[zpeti]

You are making a big assumption about it being cyclical. Never in history have we had contraception, it's a huge change to human behaviour. It's not at all obvious that women actually want more than 1.5 children on average in the west.

We also have tinder etc and a bunch of other changes that are HUGE in terms of culture.

I'm not saying any of these are bad, and there's not way we are going back to no contraceptives. But to ignore the effects of these, ESPECIALLY as birth rates are trending down EVERYWHERE, is pushing your head in the sand.

You are making a lot of assumptions, and as my example shows, if your assumptions are wrong for say ~50 years, you've already made a huge dent in your populations makeup.