How high was fertility before the Industrial Revolution? Human population had a pretty anemic growth then - were the poor then relying on the rate selection just as much?

If there is some biological-genetic encoding of historical-demographic cycles - yeah, a very unconventional if - then it is evolutionarily rational to reproduce a lot when exceptional opportunities of some industrial growth are in sight, and to reproduce reluctantly for the decline turn. In particular, Japan has much of the private sense of little perspective, cause to bring a child for some time already. Genuine resource signaling may not be that hard to catch unconsciously.