Peter Thiel about falling birth rates

"There are 8 billion on the planet. If every woman has not 2 babies, but 1 baby. Then every generation half the previous, than the next generations 4 billion...one of the Japanese demographers, his thesis was - once it flips, it doesn't flip back because you've changed all the politics to where people get disincentive and then you should jut extrapolate this is the permanent birth rate. If it's one on average of 1 baby per woman and you have a halving and then it's in 33 generations, 2 to the 33rd is about 8 billion. And if every generation is 30 years, 30 times 33 is 990 years and 990 years you'd predict there'd be one person left on the planet. And then we'd go extinct if there's only 1 person left, it doesn't work.
The claim is that once you flip it it kicks in all these social and political dimensions that are then...maybe it got flipped by the screens or the plastics, the drugs...but once it's flipped you change the whole society and it actually stays flipped and it's very hard to undo."