The evolution of fairness

 

Two evolutionary models are compared: 1) Baumard, André, and  Sperber (2013), Baumard (2016); and 2) a two-step evolution of distributive justice.  

What does the sense of fairness consist of, and where does it come from?  Why do I believe it is the right thing to do?  

These elements are all necessary for distributive justice:  

 

 

Model 1) (Baumard et al.) proposes that fairness, as a package of behaviour and psychology, evolved directly, through selection pressures acting proximately on collaborative partners.  People who took too little would be selected against because they would lose relative fitness benefits.  People who took too much would be selected against because they would lose collaborative opportunities.  This caused humans to evolve to share with collaborative partners impartially, equally, and proportionately.  

Contractualists propose that if we could, we would explicitly negotiate to maximise benefits all round on an equal basis, and therefore, an as-if contract captures the pattern of moral intuitions.  It seems true that this is the case; but the question remains, why do we have those intuitions?    

Model 2) (two-step evolution of fairness) claims that a broader set of environmental and evolutionary factors has given rise contextually to a normative sense of fairness.  Each element has a distinct evolutionary and causative story.  The norm of proportionality may be derived from the ancient norm of tit-for-tat reciprocity.  According to this model, the capturing of fairness intuitions by an as-if contract, and the evolution of fairness itself, coincide because they are both caused by the same thing – cooperative rationality: thinking and achieving goals cooperatively.  

 

In order to describe the logic of morality, "contractualist " philosophers have studied how individuals behave when they choose to follow their moral intuitions. These individuals, contractualists note, often act as if they have bargained and thus reached an agreement with others about how to distribute the benefits and burdens of mutual cooperation. Using this observation, such philosophers argue that the purpose of morality is to maximize the benefits of human interaction. The resulting "contract " analogy is both insightful and puzzling. On one hand, it captures the pattern of moral intuitions, thus answering questions about human cooperation: why do humans cooperate? Why should the distribution of benefits be proportionate to each person's contribution? Why should the punishment be proportionate to the crime? Why should the rights be proportionate to the duties? On the other hand, the analogy provides a mere as-if explanation for human cooperation, saying that cooperation is "as if " people have passed a contract-but since they didn't, why should it be so? To evolutionary thinkers, the puzzle of the missing contract is immediately reminiscent of the puzzle of the missing "designer " of life-forms, a puzzle that Darwin's theory of natural selection essentially resolved. Evolutionary and contractualist theory originally intersected at the work of philosophers John Rawls and David Gauthier, who argued that moral judgments are based on a sense of fairness that has been naturally selected. In this book, Nicolas Baumard further explores the theory that morality was originally an adaptation to the biological market of cooperation, an arena in which individuals competed to be selected for cooperative interactions. In this environment, Baumard suggests, the best strategy was to treat others with impartiality and to share the costs and benefits of cooperation in a fair way, so that those who offered less than others were left out of cooperation while those who offered more were exploited by their partners. It is with this evolutionary approach that Baumard ultimately accounts for the specific structure of human morality.

Nicolas Baumard (2016) – “The Origins of Fairness: How Evolution Explains Our Moral Nature (Foundations of Human Interaction)”; publisher’s abstract

 

We develop an approach to morality as an adaptation to an environment in which individuals were in competition to be chosen and recruited in mutually advantageous cooperative interactions. In this environment, the best strategy is to treat others with impartiality and to share the costs and benefits of cooperation equally. Those who offer less than others will be left out of cooperation; conversely, those who offer more will be exploited by their partners. In line with this mutualistic approach, the study of a range of economic games involving property rights, collective actions, mutual help and punishment shows that participants’ distributions aim at sharing the costs and benefits of interactions in an impartial way. In particular, the distribution of resources is influenced by effort and talent, and the perception of each participant’s rights on the resources to be distributed.

Nicolas Baumard, Jean-Baptiste André, and Dan Sperber (2013) – “A mutualistic approach to morality: The evolution of fairness by partner choice”

 

Sharing and distributive justice

Sharing may be done:

  1. freely; in response to need;
  2. equally;
  3. proportionately; in response to deservingness or other merit.  

2) and 3) imply a closed system, i.e., that free riders are excluded.  

 

Background evolutionary story

Fairness (distributive justice) involves cooperation and sharing – we cooperate to obtain the rewards, and then share them out on some kind of equal and impartial basis.  Each of us is treated the same, and I do not favour myself over anyone else.  Morality is the regulation of cooperation and sharing.  

Tomasello et al. (2012) propose a two-step evolution of morality, beginning with small nomadic bands of self-domesticated proto-human species just down from the trees (4-6 million years ago), progressing to larger tribal organisations, split into small linked nomadic bands, from around 150,000 years ago.  Tomasello (2016) notes a third stage in human history, beginning around 12,000 years ago: large, culturally mixed, sedentary city-states.  

