Contingency

The major theme of Wonderful Life is what Stephen Jay Gould calls Contingency. Contingency is the idea that evolutionary history is highly "path-dependent." In other words, it depends on wholly contingent factors in its path of development that were far from inevitable. The Burgess Shale fauna contain a host of unique phyla, groups, classes, genuses, and species. Many have gone extinct. Yet from Walcott forward, these fauna were classified according to already known taxonomical categories. Evolutionary biologists simply could not understand the evolution might produce broad classes of animals, completely obliterate them, and the survivors be the ones not who were most fit but that merely contingently survived. Gould goes to great pains to show that Contingency is the lesson of the Burgess Shale. The Burgess revision was so impressive precisely because it uncovered this fact. Instead of gradual increase in complexity and diversity, evolution is a wild...