I wonder how much of an effect human activity has on these cycles. Obviously, there are cycles within nature that don't include human activity but is this particular "equilibrium" (if we could call it that) the result of human settlements and all that entails or have they always happened this way but without a huge chunk of the population being in the midst of these modulations to witness it and be affected by it.

This might be a good time to recommend you all read the first 5 pages of East of Eden by George Steinbeck. It’s about how the Salinas valley goes through flood and draught cycles, and how every time they’re in one cycle they forget the other one ever happened