5 - The Epistemic Rise of Hypothetical Ancestors

Summary

In this chapter I discuss the anatomy of evolutionary storytelling. Historical narratives are woven around central subjects that lend them continuity through time. The central subjects of phylogenetic scenarios are lineages of hypothetical ancestors. These define the pathways of homology along which evolutionary change is reconstructed, and they root the power of phylogenetic hypotheses to explain the evolution of form by allowing characters in descendants to be traced back to ancestral precursors. De novo origins of novel traits are chinks in the explanatory armory of phylogenetic hypotheses. Hypothetical ancestors have therefore often been deliberately equipped with characters that provide suitable precursors of the traits that await evolutionary explanation. I will argue that the precursor potential of hypothetical ancestors functioned as an early phylogenetic optimality criterion used in the construction and judging of scenarios.