After nourishment, shelter and companionship,

stories are the thing we need most in the world.

– Philip Pullman (author) 1

The storytelling animal

Evolution is ruthlessly efficient. Any trait which does not confer a fitness advantage will be lost: cave fish living in perpetual darkness lose the use of their eyes, while many birds moving to islands without predators lose the ability to fly. Any energetically-costly display which seems to flout this general rule therefore cries out for an adaptive evolutionary explanation.

Storytelling is one such behaviour. Storytelling is a human universal, practiced by all societies. From foragers gathering around the camp-fire sharing tales of ancestors, to watching the latest big-screen Hollywood blockbuster, humans just can’t seem to get enough of stories.

But why do humans spend hours listening to and telling stories, often of exploits that never happened? This is time and effort that could be better spent engaging in fitness-enhancing activities such as foraging, reproducing, or simply doing nothing and conserving energy.

Sometimes, narratives seem to possess no obvious adaptive purpose. The following story from the Maniq, a hunter-gatherer population from Thailand, is about the origins of night and day, and exemplifies this apparent lack of evolutionary function:

“Hung, the Mani Goddess’s favorite animal, shows strange behaviour: every day it must slowly swallow its tail and then gradually spit it out again before once more swallowing it – forever. As Hung swallows its tail, the whole of the sky and earth darkens, but as it slowly spits it out again, daylight starts. When it has spit out the whole tail, it is dawn. Starting at noon, it gradually swallows its tail, bringing on darkness. This is how day and night come to be.” 2

While this story may perform a cosmological function (explaining the origins of day and night), there is no obvious fitness-enhancing rationale behind stories such as these. Perhaps the human proclivity for storytelling is merely a non-functional vestige of our evolved psychology; a series of inputs which manipulate and titillate our cognitive machinery – ‘evolutionary cheesecake’, in Steven Pinker’s3 memorable phrase.

However, given the ubiquity of human storytelling, the importance individuals appear to ascribe to it and the resources we spend on it – nearly £5 billion was spent on books in the UK in 20164 – storytelling may perform an important adaptive function in human societies.

Storytelling as ‘meta-knowledge’

My colleagues and I, as part of the Leverhulme Trust-funded ‘Hunter-Gatherer Resilience Project’5 led by Dr. Andrea Migliano, put forward the idea that storytelling may help to solve so-called ‘problems of co-ordination’ in hunter-gatherer societies, in order to promote cooperation6. This research was published in Nature Communications on December 5, 2017.

The majority of research on the evolution of cooperation has focused on the free-rider problem, in terms of how a cooperative strategy can outcompete a free-riding strategy, which in theory receives all the benefits without paying the costs (think ‘tragedy of the commons’ or the ‘prisoner’s dilemma’). In these cases, the optimal strategy in one-shot situations is to defect, meaning that cooperation is often difficult – although far from impossible – to evolve.

But the free-rider problem is not the only impediment to cooperation. In some situations, cooperation may be the best strategy for all, but due to a lack of common knowledge of how others will behave, cooperation does not occur7. Imagine two people rowing a boat, each in control of one oar; both need to row in the same direction (i.e., cooperate) in order to move the boat forwards. In this example a free-rider would not benefit, as if an individual did nothing while the other rowed, the boat would just go around in circles. Rather, the individuals need to co-ordinate their actions so that both can benefit.

Meta-knowledge – knowledge about others’ knowledge – is required to solve problems of co-ordination. In other words, it is not enough to know how to act in a given social situation; individuals need to know that others also know how to act (why expend the energy rowing your oar if the other person is doing nothing and doesn’t even know that they need to row the boat?).

We proposed that storytelling may function in hunter-gatherer societies as a mechanism to broadcast social norms, co-ordinate social behaviour and promote cooperation. Essentially, it informs others about the ‘rules of the game’ in a given society8 and the consequences for breaking these rules.

Organised religion and moralising high-gods may perform a comparable function and encourage cooperation in larger agricultural populations9, but – despite being inveterate cooperators – these are often absent in hunter-gatherer societies10. We therefore proposed that storytelling may perform an analogous function in hunter-gatherer which lack moralising high-gods.

This theory generates the testable predictions that: i) hunter-gatherer stories should overwhelmingly contain content relevant to regulating social interactions, and ii) by co-ordinating group behaviour, storytelling ought to promote cooperation.

