Synchronizing menstrual cycles with the moon

[Lvl 2 Expert]

Populations would EXPLODE!!! People wouldn't have less children. For examples please see modern Africa and Asia.

This Asia?

(Admitted, modern day Asia and Africa do have birth control, so it doesn't really invalidate what you were saying, but not the best example maybe.)

(Also, that's a logarithmic scale, so it looks flatter than a linear one would, but it does help visualize trends.)