We consider nurture's (including culture's) sculpting influences on the evolved psychological predispositions that are expressed in religious and spiritual (R&S) development. An integrated understanding of R&S development requires a move away from the largely one-sided (nature-or-nurture) and additive (nature + nurture) accounts provided in the extant literature. R&S development has been understood as an expression of evolved cognitive modules (nature) on the one hand, and of socialization and social learning (nurture) on the other, or in similar albeit additive terms (e.g., nature produces the brain/mind, culture fills in the details). We argue that humans’ evolved psychological predispositions are substantially co-shaped by environmental/cultural input, such as relational experiences and modelling at the microlevel through belief and value systems at the macrolevel. Nurture's sculpting of nature is, then, expressed in R&S development. Finally, for heuristic purposes, we illustrate a fully integrated nature–nurture model with attachment theory and its application to R&S development.