Encyclopedia of Evolutionary Psychological Science

Living Edition
| Editors: Todd K. Shackelford, Viviana A. Weekes-Shackelford

Selection for Cooperative Relationships

  • Matthew J. Johnson
  • Stephen M. ColarelliEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-16999-6_3494-1



Individuals (or groups) working together for a mutual benefit.


“Many of the benefits sought by living things are disproportionately available to cooperating groups” (Axelrod and Hamilton 1981, p. 1391)

Cooperation involves individuals (or groups) working together for a mutual benefit, often at an initial cost to each participant, although the benefits from cooperation ultimately outweigh the costs to individuals. Cooperation is associated (conceptually and empirically) with altruism – behavior in which an individual forgoes a benefit to assist another. Some degree of altruism is necessary (at least initially) for cooperation to occur. To cooperate, an individual must initially give up a benefit. Altruism becomes cooperation when two or more individuals join in giving up benefits for a common goal, which they typically perceive as greater than the cost of the benefits they gave up. Our focus here is on cooperation among humans – in particular, the selection pressures (ultimate causes) that stimulated cooperation among our ancestors, the mechanisms (proximate causes) that enable cooperation to occur, and the cues people use to select other individuals as cooperative partners. What is unique about human cooperation is that humans cooperate widely with other humans to whom they are not related. This ability to cooperate with non-kin has been critical to the complex division of labor, the widespread growth of civilizations and nation-states, large organizations, and national and international economic systems.

Selection Pressures for Cooperation

Throughout the course of human evolution, people faced selection pressures favoring interdependence and cooperation (Tomasello et al. 2012). Climate change in Africa about 2.5 to 3 million years ago likely created resource pressures on early hominids by reducing jungle and increasing savannah areas (Handwerk 2014). The capacity to cooperate probably became instrumental in helping hominids adapt to these patchier resource environments (e.g., by making foraging more successful). As humans left Africa and began to populate the globe, they encountered different environments than they had grown accustomed to, again requiring increased cooperation to survive. With the spread of humans, there was undoubtedly greater competition from other groups, adding further adaptive pressure for cooperative traits and institutions. These pressures most likely created feedback loops reinforcing cooperative behavior for both individual and group survival.

Mechanisms for Cooperation

Many species engage in cooperation among kin, which is commonly known as kin selection (Hamilton 1964). An allele promoting helpful behavior toward kin, even at a cost to one’s self, could readily evolve and remain evolutionally stable. By helping relatives (who share one’s genes), an individual can get more of his or her genes into the future. Thus, individuals should be motivated to cooperate with kin to maximize their inclusive fitness.

Cooperation among non-kin has been more difficult to explain, because it is usually in the actor’s best interest to behave selfishly when interacting with non-kin. Reciprocal altruism (Trivers 1971) provided a plausible mechanism to explain helping behavior among unrelated individuals: People help one another when they expect that the behavior will be returned in kind. Two basic forms of reciprocity have been described. The simplest form, direct reciprocity, is a tit-for-tat cooperative strategy in which two individuals exchange cooperative acts and cease cooperating if either party defects (Axelrod and Hamilton 1981). In contrast, indirect reciprocity involves cooperation based on reputation (Nowak and Sigmund 2005). Reciprocation is indirect when it is given by someone other than the initial beneficiary. In this case, individuals help those who are known to have been helpful to others. Thus, individuals must cultivate a reputation for being cooperative if they hope to receive the benefits of cooperation.

Circumstances in which cooperation is most critical (e.g., natural disasters, wars, and famines) are those where reciprocity-based cooperation is least likely to occur. Why help someone in these circumstances, because it is unlikely that he or she will be around to return the favor? To address this problem, the theory of strong reciprocity suggests that humans are predisposed to cooperate and punish non-cooperators even at their own personal cost (Gintis 2000). Thus, a trait of “cooperativeness” must have evolved and been selected for so that humans are inclined (some more than others) to be cooperative.

