Dissertation Title: Evolutionary Psychology and the Future of Evolutionary History Chairs: Professor Philip Kitcher, Professor Patricia Kitcher, Professor Alison Wylie Committee: Professor Donald Melnick, Professor Jerry Fodor, Professor David Albert Abstract Over the last fifteen years, evolutionary psychology has become an influential research program in psychology and across the social sciences generally, carrying on its predecessors' tradition of embedding accounts of human behavior in an evolutionary framework. This association with the rightly respected evolutionary sciences has made explanations offered by evolutionary psychologists appealing. But, as I demonstrate in my dissertation, the association is rather tenuous. The 1970s saw the rise of sociobiology and its attempts to explain human behavior using some of the principles behind models which had illuminated our understanding of other social (generally insect) species. The generality of these models, it was hoped, would allow researchers to explain human sociality in precisely the same way that it had helped us to explain the insect societies. By applying the firmly established theoretical machinery of evolutionary biology, human sociobiology revealed itself to be not a new science, but merely the extension of evolutionary biology to the domain of human behavior. But however honorific the inclusion into the evolutionary scientific community may have been, it turned out to be the death knell for sociobiology. For, along with the privilege of employing evolutionary biology's models came the evidentiary burden which evolutionary biologists were expected to meet. This proved to be beyond the capacity of the sociobiological community, and by the late 1980s few if any researchers claimed to be working in the field. Instead, the scientific community was introduced to a new approach to human behavior –– evolutionary psychology. Evolutionary psychologists have jettisoned the crude "genes determine behavior" framework of their forefathers, claiming to have located the "missing link" between biology and society which had eluded sociobiologists like E.O. Wilson and David Barash. The link, they tell us, is the cognitive mechanism, built by the genes, selected by nature, and capable of transforming environmental information into adaptive behavioral response. My dissertation investigates the philosophical principles behind the study of evolutionary history. Embedded within this investigation is a comprehensive critique of evolutionary psychology. What I argue, in broad outline, is that while the focus on cognitive mechanisms is certainly a welcome transition from the focus on genes, as a way of reforming evolutionary approaches to human behavior it fails to address the central difficulty faced by sociobiology: providing the kind and quantity of evidence typically required to substantiate claims about evolutionary history. The principles whose success in explaining social insects seduced sociobiologists into applying them unreflectively to humans are the very same principles structuring evolutionary psychological explanations. Yet, again, the evidence just isn't there. Apart from the eschewing of explicit genetic determinism, then, the approach of evolutionary psychologists does not differ significantly from that of sociobiologists. The structure of my critique can be broken down into two parts. I first focus on the differences between the use of patterns of reasoning and styles of investigation in evolutionary biology and paleontology (which I defend) and their use in evolutionary psychology (which I condemn). I begin by describing the methods by which we arrive at reliable accounts of evolutionary change, as well as why these methods are seen as reliable and why a researcher might favor one particular kind of explanation over another. I then show via comparison how far evolutionary psychology is from doing this kind of work. Following that, I examine the structure of explanation in evolutionary biology and the mismatch between that structure and the sorts of explanations offered by evolutionary psychologists. What emerges out of this bipartite approach is a philosophical exploration of the reach of evolutionary reasoning in the human sciences combined with the undoing of evolutionary psychological ambitions. My aim in the first part of the dissertation is to provide a philosophical understanding of the design of scientific practice across the three disciplines most relevant to the study of human evolutionary history: population biology (chapter 2), sexual selection (chapter 3), and paleoanthropology (chapter 4). After developing a general understanding of the concept of evolutionary adaptation and its role in demonstrations of selection, I critically assess the evolutionary psychological methods used to study selection by comparing them with the methods of population biology, arguing that the former are far less reliable than the latter. I then narrow my focus, examining how the conceptual and methodological points developed in chapter 2 are brought to bear upon the study of how mate choice guides evolutionary change. Here I argue that evolutionary psychologists have unjustifiably ignored the bulk of theoretical literature on sexual selection, focusing on one theory in particular. I go on to discuss important aspects of the empirical study of mate choice and mate preferences, arguing that there are significant, irremediable gaps between empirical work in evolutionary psychology and that of researchers focusing on nonhumans. I end the chapter with a rigorous illustration of prominent models of mate choice and the requirements involved in showing whether a given model is applicable to a given population. The thrust of my argument here is that evolutionary psychologists have in many places misunderstood theory and in every place failed to provide the evidence necessary to suggest the presence of a particular selection dynamic. In chapter 4 I shift the scope of my investigation away from evolutionary biology to concentrate on paleoanthropology. I look at a number of different types of paleoanthropological research, arguing for two substantive theses: first, that the best work in this area is characterized by a specific form of analogical inference which represents our only hope for gaining reliable knowledge of the past; and second, that there is a particular set of questions which can determine whether some historical inference fits the desired analogical structure. I then employ this set of questions to assess the quality and reliability of the cases under discussion. Using the conceptual and empirical conclusions derived here, I examine evolutionary psychological claims about the past and about how to learn about the past, demonstrating that the former sorts of claims are thoroughly unsupported (e.g., pace evolutionary psychologists, it's unknown whether early hominins hunted) and the latter sorts of claims describe methods which have little value for learning about evolutionary history. This is accomplished via a combination of philosophical argument and case study. At this point, I step away from the philosophical analysis of scientific practice and turn my attention towards issues associated with the evolutionary psychological use of the notion of inference to the best explanation. Gestures towards inference to the best explanation within evolutionary psychology are motivated by the view that only evolutionary psychological hypotheses (as contrasted with other social scientific hypotheses) are "consistent with evolutionary theory," and are therefore the best available explanations of the evidence. After undermining the conception of consistency with evolutionary theory invoked by evolutionary psychologists, I develop a positive conception of inter-theoretic consistency and, based on this conception, argue for a particular position regarding what sorts of a priori constraints there ought to be on scientific research. Finally, I argue that candidate accounts must satisfy the requirements placed upon an explanation in a given field in order to qualify as "explanations," that evolutionary psychologists' accounts ignore most of these requirements, and that these accounts therefore do not rise to the level of explanation. A fortiori, these accounts fail to be the best explanations. The dissertation concludes with an assessment of inference to the best explanation within evolutionary psychology in the context of in-depth analyses of two well-known research programs: Cosmides and Tooby's research on "cheater detection modules" and Daly and Wilson's work on stepparental childcare. Here I assume the explanatory adequacy of the accounts, arguing instead that there are no good reasons to favor them over rival accounts and lots of good reasons to favor rival accounts over them. The most important and general lessons from my analysis of the problems associated with evolutionary psychology concern (1) what we can reasonably expect to know about the evolutionary history of human psychology, and (2) what the appropriate role of evolutionary reasoning in philosophy might be. With respect to (1), I suggest that it is entirely dependent on whether evolutionary psychologists move towards substantiating their claims via the methods standardly employed in evolutionary biology and paleoanthropology; the alternative is to go the way of human sociobiology. With respect to (2), I argue that the strength of evolutionarily informed philosophical argumentation lies in its ability to demonstrate that certain hypotheses about phenomena relating to human nature are, in fact, possible explanations of these phenomena. Without these sorts of demonstrations, the ability of some candidate account to explain the phenomena cannot but remain in question.