In his book, To Have and Have Not: The Determinants of Social Status in England, 1600-2026, Gregory Clark argues that a simple model with genetic transmission and assortative mating is sufficient to explain why socio-economic outcomes tend to run in families. Additionally, he provides a collection of arguments against the idea that environmental effects are important contributors to the similarities in outcomes he documents within extended families. Here, I raise two criticisms of Clark’s explanatory framework, and for each criticism suggest ways to mitigate it without introducing environmental effects. First, I criticize the framework for requiring that mates are highly correlated on unobserved traits that are highly heritable and highly genetically correlated with the outcome to be explained. I here suggest allowing for genotypic population stratification. Second, I criticize the framework for underestimating the importance of zygosity for the similarity of twins. As a fix for this, I suggest incorporating non-additive genetic effects.