Cooperators could have been taken advantage of by selfish individuals within their groups, making selection for cooperativeness unlikely at the individual level. Therefore, prosocial traits and behaviors must have been beneficial at the group level. Although cooperativeness can be costly to individuals and may be disadvantageous within groups (i.e., individual selection), cooperation increases the fitness of groups relative to other groups (i.e., group selection). This is the logic of multilevel selection theory (Wilson and Wilson 2007). Cooperation allows groups to outcompete less cooperative groups, making cooperative individuals more likely to survive and reproduce. Integrating the perspectives of strong reciprocity and multilevel selection, Bowles and Gintis (2011) suggest that a genetically based predisposition to cooperate most likely coevolved alongside social institutions and cultural norms that reduce within-group competition (e.g., food sharing, monogamy) and help maintain cooperation, making groups that adopted those institutions and norms more successful than those who did not.

The transition from kin selection to reciprocal altruism to large-scale cooperation among non-kin is not well understood, although probable paths have been proposed (e.g., Tomasello et al. 2012). One possibility is that as kin-selection consolidated among early humans, associated cognitive and emotional mechanisms facilitating cooperation developed apace (e.g., prosocial emotions). These psychological mechanisms then might have generalized to small-scale cooperative practices among non-kin (e.g., cooperative breeding). As cultural learning and institutions (e.g., religion) became more widespread, these too reinforced cooperative sentiments and practices.

Identifying and Selecting Cooperative Partners

Cues signaling trustworthiness are important in selecting partners who are likely to cooperate. Trust cues can be categorized as personal or situational (Thielmann and Hilbig 2015). Personal trust cues are characteristics of a potential partner that may provide information about his or her trustworthiness. These include aspects of outward appearance, reputational information, and social category information (e.g., ingroup versus outgroup). Situational trust cues are features of the situation that may make someone more or less trustworthy (e.g., temptation to betray, sanctions for betrayal).

People use readily accessible verbal and nonverbal cues to judge others’ trustworthiness (i.e., personal trust cues). For example, people readily infer others’ (un)trustworthiness based on aspects of their faces, including its basic features or structure, emotional expressions, and similarity to the judge’s own face. Altogether, research suggests that faces are judged more trustworthy when they look happy (rather than angry), feminine (rather than masculine), mature (rather than young), and similar to the target’s own face (Todorov et al. 2015). All of these facial cues appear to have adaptive significance. For example, a similar face may be a cue of kinship, a happy face may suggest that someone is approachable, an angry face may suggest that someone has harmful intentions, and a wide, masculine face may suggest that someone has the physical stature necessary to carry out their ill-intentions. Although people make trustworthiness judgments based on facial cues quickly and show high agreement in their judgments, these judgments tend to be inaccurate (Todorov et al. 2015).

People may also use reputational and social category information as personal trust cues. Individuals are more trusting of people with positive reputations than those with negative reputations (Thielmann and Hilbig 2015). Reputational information about someone can be acquired directly by observing their behavior as well as indirectly via gossip. Additionally, people are more trusting and cooperative toward strangers who are ingroup members. Thus, cues that signal ingroup membership should make someone a more attractive cooperative partner (e.g., clothing, tattoos, tribal scars).

When selecting a cooperative partner, it is wise to consider not only characteristics of the partner, but also features of the situation that may impact his or her trustworthiness. Thus, situational trust cues include characteristics of the social context that may make someone more or less trustworthy. The two most well-studied situational trust cues are temptation to betray and sanctions for betrayal (Thielmann and Hilbig 2015). Temptation to pursue selfish interest at the expense of mutual interest is inherent in cooperative situations, and cooperation becomes less likely the more the benefits of betrayal outweigh the benefits of cooperation. On the other hand, sanctions for betrayal (e.g., punishment or diminished reputation) can be expected to elicit more trustworthy behavior and cooperation.


Cooperation helped our ancestors overcome threats to survival and is a large part of the reason why Homo sapiens has flourished as a species. Researchers have proposed several complementary reasons why cooperation may be so widespread in humans. Ultimately, we cooperate to promote our own genes, and we do so by helping our kin, cultivating mutually beneficial social exchanges, enhancing our reputations, and because the momentum of genetic and cultural evolution compels us to. These mechanisms bear on our everyday psychological tools for identifying and selecting cooperative partners who are likely to help us achieve our goals.



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© Springer Nature Switzerland AG 2019

Authors and Affiliations

  1. 1.Central Michigan UniversityMount PleasantUSA

Section editors and affiliations

  • Kevin Kniffin
    • 1
  1. 1.Cornell UniversityIthacaUSA