Development: Three Grades of Ontogenetic Involvement 189mental resource can be, whether it be a genetic, epigenetic or ecological factor.
The contribution that replicators make to phenotype is no different in kind than
that of any other developmental resource.
This is the central and important insight of Developmental Systems Theory
(DST) ([Oyama, 1985]; [Oyamaet al., 2001]). DST encompasses a cluster of the-
ses about the relation of inheritance and development. In contrast to replicator
theory, it holds that the fundamental units of inheritance and phenotypic control
are not genes or replicators, but developmental systems. A developmental system
comprises the complete set of resources — genetic, epigenetic, ecological — re-
quired for the development of a trait (or organism). Control of the phenotype is
distributed throughout the organism/environment system.The basic unit of inher-
itance, then, is that set of resources, or affordances, sufficient to secure the reliable
intergenerational recurrence of a phenotype.^8
The First Grade of ontogenetic involvement insists that inheritance and de-
velopment are wholly distinct processes. There is, consequently, a corresponding
distinction between traits that are inherited and those that are merely acquired
during development. The developmental acquisition of traits does not impinge on
the intrinsic structure of the replicators (or their ‘informational’ content).^9 DST
denies the distinction between inherited (innate) and developmentally acquired
traits, because it denies that developmental processes can be excluded from the
mechanisms of inheritance.^10 There is no principled distinction between the pro-
cesses that secure inheritance of traits and those that secure the development
of individuals. The reliable recurrence of traits across generations enlists the
full panoply of developmental resources. The schism drawn by sub-organismal,
replicator biology between the processes of inheritance and development is illicit.
Inheritance is simply the reliable transgenerational recurrence of developmental
processes. Development is the key to understanding it. I call this conception of
the role of development in evolution, ‘Grade II Ontogenetic Involvement’.
Again, the influence of C. H. Waddington is apparent in the second grade of
ontogenetic involvement. Waddington [1942; 1957] was perhaps the first to artic-
ulate the idea that we should see the variants among which selection selects as
processes rather than static traits. For Waddington, a principal message of canal-
ization, the epigenetic control of development, is that developmental processes
— not just organisms — change during adaptive evolution. Canalization lowers
the threshold for the development traits, or entrenches them (or both), render-
ing their development more easily attained, or more robust against genetic and
environmental perturbations (or both). The consequences of adaptive evolution
(^8) Griffiths and Gray stress that DST “... applies the concept of inheritance to any resource
that is reliably present in successive generations, and is part of the explanation of why each
generation resembles the last”. [2001, 196]
(^9) This is the legacy of the Weissman doctrine, nowadays usually expressed as the ‘central
dogma’.
(^10) Some authors, notably Ariew [1996; 1998, this volume] insist that nevertheless a theoretically
useful distinction (albeit one of degree) between innate and acquired traits can be salvaged.
Innate traits are canalized.