GWAS deems parents guilty by association.

Almost 150 y ago, Galton (1) pitted “nature” against “nurture.” In asking whether our biological or environmental inheritance is more important in shaping our traits, Galton implicitly suggested that their effects can be separated. Galton’s division has always been too neat. Our genes and environments intertwine to shape our bodies, capacities, and personalities. The “nature vs. nurture” dichotomy is particularly badly strained in interpreting gene-by-environment interactions, in which the effects of genetic variants depend on the environment in which they are expressed (2). Another challenge is gene–environment covariation, in which, for example, people’s genotypes make them more likely to be exposed to particular environments (3). For example, skin tone—a genetically influenced trait—affects access to health care, socioeconomic exposures, and more (4⇓–6). In PNAS, Wu et al. (7) analyze a fascinating source of gene–environment covariation: Our biological parents, who are the sources of our genes, can also shape our environment. Parental effects on environments—on prenatal environment, diet, socioeconomic circumstances, home environments during childhood, and more—may in turn be influenced by the parents’ genes. The alleles of parents can therefore affect a child’s traits either via the effects they have when inherited in the genome (“direct genetic effects”) or via their effect on the environments that parents create (“indirect parental genetic effects”; Fig. 1). Wu et al. provide new tools for studying such indirect parental genetic effects using summary data from genome-wide association studies (GWASs) (i.e., marker-level summaries that authors of GWASs typically release, even when they do not share raw data) and use them to study genetic effects on birth weight and on educational attainment. Fig. 1. Alleles of biological parents can affect a trait of their child either when inherited and expressed in the child’s genome (“direct genetic effects”; dark blue arrow) or when they are expressed in … [↵][1]1To whom correspondence may be addressed. Email: arbelharpak{at}utexas.edu. [1]: #xref-corresp-1-1