Ratcheting up the ratchet: on the evolution of cumulative culture

Abstract

Some researchers have claimed that chimpanzee and human culture rest on homologous cognitive and learning mechanisms. While clearly there are some homologous mechanisms, we argue here that there are some different mechanisms at work as well. Chimpanzee cultural traditions represent behavioural biases of different populations, all within the species' existing cognitive repertoire (what we call the 'zone of latent solutions') that are generated by founder effects, individual learning and mostly product-oriented (rather than process-oriented) copying. Human culture, in contrast, has the distinctive characteristic that it accumulates modifications over time (what we call the 'ratchet effect'). This difference results from the facts that (i) human social learning is more oriented towards process than product and (ii) unique forms of human cooperation lead to active teaching, social motivations for conformity and normative sanctions against non-conformity. Together, these unique processes of social learning and cooperation lead to humans' unique form of cumulative cultural evolution.

Limitations to the cultural ratchet effect in young children

“…What currently remains to be shown in children is an "additive" ratchet effect, where techniques are added or changed that lead, eventually, to efficient behavior outside the reach of the individual (e.g., Tennie, et al, 2009). It is possible that young children do not show the additive type of ratchet effect at all.…”

“…Demonstrations using such a very "unlikely" tool might therefore have engendered additional pedagogical inferences in the Ratchet effect in children 14 children, which could have increased the copying fidelity for this type of tool (Csibra & Gergely, 2006). Along with future empirical work in this area, theoretically, more work needs to be done to distinguish different levels or types of cultural evolution, perhaps especially in children and in other animals who likely do not have fully developed skills of cumulative culture (for a start see Dean et al, 2013, andTennie et al, 2009, who distinguish, for example, accumulations or 'step-wise traditions' from cumulative culture). Distinguishing between additive and subtractive ratchet effects, as we have done here, is one step in this direction.…”

The ontogeny of cultural learning

“…Generally, a consistent finding in comparative studies is that human children are much more concerned than are other great apes to copy the exact actions of others, including arbitrary gestures, conventions, and rituals (see [4], for a review). Indeed, this tendency is so strong that some researchers have even coined the term 'ritual stance' to capture the fact that when children do not see a clear goal to an actor's action, they imitate even more precisely than if they do see a goal -presumably because the lack of a goal signals a noninstrumental function for the action, which therefore (given that it is being demonstrated) may be of cultural importance (e.g., [5,6]).…”

Even simple forms of social learning rely on intention attribution in marmoset monkeys (Callithrix jacchus).

“…Some nonhuman animals show simple cultural systems in which individual innovations spread through the population via social learning (Whiten & van Schaik, 2007). Nevertheless, human cultures remain unique with regard to the accumulation of cultural elements whose cognitive complexity far exceeds an individual's inventive potential (cumulative cultural evolution, Tennie, Call, & Tomasello, 2009). The most prominent attempts to explain this idiosyncrasy attribute a key role to distinct social learning processes (reviewed in Caldwell & Millen, 2009;Hill, 2010).…”