CHAOTIC motion of planets in the inner Solar System results in transitions between different dynamical regimes.
Evolutionary periodograms of Earth's perihelion motion (left and right below) show two vertical ridges that correspond
to the g3 (~0.0134 cycles/ka) and g4 (~0.0138 cycles/ka) principal secular frequencies.
The first 70 Ma before the present show the same features, including the same transitions.
Earlier times are strikingly different.

There is also a clear overall drift in the principal frequencies which pushes the system through several transitions.

Background image: NASA/JPL/Malin Space Science Systems

(F. Varadi)