… contingency dominates and the predictability of general form recedes to an irrelevant background.
Final post from Wonderful Life: The Burgess Shale and the Nature of History by Stephen Jay Gould (1989):
… I have been too apologetic so far. I have even slipped into the rhetoric of inferiority — by starting from the premise that historical explanations may be less interesting and then pugnaciously fighting for equality. No such apologies need be made. Historical explanations are endlessly fascinating in themselves, in many ways more intriguing to the human psyche than the inexorable consequences of nature’s laws.
[line break added] We are especially moved by events that did not have to be, but that occurred for identifiable reasons subject to endless mulling and stewing. By contrast, both ends of the usual dichotomy — the inevitable and the truly random — usually make less impact on our emotions because they cannot be controlled by history’s agents and objects, and are therefore either channeled or buffeted, without much hope for pushing back.
[line break added] But, with contingency, we are drawn in; we become involved; we share the pain of triumph or tragedy. When we realize that the actual outcome did not have to be, that any alteration in any step along the way would have unleashed a cascade down a different channel, we grasp the causal power of individual events. We can argue, lament, or exult over each detail — because each holds the power of transformation.
… Our own evolution is a joy and a wonder because such a curious chain of events would probably never happen again, but having occurred, makes eminent sense. Contingency is a license to participate in history, and our psyche responds.
… Invariant laws of nature impact the general forms and functions of organisms; they set the channels in which organic design must evolve. But the channels are so broad relative to the details that fascinate us! The physical channels do not specify arthropods, annelids, mollusks, and vertebrates, but, at most, bilaterally symmetrical organisms based on repeated parts. The boundaries of the channels retreat even further into the distance when we ask the essential questions about our own origin.
[line break added] Why did mammals evolve among vertebrates? Why did primates take to the trees? Why did the tiny twig that produced Homo sapiens arise and survive in Africa? When we set our focus above the level of detail that regulates most common questions about the history of life, contingency dominates and the predictability of general form recedes to an irrelevant background.