Developmental systems theory (DST) is a wholeheartedly epigenetic approach to development, inheritance and evolution. The developmental
system of an organism is the entire matrix of resources that are needed to reproduce the life cycle. The range of developmental resources that
are properly described as being inherited, and which are subject to natural selection, is far wider than has traditionally been allowed. Evolution acts on this extended set of developmental resources. From a developmental systems perspective, development does not proceed according to a preformed plan; what is inherited is much more than DNA; and evolution is change not only in gene frequencies, but in entire developmental systems.