Cooperation is needed for evolution to construct new levels of organization. Genomes, cells, multicellular organisms, social insects, and human society are all based on cooperation. Cooperation means that selfish replicators forgo some of their reproductive potential to help one another. But natural selection implies competition and therefore opposes cooperation unless a specific mechanism is at work. Here I discuss five mechanisms for the evolution of cooperation: kin selection, direct reciprocity, indirect reciprocity, network reciprocity, and group selection. For each mechanism, a simple rule is derived that specifies whether natural selection can lead to cooperation.

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Five Rules for the Evolution of Cooperation

Evolutionary games on graphs

In the Hamadryas baboon, males are substantially larger than females. A troop of baboons is subdivided into a number of ‘one-male groups’, consisting of one adult male and one or more females with their young. The male prevents any of ‘his’ females from moving too far from him. Kummer (1971) performed the following experiment. Two males, A and B, previously unknown to each other, were placed in a large enclosure. Male A was free to move about the enclosure, but male B was shut in a small cage, from which he could observe A but not interfere. A female, unknown to both males, was then placed in the enclosure. Within 20 minutes male A had persuaded the female to accept his ownership. Male B was then released into the open enclosure. Instead of challenging male A , B avoided any contact, accepting A’s ownership.

Evolution and the Theory of Games

Natural selection is conventionally assumed to favour the strong and selfish who maximize their own resources at the expense of others. But many biological systems, and especially human societies, are organized around altruistic, cooperative interactions. How can natural selection promote unselfish behaviour? Various mechanisms have been proposed, and a rich analysis of indirect reciprocity has recently emerged: I help you and somebody else helps me. The evolution of cooperation by indirect reciprocity leads to reputation building, morality judgement and complex social interactions with ever-increasing cognitive demands.

/pdf/evolution-of-indirect-reciprocity-5c263ljns6.pdf

Evolution of indirect reciprocity.

People are selfish, yet morally motivated. Morality is universal, yet culturally variable. Such apparent contradictions are dissolving as research from many disciplines converges on a few shared principles, including the importance of moral intuitions, the socially functional (rather than truth-seeking) nature of moral thinking, and the coevolution of moral minds with cultural practices and institutions that create diverse moral communities. I propose a fourth principle to guide future research: Morality is about more than harm and fairness. More research is needed on the collective and religious parts of the moral domain, such as loyalty, authority, and spiritual purity.

/pdf/the-new-synthesis-in-moral-psychology-5577zqkwca.pdf

The new synthesis in moral psychology.

Models of large-scale human cooperation take two forms 'Indirect reciprocity' occurs when individuals help others in order to uphold a reputation and so be included in future cooperation In 'collective action', individuals engage in costly behaviour that benefits the group as a whole Although the evolution of indirect reciprocity is theoretically plausible, there is no consensus about how collective action evolves Evidence suggests that punishing free riders can maintain cooperation, but why individuals should engage in costly punishment is unclear Solutions to this 'second-order free rider problem' include meta-punishment, mutation, conformism, signalling and group-selection The threat of exclusion from indirect reciprocity can sustain collective action in the laboratory Here, we show that such exclusion is evolutionarily stable, providing an incentive to engage in costly cooperation, while avoiding the second-order free rider problem because punishers can withhold help from free riders without damaging their reputations However, we also show that such a strategy cannot invade a population in which indirect reciprocity is not linked to collective action, thus leaving unexplained how collective action arises

Indirect reciprocity can stabilize cooperation without the second-order free rider problem

https://faculty.missouri.edu/~panchanathank/papers/2003/Panchanathan2003.pdf

A tale of two defectors: the importance of standing for evolution of indirect reciprocity.

In environments that are harsh and unpredictable, people are typically more vigilant, act more impulsively, and discount the future more. In this paper, we argue that these behaviors reflect a present-orientation produced by biological adaptations, despite potential harm to health and wellbeing. We review recent studies showing that people in stressful environments have a stronger preference for immediate over delayed rewards, have children at a younger age, and develop enhanced cognition for dealing with threat and rapidly changing conditions, compared with people from supportive environments. Moreover, people from supportive environments, when exposed to harsh-unpredictable environmental cues, shift toward a present-orientation. These findings underscore the benefits of integrating evolutionary and developmental psychology.

https://www.staff.ncl.ac.uk/daniel.nettle/Frankenhuis2016.pdf

Cognition in harsh and unpredictable environments

Development is typically a constructive process, in which phenotypes incrementally adapt to local ecologies. Here, we present a novel model in which natural selection shapes developmental systems based on the evolutionary ecology, and these systems adaptively guide phenotypic development. We assume that phenotypic construction is incremental and trades off with sampling cues to the environmental state. We computed the optimal developmental programmes across a range of evolutionary ecological conditions. Using these programmes, we simulated distributions of mature phenotypes. Our results show that organisms sample the environment most extensively when cues are moderately, not highly, informative. When the developmental programme relies heavily on sampling, individuals transition from sampling to specialization at different times in ontogeny, depending on the consistency of their sampled cue set; this finding suggests that stochastic sampling may result in individual differences in plasticity itself. In addition, we find that different selection pressures may favour similar developmental mechanisms, and that organisms may incorrectly calibrate development despite stable ontogenetic environments. We hope our model will stimulate adaptationist research on the constructive processes guiding development.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2011.0055

Balancing sampling and specialization: an adaptationist model of incremental development

Sensitive periods, in which experience shapes phenotypic development to a larger extent than other periods, are widespread in nature. Despite a recent focus on neural–physiological explanation, few formal models have examined the evolutionary selection pressures that result in developmental mechanisms that produce sensitive periods. Here, we present such a model. We model development as a specialization process during which individuals incrementally adapt to local environmental conditions, while receiving a constant stream of cost-free, imperfect cues to the environmental state. We compute optimal developmental programmes across a range of ecological conditions and use these programmes to simulate developmental trajectories and obtain distributions of mature phenotypes. We highlight four main results. First, matching the empirical record, sensitive periods often result from experience or from a combination of age and experience, but rarely from age alone. Second, individual differences in sensitive periods emerge as a result of stochasticity in cues: individuals who obtain more consistent cue sets lose their plasticity at faster rates. Third, in some cases, experience shapes phenotypes only at a later life stage (lagged effects). Fourth, individuals might perseverate along developmental trajectories despite accumulating evidence suggesting the alternate trajectory is more likely to match the ecology.

https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.2015.2439

Karthik Panchanathan

Papers

Indirect reciprocity can stabilize cooperation without the second-order free rider problem

A tale of two defectors: the importance of standing for evolution of indirect reciprocity.

Cognition in harsh and unpredictable environments

Balancing sampling and specialization: an adaptationist model of incremental development

The evolution of sensitive periods in a model of incremental development