Optimizing Evolution with Fitness-Dependent Mutation Rates

Diversification through random mutation, selection, and proliferation is a fundamental driving force of evolution in living systems. The rate at which a population accumulates beneficial mutations is governed by the variation in fitness within the population, which arises from a balance between opposing forces—mutation and selection. Typically, mutation rates are assumed to be constant across the population. However, recent findings suggest that some biological systems, such as B cell affinity maturation, exhibit mutation rates that depend on an individual's fitness relative to the average fitness of the population. Motivated by these observations, we theoretically analyze an evolutionary hill-climbing model with fitness-dependent mutation rates. Our results show that a mutation rate that decreases with increasing relative fitness can significantly accelerate the accumulation of beneficial mutations. Moreover, lowering the mutation rate for fitter individuals can slow down Muller's ratchet by decreasing the fixation of deleterious mutations. These findings suggest potential strategies for enhancing the robustness of populations to environmental changes through faster adaptation, as well as improving the efficiency of evolutionary algorithms and directed evolution.