  Why evolvability appears to have increased over evolutionary time is an
important unresolved biological question. Unlike most candidate explanations,
this paper proposes that increasing evolvability can result without any
pressure to adapt. The insight is that if evolvability is heritable, then an
unbiased drifting process across genotypes can still create a distribution of
phenotypes biased towards evolvability, because evolvable organisms diffuse
more quickly through the space of possible phenotypes. Furthermore, because
phenotypic divergence often correlates with founding niches, niche founders may
on average be more evolvable, which through population growth provides a
genotypic bias towards evolvability. Interestingly, the combination of these
two mechanisms can lead to increasing evolvability without any pressure to
out-compete other organisms, as demonstrated through experiments with a series
of simulated models. Thus rather than from pressure to adapt, evolvability may
inevitably result from any drift through genotypic space combined with
evolution's passive tendency to accumulate niches.
