UC Irvine

Why do some explanations seem to take the form of a narrative? And why should evolutionary theorists in particular have recently proposed narrative explanations for the evolution of human cognition, when ‘storytelling’ is a commonplace pejorative for evolutionary explanation? In recent work on human cognitive evolution, several biologists and philosophers have put forth hypotheses in which they attempt to synthesize knowledge from a broad range of disciplines into comprehensive narratives. In this dissertation, I focus on one question raised by this broad and interdisciplinary approach: How does narrative structure affect the strategies and challenges for theorists of human cognitive evolution, especially compared to alternative approaches? I argue for three theses to demonstrate that the narrative structure of these hypotheses and the approach that theorists use to construct them are effects of the instability of the central causal relationship in question – the connection between the cognitive capacities of modern humans and those of the LCA. I first develop a novel account of narrative explanation: causal explanation takes the form of a narrative when the explanandum is a token event that stands in an unstable causal relationship with the first relevant cause in its causal history. I then use this account to make sense of two strategies that theorists use when building narratives of the evolution of human cognition in order to maximize detail under evidential scarcity: functional and historical associations. Finally, I consider some of the difficulties inherent to this approach, despite its potential advantages.For example, narratives seem to invite speculation to fill missing causal steps. My dissertation shows that narrative hypotheses of human cognitive evolution are a fruitful case for understanding narrative explanation generally, and conversely, that once these hypotheses are characterized and evaluated as narrative explanations, we can better understand this recent, promising approach to human cognitive evolution.In Chapter 2, “Causal properties of narrative explanations tell us what they are and when we’ll find them,” I present my account of narrative explanation. Some scientists produce explanations that seem to have a story-like, or narrative form. Such explanations are especially prominent in the historical sciences, including evolutionary history. To achieve an understanding of explanatory practice in historical science as well as a fuller understanding of the diversity of explanatory practices across the sciences, philosophers of science have proposed accounts of narrative explanation that seek to identify their unique explanatory features. However, such accounts neglect or misidentify the features that distinguish mere narratives from narrative explanations, and narrative explanations from other causal explanations. In this chapter, I propose a novel account of narrative explanation that situates it within an interventionist account of causal explanation. Using my account, I propose three dimensions along which narrative explanations can be evaluated and draw several consequences for outstanding disagreements in the literature on narrative explanations. Ultimately, my account clarifies and justifies narrative explanation as a legitimate and distinct form of explanation.In Chapter 3, “Implications of instability for the construction of narrative explanations,” I argue that instability that underlies the structure of narrative explanation also underlies one of its characteristic features – narratives seem to be most satisfying when they include a lot of detail. This connection explains two inferential strategies that theorists use to build narratives that help them to add detail under the constraints of limited evidence. These two strategies are (1) to show that one capacity emerged at a certain point in evolutionary history by connecting it functionally with another capacity whose emergence is evidenced in the material record, and (2) to show that past traits have high evolvability with respect to their enhancement toward traits in modern humans. Both such strategies inherently invoke what I call a “close-enough judgment,” wherein a theorist judges that the functional difference between one capacity and another, or that the evolutionary steps between a capacity and an enhanced version of that capacity, are small enough or close enough in an evolutionarily relevant sense. Close-enough judgments are not formally problematic but given the challenge of sparse material evidence in the hominin lineage, they constitute a potential weak point in narrative hypotheses.In Chapter 4, “What would imaginary ancestors do?” I consider the challenges and potential pitfalls of the narrative approach. The reconstruction of the evolutionary history of human cognition is a complex, interdisciplinary science. Human evolutionary theorists generally use a wide variety of evidential sources to construct hypotheses for the emergence of novel cognitive capacities in the hominin lineage. But sometimes, they take certain associations among cognitive capacities to be intuitively plausible – so much so that they accept and include them in their hypotheses. I argue that when they make these plausibility judgments, they are actually attempting (explicitly or implicitly) to reason from the perspective of an ancestral hominin. They reason about whether some inference would be easy, natural, or obvious for a hominin with only a hypothesized set of ancestral capacities. When they do this, they invoke their intuitive sense of ease or obviousness as evidence for the association among cognitive capacities. But such intuitions are systematically misleading, because they are influenced by the very cognitive capacity whose evolution the theorist seeks to explain. Intuitions that stem from the evolved capacity in question thus make some associations among cognitive capacities appear artificially plausible. I analyze examples of this kind of reasoning from three recent hypotheses for human cognitive evolution. I argue that this is a particularly pervasive challenge for evolutionary theorists. Even though they are typically highly attuned to similar errors, theorists should expect to keep contending with this challenge, even in our best approaches to human cognitive evolution.