Part 6
Attractor Basins
and
Evolution
Darwin imagined evolution as a slow, gradual process. The fossil record largely disagrees. The compossibility landscape explains why.
In 1972, Niles Eldredge and Stephen Jay Gould published a paper that reframed how biologists think about the fossil record. Darwin's gradualism, the view that evolution proceeds by the steady accumulation of small changes, implied that the fossil record should show continuous transitions between species and body plans. What the fossil record actually shows in most lineages is long periods of morphological stasis punctuated by geologically rapid transitions to new forms. Eldredge and Gould called this pattern punctuated equilibrium. The details remain debated, but the basic observation is now widely accepted: evolution often proceeds in bursts.
Why should this be? The standard evolutionary explanations involve changes in selection pressure, allopatric speciation, developmental constraints, and various mechanisms that could cause evolutionary change to accelerate at certain times and decelerate at others. These are real factors. But they are largely post hoc explanations for a pattern that remains, in the standard framework, somewhat puzzling. Why should stasis be the default? Why should change be concentrated in brief intervals?
Basins in the Compossibility Landscape
The compossibility landscape account makes punctuated equilibrium feel expected rather than puzzling. A stable biological configuration occupies an attractor basin in the compossibility landscape, a region where the configuration's internal coherence is reinforced by its relationship with the surrounding ecological and physical field. In evolutionary terms, this basin corresponds to what biologists call an adaptive zone: a set of ecological relationships that a body plan or life history strategy can exploit stably over time.
Within a basin, variation is abundant but transformative change is constrained. Natural selection operates continuously, producing adaptation and local optimisation, yet the basic architecture of the organism remains stable because the basin strongly reinforces the configurations that fit it. Variation that pushes a lineage away from those stable configurations is selected against. The reason is simple: the terrain of the basin makes those variants less coherent with their environment.
Stasis is what a system in a deep, stable basin looks like over time. Evolution has not stopped. It is still producing local adaptation, but not the kind of architectural change that would amount to a new body plan or a major shift in life history.
When a New Basin Opens
The transitions between periods of stasis are what produce the bursts of diversification that appear in the fossil record. They occur when a threshold is crossed: when some combination of accumulated change, environmental shift, or new ecological opportunity crosses the edge of the existing basin and opens access to a new region of the compossibility landscape.
Once a new basin becomes accessible, the dynamics change dramatically. Configurations within the new basin are no longer constrained by the old terrain. The compossibility landscape of the new basin accommodates a wide range of architectural variations that were impossible or highly disadvantageous in the old one. Lineages explore the new basin rapidly, because the terrain does not yet strongly constrain which specific configurations are most stable. Multiple viable forms proliferate in the early stages of basin exploration, before the selective pressure of competition and ecological specialisation deepens particular sub-basins within the new region.
The pattern is straightforward: long stability within a deep basin, rapid exploration once a new basin opens, gradual deepening of sub-basins through competition, and then another period of relative stasis as the new terrain settles. The cycle repeats across evolutionary time.
The Cambrian Explosion
The most dramatic example in the history of life is the Cambrian explosion, approximately 538 to 520 million years ago. In a geologically brief window of perhaps twenty million years, the fossil record reveals the appearance of most major animal body plans, including arthropods, molluscs, echinoderms, chordates, annelids, and many others, along with an extraordinary diversity of forms that later went extinct. The Cambrian fauna include creatures whose body plans have no living descendants and no clear relatives. They were experiments in animal architecture that later evolution did not continue.
What triggered the Cambrian explosion is still debated. Proposed factors include rising atmospheric oxygen levels that crossed the threshold needed to support active, complex animals; the evolution of predation, which created selection pressure for defensive adaptations; the development of new gene networks such as the Hox genes, which enabled modular body-plan innovation; and shifts in ocean chemistry that made calcification possible, allowing shells and skeletons to preserve well in the fossil record. Almost certainly, several factors combined.
In compossibility landscape terms, the Cambrian explosion marks the opening of an enormous new basin in animal life. The preceding Ediacaran fauna, soft-bodied, sessile or slow-moving organisms living in a low-oxygen world with little predation, occupied a relatively constrained basin. As oxygen accumulated, predation evolved, and developmental gene networks expanded, the threshold was crossed. A much larger region of the compossibility landscape opened to animal life. The rapid diversification that followed was the first exploration of that terrain, before competition and ecological specialisation began to narrow the field.
Extinction as Basin Collapse
Mass extinctions are the inverse of explosive radiations: rapid collapses of configurations that had been stable within particular basins, triggered by environmental changes that make those basins unviable. The end-Cretaceous extinction 66 million years ago, the one that ended the non-avian dinosaurs, was triggered by the impact of a large asteroid combined with extensive volcanism. Together they altered the climate, reduced sunlight through atmospheric particulates, and collapsed food chains from the base.
In compossibility landscape terms, that event rapidly reshaped the available ecological terrain. Configurations that had been deeply stable within the Mesozoic landscape, large-bodied dinosaurs, marine reptiles, pterosaurs, suddenly occupied a world where their compossibility conditions could no longer be satisfied. Their basins had collapsed. The lineages that survived and later radiated, small-bodied, endothermic, often burrowing forms that became the basis of the Cenozoic mammal radiation, were the ones whose compossibility conditions still held in the degraded post-impact landscape.
The evolutionary recovery after mass extinctions typically shows the same pattern as the Cambrian explosion: rapid exploration of newly opened ecological terrain, followed by progressive specialisation and deepening of sub-basins as competition intensifies. The dynamics are identical. Basin collapse is followed by landscape reorganisation and basin exploration.
Direction in Evolution
Does evolution have a direction? Darwin was cautious about the question. Many later biologists have been openly hostile to it, seeing claims of directionality as smuggling in teleology or progress narratives that the evidence does not support. Evolution has produced extraordinary complexity, but it has also maintained bacteria for three billion years and cockroaches for three hundred million. Complexity rises at the upper edge of the distribution, while the modal organism on Earth, judged by biomass, diversity, and evolutionary longevity, is still microbial.
The compossibility landscape account suggests a more precise statement. The closure gradient creates a structural bias toward increasing compossibility across the whole system. That does not mean every lineage becomes more complex, or that complexity is the only direction available. It means the landscape itself tends to become richer over time. New basins are often, though not always, larger and more complex than the ones they replace. The maximum level of complexity reached in a given geological era tends to exceed that of earlier eras, even while the modal complexity of life remains microbial.
This is a statistical claim about the distribution of compossibility basins over time. No particular lineage is guaranteed to progress toward a goal. The direction is real at the level of the whole landscape and says little by itself about the fate of any single configuration within it.
Next
7. Morphic Fields and Synchronicity
What Sheldrake and Jung were pointing at, and why ART gives the underlying pattern a formal grounding neither could provide.