 

1. Dominance and egalitarianism

Fairness cannot happen in the presence of dominance relations, as is the social lifestyle of other great apes, and which is the reason why they can never develop a full sense of other-directed fairness.  1) a dominants will not give up their resources to a subordinate, and 2) a dominant is able to take what they want from a subordinate.  Both are inimical to fairness, and by extension, cooperation.  In this situation, cooperation falls apart over time as subordinates are not rewarded for their labour (Tomasello et al., 2012).  

Hence, for sharing and fairness to be possible in humans, great ape dominance relations had to be removed.  

 

2. Self-domestication of the human race

The African forest provides a very easy and comfortable foraging niche for the great apes who live there.  They do not need to cooperate or share in order to obtain their plentiful food of ripe fruit and other forest fare.  In contrast, 4-6 million years ago, after their areas of forest died back, proto-humans were forced onto the harsh, risky and variable environment of the savannah and mixed woodland.  This meant they needed to share to survive.  Therefore, females sexually selected males who would share and not compete, and males from then on changed size and shape: the upper canines of the males and females became almost the same size, and in the human line have stayed that way (Suwa et al., 2021).

Thereby, male-male dominance relations were largely removed from the human race by female sexual selection, this being reinforced by a strong social ethos of egalitarianism, which would have been appropriate for a nomadic lifestyle (Woodburn, 1982).  

 

3. Cooperation and sharing in small nomadic bands

In small nomadic bands, everyone gets fed regardless of their input (Gurven, 2004).  Free riding and stinginess are discouraged through harassment and ridicule.  Sharing is done in response to need.  The choice of partners is from whomever is around, although people are mobile and may change camps if they wish.  

 

4. Cooperation and sharing in large, mixed, sedentary city states

In large mixed city states, a partner’s reputation may be unknown, and after the collaboration, they may disappear back into anonymity.  Partner choice is from a large pool of specialised workers.  There is a risk that I will be exploited in a one-shot interaction.  It is important that I am paid back immediately for my full contribution.  Therefore, when it comes to distributing the rewards of a collaboration, or making an exchange, there need to be rules, contracts, and restrictions.  Free riders are excluded altogether.

 

5. Tit-for-tat reciprocity is the basis of proportionality in fairness

 

“The norm of reciprocity is universal.” If we do a favor, we expect one in return. If we receive a favor we cannot return, we are distressed.

Donald W Pfaff, PhD – “The Neuroscience of Fair Play”

 

Male-female partners [rhesus macaques] demonstrated near-perfect reciprocity in grooming, a key behavioural mechanism supporting friendships and alliances, and neural activity maintained a running account of these social investments. …

Macaques form strong and stable bonds with specific individuals selected based on attributes such as kinship and social status … . These friendships and alliances, in part built and maintained through reciprocal grooming, enable mutual support to gain access to limited resources or fend off threats … .

Testard et al. (2024:1…2) – “Neural signatures of natural behaviour in socializing macaques”

 

Proportionality means giving in response to deservingness, rather than in response to need (charity); an equal return per unit of deservingness, rather than per unit of need.  

Proportional fairness involves a tit-for-tat exchange of two things of equal value, translated from one to the other at some standard impartial rate.  This could be according to a number of criteria of deservingness, for example: work done, resources contributed, risks taken, merit, age, etc.  

Therefore, proportionality in fairness is a form of tit-for-tat reciprocity; of equal exchange.  Because it is apparently evolutionarily ancient in primates, in whom it promotes survival and well being, we propose that account-keeping tit-for-tat reciprocity provides the neural basis for normative calculations of proportionality in fairness.  

 

6. Two-step evolution of distributive justice

The claim is that distributive justice evolved in two steps:

  1. Free sharing in response to need (small nomadic groups) (free riders discouraged);
  2. Restricted proportional or equal sharing (large settled groups) (free riders excluded).  

Distributive justice, restricted sharing, grew out of the evolutionarily ancient free sharing.  The norm of proportionality is derived from the evolutionarily ancient tit-for-tat reciprocity.  

 

 

7. Gene’s eye-view of the basis of egalitarianism and fairness

Each organism seeks to maximise its own fitness benefits (instrumental normativity).  

Fitness benefits can either be absolute, in myself, or relative to those of others (survival of the fittest).  

 

The evolution of cooperation requires that its benefits reach all contributing parties in roughly similar amounts. Natural selection works on every individual’s relative advantage compared with others; hence, gaining an absolute benefit is insufficient. If individuals were satisfied with any absolute benefit, they might still face negative fitness consequences if they were doing less well than competing others. It makes sense, therefore, to compare one's gains with those of others.

