180 D. M. Walsh
developing the space of possibilities, it will help if we understand the rationale
behind the original marginalization of ontogeny. The humble status of development
more or less follows from the precepts of the modern synthesis, at least the version
that was forged in the early 20thCentury, and which solidified in the latter half
[Gould, 1983]. The more we understand about these precepts, on the one hand,
and the mechanisms of development, on the other, the more apparent it should
become that the marginalization of development from the theory of evolution is
no longer tenable, if it ever was.
2 THE FRAGMENTATION OF EVOLUTIONEvolution is a process. Since the advent of the modern synthesis theory of the
early 20th Century it has come to be seen as an amalgam of three more or
less distinct processes: (i)Development: an intra-organismal process by which
genotype becomes phenotype, or by which an undifferentiated organism precur-
sor becomes a highly complex, highly differentiated organism; (ii)Inheritance:
an inter-organismal process that secures the resemblance of offspring to parent;
(ii)Adaptation: a supra-organismal process, in which populations of organisms
come to comprise individuals well suited to their conditions of existence. When
there is variation with respect to the inherited traits of organisms, adaptive evolu-
tion will occur over time. Crucially for the modern synthesis, these processes are
thought to have a significant degree of independence. The process of development
within a generation doesn’t affect the content of those traits transmitted between
generations by the process of inheritance. The mechanisms by which traits are
transmitted between generations, and develop within individuals, are indifferent
to the adaptiveness of those traits. That is to say transmission and development
are not what cause an individual’s adaptedness to the conditions of its existence.
At the same time, the process that promotes adaptation does not alter the con-
tent of the traits that are inherited and developed: a single iteration of selection
doesn’t change traits, it simply selects between them.
This fragmentation of processes is not a prerequisite for the occurrence of evo-
lution; it is a theoretical commitment of the modern synthesis. It is possible to
have a theory of evolution that does not dissociate these three processes so com-
prehensively. For example, in Lamarck’s theory, inheritance, development and
adaptation are all consequences of the same process. According to Lamarck, or-
ganisms develop in response to two distinct sorts of factors, an inner striving
for the realization of their type and external environmental influences. Develop-
ment adapts an organism to environmental pressures and the adaptive novelties
thus generated are inherited. Inheritance, development and adaptation are inti-
mately intertwined, consequences of the principles that guide ontogeny. Similarly,
Haeckel’s later biology, while formally consistent with Darwin’s, is essentially a
theory of the evolution heritable ontogenies. Diversity is explained by the Bio-
genic law; new variants are introduced into development as ‘terminal additions’
(Gould’s [1977] term) and then passed on. The adaptedness of form is, on Haeckel’s