek to predict a less fanciful Earth-bound future where people can no longer reproduce easily, causing collective despair and the loss of personal freedom for those who are capable of having babies.
Two of my favorite books along these lines are ' The Handmaid's Tale,' by Canadian writer Margaret Atwood, and ' The Children of Men,' by British writer P.D. James. They are dystopian stories, meaning that they take place in an unpleasant future with a great deal of human suffering and disorder. And both have become the basis of television series and movies.
In the 1960s and 1970s, many people also worried that there would be too many people on Earth, which would cause different kinds of catastrophes. Those scenarios also became the focus of dystopian books and movies.
Heading toward 10 billion people
To be sure, the number of people in the world is still growing, even though the pace of that growth has slowed down. Experts who study population changes predict that the total will peak at 10 billion in the 2080s, up from 8 billion today and 4 billion in 1974.
The U.S. population currently stands at 342 million. That's about 200 million more people than were here when I was born in the 1930s. This is a lot of people, but both worldwide and in the U.S. these numbers could gradually fall if more people die than are born.
About 3.6 million babies were born in the U.S. in 2024, down from 4.1 million in 2004. Meanwhile, about 3.3 million people died in 2022, up from 2.4 million 20 years earlier.
One thing that will be important as these patterns change is whether there's a manageable balance between young people and older people. That's because the young often are the engine of society. They tend to be the ones to implement new ideas and produce everything we use.
Also, many older people need help from younger people with basic activities, like cooking and getting dressed. And a wide range of jobs are more appropriate for people under 65 rather than those who have reached the typical age for retirement.
Declining birth rates
In many countries, women are having fewer children throughout their reproductive lives than used to be the case. That reduction is the most stark in several countries, including India and South Korea.
The declines in birth rates occurring today are largely caused by people choosing not to have any children or as many as their parents did. That kind of population decline can be kept manageable through immigration from other countries, but cultural and political concerns often stop that from happening.
At the same time, many men are becoming less able to father children due to fertility problems. If that situation gets much worse, it could contribute to a steep decline in population.
Neanderthals went extinct
Our species, Homo sapiens, has been around for at least 200,000 years. That's a long time, but like all animals on Earth we are at risk of becoming extinct.
Consider what happened to the Neanderthals, a close relative of Homo sapiens. They first appeared at least 400,000 years ago. Our modern human ancestors overlapped for a while with the Neanderthals, who gradually declined to become extinct about 40,000 years ago.
Some scientists have found evidence that modern humans were more successful at reproducing our numbers than the Neanderthal people. This occurred when Homo sapiens became more successful at providing food for their families and also having more babies than the Neanderthals.
If humans were to go extinct, it could open up opportunities for other animals to flourish on Earth. On the other hand, it would be sad for humans to go away because we would lose all of the great achievements people have made, including in the arts and science.
In my view, we need to take certain steps to ensure that we have a long future on our own planet. These include controlling climate change and avoiding wars. Also, we need to appreciate the fact that having a wide array of animals and plants makes the planet healthy for all creatures, including our own species.
Hello, curious kids! Do you have a question you'd like an expert to answer? Ask an adult to send your question to [e-mail]. Please tell us your name, age and the city where you live.
And since curiosity has no age limit – adults, let us know what you're wondering, too. We won't be able to answer every question, but we will do our best.