This article investigates the evolutionary dynamics of morphogenesis. In th
is study, morphogenesis arises as a side-effect of maximization of number o
f cell types. Thus, it investigates the evolutionary dynamics of side-effec
ts. Morphogenesis is governed by the interplay between differential cell ad
hesion, gene-regulation, and intercellular signaling. Thus, it investigates
the potential to generate complex behavior by entanglement of relatively "
boring" processes, and the (automatic) coordination between these processes
.
The evolutionary dynamics shows all the hallmarks of evolutionary dynamics
governed by nonlinear genotype phenotype mapping: for example, punctuated e
quilibria and diffusion on neutral paths. More striking is the result that
interesting, complex morphogenesis occurs mainly in the "shadow" of neutral
paths which preserve cell differentiation, that is, the interesting morpho
logies arise as mutants of the fittest individuals.
Characteristics of the evolution of such side-effects in the shadow appear
to be the following: (1) The specific complex morphologies are unique (or a
t least very rare) among the set of de novo initiated evolutionary historie
s. (2) Similar morphologies are reinvented at large temporal distances duri
ng one evolutionary history and also when evolution is restarted after the
main cell differentiation pattern has been established. (3) A mosaic-like e
volution at the morphological level, where different morphological features
occur in many combinations, while at the genotypic level recombination is
nor implemented and genotypes diverge linearly and at a constant rate.