In developmental psychology, developmental systems theory (DST) is an overarching theoretical perspective on biological development, heredity, and evolution. It emphasizes the equal contributions of genes, environment, and epigenetic factors on developmental processes. DST, unlike conventional scientific theories, is not directly used to help make predictions for testing experimental results; instead, it is seen as a collection of philosophical, psychological, and scientific models of development and evolution. As a whole, these models argue the inadequacy of modern evolutionary views on the roles of genes and natural selection as the principle explanation of living structures. Developmental systems theory embraces a large range of positions that expand biological explanations of human development and hold modern evolutionary theory as a misconception of the nature of living processes.