This chapter contains section titled: Introduction: What is Phenotypic Plasticity? Developmental Conversion and Developmental Sensitivity: Two Forms of Phenotypic Plasticity Environmental Heterogeneity, Cues, and Plasticity Phenotypic Plasticity and Developmental Buffering The Future of Phenotypic Plasticity Research Acknowledgments References Further Reading.

Culture or Biology? The question can seem deep and important. Yet, I argue in this chapter, if you are enthralled by questions about our biological differences, then you are probably confused. My goal is to diagnose the confusion. In debates about the role of biology in the social world it is easy to ask the wrong questions, and it is easy to misinterpret the scientific research. We are intuitively attracted to what is called psychological essentialism, and therefore interpret what is (...) biological as what can be traced to “essences”. On this interpretation, it would be deep and important to know what about, say, the differences between the genders is biological: it would correspond to what is essential to being a man or being a woman, and be opposed to what is a mere accidental feature that some women or some men have. Yet, the psychological essentialist understanding of ‘biological differences’ is deeply mistaken about biology. It has the wrong conception of biological kinds, of biological heritability, and of how genes and hormones work. Those who argue for an important role of ‘biology’ in the explanation of human differences often see ‘the science’ on their side. But this is false – on the interpretation of ‘biological differences’ that is most intuitive and that makes the question appear to be most interesting. Defenders of ‘biology’ often have the science against them. What is often called ‘biology’ is a myth: a myth created by an intuitive tendency that grotesquely distorts real biological research. (shrink)

Following Mayr (1961) evolutionary biologists often maintain that the hallmark of biology is its evolutionary perspective. In this view, biologists distinguish themselves from other natural scientists by their emphasis on why-questions. Why-questions are legitimate in biology but not in other natural sciences because of the selective character of the process by means of which living objects acquire their characteristics. For that reason, why-questions should be answered in terms of natural selection. Functional biology is seen as a reductionist science that applies (...) physics and chemistry to answer how-questions but lacks a biological point of view of its own. In this paper I dispute this image of functional biology. A close look at the kinds of issues studied in biology and at the way in which these issues are studied shows that functional biology employs a distinctive biological perspective that is not rooted in selection. This functional perspective is characterized by its concern with the requirements of the life-state and the way in which these are met. (shrink)

As emphasized in early cultural evolutionary theory, understanding heritability of human traits – especially, behavioural traits – is difficult. The target article describes important ways that culture can enhance, or obscure, signatures of heritability in genetic studies. Here, we discuss the utility of calculating heritability for behavioural traits influenced by cultural evolution and point to conceptual and technical complications to consider in future models.

Metaphors of adorning, crafting, water flowing downward, and growing sprouts appear in the Analects , the Mencius , and the Xunzi 荀子. They express and guide thinking about what there is in human nature to cultivate and how it is to be cultivated. The craft metaphor seems to imply that our nature is of the sort that must be disciplined and reshaped to achieve goodness, while the adorning, water, and sprout metaphors imply that human nature has an inbuilt directionality toward (...) the ethical that should be protected or nurtured. I argue that all the metaphors capture different aspects of human nature and how one must work with these aspects. There is much in contemporary psychology and neuroscience to suggest that the early Confucians were on the right track. It is also argued that they point to a fruitful conception of ethical development that is relational and holistic. (shrink)

