Chapter 5, Possible Worlds Summary and Analysis

This chapter attempts to make concrete the lesson of the last. Chapter 4 argues that the story of history is Contingency. However, Gould realizes that this lesson is abstract and so he attempts to illustrate the contingency of evolution through alternative scenarios, which he realizes are difficult to describe (they did not happen, after all). He begins by describing various Burgess Shale animals, wondering what might have happened had they survived rather than the arthropods we know today. Contingency is powerful in the details of Darwin's theory, despite how well-adapted many creatures are to their environments. The Burgess Shale represents contingency due to the massive disparity of the Cambrian explosion and the apparent luck of those species that survive its eventual decimation. Maybe the Cambrian explosion did not have to happen that way. Perhaps diversity could have expanded...