When the environment in which an organism lives deviates in some essential way from that to which it is adapted, this is described as “evolutionary mismatch,” or “evolutionary novelty.” The notion of mismatch plays an important role, explicitly or implicitly, in evolution-informed cognitive psychology, clinical psychology, and medicine. The evolutionary novelty of our contemporary environment is thought to have significant implications for our health and well-being. However, scientists have generally been working without a clear definition of mismatch. This paper defines (...) mismatch as deviations in the environment that render biological traits unable, or impaired in their ability, to produce their selected effects. The machinery developed by Millikan in connection with her account of proper function, and with her related teleosemantic account of representation, is used to identify four major types, and several subtypes, of evolutionary mismatch. While the taxonomy offered here does not in itself resolve any scientific debates, the hope is that it can be used to better formulate empirical hypotheses concerning the effects of mismatch. To illustrate, it is used to show that the controversial hypothesis that general intelligence evolved as an adaptation to handle evolutionary novelty can, contra some critics, be formulated in a conceptually coherent way. (shrink)

Following Wallace’s suggestion, Darwin framed his theory using Spencer’s expression “survival of the fittest”. Since then, fitness occupies a significant place in the conventional understanding of Darwinism, even though the explicit meaning of the term ‘fitness’ is rarely stated. In this paper I examine some of the different roles that fitness has played in the development of the theory. Whereas the meaning of fitness was originally understood in ecological terms, it took a statistical turn in terms of reproductive success throughout (...) the 20th Century. This has lead to the ever-increasing importance of sexually reproducing organisms and the populations they compose in evolutionary explanations. I will argue that, moving forward, evolutionary theory should look back at its ecological roots in order to be more inclusive in the type of systems it examines. Many biological systems can only be satisfactorily accounted for by offering a non-reproductive account of fitness. This argument will be made by examining biological systems with very small or transient population structures. I argue this has significant consequences for how we define Darwinism, increasing the significance of survival over that of reproduction. (shrink)

I defend the historical definition of "function" originally given in my Language, Thought and Other Biological Categories (1984a). The definition was not offered in the spirit of conceptual analysis but is more akin to a theoretical definition of "function". A major theme is that nonhistorical analyses of "function" fail to deal adequately with items that are not capable of performing their functions.

Two decades ago, the eminent evolutionary biologist George C. Williams and his physician coauthor, Randolph Nesse, formulated the evolutionary medicine research program. Williams and Nesse explicitly made adaptationism a core component of the new program, which has served to undermine the program ever since, distorting its practitioners’ perceptions of evidentiary burdens and in extreme cases has served to warp practitioner’s understandings of the relationship between evolutionary benefits/detriments and medical ones. I show that the Williams and Nesse program more particularly embraces (...) the panselectionist variety of adaptationism (the empirical assumption that non-adaptive evolutionary processes are causally unimportant compared to natural selection), and argue that this has harmed the field. Panselectionism serves to conceal the enormous evidentiary hurdles that evolutionary medicine hypotheses face, making them appear stronger than they are. I use two examples of evolutionary medicine texts, on neonatal jaundice and on asthma, to show that some evolutionary medicine practitioners have allowed their fervent panselectionism to directly shape their recommendations for clinical practice. I argue that this escalation of panselectionism’s influence is inappropriate under Williams’ and Nesse original stated standards, despite being inspired by their program. I also show that the examples’ conflation of clinical and evolutionary considerations is inappropriate even under Christopher Boorse’s controversial evolution-rooted concepts of disease and health. (shrink)

The concept of "fitness" is a notion of central importance to evolutionary theory. Yet the interpretation of this concept and its role in explanations of evolutionary phenomena have remained obscure. We provide a propensity interpretation of fitness, which we argue captures the intended reference of this term as it is used by evolutionary theorists. Using the propensity interpretation of fitness, we provide a Hempelian reconstruction of explanations of evolutionary phenomena, and we show why charges of circularity which have been levelled (...) against explanations in evolutionary theory are mistaken. Finally, we provide a definition of natural selection which follows from the propensity interpretation of fitness, and which handles all the types of selection discussed by biologists, thus improving on extant definitions. (shrink)