Sarah F Brosnan and Frans B M de Waal (2014) – “Evolution of responses to (un)fairness”

 

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In collective actions aimed at a common goal, there is a right way to share the benefits: Those who have contributed more should receive more. When helping others, there is a right amount to give. One may have the duty to give a few coins to beggars in the street, but one does not owe them half of one’s wealth, however helpful it would be to them. When people deserve to be punished, there is a right amount of punishment. Most people in societies with a modern penal system would agree that a year in jail is too much for the theft of an apple and not enough for a murder. People have strong intuitions regarding the right way to share the benefits of activity, the right way to help the needy, and the right way to punish the guilty. Do these intuitions, notwithstanding their individual and cultural variability, have a common logic, and, if so, to what extent is this logic rooted in evolved dispositions?

To describe the logic of morality, many philosophers have noted that when humans follow their moral intuitions, they behave as if they had bargained with others in order to reach an agreement about the distribution of the benefits and burdens of cooperation … . Morality, these “contractualist” philosophers argue, is about maximizing the mutual benefits of interactions. The contract analogy is both insightful and puzzling. On the one hand, it well captures the pattern of moral intuitions, and to that extent well explains why humans cooperate, why the distribution of benefits should be proportionate to each cooperator’s contribution, why the punishment should be proportionate to the crime, why the rights should be proportionate to the duties, and so on. On the other hand, it provides a mere as-if explanation: It is as if people had passed a contract – but since they didn’t, why should it be so?

Nicolas Baumard, Jean-Baptiste André, and Dan Sperber (2013:59) – “A mutualistic approach to morality: The evolution of fairness by partner choice”

 

Impartiality and self-other equivalence

Self-other equivalence among collaborative partners is the basis of impartiality.  Psychologically, the collaboration has two levels: 1) individual agents you and I; 2) the joint agent “we” or “us” (Tomasello, 2016).  From the point of view of “us”, a “bird’s eye view” of the collaboration, there are just roles with interchangeable players.  To “us”, i.e., “you and I”, we all feel equivalent, for a number of reasons:

Hence, when “we” think about, judge, and regulate “us”, it is done from the bird’s eye view, i.e., impartially.    

 

Mutual respect and deservingness; other-directed inequity aversion

Partners have mutual value, as collaborators and causative agents.  Because of this, and because of self-other equivalence, they respect each other in important ways (Tomasello, 2016).  

Since I feel that my partners are as deserving as myself, I believe they should be given an impartial share of the rewards, whether that is an equal share or a share proportional to merit.  

 

Normative pressure to be fair

Normative moral pressure comes in three kinds: obligation (because I have to); volition (because I want to); and compassion (because I care).  

There are a number of common sources of obligation to be fair: that proximately force me to be fair.  For example:

I also wish to be fair, because I believe that fairness is the right thing to do, the morally right way to behave.  The reasons I wish to be fair, that it is the right thing to do, include:

Compassion, because I care, does not really apply as a moral motivation to be fair, as distributive justice depends on deservingness rather than charity.  However, compassion can provide personal motives (through mutual value) for partners to want to be fair to each other.  

 

Fairness around the world

A study by Schäfer, Haun, and Tomasello (2015) found that:

 

 

References

Baumard, Nicolas; Jean-Baptiste André; and Dan Sperber (2013) – “A Mutualistic Approach to Morality: The Evolution of Fairness by Partner Choice”; Behavioral and Brain Sciences, 36 (1), 59-78

Gurven, Michael (2004) – “To give and to give not: The behavioral ecology of human food transfers”: Behavioral and Brain Sciences 27, 543-583

Schäfer, Marie; Daniel B M Haun; and Michael Tomasello (2015) – “Fair is not fair everywhere”; Psychological Science, Vol 26(8), 1252–1260

Suwa, Gen; Tomohiko Sasaki; Sileshi Semaw; Michael J Rogers; Scott W Simpson; Yutaka Kunimatsu; Masato Nakatsukasa; Reiko T Kono; Yingqi Zhang; Yonas Beyene; Berhane Asfaw; and Tim D White (2021) – “Canine sexual dimorphism in Ardipithecus ramidus was nearly human-like”; PNAS Vol. 118 No. 49 e2116630118; https://doi.org/10.1073/pnas.2116630118

Testard, Camille; Sébastien Tremblay; Felipe Parodi; Ron W DiTullio; Arianna Acevedo-Ithier; Kristin L Gardiner; Konrad Kording; and Michael L. Platt (2024) – “Neural signatures of natural behaviour in socializing macaques”. Nature 628, 381–390. https://doi.org/10.1038/s41586-024-07178-6

Tomasello, Michael; Alicia P Melis; Claudio Tennie; Emily Wyman; Esther Herrmann (2012) – “Two Key Steps in the Evolution of Human Cooperation – The Interdependence Hypothesis” – Current Anthropology, vol. 53, no. 6, Dec 2012

Tomasello, Michael (2016) – “A Natural History of Human Morality”; Harvard University Press, Cambridge MA  

Woodburn, James (1982) – “Egalitarian Societies”: Man, New Series, Vol. 17, No. 3. pp. 431-451; Sep. 1982