Trait specialization, innovation, and the evolution of culture in fluctuating environments

Individuals often respond phenotypically to environmental challenges by innovating and adopting novel behavioral variants. Behavioral (or ‘cultural’) variants are defined here as alternative ways to solve adaptive problems, such as finding food or building shelter. In unpredictable environments, individuals must both be able to adapt to current conditions but also to cope with potential changes in these conditions, they must “hedge their evolutionary bets” against the variability of the environment. Here, we loosely apply this idea to the context of behavioral adaptation and develop an evolutionary model, where cultural variants differ in their level of generality, i.e. the range of environmental conditions in which they provide fitness benefits: generalist variants are characterized by large ranges, specialist variants by small ranges. We use a Moran model (with additional learning opportunities) and assume that each individual’s propensity for innovation is genetically determined, while the characteristics of cultural variants can be modified through processes of individual and social learning. Our model demonstrates that flexibly adjusting the level of generality allows individuals to navigate the trade-off between fast and reliable initial adaptation and the potential for long-term improvements. In situations with many (social or individual) learning opportunities, no adjustment of the innovation rate, i.e. the propensity to learn individually, is required to adapt to changed environmental conditions: fast adaptation is guaranteed by solely adjusting the level of generality of the cultural variants. Few learning opportunities, however, require both processes, innovation and trait generality, to work hand in hand. To explore the effects of different modes of innovation, we contrast independent invention and modification and show that relying largely on modifications improves both short-term and long-term adaptation. Further, inaccuracies in social learning provide another source of variant variation that facilitates adaptation after an environmental change. However, unfaithful learning is detrimental to long-term levels of adaptation. Our results demonstrate that the characteristics of cultural variants themselves can play a major role in the adaptation process and influence the evolution of learning strategies.