Math predicts humans could go extinct in about 17,000 years

Some mathematicians have predicted when humanity’s downfall might occur—though the circumstances are unspecified

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Whether it’s the climate crisis, a pandemic or a nuclear war, some doomsday scenarios seem more plausible than they did a few years ago. Mathematicians who make predictions about the end of humanity, basing their arguments solely on statistical considerations, have come up with multiple conclusions about when human beings will go extinct. One estimate, which I will break down in detail, concludes with 95 percent certainty that we humans will inhabit the planet for, at most, another 17,100 years.

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The “doomsday argument,” developed from work put forward by astrophysicist Brandon Carter in 1983, makes predictions about the total number of humans who will ever live . It is based on the fundamental idea that we, as observers, do not occupy a privileged position in the universe—but rather a completely random one. This is known as the Copernican principle, named after astronomer Nicolaus Copernicus, who, in the 16th century, realized that the Earth is not the center of the universe. This idea is frequently used in cosmology, for example, to argue that our surroundings (such as our solar system) are nothing special and are rather quite common in the universe.

The idea can be taken further. Imagine plotting the total number of people who have ever lived on a timeline that encompasses both the past and the future. That’s a tricky thing to reckon with, as I’ve written about for Scientific American . But we can say that the world’s population continues to grow with every passing year. We can also say that eventually humanity will perish, either because we destroy ourselves (which currently seems possible) or because the sun has exhausted its fuel and engulfed Earth. But perhaps by then we will have managed to colonize other planets and galaxies. In the most extreme case, we could survive until the end of the universe.

If we believe that humanity will conquer the universe—that is, that we will spread across vast distances and survive for extremely long periods—then the total number of people who have ever existed will be extremely high. If, on the other hand, we destroy ourselves in a few thousand years, the number of people who have ever lived might double or quintuple but will be significantly smaller than in the first scenario. But how can this information lead to a prediction of when humanity will perish?

Suppose you are the x th person ever born. It seems only logical that the probability of having been born before or after a particular person is equally distributed. According to current estimates, approximately 117 billion people have lived on Earth so far. This knowledge can now be used to estimate the total number N of people who will have existed at some point.