We defend a view of the distinction between the normal and the pathological according to which that distinction has an objective, biological component. We accept that there is a normative component to the concept of disease, especially as applied to human beings. Nevertheless, an organism cannot be in a pathological state unless something has gone wrong for that organism from a purely biological point of view. Biology, we argue, recognises two sources of biological normativity, which jointly generate four “ways of (...) going wrong” from a biological perspective. These findings show why previous attempts to provide objective criteria for pathology have fallen short: Biological science recognizes a broader range of ways in which living things can do better or worse than has previously been recognized in the philosophy of medicine. (shrink)

This article discusses various dangers that accompany the supposedly benign methods in behavioral evoltutionary biology and evolutionary psychology that fall under the framework of "methodological adaptationism." A "Logic of Research Questions" is proposed that aids in clarifying the reasoning problems that arise due to the framework under critique. The live, and widely practiced, " evolutionary factors" framework is offered as the key comparison and alternative. The article goes beyond the traditional critique of Stephen Jay Gould and Richard C. Lewontin, to (...) present problems such as the disappearance of evidence, the mishandling of the null hypothesis, and failures in scientific reasoning, exemplified by a case from human behavioral ecology. In conclusion the paper shows that "methodological adaptationism" does not deserve its benign reputation. (shrink)

Human psychological mechanisms are adaptations that evolved to process environmental inputs, turning them into behavioral outputs that, on average, increase survival or reproductive prospects. Modern contexts, however, differ vastly from the environments that existed as human psychological mechanisms evolved. Many inputs now differ in quantity and intensity or no longer have the same fitness associations, thereby leading many mechanisms to produce maladaptive output. We present the precepts of this evolutionary mismatch process, highlight areas of mismatch, and consider implications for psychological (...) science and policy. (shrink)

Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands (...) of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior. (Published Online November 9 2006) Key Words: adaptation; behavior genetics; Darwinian psychiatry; evolution; evolutionary genetics; evolutionary psychology; mental disorders; mutation-selection balance; psychiatric genetics; quantitative trait loci (QTL). (shrink)

The next time you get sick, consider this before picking up the aspirin: your body may be doing exactly what it's supposed to. In this ground-breaking book, two pioneers of the science of Darwinian medicine argue that illness as well as the factors that predispose us toward it are subject to the same laws of natural selection that otherwise make our bodies such miracles of design. Among the concerns they raise: When may a fever be beneficial? Why do pregnant women (...) get morning sickness? How do certain viruses "manipulate" their hosts into infecting others? What evolutionary factors may be responsible for depression and panic disorder? Deftly summarizing research on disorders ranging from allergies to Alzheimer's, and form cancer to Huntington's chorea, Why We Get Sick, answers these questions and more. The result is a book that will revolutionize our attitudes toward illness and will intrigue and instruct lay person and medical practitioners alike. (shrink)

For some, biology explains all there is to know about the mind. Yet many big questions remain: is the mind shaped by genes or the environment? If mental traits are the result of adaptations built up over thousands of years, as evolutionary psychologists claim, how can such claims be tested? If the mind is a machine, as biologists argue, how does it allow for something as complex as human consciousness? The Biological Mind: A Philosophical Introduction explores these questions and more, (...) using the philosophy of biology to introduce and assess the nature of the mind. Drawing on the four key themes of evolutionary biology; molecular biology and genetics; neuroscience; and biomedicine and psychiatry Justin Garson addresses the following key topics: moral psychology, altruism and levels of selection evolutionary psychology and modularity genes, environment and the nature-nurture debate neuroscience, reductionism and the relation between biology and free will function, selection and mental representation psychiatric classification and the maladapted mind. Extensive use of examples and case studies is made throughout the book, and additional features such as chapter summaries, annotated further reading and a glossary make this an indispensable introduction to those teaching philosophy of mind and philosophy of psychology. It will also be an excellent resource for those in related fields such as biology. (shrink)