So you think that as soon as the population peaks at 9.7B some sort of magic sets in to stop exponential growth?
No, this is
math. It's not even that complicated math. When you fall below replacement rate reproduction, over time the population decreases.
A very simplified example:
We have a community of 100 wolves, in 50 breeding pairs. Each breeding pair produces 4 pups, but only once, meaning that the birthrate is above replacement level. A wolf can live long enough to see their grandpups, and then dies.
* Iteration 0: 100 Gen A Wolves (100 total)
* Iteration 1: 100 Gen A Wolves; 200 Gen B Wolves (300 total)
* Iteration 2: 100 Gen A Wolves; 200 Gen B Wolves, 400 Gen C Wolves (700 total)
* Iteration 3: 200 Gen B Wolves, 400 Gen C Wolves, 800 Gen D Wolves (1400 total)
Then you change the experiment, and you genetically modify the wolves so that each breeding pair only produces 1 pup, only once, causing the birthrate to fall below replacement level.
* Iteration 4: 400 Gen C Wolves, 800 Gen D Wolves, 400 Gen E Wolves (1600 total. note that this is larger than iteration 3, because the generations produced under higher birthrates are still alive, even though birthrates have now dipped below replacement level)
* Iteration 5: 800 Gen D Wolves, 400 Gen E Wolves, 200 Gen F Wolves (1400 total)
* Iteration 6: 400 Gen E Wolves, 200 Gen F Wolves, 100 Gen G Wolves (700 total)
* Iteration 7: 200 Gen F Wolves, 100 Gen G Wolves, 50 Gen H Wolves (350 total)
* Iteration 8: 100 Gen G Wolves, 50 Gen H Wolves, 25 Gen I Wolves (175 total)
Now, it's a lot more complex than that for the human population - differing birthrates in different areas are lowering at different speeds. Africa still has a high enough birthrate that it will continue to grow for decades to come, absent, I suppose, economic advancement on the Continent that would drive birthrates down faster than anticipated. Europe, North America, East Asia, and Russia are all already on the downward curve in terms of replacing themselves, and will have to import people from elsewhere if they want to avoid a net total loss in population.
Why do you think the Eugenicists were so interested in reducing reproduction among what they believed were the "lower" ethnicities?
Because they wanted the future to have a lot less of them.
and life goes on same as ever. Wrong! It keeps right on going up until all resources are used or somebody, somewhere, somehow starts a movement to curb the birthrate.
The birthrate is
already cut and it is
cutting further.
View attachment 67387830
This is exponential growth. If you graph the growth of these paramecium the chart looks exactly the same as the world population growth. We are at day 4.
We (the US) are at Day 5, but, a change has been introduced that will result in each bacterium that that
does reproduce does so so only once before dying, and 1/4th of the bacterium will not reproduce at all.
You will get a Day 6 when the generations produced under higher growth rates are still living.
And after that, the population begins to shrink.
