How many people will be born in the future? We don’t know.
But we know one thing: The future is immense, the universe will exist for trillions of years.
We can use this fact to get a sense of how many descendants we might have in that vast future ahead.
The number of future people depends on the size of the population at any point in time and how long each of them will live. But the most important factor will be how long humanity will exist.
Before we look at a range of very different potential futures, let’s start with a simple baseline.
We are mammals. One way to think about how long we might survive is to ask how long other mammals survive. It turns out that the lifespan of a typical mammalian species is about 1 million years.5 Let’s think about a future in which humanity exists for 1 million years: 200,000 years are already behind us, so there would be 800,000 years still ahead.