A narrative of recurrent causation, the Nemesis hypothesis, holds that the Sun has a companion star, Nemesis, whose orbit perturbs comets from the Oort cloud into earth-crossing orbits leading to mass extinction by impact with a nearly clocklike periodicity. Here I discuss the pursuit of the Nemesis hypothesis as the pursuit of narrative closure. Using a framework drawing on formalist analysis of narratives that distinguishes between the ordering of events in the narrative discourse (the syuzhet) and in their chronological sequence (the fabula), I describe the processes of reading and rereading the fossil and geologic records. The resulting analysis dissolves false dichotomies between nomothetic and idiographic, and catastrophic and uniformitarian approaches in the historical sciences. It also accommodates diverse philosophical views about the nature of epistemic access to the past.

This chapter is all about mass extinctions. I have talked about them previously but here I provide much more detail. I introduce the Gubbio section in Italy where a complete end – Cretaceous record allowed Louis and Walter Alvarez to recognised in possibility that a meteor played a significant role in triggering the end-Cretaceous mass extinction. I provide a definition of what constitutes a mass extinction, talk about how many there are in the fossil record and explain how we know how many species go extinct at each of the big five mass extinctions. Scientists have always been fascinated by the possibility of there being a cyclic pattern of mass extinctions. After reviewing the data and spending a little time the Nemesis model of cyclicity I suggest that this is not the case. Mass extinctions are associated with major shifts in the Earth System. Reflecting on this linkage, the chapter ends with what amounts to a general model for all mass extinctions.