Cooperation is a phenomenon which is widespread across species. It is defined as a behaviour which causes an increase in fitness (the ability to survive and reproduce) of the actor’s social partner. Due to inclusive fitness theory, it is known cooperation leads to an overall increase in the fitness of the actor. Human cooperation stands out as a monolith in this regard- the size of human societies and the magnitude of our cooperation even between unrelated individuals is astounding. This attribute forms a key part of what it means to be human and so understanding human cooperation and the mechanisms which permit humans to maintain this behaviour (maintain evolutionary stability) are arguably of personal significance in understanding our behaviour.
An Eye for an Eye
One explanation for human cooperation is reciprocal altruism. An investment where the role of actor and recipient alternate as do costs and benefits. Reciprocity can evolve when there is repeated contact between two individuals. This interaction can be divided into two categories- direct and indirect. Whilst direct reciprocity relates to two individuals, indirect reciprocity is where an actor helps a recipient and the actor is then rewarded by a third party.
However, defection, where one individual does not return the investment, may occur so it is important to detect and control cheaters. Without this capacity, reciprocity cannot be evolutionarily stable as cheaters would always exploit unconditional help. Both kinds of reciprocity maintain evolutionary stability through punishment, such as ostracism seen in partner switching. This entails the cheated individual switching partners and ceasing interaction with the cheater, who incurs a cost by being left out without potential partners. Punishment is a key mechanism for enforcement of cooperation, used even at the punisher’s expense, possibly because of anticipated future interactions with the defector, or altruistic punishment, where punishment is carried out regardless of future contact. The latter has been shown in experimental games but due to strong artificial conditions, it is difficult to surmise how these behaviours could be evolutionarily stable.
Indirect reciprocity is kept evolutionarily stable in humans particularly through the use of reputation. Cooperative behaviour begets helpful behaviour from a third party, who is in turn rewarded for similar behaviour. Reputations can be built by image scoring, where every cooperative act increases one’s image by one unit and every defective act decreases one’s image by one unit. Alternatively, reputations are moderated by standing, which is similar to image scoring but allows justified defection (by not incurring penalties) against a receiver, who is in bad standing due to previous unjustified defections. It has been suggested the interplay of punishment and reputation building enables more efficient cooperation. For example, although it is unclear how costly punishment is evolutionarily stable due to the detriment incurred to fitness, it has been suggested some additional benefit (e.g. reputation gain) is achieved by punishing others resolves this.
Another explanation for human cooperation is interdependence. This suggests individuals have a stake in the welfare of others since the prosperity of other individuals impacts personal. Tomasello et al (2012) proposed that initially, humans became obligate collaborative foragers, creating an interdependent lifestyle, and in a second step, the subsequent collaborative skills developed were scaled up to general group life when facing competition from other groups of humans.
To maintain evolutionary stability new capacities were developed to enable interdependence. A key feature of humans is language. From a young age humans coordinate their behaviour with their partners, particularly verbally. It has been argued that this unique capacity to convey intention allows the emergence of shared goals, as opposed to simply coordinating your efforts with another to achieve your own ends, which achieves more complex cooperation. On a greater scale this permitted collective intentionality where cultural conventions and institutions could be formed to help partners and punish defectors, thereby increasing interdependence and encouraging extensive cooperation. Furthermore, societal institutions that reduce socially undesirable behaviour (i.e. punishment) ensure that costs of sanctioning are shared among the group.
These mechanisms supposedly maintain the delicate balance of extensive human cooperation. This trait has proved beneficial in enabling division of labour, trade and care for the sick. Despite this these mechanisms are not all powerful and failure to enforce cooperation by these mechanisms allows problems like climate regulation and overfishing. The increased connectedness of the modern world means an enhanced effect of trade, violence, and information enabled by the failings of mechanisms governing our cooperation.