The Modern Synthesis has been receiving bad press for some time now. Back in 1983, in an article entitled “The Hardening of the Modern Synthesis” Stephen Jay Gould criticized the way the Modern Synthesis had developed since its inception in the 1930s and early 1940s (Gould 1983). Back then, those who would later become known as ‘architects’ of the synthesis were united in their call for explaining evolution at all levels in terms of causation at one level: genetics. What drove (...) changes in gene frequency remained an open question. It could be mainly selection, or drift, or some (other) form of constraint. But in the two decades that followed, the synthesis underwent a major change. By the late 1940s the synthesis had ‘hardened’ around adaptationism, according to Gould. Influential contributors like Dobzhansky, Simpson and Wright had increasingly expressed adaptationist views in the later editions of their landmark books. Not because evidence had piled up, showing that selection was in fact pervasive. Instead, Gould argued, adaptationist tendencies had been preserved by some kind of cultural inertia, and were now being revived. “Certain ‘national styles’ persisted from the eighteenth century, through Darwin’s era, and into our own time. Views on adaptation provide a good example” (Gould 1983). Gould did not just argue that some form of adaptationism had resurfaced. He became well-known for his efforts to intervene on this status quo by attempting to make evolutionary biology more ‘pluralistic’. In collaborative work with Richard Lewontin (Gould and Lewontin 1979), Elisabeth Vrba (Gould and Vrba 1982; Vrba and Gould 1986) and Niles Eldredge (Eldredge and Gould 1972; Gould and Eldredge 1977) he criticized the synthesis for its adaptationism and its lack of appreciation for hierarchical perspectives. Gould exerted his influence in a different way as well. Together with Eldredge, he had facsimiles reprinted of the first editions of two books that had shaped synthesis, but with their own critical introductions (Eldredge 1982; Gould 1982). Dobzhansky’s Genetics and the Origin of Species and Mayr’s Systematics and the Origin of Species appeared as reprints in the ‘Columbia Classics in Evolution’ series, sending an unambiguous message to the readers: these are foundational works, but they have been superseded. In the summer of 2008, some 25 years after Gould made his point about the hardening of the Modern Synthesis, a group of sixteen biologists and philosophers gathered at the Konrad Lorenz Institute for Evolution and Cognition Research (KLI) near Vienna, Austria, to discuss cutting-edge research that reaches beyond the synthesis framework. Before it even started, this workshop on the ‘Extended Synthesis’ had already attracted a fair share of attention in the blogosphere and had resulted in a news feature in Science (Pennisi 2008). After the meeting, Nature weighed in on the matter (Whitfield 2008). The results of over 3 days of presentations and extensive discussion have now been published as Evolution—The Extended Synthesis. 1 The publication of this collection of sixteen essays is accompanied by the republication of Julian Huxley’s Evolution: The Modern Synthesis; the book that introduced the term ‘Modern Synthesis’. Both books are introduced by the organizers of the KLI workshop, Massimo Pigliucci and Gerd Müller. Like Gould and Eldredge before them, Pigliucci and Müller did not reissue one of the canons of the Modern Synthesis without giving the readers some ‘guidance’. Starting with the cover, the editors proclaim boldly that this is ‘the definitive edition’ of Huxley’s book. In a new foreword, they sketch the context in which the book was written and assess some of its features. They voice some mild criticism of alleged ‘adaptationism’. But their tone is different from that of Gould and Eldredge. Pigliucci and Müller praise Huxley for his pluralistic outlook, which has again become essential in the forging of an Extended Synthesis. That makes Huxley’s book more than just an interesting but obsolete classic. Instead, it can teach valuable lessons about how to ‘soften up’ a synthesis that has become hardened over time. (shrink)

Most psychological research aims to uncover generalizations about the mind that hold across subjects. Philosophical discussions of scientific explanation have focused on such generalizations, but in doing so, have often overlooked an important phenomenon: variation. Variation is ubiquitous in psychology and many other domains, and an important target of explanation in its own right. Here I characterize explananda that concern individual differences and formulate an account of what it takes to explain them. I argue that the notion of actual difference (...) making, the only causal concept in the literature that explicitly addresses variation, cannot be used to ground such an account. Instead, I propose a view on which explaining individual differences involves identifying causes that could be intervened on to reduce the variability in the population. This account provides criteria of success for explaining variation and deepens our understanding of causal explanation. (shrink)

