Can heritability estimates provide causal information? This paper argues for an affirmative answer: since a non-nil heritability estimate satisfies certain characteristic properties of causation (i.e., association, manipulability, and counterfactual dependence), it increases the probability that the relation between genotypic variance and phenotypic variance is (at least partly) causal. Contrary to earlier proposals in the literature, the argument does not assume the correctness of any particular conception of the nature of causation, rather focusing on properties that are characteristic of causal relationships. (...) The argument is defended against Lewontin's (1974) locality objection and Kaplan and Turkheimer's (2021) recent critique of Genome-Wide Association Studies (GWAS). (shrink)

Heritability is routinely interpreted causally. Yet, what such an interpretation amounts to is often unclear. Here, I provide a causal interpretation of this concept in terms of range of causal influence, one of several causal dimensions proposed within the interventionist account of causation. An information-theoretic measure of range of causal influence has recently been put forward in the literature. Starting from this formalization and relying upon Woodward’s analysis, I show that an important problem associated with interpreting heritability causally, namely the (...) locality problem, amounts, at least partly, to a low invariance and low stability between the genotype/environment and the phenotype of individuals. In light of this, I plead for a causal interpretation of heritability that takes the notions of Woodward’s invariance and stability into consideration. In doing so, I defuse naive causal interpretations of heritability. (shrink)

Lucas Matthews and I substantially revised my SEP entry on Heritability. This version includes discussion of the missing heritability problem and other issues that arise from the use of Genome Wide Association Studies by Behavioral Geneticists.

According to The Bell Curve, Black Americans are genetically inferior to Whites. That's not the only point in Richard Herrnstein and Charles Murray's book. They also argue that there is something called "general intelligence" which is measured by IQ tests, socially important, and 60 percent "heritable" within whites. (I'll explain heritability below.) But the claim about genetic inferiority is my target here. It has been subject to wide-ranging criticism since the book was first published last year. Those criticisms, however, (...) have missed its deepest flaws. Indeed, the Herrnstein/Murray argument depends on conceptual confusions that have been tacitly accepted to some degree by many of the book's sharpest critics. (shrink)

A high heritability estimate usually corresponds to a situation in which trait variation is largely caused by genetic variation. However, in some cases of gene-environment covariance, causal intuitions about the sources of trait difference can vary, leading experts to disagree as to how the heritability estimate should be interpreted. We argue that the source of contention for these cases is an inconsistency in the interpretation of the concepts ‘genotype’, ‘phenotype’, and ‘environment’. We propose an interpretation of these terms under which (...) trait variance initially caused by genetic variance is subsumed into a heritability for all cases of gene-environment covariance. (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)

Diseases of complex origin have a component of quantitative genetics that contributes to their susceptibility and phenotypic variability. However, after several studies, a major part of the genetic component of complex phenotypes has still not been found, a situation known as “missing heritability.” Although there have been many hypotheses put forward to explain the reasons for the missing heritability, its definitive causes remain unknown. Complex diseases are caused by multiple intermediate phenotypes involved in their pathogenesis and, very often, each one (...) of these intermediate phenotypes also has a component of quantitative inheritance. Here we propose that at least part of the missing heritability can be explained by the genetic component of intermediate phenotypes that is not detectable at the level of the main complex trait. At the same time, the identification of the genetic component of intermediate phenotypes provides an opportunity to identify part of the missing heritability of complex diseases. (shrink)

The Guidelines for Stem Cell Research and Clinical Translation, recently issued by the International Society for Stem Cell Research (ISSCR), include a number of substantive revisions. Significant changes include: (1) the bifurcation of ‘Category 3 Prohibited research activities’ in the 2016 Guidelines into ‘Category 3A Research activities currently not permitted’ and ‘Category 3B Prohibited research activities’ in the 2021 guidelines and (2) the move of heritable human genome editing research out of the ‘prohibited’ category and into the ‘currently not (...) permitted’ category. These changes are noteworthy because of the absence of a clear demarcation line between the two categories insofar as, by definition, that which is ‘prohibited’ is ‘currently not permitted’, and vice versa. Permanence is not part of the definition of ‘prohibition’. In principle, a prohibition can be rescinded at any time. This begs the question ‘Why make a policy change that has no apparent practical effect?’ One hypothesis is that the recategorisation of specific ‘prohibited’ research activities as ‘currently not permitted’ is meant to seed intuitions about which prohibited research activities should ‘soon’ be permitted subject to specialised scientific and ethics review and approval. (shrink)

