On the origin and evolution of social learning: reducing individual requirements for the emergence of cultural evolutionary systems

Abstract

The apparent adaptive value of culture was once assumed to be an explanation for the evolution of social learning. The original argument was that obtaining information from others, even if it was just by unbiased imitation, would save social learners the costs and risks of finding solutions as individual learners or instinctive actuators. These assumptions have been challenged by existing theoretical work where the evolution of social learning and the consequent emergence of culture are shown to require more than just unbiased imitation. The consensus is that an extra source of selection, apart from natural selection, is required for social learning to evolve. This consensus is based on two basic problems of unbiased imitation in the context of existing models. The first problem is that, when only natural selection is considered, unbiased imitation breaks the relation between phenotypic fitness and the frequency of phenotypic replication. The second problem is that perfect imitation can cause phenotypic stagnation as populations with a large proportion of social learners maintain low phenotypic variance, which in turn prevents the fixation of social learners under any rate of environmental change. Subsequently, researchers in the field have developed models that necessitate individual learners (i.e., individuals with the ability to improve on innate behaviours) and different forms of decision-making processes, like biases towards imitating fitter strategies or the ability to improve on the strategies already acquired, in order to explain the evolution of social learners and the emergence of cultural evolutionary systems.

Here we claim individual learning and decision-making processes are unnecessary for the emergence of cultural evolutionary systems. These systems can be explained because, when allowed to explore an extended strategy space, they are faster problem solvers than genetic evolutionary systems. We base this conclusion on the results of a series of individual based simulations, which show that under strong survival selection and while imitation error rates are higher than genetic mutation, culture can find solutions to environmental problems faster than genetic systems. Our work shows that unbiased horizontal imitation - a particular form of social learning that is generally considered a hindrance in classical models of the origin of culture - can also be adaptive under certain conditions of selection pressures and error rates. Furthermore, we show moderate environmental change increases the chances of culture emerging in a population of pure social learners; a process previously thought to require a mixed strategy of social and individual learning. Compared to existing models our approach makes fewer and more plausible assumptions, as it does not involve additional sources of selection in the form of individual learning or decision making processes. This broadens the range of species for which culture could evolve as it reduces individual-level requirements for its evolution.

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ORCID for Richard Watson: orcid.org/0000-0002-2521-8255

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