I worked out how long it could take for the human race to die out if the number of births per woman falls to the current low rate in Japan.
There may be no human beings left on Earth in only 24,000 years.
That means human beings as a species only existed for 224,000 years - just a blink in time.
The last two people on Earth could be two old grannies wandering through an empty ruined city, eating rotten food off empty supermarket shelves and drinking stagnant water.
That is how the end of our time might look.
