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Say a continent area had 1 billion people. And they had the current US fertility rate of 1.65 children per woman. The replacement fertility rate is 2.10. So we can get a ratio... 1.65 / 2.10 = 0.785.
So each generation would be 78.5% the size of the last generation. And we know a generation is about 25 years. So in 1,000 years there is 40 generations.
Then we can do a calculation 0.785 y/x 40. To see what the population would be in 1,000 years, starting with 1 billion people.
Starting population: 1,000,000,000
1,000 years later population: 64,000
So each generation would be 78.5% the size of the last generation. And we know a generation is about 25 years. So in 1,000 years there is 40 generations.
Then we can do a calculation 0.785 y/x 40. To see what the population would be in 1,000 years, starting with 1 billion people.
Starting population: 1,000,000,000
1,000 years later population: 64,000
