The Doomsday Argument is the idea that we can estimate the total number of humans that will ever exist, given the number that have lived so far. This in turn tells us how likely it is that human civilisation will survive far into the future.
The numbers are not optimistic. Anthropologists think some 70 billion humans have so far lived on Earth. If we assume that we have no special status in human history, then simple probabilistic arguments suggest that there is a 95 per cent chance that we are among the last 95 per cent of humans that will ever be born. And this means there is a 95 per cent chance that the total number of humans that will ever exist will be less than 20 x 70 billion or 1.4 trillion.
Now suppose that the world population stabilises at 10 billion and our life expectancy is 80 years, then the remaining humans will be born in the next 10,000 years. That’s not a long future for humanity. Today, Austin Gerig at the University of Oxford and a couple of pals put forward a new argument with a (slightly) happier ending.
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