Hunter-gatherer stories co-ordinate social behaviour

To test the first prediction, in collaboration with Agta Aid11 we collected four stories among the Agta, a Filipino hunter-gatherer population characterised by social and gender egalitarianism12. We found that each story concerned regulating social behaviour by broadcasting how to act in different situations.

In one story (“The sun and the moon”) norms of sex equality and cooperation between the sexes, which are recurring features of forager societies13, are extolled:

“There is a dispute between the sun (male) and the moon (female) to illuminate the sky. After a fight, where the moon proves to be as strong as the sun, they agree in sharing the duty – one during the day and the other during the night.”

A further story (“The monkey and the giant”) promotes norms of cooperation and team-work in pursuit of a shared goal, as well as highlighting how egalitarianism can be achieved via mechanisms of ‘reverse dominance hierarchies’14 against others in a potential position of power:

“The monkey and his other animal friends would like to camp close to the river. However, there was a giant there who would attack whoever went close to the river. They went anyway, and had to take turns to look after the camping site during the night. The giant came and said to the monkey that he was going to eat them. Together they plot a defence plan against the giant: the monkey tricked the giant into a cave where they had hidden bee and ant nests. The giant died. The monkey was the leader of the plan. His friends congratulated him, but reminded him that even though he was the smartest animal in the forest, he was still vulnerable, as the monkey-eating eagle could take him.”

The same themes were found in narratives from other hunter-gatherer societies from South-East Asia and Africa. Over 89 stories, around 70% concerned social behaviour, in terms of food-sharing, marriage, interactions with in-laws, hunting norms, interactions with out-groups, and so forth. These stories also possessed a moral dimension, by either rewarding norm-followers or punishing norm-breakers, as the following Andamanese story highlighting the importance of food-sharing illustrates:

“Ta Mita (dove) and Ta Koio (a small bird) went hunting together and got a great number of pigs. Ta Koio told Ta Mita to get some canes to tie up all the pigs. As soon as Ta Mita had gone to look for the cane, Ta Koio went up a big Dipterocarpus tree, taking half of the pigs with him. He came down and took the rest of the pigs. He stayed up in the tree with the pigs. When Ta Mita came back he found that the pigs had disappeared. He was very angry and went home. As there was nothing to eat, Mita and his two children, Cada and Coda (two species of fish) went fishing. Koio was still up in the tree. He was cooking the pigs up there. Mita and his children passed under the tree and some burning resin fell on them. In this way they discovered that Koio was in the tree. Mita planned to punish Koio. He cut a great number of sharp stakes of Areca wood and fixed them all round the tree, pointing upwards. Koio was asleep. Mita made the tree sink into the ground. As soon as it was low enough he took some water and threw it onto the ear of the sleeping Koio, who awoke in a fright and jumped from his tree. He was impaled on the stakes of wood so died.”15

Storytellers promote cooperation in camp

Given that stories overwhelmingly contained social content, ostensibly to co-ordinate social behaviour, we next explored our second prediction: whether storytelling does in fact promote cooperation.

We tested whether the presence of skilled storytellers in camp predicted levels of cooperation. Nearly 300 camp-mates, over 18 separate camps, were asked to name the best storytellers, and from this we derived a camp-level variable of ‘average proportion of nominations per individual’ as a proxy for the level of storytelling skill in each camp. This varied considerably between camps, with some camps containing more skilled storytellers than others.

To assess levels of cooperation in camps, we played a simple resource allocation game where individuals were given a number of tokens (representing a portion of rice) and asked to distribute these between themselves and their camp-mates16. Again, there was substantial between-camp variation in cooperativeness.

We found that overall levels of cooperation were higher in camps with a greater proportion of skilled storytellers, consistent with our theory that storytellers coordinate social behaviour and in turn promote cooperation.

How do storytellers benefit?

While this suggests that storytelling may perform a group-level function, it does not explain why individuals would invest time and energy in becoming a skilled storyteller, rather than just free-riding on existing storytellers. In other words, the information provided by storytellers is a public good on which non-storytellers can free-ride. Thus, despite this group-level benefit, all else being equal non-storytellers should outcompete storytellers.