Brain damage may doubly dissociate cognitive modules, but the practice of revealing dissociations is predicated on modularity being true (T. Shallice, 1988). This article questions the utility of assuming modularity, as it examines a paradigmatic double dissociation of reading modules. Reading modules illustrate two general problems. First, modularity fails to converge on a fixed set of exclusionary criteria that define pure cases. As a consequence, competing modular theories force perennial quests for purer cases, which simply perpetuates growth in the list (...) of exclusionary criteria. The first problem leads, in part, to the second problem. Modularity fails to converge on a fixed set of pure cases. The second failure perpetuates unending fractionation into more modules. (shrink)

Behavioral genetics and cultural evolution have both revolutionized our understanding of human behavior – largely independent of each other. Here, we reconcile these two fields under a dual inheritance framework, offering a more nuanced understanding of the interaction between genes and culture. Going beyond typical analyses of gene–environment interactions, we describe the cultural dynamics that shape these interactions by shaping the environment and population structure. A cultural evolutionary approach can explain, for example, how factors such as rates of innovation and (...) diffusion, density of cultural subgroups, and tolerance for behavioral diversity impact heritability estimates, thus yielding predictions for different social contexts. Moreover, when cumulative culture functionally overlaps with genes, genetic effects become masked, unmasked, or even reversed, and the causal effects of an identified gene become confounded with features of the cultural environment. The manner of confounding is specific to a particular society at a particular time, but a WEIRD (western, educated, industrialized, rich, and democratic) sampling problem obscures this boundedness. Cultural evolutionary dynamics are typically missing from models of gene-to-phenotype causality, hindering generalizability of genetic effects across societies and across time. We lay out a reconciled framework and use it to predict the ways in which heritability should differ between societies, between socioeconomic levels, and other groupings within some societies but not others, and over the life course. An integrated cultural evolutionary behavioral genetic approach cuts through the nature–nurture debate and helps resolve controversies in topics such as IQ. (shrink)

The methodological shift from twin studies to genome-wide association studies (GWASs) diminished estimates of true genetic causation underlying statistical heritability of behavioral differences. The sum total of causal genetic influence on behavior is not zero, but, (a) no one cited in the target article ever thought this was the case, and (b) there is still little known about concrete instances of genetic causation.

This article examines eight “gaps” in order to clarify why the quantitative genetics methods of partitioning variation of a trait into heritability and other components has very limited power to show anything clear and useful about genetic and environmental influences, especially for human behaviors and other traits. The first two gaps should be kept open; the others should be bridged or the difficulty of doing so should be acknowledged: 1. Key terms have multiple meanings that are distinct; 2. Statistical patterns (...) are distinct from measurable underlying factors; 3. Translation from statistical analyses to hypotheses about measurable factors is difficult; 4. Predictions based on extrapolations from existing patterns of variation may not match outcomes; 5. The partitioning of variation in human studies does not reliably estimate the intended quantities; 6. Translation from statistical analyses to hypotheses about the measurable factors is even more difficult in light of the possible heterogeneity of underlying genetic or environmental factors; 7. Many steps lie between the analysis of observed traits and interventions based on well-founded claims about the causal influence of genetic or environmental factors; 8. Explanation of variation within groups does not translate to explanation of differences among groups. At the start, I engage readers’ attention with three puzzles that have not been resolved by past debates. The puzzles concern generational increases in IQ test scores, the possibility of underlying heterogeneity, and the translation of methods from selective breeding into human genetics. After discussing the gaps, I present each puzzle in a new light and point to several new puzzles that invite attention from analysts of variation in quantitative genetics and in social science more generally. The article’s critical perspectives on agricultural, laboratory, and human heritability studies are intended to elicit further contributions from readers across the fields of history, philosophy, sociology, and politics of biology and in the sciences. (shrink)

