This project examines the relationship between behavioural genetics and cultural evolutionary theory (CET). In particular, it focuses on the recent attempts to integrate the two fields, such as the “cultural evolution of heritability” integrative proposal by Uchiyama et al. (2022). This proposal argues that perspectives on sociocultural change – especially the diffusion of cultural practices – from CET can be fruitfully applied to explain fluctuating heritability estimates of behavioural and psychological phenotypes. I aim to provide a critical examination of this proposal, pointing out its limitations, such as 1) the tension between its mechanistic aims and the use of mechanistically opaque heritability coefficients; 2) its reliance on cases that contrast with the high polygenicity and causal complexity of behavioural traits; and 3) the secondary explanatory import of cultural diffusion compared to the role of specific cultural practices themselves and their ability to interact with genetic effects on behavioural characteristics. I argue that, while an integration along the lines of “cultural evolution of heritability” may be theoretically attractive, an empirical research programme informed by the proposal is unlikely to be very fruitful, at least in the short term. Nevertheless, it raises more fundamental questions about the possibility of integration between behavioural genetics and the social sciences, the limitations of behavioural genetic methodology, and the aims of explanation itself.