The method in human genetics of ascribing causal responsibility to genotype by the use of heritability estimates has been heavily criticized over the years. It has been argued that these estimates are rarely valid and do not serve the purpose of tracing genetic causes. Recent contributions strike back at this criticism. I present and discuss two opposing views on these matters represented by Richard Lewontin and Neven Sesardic, and I suggest that some of the disagreement is based on differing concepts (...) of genetic causation. I use the distinction of structuring and triggering causes to help clarifying the basis for the opposing views. (shrink)

Following the Second Summit on Human Gene Editing in Hong Kong in 2018, where the birth of two girls with germline genome editing was revealed, the need for a responsible pathway to the clinical application of human germline genome editing has been repeatedly emphasised. This paper aims to contribute to the ongoing discussion on research ethics issues in germline genome editing by exploring key issues related to the initial applications of CRISPR in reproductive medicine. Following an overview of the current (...) discussion on bringing germline genome editing into clinical practice, we outline the specific challenges associated with such interventions and the features that distinguish them from conventional clinical testing of new medical treatments. We then review proposed ethical requirements for initial heritable genome editing, such as the absence of reasonable alternatives, the existence of sufficient and reliable preclinical data, appropriate informed consent, requirements related to safety, and long-term follow-up. (shrink)

Gene–environment covariance is the phenomenon whereby genetic differences bias variation in developmental environment, and is particularly problematic for assigning genetic and environmental causation in a heritability analysis. The interpretation of these cases has differed amongst biologists and philosophers, leading some to reject the utility of heritability estimates altogether. This paper examines the factors that influence causal reasoning when G–E covariance is present, leading to interpretive disagreement between scholars. It argues that the causal intuitions elicited are influenced by concepts of agency (...) and blame-worthiness, and are intimately tied with the conceptual understanding of the phenotype under investigation. By considering a phenotype-specific approach, I provide an account as to why causal ascriptions can differ depending on the interpreter. Phenotypes like intelligence, which have been the primary focus of this debate, are more likely to spark disagreement for the interpretation of G–E covariance cases because the concept and ideas about its ‘normal development’ relatively ill-defined and are a subject of debate. I contend that philosophical disagreement about causal attributions in G–E covariance cases are in essence disagreements regarding how a phenotype should be defined and understood. This moves the debate from one of an ontological flavour concerning objective causal claims, to one concerning the conceptual, normative and semantic dependencies. (shrink)

A central problem for the international governance of heritable germline gene editing is that there are important differences in attitudes and values as well as ethical and health care considerations around the world. These differences are reflected in a complicated and diverse regulatory landscape. Several publications have discussed whether reproductive uses would be legally permissible in individual countries and whether clinical applications could emerge in the context of regulatory gaps and gray areas. Systematic comparative studies that explore issues related (...) to the governance of this technology from different national and international perspectives are needed to address the lack of knowledge in this area. In this research report, we contribute to filling this gap by presenting views of stakeholders in the United Kingdom on challenges to the governance of heritable genome editing. We present findings from a multistakeholder study conducted in the United Kingdom between October 2016 and January 2018 and funded by the Wellcome Trust. This research included interviews, literature analysis, and a workshop. We involved leading U.K. scientists, in vitro fertilization clinicians, and representatives from regulatory bodies, patient organizations, and other civil societal organizations, as well as fertility companies. Part one of this article explores stakeholder perceptions of possible global developments in heritable genome editing and associated risks and governance challenges. Part two presents a range of policy options that were generated during the workshop in relation to the challenges discussed in part one. (shrink)

Heritability is not a measure of the relative contribution of nature vis-à-vis nurture, nor is it the phenotypic variance explained by or because of genetic variance. Heritability is a correlative value. The evolutionary and developmental processes associated with human culture challenge the use of “heritability” for understanding human behavior.

