Cultural evolution of genetic heritability

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

Cultural evolutionary production of human psychobiological variation and function

This thesis presents a framework for understanding how the organisation of the human mind and its psychobiological basis are produced through the mechanisms of cultural evolution. It foregrounds three characteristics of the human mind: its cross-cultural variation, its responsiveness to environmental inputs, and its collective construction. Each of these characteristics has been studied on its own, but cultural evolution serves as an integrative theoretical framework for understanding how they relate to each other. A key insight is how the developmental environment is shaped extensively by cumulative cultural evolution, allowing culture and nervous system to be meshed in a functionally productive and highly evolvable coupling. Classical conceptions of nature and nurture are insufficient for capturing this dynamic, and instead reinforce conceptual and methodological barriers that obscure the effect of culture. This thesis articulates a theoretical interface that allows a number of insights derived from cultural evolutionary theory to be productively employed within the psychological sciences—fields such as psychology, behavioural biology, behavioural genetics, developmental science, and cognitive neuroscience. Chapter 1 briefly introduces the subsequent chapters, and Chapter 2 charts the overall theoretical framework of the thesis. Chapter 3 attempts a theoretical integration of cultural evolution and behavioural genetics in particular, offering new insights about the interpretation of genetic effects like heritability. Chapter 4 is an empirical test of a prediction given in the prior chapter, and demonstrates how cultural variance influences heritability across countries. Chapter 5 shows cross-cultural variation in the structure of internal representations using factor analysis and a questionnaire, and provides preliminary evidence that writing systems shape mental organisation. Chapter 6 proposes a theoretical integration between cultural evolution and neuroscience. Taken together, these studies give substance to a novel theoretical framework for the psychological sciences that elucidates the rich coordination of mind, biology, the developmental environment, and cultural dynamics

What the Baldwin Effect affects

The Baldwin Effect is a proposed mechanism by which plasticity facilitates adaptive phenotypic and genetic evolution. In particular it has been proposed to be involved in the evolution of language. Here we investigate three factors affecting the extent to which plastic traits are fixed by selection: (i) the difficulty with which traits can be acquired through plasticity, (ii) the importance of traits to fitness, and (iii) the nature of dependencies between different traits. We find that selection preferentially fixes traits that are difficult to acquire through plasticity, traits that have larger fitness benefits, and traits that affect the acquisition of, or benefits from, other traits. We conclude by discussing the implications of these findings for the evolution of language as well as non-human behaviors and reconsider the evolutionary significance of the Baldwin Effec