When cumulative culture functionally overlaps with genes, genetic effects become masked, unmasked, or even reversed, & the causal effects of an identified gene become confounded with features of the cultural environment

Cultural Evolution of Genetic Heritability. Ryutaro Uchiyama, Rachel Spicer and Michael Muthukrishna. Behavioral and Brain Sciences, May 21 2021. https://doi.org/10.1017/S0140525X21000893. Pre-print heritability-165_final(1) (muthukrishna.com)

Abstract: 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 sub-groups, 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, 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.

Comments on this paper... Mitchell, Kevin J. 2021. “Developmental Noise Is an Overlooked Contributor to Innate Variation in Psychological Traits.” PsyArXiv. September 21. Developmental Noise Is an Overlooked Contributor to Innate Variation in Psychological Traits

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From the 2020 version:

The question, “Which SNPs  are associated with skin cancer?” is similarly culturally dependent. In societies where sunscreen use is common, we expect genes that govern skin pigmentation to be less predictive of skin cancer compared to societies where it is not.

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A gene can be beneficial in one environment but not in another. For example, we have known for a long time that increasing nutrition (Lynn 1990; Stoch et al. 1982), improving schooling (Ceci 1991; Davis 2014; Ritchie and Tucker-Drob 2018), and removing parasites (Wieringa et al. 2011) have positive effects on general intelligence. None of this is surprising, but it means that in a society where parasite infection is kept under control, we would not notice that parasite status correlates with intelligence, due to a lack of sufficient variation in parasite load. For the same reason, a correlation between lead exposure and IQ (Needleman and Gatsonis 1990; Wasserman et al. 1997) will not be revealed in a society where lead is not a problem. The same principle applies to genes: genes that provide protection against malnutrition, parasites, or pollution would only be positively associated with intelligence in environments where these insults occur. In environments where these challenges have been overcome, the same genes would not be associated with intelligence, and can even be deleterious. For example, being a carrier (heterozygous) for abnormal hemoglobin via sickle cell trait (Elguero et al. 2015) or thalassemia (Mockenhaupt et al. 2004) protects against malaria and is thus beneficial in an environment with the Plasmodium falciparum parasite. Because malaria is known to have a negative impact on cognitive development (Holding and Snow 2001), we would expect the gene for abnormal hemoglobin to be positively associated with intelligence in environments with a high risk of malaria. As the risk of malaria decreases heterozygosity will be neutral or deleterious, but this too depends on environmental factors such as diet. Similarly, alleles that protect against parasite infection (Carter 2013) or lead poisoning (Onalaja and Claudio 2000) will be predictive of IQ only if the environmental risk factors are present in sufficient quantities. In an environment with arsenic contamination, variants in AS3MT associated with more efficient arsenic metabolism (Schlebusch et al. 2015) may be predictive of intelligence (Wang et al. 2007).