The critics of "hereditarianism" often claim that any attempt to explain human behavior by invoking genes is confronted with insurmountable methodological difficulties. They reject the idea that heritability estimates could lead to genetic explanations by pointing out that these estimates are strictly valid only for a given population and that they are exposed to the irremovable confounding effects of genotype-environment interaction and genotype-environment correlation. I argue that these difficulties are greatly exaggerated, and that we would be wrong to regard them (...) as presenting a fundamental obstacle to the search for genetic explanations. I also show that, to the extent they are cogent, these objections may prove to be even more damaging to the "environmentalist" standpoint. (shrink)

Immunology and its philosophy are a primary source for thinking about biological individuality. Through its discriminatory function, the immune system is believed to delineate organism and environment within one generation, thus defining the physiological individual. Based on the paradigmatic instantiations of immune systems, immune interactions and, thus, the physiological individual are believed to last only for one generation. However, in recent years, transgenerationally persisting immune responses have been reported in several phyla, but the consequences for physiological individuality have not yet (...) been explored. In this article, I will introduce an invertebrate immune system that is RNA-based and operates through a heritable silencing/licensing paradigm. I will discuss how such a perspective on immune systems can illuminate our conceptions of individuality. I will particularly introduce an account of immunological individuality that is not restricted to one generation. (shrink)

Genetic differences can lead to phenotypic differences either directly or indirectly (via causing differences in external environments, which then affect phenotype). This possibility of genetic effects being mediated by environmental influences is often used by scientists and philosophers to argue that heritability is not a very helpful causal or explanatory notion. In this paper it is shown that these criticisms are based on serious misconceptions about methods of behavior genetics.

Many psychometricians and behavioral geneticists believe that high heritability of IQ test scores within racial groups coupled with environmental hypotheses failing to account for the differences between the mean scores for groups lends plausibility to explanations of mean differences in terms of genetic factors. I show that heritability estimates and the statistical analysis of variance on which they are based have limited relevance in exposing genetic and environmental factors operating within any single group or population. I begin with agricultural investigations, (...) where replication of genetic types and control over environmental factors are possible, and highlight the difficulties of moving from AOV of observed traits to investigation of measurable genetic factors. The difficulties can only be exacerbated for human data sets, which are equivalent to a crop trial in which each variety is replicated in only one or two of the locations. (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)

Keller & Miller (K&M) briefly mention and promptly dismiss the idea that genes for harmful mental disorders may confer certain advantages to affected individuals. However, the authors fail to consider that the same genes (in low doses or reduced penetrance) may be adaptive for relatives, and that this may in part explain why they are retained in the gene pool. (Published Online November 9 2006).

Many psychometricians and behavioral geneticists believe that high heritability of IQ test scores within racial groups coupled with environmental hypotheses failing to account for the differences between the mean scores for groups lends plausibility to explanations of mean differences in terms of genetic factors. This two-component argument cannot be sustained when viewed in the light of the conceptual and methodological themes introduced in Taylor . These themes concern the difficulties of moving from the statistical analysis of variance of observed traits (...) to investigation of measurable genetic factors and measurable environmental factors. One such theme is that quantities estimated by an AOV of observed traits cannot be equated with measurable genetic or environmental factors involved in the development of those traits. Once this distinction is clear, the argument that environmental factors have failed to explain the differences lacks weight because it does not consider whether genetic factors have been more successful. This article exposes additional flaws in the lines of thinking associated with the two-component argument, with the distinction between passive, reactive, and active associations between genetic and environmental factors, and with the reciprocal causation models Dickens and Flynn propose in order to reconcile high estimates of heritability and large IQ test score gains between generations. Human heritability estimates are irrelevant in developing explanations of differences across groups or across generations. My critique is directed at opening up more conceptual space for deriving empirically validated models of developmental pathways whose components are heterogeneous and differ among individuals at any one time and over generations. (shrink)

