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By Root 587 0

remain modest and constant, relative stasis in the system is the norm. If the fluctuation becomes powerful enough that it upsets the preexisting organization and balance, a major change or revolution may occur, at which point the system may become chaotic. Necessity takes a system down a certain path until it reaches a bifurcation point. At this time contingency plays an exaggerated role in nudging the system down a new path, which in time develops its own powerful necessities such that contingency is attenuated until the next bifurcation. It is the alloy of contingency and necessity that guides and controls the presence or absence of these bifurcations, and elsewhere I have provided numerous historical examples.

GLORIOUS CONTINGENCY: A LITTLE TWIG CALLED HOMO SAPIENS

The model of contingent-necessity and its corollaries is a formalization of Gould’s dangerous idea. In an essay entitled “Fungal Forgery,” Gould applied the model to a complex insect-flower system to show how it could have evolved, but in a very unpredictable manner in its early stages: “Fungal pseudoflowers are late necessities, and they give us no reason to suppose that the complex contingent prerequisite for this sensible story—the evolution of the insect-flower system—has any similar predictability.” Before turning from this fascinating particular to broader generalities about contingency, Gould offered his usual caveat: “I do not, of course, deny that the history of life includes predictable events and recurrent patterns. I do, however, suspect that most predictable aspects of life lie at too ‘high’ a level of generality to validate what really stirs and troubles our souls—the hope that we might ratify as a necessary event the evolutionary origin of a little twig called Homo sapiens.” But beyond such anthropomorphic concerns, Gould shows why necessities may not always dominate:

As an interesting consequence of Shermer’s model, we may ask why life as a whole doesn’t finally settle down to globally predictable unrolling, whatever the massive contingency of initial stages. Shermer points, correctly I think, to the importance of infrequent and highly disturbing events (such as mass extinction for faunas or punctuated equilibria for lineages) in derailing the stasis or predictable unrolling of systems otherwise stabilized. The theoretical importance of rare, and sometimes cataclysmic, events—as the preservers and reinvigorators of global contingency—may best be appreciated in the light of such historical models.

Gould then returns to his familiar metaphor of the tape, applying the model to the entire history of life:

But if I could rerun the tape of life from the origin of unicellular organisms, what odds would you give me on the reevolution of this complex and contingent insect-flower system…? Would we see anything like either insects or flowers in the rerun? Would terrestrial life originate at all? Would we get mobile creatures that we could call animals? Fine-scale predictability only arises when you are already 99 percent of the way toward a particular result—and the establishment of this 99 percent lies firmly in the domain of unrepeatable contingency.

The contingent evolution of insect-flower systems, however, is not what makes contingency dangerous. It is that contingent little twig called Homo sapiens that tasks us. We want to be special. We want our place in the cosmos to be central. We want evolution—even Godless evolution—to have been directed toward us so that we stand at the pinnacle of nature’s ladder of progress. Rewind that tape of life and we want to believe that we (Homo sapiens) would appear again and again. Would we? Most likely not. There are simply too many contingent steps along the way, too many trigger points where the sequence could have bifurcated down some other equally plausible path. Alfred Russel Wallace, the codiscoverer of natural selection, toward the end of his life realized this in his book, Man’s Place in the Universe: “The ultimate development of man has, therefore roughly speaking, depended on