This essay extends Levins'' 1966 analysis of modelbuilding in ecology and evolutionary biology. Amodel, as the product of modeling, might bevalued according to its correspondence to reality. Yet Levins'' emphasis on provisionality and changeredirects attention to the processes ofmodeling, through which scientists select and generatetheir problems, define their categories, collect theirdata, compare competing models, and present theirfindings. I identify several points where decisionsare required that are not determined by nature. Thisinvites examination of the social considerationsmodelers are reacting to at the (...) sites of sociality.Modelers must weave socio-ecological webs so thatthe models can be seen to represent their subjectmatter at the same time as the modelers secure thesupport of colleagues, collaborators and institutions,and enjoin others to act upon their conclusions. Notonly do theory justification and theory generationmerge, but the joint project becomes simultaneouslyphilosophical and sociological. (shrink)

A key challenge in conceptualizing ecological complexity is to allow simultaneously for particularity, contingency, and structure, and for such structure to be internally differentiated,dynamically tied to its context, and subject torestructuring. Because all organisms live insuch dynamic ecological circumstances, philosophy of ecology could become the leading site for addressing difficult conceptual questions concerning the situatedness or positionality of organisms –humans included – in their changing and intersecting worlds.

I explore heterogeneous constructionism, my term for the perspective that science in the making is a process of agents building by combining a diversity of components. Issues addressed include causality and explanation; transcending both realism and relativism; scientists as acting, intervening, and imaginative agents; explanations that span many levels of social practice; counterfactuals in the analysis of causal claims; and practical reflexivity. An analogy from research on the social origins of depression and a sketch from my own experience in socioeconomic (...) modeling are used to motivate and render more concrete the form of heterogeneous constructionism I am advocating. (shrink)

Quantitative genetics (QG) analyses variation in traits of humans, other animals, or plants in ways that take account of the genealogical relatedness of the individuals whose traits are observed. “Classical” QG, where the analysis of variation does not involve data on measurable genetic or environmental entities or factors, is reformulated in this article using models that are free of hypothetical, idealized versions of such factors, while still allowing for defined degrees of relatedness among kinds of individuals or “varieties.” The gene (...) - free formulation encompasses situations encountered in human QG as well as in agricultural QG. This formulation is used to describe three standard assumptions involved in classical QG and provide plausible alternatives. Several concerns about the partitioning of trait variation into components and its interpretation, most of which have a long history of debate, are discussed in light of the gene-free formulation and alternative assumptions. That discussion is at a theoretical level, not dependent on empirical data in any particular situation. Additional lines of work to put the gene-free formulation and alternative assumptions into practice and to assess their empirical consequences are noted, but lie beyond the scope of this article. The three standard QG assumptions examined are: (1) partitioning of trait variation into components requires models of hypothetical, idealized genes with simple Mendelian inheritance and direct contributions to the trait; (2) all other things being equal, similarity in traits for relatives is proportional to the fraction shared by the relatives of all the genes that vary in the population (e.g., fraternal or dizygotic twins share half of the variable genes that identical or monozygotic twins share); (3) in analyses of human data, genotype-environment interaction variance (in the classical QG sense) can be discounted. The concerns about the partitioning of trait variation discussed include: the distinction between traits and underlying measurable factors; the possible heterogeneity in factors underlying the development of a trait; the kinds of data needed to estimate key empirical parameters; and interpretations based on contributions of hypothetical genes; as well as, in human studies, the labeling of residual variance as a non-shared environmental effect; and the importance of estimating interaction variance. (shrink)

The presence of gene–environment statistical interaction and correlation in biological development has led both practitioners and philosophers of science to question the legitimacy of heritability estimates. The paper offers a novel approach to assess the impact of GxE and rGE on the way genetic and environmental causation can be partitioned. A probabilistic framework is developed, based on a quantitative genetic model that incorporates GxE and rGE, offering a rigorous way of interpreting heritability estimates. Specifically, given an estimate of heritability and (...) the variance components associated with estimates of GxE and rGE, I arrive at a probabilistic account of the relative effect of genes and environment. (shrink)

