From information free-riding to information sharing: how have humans solved the cooperative dilemma at the heart of cumulative cultural evolution?

Cumulative cultural evolution, where populations accumulate ever-improving knowledge, technologies and social customs, is arguably a unique feature of human sociality and responsible for our species’ ecological dominance of the planet. However, at the heart of cumulative cultural evolution is a cooperative dilemma. Assuming asocial learning is more costly than social learning, social learners can act as ‘information free-riders’ by copying innovations from asocial learners without paying the cost. This cost asymmetry will reduce innovation, inhibiting cumulative culture. Innovators might respond by protecting their knowledge and keeping the benefits to themselves – ‘information hoarding’ - but then others cannot build on their discoveries and again cumulative culture is inhibited. Here we formally model information free-riding and information hoarding within a cumulative cultural evolution framework using both analytical and agent-based models. Model 1 identifies the restrictive conditions under which information sharing can evolve in the face of information free-riding and hoarding. Models 2-4 then show how three mechanisms known to favour cooperation in non-informational contexts - kin selection, reputation-based partner choice and cultural group selection – can also solve the informational cooperative dilemma and facilitate cumulative cultural evolution, each with distinct signatures potentially detectable in historical, ethnographic and other empirical data.