Figure 1

Step-wise evolution. Adaptation to a complex environment (A) can be accelerated (B) or decelerated (C) if guided through intermediate steps of a lesser complexity. Fitness profile for a population evolving in a target complex environment (solid black curve) is a multidimensional surface with multiple local maxima. Adaptation to intermediate environments (dashed grey fitness profiles) can direct evolution towards to (or away from) the global fitness maximum of the target environment.