Can a heritability value tell us something about the weight of genetic versus environmental causes that have acted in the development of a particular individual? Two possible questions arise. Q1: what portion of the phenotype of X is due to its genes and what portion to its environment? Q2: what portion of X’s phenotypic deviation from the mean is a result of its genetic deviation and what portion a result of its environmental deviation? An answer to Q1 provides the full (...) information about X’s development, while an answer to Q2 leaves out a large portion unexplained—that portion which corresponds to the phenotypic mean. Q1 is unanswerable, but I show it is nevertheless legitimate under certain quantitative genetics models. With regard to Q2, opinions in the philosophical and biological literature differ as to its legitimacy. I argue that not only is it legitimate, but in particular, under a few simplifying assumptions, it allows for a quantitative probabilistic answer: for normally distributed quantitative traits with no G-E correlation or statistical G × E interaction, we can assess the probability that X’s genes had a greater effect than its environment on its deviation from the mean population value. This probability is expressed as a function the heritability and the individual’s phenotypic value; we can also provide a quantitative probabilistic answer to Q2 for an arbitrary individual where the probability is a function only of heritability. (shrink)

This essay examines the origin of genotype-environment interaction, or G×E. "Origin" and not "the origin" because the thesis is that there were actually two distinct concepts of G×E at this beginning: a biometric concept, or \[G \times E_B\], and a developmental concept, or \[G \times E_D \]. R. A. Fisher, one of the founders of population genetics and the creator of the statistical analysis of variance, introduced the biometric concept as he attempted to resolve one of the main problems in (...) the biometric tradition of biology - partitioning the relative contributions of nature and nurture responsible for variation in a population. Lancelot Hogben, an experimental embryologist and also a statistician, introduced the developmental concept as he attempted to resolve one of the main problems in the developmental tradition of biology - determining the role that developmental relationships between genotype and environment played in the generation of variation. To argue for this thesis, I outline Fisher and Hogben's separate routes to their respective concepts of G × E; then these separate interpretations of G × E are drawn on to explicate a debate between Fisher and Hogben over the importance of G × E, the first installment of a persistent controversy. Finally, Fisher's \[G \times E_B\] and Hogben's \[G \times E_D \] are traced beyond their own work into mid-2Oth century population and developmental genetics, and then into the infamous IQ Controversy of the 1970s. (shrink)

Philosophers of science have developed an account of causal-mechanical explanation that captures regularity, but this account neglects variation. In this article I amend the philosophy of mechanisms to capture variation. The task is to explicate the relationship between regular causal mechanisms responsible for individual development and causes of variation responsible for variation in populations. As it turns out, disputes over this relationship have rested at the heart of the nature–nurture debate. Thus, an explication of the relationship between regular causal mechanisms (...) and causes of variation and between individual development and variation offers both the necessary amendment to the philosophy of mechanisms and the resources to mediate the dispute. (shrink)

In a widely acclaimed study from 2002, researchers found a case of gene-environment interaction for a gene controlling neuroenzymatic activity (low vs. high), exposure to childhood maltreatment, and antisocial personality disorder (ASPD). Cases of gene-environment interaction are generally characterized as evincing a genetic predisposition; for example, individuals with low neuroenzymatic activity are generally characterized as having a genetic predisposition to ASPD. I first argue that the concept of a genetic predisposition fundamentally misconstrues these cases of gene-environment interaction. This misconstrual will (...) be diagnosed, and then a new concept—interactive predisposition—will be introduced. I then show how this conceptual shift reconfigures old questions and raises new questions for genetic screening. Attempts to screen embryos or fetuses for the gene associated with low neuroenzymatic activity with an eye towards selecting against the low-activity variant fall prey to the myth of pre-environmental prediction; attempts to screen newborns for the gene associated with low neuroenzymatic activity with an eye towards early intervention will have to face the interventionist’s dilemma. (shrink)

