The Doomsday Argument, a controversial mathematical theory first proposed by astrophysicist Brandon Carter in 1983, suggests that humans are closer to extinction than the beginning of our species, with an estimated 17,100 years remaining. The theory does not predict a specific cause of extinction but uses statistical reasoning based on the total number of humans who have ever lived.
What is the Doomsday Argument?
The theory is grounded in the Copernican Principle, which posits that humans do not occupy a special position in the universe or in history. It argues that we should not assume we are living at an unusually early or late stage of human existence. Using a person's place in the overall sequence of humans who have ever lived, the argument derives a statistical clue about how many people may come after them.
Researchers estimate that approximately 117 billion people have lived throughout human history. They then assume there is a 95% chance that we are not among the first 5% of all humans who will ever exist. From this, the calculation suggests that the total number of humans ever born is unlikely to exceed around 2.34 trillion. This figure is reached by multiplying the current number of humans who have lived by 20, based on the idea that our position in history is not unusually early.
Population Projections and Timeline
At today's birth rates, that total would be reached roughly 17,100 years from now, placing the potential extinction date around the year 19,126. However, the theory does not predict that humanity will definitely disappear at that point. Instead, it argues there is a 95% probability that humanity would become extinct before reaching that total population figure. It serves as a warning about the limits of assuming that our species will continue indefinitely.
The maths does not attempt to explain what might wipe us out. Potential risks often discussed by scientists include nuclear war, climate change, pandemics, asteroid impacts, artificial intelligence, and other global catastrophes. Some researchers point out that future threats may come from technologies or events that do not yet exist, making them impossible to predict.
Controversy and Criticisms
The Doomsday Argument has remained controversial since its introduction. Critics argue that the assumptions behind the calculation are too uncertain. Humanity's future population is not random and could be heavily influenced by factors such as falling birth rates, medical advances, economic changes, and technological development. Another criticism is that the argument does not account for the possibility of humans expanding beyond Earth. If future generations establish permanent settlements on other planets, humanity's long-term survival could look very different from the scenario imagined by the theory.
Even researchers who support the idea generally describe it as a statistical argument rather than a firm forecast. They argue it should be viewed as a mathematical exercise that encourages discussion about humanity's future, rather than a countdown clock ticking towards extinction.
Related Studies
A more recent study published in August 2025 used probability to predict humanity's future, giving us only a little more than 300 years before extinction. It states: 'Given the decline in fertility between 2019 and 2024 and employing a probabilistic forecasting method, by 2139 the world population will be between 1.55 billion and 1.81 billion… by 2339 there will be no humans.'
Whether the Doomsday Argument proves useful as a way of thinking about humanity's future remains debated. For now, it is best viewed as an intriguing piece of probability theory rather than a warning that civilisation has a set expiry date.