In a previous study, using experimental metapopulations of the flour beetle, Tribolium castaneum, we investigated phase III of Wright's shifting balance process (Wade and Griesemer 1998). We experimentally modeled migration of varying amounts from demes of high mean fitness into demes of lower mean fitness (as in Wright's characterization of phase III) as well as the reciprocal (the opposite of phase III). We estimated the meta-populational heritability for this level of selection by regression of offspring deme means on the weighted (...) parental deme means.Here we develop a Punnett Square representation of the inheritance of the group mean to place our empirical findings in a conceptual context similar to Mendelian inheritance of individual traits. The comparison of Punnett Squares for individual and group inheritance shows how the latter concept can be rigorously defined and extended despite the lack of explicitly formulated, simple Mendelian laws of inheritance at the group level. Whereas Wright's phase III combines both interdemic selection and meta-populational inheritance, our formulation separates the issue of meta-populational heritability from that of interdemic selection. We use this conceptual context to discuss the controversies over the levels of selection and the units of inheritance. (shrink)

The retrotransposon Long Interspersed Element 1 (LINE‐1 or L1) has played a major role in shaping the sequence composition of the mammalian genome. In our recent publication, “Heritable L1 retrotransposition in the mouse primordial germline and early embryo,” we systematically assessed the rate and developmental timing of de novo, heritable endogenous L1 insertions in mice. Such heritable retrotransposition events allow L1 to exert an ongoing influence upon genome evolution. Here, we place our findings in the context of (...) earlier studies, and highlight how our results corroborate, and depart from, previous research based on human patient samples and transgenic mouse models harboring engineered L1 reporter genes. In parallel, we outline outstanding questions regarding the stage‐specificity, regulation, and functional impact of embryonic and germline L1 retrotransposition, and propose avenues for future research in this field. -/- . (shrink)

The paper addresses the question of whether heritability can be useful in establishing genetics as an explanation for an individual’s display of some trait or behavior. After reviewing the fundamental philosophical challenge to heritability—that heritability is a population level measure—an argument is presented for rethinking the role heritability occupies in both causal and explanatory claims. It is argued that heritability can be useful for genetically based explanations of individual traits, if the conditions for proper genetic explanation are modestly reconceived, and (...) the measure is seen as an evidential tool which conforms to standard methods for determining causal factors. (shrink)

When Genotype × Environment (G × E) interactions are present, heritability estimates are not interpretable. Mealey cites abundant evidence for G × E interactions in the etiology of sociopathy, thereby completely undermining estimates of the heritability of sociopathy which form the foundation of her model. Without proper evidence for a genetic basis of sociopathy, Mealey's sociobiological model collapses under its own great weight.

It is impossible to discuss the constructs and in a single coherent essay. The following three rejoinders address each of these exceedingly complex constructs individually, as each relates to the two-path model of sociopathy and psychopathy.

Charney describes several mechanisms that will bias estimates of heritability in unpredictable directions. In addition, the mechanisms described by Charney explain the puzzling fact that research in human-behavior genetics routinely reports higher heritabilities than animal studies do. However, I argue that the concept of heritability has no real place in human research anyway.

Uchiyama et al. rightly consider how cultural variation may influence estimates of heritability by contributing to environmental sources of variation. We disagree, however, with the idea that generalisable estimates of heritability are ever a plausible aim. Heritability estimates are always context-specific, and to suggest otherwise is to misunderstand what heritability can and cannot tell us.

