If cusp enlargement results in a new, functionally significant contact with occluding teeth. However, origin of a new cusp in the first place, to use Carabelli expression as a model, can occur as a byproduct of natural variation in the spacing of enamel knots and offset of morphogenesis, which impacts intercusp spacing and tooth size. It is rarely possible to study population-level variation in the early evolutionary stages of the origin of a new cusp in extinct species. Instead, we rely on analyses, such as this one, of variation in small dental features in living species to provide insight in to the origin and evolution of new dental features in the past. In addition, Wnt/b-catenin signaling may exert distinct functions in a dose dependent manner. It is conceivable that the two functions of Wnt/b-catenin signaling are also dose-dependent: Anti-mutator mutants, with lower than normal mutation rates, have been observed in bacteria, in the phage T4, and in RNA viruses evolving in the presence of mutagens. In the latter case, the anti-mutator phenotype can be Doxorubicin produced by single changes in the viral polymerase, without requiring the expression of corrector activities. These observations suggest that RNA viruses could easily evolve to lower mutation rates. If they do not, it could be due to the major adaptive advantages provided by high mutation rates. The finding that high-fidelity genotypes of an RNA virus have lost some of their adaptive properties in mice constitutes a strong support of this hypothesis. Other studies, however, point to the existence of a trade-off between rapid replication and fidelity to explain the high mutation rates of RNA viruses. Asexual populations of replicators, such as RNA molecules evolving in silico, with selection acting on their folded conformation, constitute a simple system to study how the variation of the mutation rates influences adaptation. After a sufficiently long time, these virtual populations reach a stationary state characterized by mutation-selection equilibrium and a quasispecies structure. Populations of RNA molecules have been very successfully used as a computational model for the study of evolutionary processes. The influence of the mutation rate on the degree of adaptation attained at the stationary state, and on the genotypic and phenotypic diversity of the population are questions that have been addressed previously with this model. In this work we focus on the adaptability of populations of RNA molecules that reached the stationary state at different error rates, and that are affected by a sudden environmental change. To this end, we determine those mutation rates promoting maximal adaptation after a short number of generations. In practice, our population evolves under selection for folding into a given secondary structure until mutation-selection equilibrium is reached.