Mathematicians have employed a statistical method known as the 'doomsday argument' to calculate a potential end date for humanity, suggesting with 95% certainty that the species will cease to exist within the next 17,100 years. This prediction is based on the premise that current humans occupy a random point in the species' timeline, rather than an exceptionally early one.
The calculation begins with an estimate that approximately 117 billion people have lived throughout human history. Under the assumption of a random position in time, there is a 95% probability that these 117 billion individuals represent at least five percent of all humans who will ever exist. By extrapolating this figure, mathematicians arrive at a maximum potential human population of about 2.34 trillion. Factoring in current birth rates, this threshold would be reached in approximately 17,100 years, thus marking the predicted limit for human existence.
Supporters of the doomsday argument posit that this figure serves as a statistical upper bound for humanity's future, implying a high likelihood of extinction from various catastrophic causes, including climate change, nuclear war, or pandemics, within this timeframe. The argument is rooted in the Copernican Principle, which posits that humans do not hold a unique or privileged position in the universe.
For illustration, researchers liken the concept to drawing numbered ping-pong balls from two boxes. If one box contains 10 balls and another 100,000, drawing ball number four makes it statistically more probable that it came from the smaller box. Similarly, if 117 billion people have already lived, the argument suggests it is less likely that humanity will continue for trillions more to be born. The theory's adherents calculate that if 117 billion represents five percent of the total possible human population, then the full population would be around 2.34 trillion, leading to the 17,100-year extinction estimate.
However, the doomsday argument remains highly contentious and has been refuted by many scientists. Critics contend that its underlying assumptions are overly simplistic and fail to account for numerous factors that could significantly influence humanity's future trajectory. Concerns have also been raised that the calculation breaks down if humans colonize other planets, develop advanced technologies, or survive for millions of years.
Separately, a study published in May projected a potential global population crash by 2064. Researchers from the University of Milan modeled hypothetical scenarios where severe environmental crises impose drastic carrying-capacity limits on Earth. Under a conservative worst-case assumption of Earth's sustainable carrying capacity suddenly dropping to two billion people, their model predicted a rapid global population decline, with the population potentially halving by 2064. The researchers emphasized that this scenario is illustrative of population dynamics' sensitivity to abrupt changes rather than a definitive forecast.