Heritability estimates obtained from genome-wide association studies are much lower than those of traditional quantitative methods. This phenomenon has been called the “missing heritability problem.” By analyzing and comparing GWAS and traditional quantitative methods, we first show that the estimates obtained from the latter involve some terms other than additive genetic variance, while the estimates from the former do not. Second, GWAS, when used to estimate heritability, do not take into account additive epigenetic factors transmitted across generations, while traditional quantitative (...) methods do. Given these two points we show that the missing heritability problem can largely be dissolved. (shrink)

Our view of heredity can potentially be distorted by the ease of introducing heritable changes in the replicating gene sequences but not in the cycling assembly of regulators around gene sequences. Here, key experiments that have informed the understanding of heredity are reinterpreted to highlight this distortion and the possible variety of heritable changes are considered. Unlike heritable genetic changes, which are always associated with mutations in gene sequence, heritable epigenetic changes can be associated with physical (...) or chemical changes in molecules or only changes in the system. The transmission of cycling stores along the continuous lineage of cells that connects successive generations creates waves of activity and localization of the molecules that together form the cell code for development in each generation. As a result, heritable epigenetic changes can include any that can alter a wave such as changes in form, midline, frequency, amplitude, or phase. Testing this integrated view of all heritable information will require the concerted application of multiple experimental approaches across generations. (shrink)

One of the current problems in microbiology concerns the understanding of fitness in host-symbiont systems. A great deal of research and conceptual work has analysed how the host benefits from such associations; however, very little of this work has attempted to take the microbial perspective. Nevertheless, some scientists have argued that we should conduct more comparative studies of both microorganisms that interact with a host and their free-living counterparts in order to determine whether or not symbiosis is beneficial for these (...) microorganisms. In this paper, by means of analysing heritable symbiosis as a case study, I intend to provide a different perspective on this subject. Mainly, I argue that asking how the fitness of a given microorganism was changed during the evolution of heritable symbiosis may be theoretically unjustified at both the early and late stages of this process. The reason for this, I argue, is that, during the evolution of heritable symbiosis, the fitness of a microorganism becomes incommensurable with that of its free-living counterparts because their contexts become radically different; therefore, comparing their fitness makes little sense. My analysis is driven by the use of the ecological concept of fitness; accordingly, my conclusions are bound to this specific interpretation of fitness. (shrink)

In this book, Neven Sesardic defends the view that it is both possible and useful to measure the separate contributions of heredity and environment to the explanation of human psychological differences. He critically examines the view - very widely accepted by scientists, social scientists and philosophers of science - that heritability estimates have no causal implications and are devoid of any interest. In a series of clearly written chapters he introduces the reader to the problems and subjects the arguments to (...) close philosophical scrutiny. His conclusion is that anti-heritability arguments are based on conceptual confusions and misunderstandings of behavioural genetics. His book is a fresh and compelling intervention in a very contentious debate. (shrink)

We argue that heritability estimates cannot be used to make informed judgments about the populations from which they are drawn. Furthermore, predicting changes in heritability from population changes is likely impossible, and of limited value. We add that the attempt to separate human environments into cultural and non-cultural components does not advance our understanding of the environmental multiplier effect.

There are two ways evolution by natural selection is conceptualized in the literature. One provides a ‘recipe’ for ENS incorporating three ingredients: variation, differences in fitness, and heritability. The other provides formal equations of evolutionary change and partitions out selection from other causes of evolutionary changes such as transmission biases or drift. When comparing the two approaches there seems to be a tension around the concept of heritability. A recent claim has been made that the recipe approach is flawed and (...) should be abandoned. In this article, I show that the tension is only a superficial one. If one uses a concept of heritability strictly in line with the formal equations of evolutionary change, the recipe approach keeps its validity and generality. To demonstrate that the intuitive concept of heritability is not a general one, I use one formulation of the Price equation formulated by Okasha, show that the concept of heritability in his formulation incorporates both the intuitive notion of heritability as a measure of similarity between parent and offspring characters, and a measure of persistence. I advocate for persistence to be incorporated in the concept of heritability used in recipes for ENS in the same way heredity is, show that this is readily attainable and thereby dissolve any point of tension concerning heritability between the recipe and the analytical approach to ENS. 1 Introduction2 Heritability in the Price Equation2.1 Different approaches to heredity and heritability2.2 Heritability: From recipes to the Price equation3 A Problem for the Recipes?4 Reinterpreting Heritability for Recipes5 Conclusion Appendix. (shrink)