  Understanding how systems can be designed to be evolvable is fundamental to
research in optimization, evolution, and complex systems science. Many
researchers have thus recognized the importance of evolvability, i.e. the
ability to find new variants of higher fitness, in the fields of biological
evolution and evolutionary computation. Recent studies by Ciliberti et al
(Proc. Nat. Acad. Sci., 2007) and Wagner (Proc. R. Soc. B., 2008) propose a
potentially important link between the robustness and the evolvability of a
system. In particular, it has been suggested that robustness may actually lead
to the emergence of evolvability. Here we study two design principles,
redundancy and degeneracy, for achieving robustness and we show that they have
a dramatically different impact on the evolvability of the system. In
particular, purely redundant systems are found to have very little evolvability
while systems with degeneracy, i.e. distributed robustness, can be orders of
magnitude more evolvable. These results offer insights into the general
principles for achieving evolvability and may prove to be an important step
forward in the pursuit of evolvable representations in evolutionary
computation.
