I think people completely discount this effect, when discussing politics or larger societal movements. There's a lot of emphasis on number of children, but I've only once seen someone mention reproductive cycle length, as a societal factor.

In fact, I think this has a much higher impact on the direction a society moves, than the TFR, as

1) each generation is best-adapted to its original environment, so this maximizes the power of sexual reproduction and evolution, whilst the rest of society focuses on hand-crafting perfect specimens, for the way they environment previously was

2) you quickly reach a critical mass, even if you're a relatively small group, and you are probably geographically-concentrated, so you can dictate governance (even under anarchy, where you can dictate EVEN HARDER)

3) you have more young men and therefore wield a disproportionate amount of violence

4) you have lots of children, at a constant rate, without any particular woman being heavily burdened