All else is not equal, however. Skilled storytellers were found to be preferred social partners, both in terms of being selected as future camp-mates and receiving resources in the cooperative game. Skilled storytellers were almost twice as likely to be nominated as camp-mates relative to unskilled storytellers, an effect size on par with choosing to live with primary kin. Despite the fact that food-sharing is an everyday occurrence in Agta society17, skilled storytellers were even more preferred as social partners than skilled foragers.

This suggests that skilled storytellers receive fitness benefits in terms of increased social support, which has been linked with fitness among numerous primate species18. The same also appears to hold true among the Agta, as skilled storytellers were found to have increased reproductive success relative to unskilled storytellers, with an average additional 0.5 living offspring.

Storytelling is a group-beneficial behaviour – and therefore susceptible to free-riding – yet by demonstrating that skilled storytellers receive increase social support and have increased reproductive success this research provides a mechanism by which group-beneficial behaviour can evolve via individual-level selection.

Storytelling and human evolution

Although several hypotheses regarding the evolution of storytelling have been proposed, such as disseminating knowledge on foraging or the environment, or simply to hold the audience’s attention19 (such as the Maniq story, above), these have rarely been tested using real-world empirical data. While we do not dispute these other putative hypotheses – narratives may serve multiple adaptive functions – our results suggest that one of the main functions of storytelling among hunter-gatherers may be to coordinate social behaviour and promote cooperation.

Humans have evolved the capacity to create and believe in stories. These features may have evolved in hunter-gatherer societies as precursors to more elaborate forms of narrative fiction, such as moralising high-gods, nation states and other ideologies found in post-agricultural societies20.

From simple storytelling to organised religion, and later formal institutions such as nation states, the evolution of storytelling may have been pivotal in organising and promoting human cooperation – so much for ‘evolutionary cheesecake’!

Now, wouldn’t that be a nice story?

References

1 https://clubs-kids.scholastic.co.uk/clubs_content/7922

2 Thonghom, S. The Negrito of Thailand: The Mani. (2006). Available at: http://archive.li/cgA9l

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4 https://www.publishers.org.uk/media-centre/news-releases/2017/uk-publishing-has-record-year-up-7-to-48bn/

5 https://www.ucl-hg.co.uk/

6 Smith, D. et al. Cooperation and the evolution of hunter-gatherer storytelling. Nature Communications (2017). Available at: http://dx.doi.org/10.1038/s41467-017-02036-8

7 Cronk, L. & Leech, B. L. Meeting at Grand Central: Understanding the Social and Evolutionary Roots of Cooperation. (Princeton University Press, 2013).

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11 https://www.agtaaid.org/

12 Migliano, A & Vinicius, L. Why our ancestors were more equal than us. The Conversation (2015). Available at: https://theconversation.com/why-our-ancestors-were-more-gender-equal-than-us-41902

13 Dyble, M. et al. Sex equality can explain the unique social structure of hunter-gatherer bands. Science. 348, 796–798 (2015). Available at: http://dx.doi.org/10.1126/science.aaa5139

14 Boehm, C. Hierarchy in the Forest: The Evolution of Egalitarian Behavior. (Harvard University Press, 1999).

15 Radcliffe-Brown, A. The Andaman Islanders: A Study in Social Anthropology. (Cambridge University Press, 1922).

16 Smith, D. et al. Camp stability predicts patterns of hunter-gatherer cooperation. R. Soc. Open Sci. 3, 160131 (2016). Available at: http://dx.doi.org/10.1098/rsos.160131

17 Dyble, M. et al. Networks of Food Sharing Reveal the Functional Significance of Multilevel Sociality in Two Hunter- Gatherer Groups. Curr. Biol. 26, 2017-2021 (2016). Available at: http://dx.doi.org/10.1016/j.cub.2016.05.064

18 Silk, J. B. Social components of fitness in primate groups. Science 317, 1347–1351 (2007). Available at: http://dx.doi.org/10.1126/science.1140734

19 Boyd, B. On the Origin of Stories: Evolution, Cognition, and Fiction. (Harvard University Press, 2009).

20 Harari, Y. N. Sapiens: A Brief History of Humankind. (Penguin, 2011).

Banner image: “The Sun and the Moon: An Agta Story about Cooperation and Equality Between Men and Women.” Credit: Paulo Sayeg