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.

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.

Uchiyama et al. present a dual inheritance framework for conceptualizing how behavioural genetics and cultural evolution interact and affect heritability. We posit that to achieve a holistic and nuanced representation of the cultural environment and evolution against which genetic effects should be evaluated, it is imperative to consider the multiple geographic cultural layers impacting individuals and genetic heritability.

Uchiyama et al. question heritability estimates in a convincing manner. We offer additional arguments to further bolster their claims, highlighting methodological issues in heritability coefficients' derivation, their misuse in various contexts, and their potential contributions to exacerbating common erroneous intuitions that have been shown to lead to deleterious social phenomena. We conclude that science should move away from using them.

Although compelling and insightful, the proposal by Uchiyama et al. largely neglects within-person change over time, arguably the central topic of interest within their framework. Longitudinal behavioural genetics modelling suggests that the heritability of trajectories is low, in contrast to high and increasing cross-sectional heritability across development. Better understanding of the mechanisms of trajectories remains a crucial outstanding challenge.

The target article offers an important cautionary note on the interpretation of the heritability index. However, it does not directly address how culture and genes might interact. Here, we suggest that one allele of the dopamine D4 receptor gene promotes the acquisition of cultural values and practices and likely has coevolved with the human culture over the last 50,000 years.

Uchiyama et al. emphasize that culture evolves directionally and differentially as a function of selective pressures in different populations. Extending these principles to the level of families, lineages, and individuals exposes additional challenges to estimating heritability. Cultural traits expressed differentially as a function of the genetics whose influence they mask or unmask render inseparable the influences of culture and genetics.

Interpreting heritability estimates through the lens of cultural evolution presents two broad and interlinking problems for educational behavior genetics. First, the problem of interpreting high heritability of educational phenotypes as indicators of the genetic basis of traits, when these findings also reflect cultural homogeneity. Second, the problem of extrapolating from genetic research findings in education to policy and practice recommendations.

Cognitive scientists and psychometricians are unaccustomed to thinking about culture, often treating their measures – memory, vocabulary, intelligence – as natural kinds. Relying on these measures, behavioral geneticists likewise seem to not wonder about their origin and cultural provenance. I argue that complex human traits – the sort we are most interested in measuring – are cultural products. We can measure them and their heritability, but to conclude that what we have measured is unbound to a time and place is hubris.

We advocate for an integrative long-term perspective on time, noting that culture changes on timescales amenable to behavioral genetic study with appropriate design and modeling extensions. We note the need for replications of behavioral genetic studies to examine model invariance across long-term timescales, which would afford examination of specified as well as unspecified cultural moderators of behavioral genetic effects.

Stochastic developmental variation is an additional important source of variance – beyond genes and environment – that should be included in considering how our innate psychological predispositions may interact with environment and experience, in a culture-dependent manner, to ultimately shape patterns of human behaviour.

In theory, observed correlations between genetic information and behaviour might be useful to members of the WEIRD (western, educated, industrialized, rich, and democratic) populations. Guiding young people to choose educational opportunities that best match their abilities would benefit both the individual and society. In practice, however, such choices are far more profoundly limited by the culture people have inherited than their genes.

Uchiyama et al. provide a compelling analysis of cultural influences on estimates of the genetic contribution to psychological and behavioral traits. Their focus is on the relevance of their arguments for behavioral genetics and their work resonates with other contemporary approaches that emphasize extra-genetic influences on phenotype. I extend their analysis to consider its relevance for evolutionary psychology.

Epigenetics impacts gene–culture coevolution by amplifying phenotypic variation, including clustering, and bridging the difference in timescales between genetic and cultural evolution. The dual inheritance model described by Uchiyama et al. could be modified to provide greater explanatory power by incorporating epigenetic effects.

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.

A framework that brings together cultural perspectives and behavior genetics has long been needed. To be successful, however, we need sophistication in the conceptualization of culture. Here, we highlight three imperatives to this end: the need for a clear definition of cultural traits, inclusion of the role of societal power, and recognizing the distinction between traits and characteristic adaptations.

The target article is skeptical of the heritability concept while maintaining an old-fashioned point of view about it. As a descriptive statistic, it is to be expected that heritability goes up and down in different circumstances, but the relationship between heritability coefficients and the biological processes that underlie them is difficult to specify, and may be impossible in humans.

Hidden cluster problems can manifest when broad ethnic categories are used as proxies for cultural traits, especially when traits are assumed to encode cultural distances between groups. We suggest a granular understanding of cultural trait distributions within and between ethnic categories is fundamental to the interpretation of heritability estimates as well as general behavioral outcomes.

Uchiyama et al. reveal how group-structured cultural variation influences measurements of trait heritability. We argue that understanding culture's influence on phenotypic heritability can clarify the impact of culture on genetic inheritance, which has implications for long-term gene–culture coevolution. Their analysis may provide guidance for testing our hypothesis that cultural adaptation is superseding genetic adaptation in the long term.

The cultural evolutionary approach to the dynamics of cumulative culture is insufficient for understanding how culture affects heritability estimates; it ignores the agency of individuals and internal complexity of social groups that drive cultural evolution. Both environmental and social selection need consideration. The WEIRD (western, educated, industrialized, rich, and democratic) problem has never plagued anthropology: A wealth of ethnography is available for the problem at hand.