BIOTIC AND CULTURAL TURNING POINTS: MASS EXTINCTIONS, INNOVATIONS AND ENVIRONMENTAL PERTURBATIONS
Geological evidence indicates that the physical nature of Earth
is the product of the interaction of a number of independent key--variables,
e.g. global geology, internal dynamics of the planet, climate, sea level
and biosphere, with different relative importance. During the history of
Earth each of these variables has been subject to variations, affecting
the overall configuration of the Earth system. In particular we observe
that the Phanerozoic epoch was characterized by the alternation of two
regimes, one "continental" and one "oceanic".
In times of transition between different regimes, especially from the continental one to the oceanic one, the system becomes unstable, with perturbations in the physical and in the living world, including mass extinctions, that appear as continuity interruptions and evolutionary discontinuities. Both the Earth system and the living system evolve therefore not in a linear way, but via jumps and discontinuities. While the principal episodes of biological crisis are found between geological era (Pz-Mz, K-T), intermediate crises are found between geological epochs (O-S, F-F, T-J). In proximity of such variation points the system is first destabilized and then reorganized; old structures decline and disappear and new forms appear (catastrophical extinctions and anastrophic appearance of new biological forms).
We can also note that even cultural and socioeconomic changes seem to
appear in a discontinuous way that may be correlated with global changes
in the physical world.