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 – “Evolution of responses to (un)fairness”


the morality of fairness is neither ... basic nor ... straightforward – and it may very well be confined to the human species.  The fundamental problem is that in situations requiring fairness there is typically a complex interaction of the cooperative and competitive motives of multiple individuals.  Attempting to be fair means trying to achieve some kind of balance among all of these, and there are typically many possible ways of doing this based on many different criteria.  Humans thus enter into such complex situations prepared to invoke moral judgments about the “deservingness” of the individuals involved, including the self, but they are at the same time armed with more punitive moral attitudes such as resentment or indignation against unfair others.  In addition, they have still other moral attitudes that are not exactly punitive but nevertheless stern, in which they seek to hold interactive partners accountable for their actions by invoking interpersonal judgments of responsibility, obligation, commitment, trust, respect, duty, blame and guilt.  The morality of fairness is thus much more complicated than the morality of sympathy [helping in response to need].  Moreover, and perhaps not unrelated, its judgments typically carry with them some sense of responsibility or obligation: it is not just that I want to be fair to all concerned, but that one ought to be fair to all concerned.  In general, we may say that whereas sympathy is pure cooperation, fairness is a kind of cooperativization of competition in which individuals seek balanced solutions to the many and conflicting demands of multiple participants’ various motives.  

Michael Tomasello – “The Natural History of Human Morality”





The domain of fairness includes ideas of

  1. impartiality
  2. procedural justice (sticking to the rules of a fair and impartial process)
  3. respect
  4. deservingness
  5. reciprocity (fairness in exchanges; like for like)
  6. sharing (distributive justice – distributing goods or burdens according to various criteria, for example: 1) proportionality to merit (like for like); 2) equality (equal shares for all); 3) on-demand, or based on need (charity); 4) age; 5) authority; 6) according to some agreed upon rule; etc.)  
  7. retributive and restorative justice (including the legal system)
  8. resentment, indignation and moral anger if fairness is not carried out.   




Fairness generally refers to two distinct but related things:

  1. how we treat people (i.e. with respect; as equally deserving, depending on circumstances)  
  2. how we share out goods or burdens (i.e. equally, or proportionally to merit, or in response to need, or to satisfy some agreed-upon rule, etc.)  

Both these things are represented by Perfect Compassion: "distributing benefit and harm so that all concerned can be satisfied".  




Universal social norm

Along with concerns about benefit and harm, a sense of fairness is universal among the human race.  As we would expect of a complex moral emotion, the way it plays out varies greatly according to context and culture (Niemi, Schäfer).  

It has been found that in the West, those on the political right wing tend to favour proportionality (i.e. distribution according to merit) and those on the left tend to favour equal distribution of goods (Niemi, Haidt).  In addition, it is found that males tend to favour proportionality and females tend to favour equality (Wilson).  




Sharing and distributive justice

Goods or burdens may be distributed in a number of different ways, i.e. according to a number of different principles of equity; for example:


1.  equally

An equal division for each person: equality of outcome, or equality of opportunity.  


2.  proportionally (tit-for-tat)

including proportionality to effort or resources put in by each person; or to merit, or age, gender, race, or social position, etc.  

Proportional distribution is a “merit-based distribution that reflects the productivity of recipients in an attempt to distribute an  equal reward for each unit of work.” (Schäfer)  

Proportional distribution arises in the contexts of collaboration and reciprocity.  When a number of people are working together, each wishes to obtain a reward proportional to the work, skill or other resources they have put into the collaboration.  Often, however, sharing after collaboration will be done equally.


A study by Schäfer et al. (2015) found that:


3.  reciprocally

Reciprocity is an example of proportionality – I give in proportion to what I get.

Sharing as a reciprocal favour can be seen by others as somewhat self-serving (Niemi et al., 2017), but that doesn't necessarily make it “wrong”: reciprocity forms the necessary give-and-take within personal relationships and business or trade relationships.  Reciprocal favours may be used unfairly to foster alliances within an elite in-group, making the system less impartial (i.e. less open to all with the right qualities) overall.  (Niemi et al., 2017)

A study of Hadza hunter-gatherers in Tanzania found experimentally that people in each camp shared approximately the same as each other, while there was fairly wide variation in sharing between camps.  It was also found that overall, Hadza share approximately half of everything they have.  (Smith, Kristopher M et al., 2018)


4.  on-demand; in response to need

Homo sapiens ... [are] the only primate species to have evolved widespread sharing among adults accompanied by a high degree of economic interdependence, which is characteristic of the risky human foraging niche.  