Scholars employing an evolutionary approach to the study of religion and religious beliefs search for ultimate explanations of the origin, propagation, and persistence of religious beliefs. This quest often pairs in debate two opposing perspectives: the adaptationist and “by-product” explanations of religion and religious beliefs. The majority of scholars prefer the by-product approach, which is agnostic and even doubtful of the usefulness of religious beliefs. Despite this pervasive negativity, it seems unwarranted to deny the great usefulness of religious beliefs—particularly concerning (...) their past utility. Instead, adaptationist explanations of religion and religious beliefs must be re-established as interesting and useful approaches to the study of religious beliefs. (shrink)

Many scientists have argued that they can determine to what extent human happiness levels are controlled by genes by comparing the average happiness levels of identical twins raised apart. If we discover that identical twins raised apart tend to be more hedonically similar than fraternal twins raised apart, this is interpreted as evidence for the thesis that genes have a strong influence on our happiness levels. If identical twins are hedonically dissimilar, as dissimilar as fraternal twins raised apart, this has (...) been taken as evidence for the thesis that happiness levels are determined in large part by the environment. I shall show that that these interpretations of these studies rely on a set of false assumptions. There is no good evidence our genes determine how happy we can be. (shrink)

Several influential psychologists have attempted to estimate to what extent human happiness levels are directly controlled by genes by comparing the happiness levels of identical twins raised apart. If we discover that the happiness levels of identical twins raised apart tend to be closer than the happiness levels of fraternal twins raised apart, this is taken as evidence that average happiness levels are largely controlled by genes. However, if it turns out that identical twins' happiness levels tend to be substantially (...) different, as different as fraternal twins raised apart, it has been argued that this implies that the environment largely determines happiness levels. I contend that this interpretation of the data rests on a set of questionable, closely related assumptions: a) that pairs of identical twins raised apart are raised in substantially different environments; b) that genetically identical twins aren't identical in other pertinent ways; and c) that average levels of affect that are correlated with certain sets of genes in the environments the twin studies were conducted in will be correlated with those genes in other relevant environments because those genes govern average affect levels. In this paper, I will show that these assumptions are false and explain how to properly go about investigating the contingent causal links between genes and happiness. In the end, I argue that there is no good evidence that our genes delimit our hedonic potential and that the fact that this misinterpretation of the data has been widely disseminated is potentially harmful to human well-being. (shrink)

The concept of innateness is used to make inferences between various better-understood properties, like developmental canalization, evolutionary adaptation, heritability, species-typicality, and so on (‘innateness-related properties’). This article uses a recently-developed account of the representational content carried by inheritance systems like the genome to explain why innateness-related properties cluster together, especially in non-human organisms. Although inferences between innateness-related properties are deductively invalid, and lead to false conclusions in many actual cases, where some aspect of a phenotypic trait develops in reliance on (...) a genetic representation it will tend, better than chance, to have many of the innateness-related properties. The account also shows why inferences between innateness-related properties sometimes fail and argues that such inferences are especially misleading when applied to human psychology and behaviour because human psychological development is especially reliant on non-genetic inherited representations. (shrink)

It has been known for decades that inference concerning genetic causes of human behavioral phenotypes cannot be legitimately made from correlations among relatives. We claim that these inferential difficulties cannot be overcome by assigning different names to causes inferred from within-family and population-level genome-wide association studies (GWASs). For educational attainment, for example, unraveling gene–environment interactions requires more than new names for causes.

Developmental Systems Theory (DST) emphasises the importance of non-genetic factors in development and their relevance to evolution. A common, deflationary reaction is that it has long been appreciated that non-genetic factors are causally indispensable. This paper argues that DST can be reformulated to make a more substantive claim: that the special role played by genes is also played by some (but not all) non-genetic resources. That special role is to transmit inherited representations, in the sense of Shea (2007: Biology and (...) Philosophy, 22, 313-331). Formulating DST as the claim that there are non-genetic inherited representations turns it into a striking, empirically-testable hypothesis, driving the sort of investigations that are only now beginning to appear in the scientific literature. DST’s characteristic rejection of a gene vs. environment dichotomy is preserved, but without dissolving all potentially explanatory distinctions into an interactionist causal soup, as some have alleged. (shrink)