What is the Doomsday Argument?
The Doomsday Argument, first proposed by astrophysicist Brandon Carter in 1983, is a statistical idea that attempts to estimate when humanity might face extinction. It does not predict the specific cause of extinction but uses mathematical probability to suggest a timeline. According to the theory, humans have approximately 17,100 years left, meaning extinction could occur around the year 19,126.
How does the theory work?
The argument is based on the Copernican Principle, which asserts that humans do not occupy a special position in the universe or in history. Researchers estimate that around 117 billion people have lived so far. They assume a 95% probability that we are not among the first 5% of all humans who will ever exist. From this, they calculate that the total number of humans ever born is unlikely to exceed 2.34 trillion—about 20 times the current total. At today's birth rates, that number would be reached in roughly 17,100 years.
However, the theory does not claim humanity will definitely go extinct at that point. Instead, it argues there is a 95% probability that extinction will occur before reaching that population figure. It serves as a warning against assuming indefinite human survival.
Potential extinction risks
While the Doomsday Argument does not specify what might cause extinction, scientists often discuss risks such as nuclear war, climate change, pandemics, asteroid impacts, and artificial intelligence. Some researchers note that future threats could come from technologies or events not yet known, making them impossible to predict.
Criticism and limitations
Many experts reject the Doomsday Argument due to its uncertain assumptions. Critics argue that humanity's future population is not random and could be influenced by falling birth rates, medical advances, economic changes, and technological development. The theory also fails to account for the possibility of humans colonizing other planets, which could drastically alter long-term survival prospects.
Even supporters describe the argument as a statistical exercise rather than a firm forecast. They emphasize it should encourage discussion about humanity's future, not serve as a countdown to extinction.
Other predictions
A more recent study published in August 2025 used probabilistic forecasting to predict that the world population will decline to between 1.55 billion and 1.81 billion by 2139, with no humans left by 2339. This study noted the decline in fertility between 2019 and 2024 as a key factor.
Ultimately, the Doomsday Argument remains a controversial piece of probability theory. For now, it is best viewed as an intriguing thought experiment rather than a definitive expiration date for humanity.