Jaeggi et al – “Natural Cooperators”

Needs-based allocation of resources can be seen as impartial – granting equality of opportunity, and providing a minimum amount of resources to any and every person who needs it.  On the other hand, it may be seen as favouring the needy and therefore not impartial.  But it can also have the effect of allowing disadvantaged people to take advantage of an impartial system, and so, can be fair.  (Niemi at al., 2017)  Giving in response to need may also conflict with ideas of deservingness.  

[Our findings in the laboratory suggest] that, at some level, people intuit that charity is not a simple solution to a resource allocation problem and is liable to be perceived as unfair.  People may be most likely to endorse allocation systems in which needy individuals will be helped while systematic favoritism (i.e., partiality-based unfairness) will be counteracted.  

Niemi et al., 2017

Results from mathematical game theory show that in small isolated societies, helping the needy provides a social insurance that allows everyone to survive very well in the long term, compared with people who do not share or receive help from others (Lewis 2014).  In computer simulations of cattle-keeping societies, based on the Maasai, it is found that sharing in response to need, compared with reciprocal exchange, produces a longer-lasting herd and more wealth equality (Shaffer 2019).  

This pattern of community-based social insurance is found in isolated communities around the world.  See: Shaffer 2019.  In this case, giving based on need is like a form of reciprocity extended over time that we may or may not need to redeem in the future.  It is a way of pooling risks and rewards within a difficult survival niche.  

Anecdotally, modern hunter-gatherer societies routinely share large game on demand (so that those more in need receive more), but lazy or stingy people are disapproved of and heavily criticised, and may be ostracised (Gurven 2004).  

A study of Agta hunter-gatherers in the Philippines found experimentally that a quarter of sharing in this group is done in response to need.  (Smith, Daniel et al., 2019 - see figure below.)  


5.  other critieria for sharing

We may also share according to seniority, authority (place in a hierarchy), or some agreed-upon rule, or favour in-group over out-group members (Schäfer 2015, Schmidt 2016).  











Inequity aversion

Equity is the quality of abiding by the abstract principles of fairness (e.g. equality, proportionality).  

Inequity aversion is a feeling of dislike of unfair treatment.  

Inequity aversion comes in two forms: self-directed, and other-directed.  

I feel bad because I have received less than I feel I deserve.

I feel bad because someone else has received less than I feel they deserve.  

People will go to some lengths to redress the balance of fairness if they feel that they themselves, or another person, have been treated unfairly.  The risk of inequity aversion, the feeling of treating others unfairly or of being treated unfairly, occurs particularly when resources have been acquired jointly.  (Schäfer et al. (2015))  

If people feel that they have been short-changed after a collaboration, then they are less likely to want to collaborate with the same individuals in the future.  In other words, fair sharing and respect motivate further cooperation.  Because of the interdependence of human beings, and our need to cooperate together in order to survive, we are sensitive to other-directed inequity aversion: we wish for our cooperative partners to be satisfied with their proceeds (Brosnan et. al. 2014).  

It requires self control to voluntarily give up an advantage to oneself in order to benefit another, fairly.  Humans have large well developed brains that are capable of regulating our immediate behaviour in favour of long term advantages (Sarah E Ainsworth and Roy F Baumeister in Baumard et al.).  





“Impartiality” means adhering to standard procedures without favour or bias towards any particular side.  In an impartial system, each person's human rights are given equal weight, in that each person's need to thrive ethically is respected equally, since after all, each is equally a person.  Each individual’s personhood is respected equally.  

Experimentally, it has been found that we see impartiality as the most basic and important aspect of fairness.  (Niemi et al., 2017)

Recent experimental work has found that impartial behaviour may be motivated by a desire to be, and to be seen to be, unbiased.  Therefore, when evaluating someone's "impartial" behaviour, we can be drawn to evaluate just how biased or impartial they really were.  Since impartiality represents a specific attempt to sidestep personal bias by using a standardised procedure, our psychological demands for fairness are more easily satisfied if impartiality is seen to be done.  (Niemi et al. 2017)  

Role ideals and social norms provide an external, impartial arbiter and standard of behaviour.  (Tomasello)


The hallmark of the human sense of fairness is the idea of impartiality; that is, human fairness or justice is based on the idea of appropriate outcomes applied to everyone within the community, not just a few individuals, and, in particular, not just oneself.  Thus, outcomes are judged against a standard, or an ideal.  There is variation in this ideal across cultures or situations, but there is consistency within a given context.  

Sarah F Brosnan and Frans B M de Waal – “Evolution of responses to (un)fairness”: Science vol 346, issue 6207, 17 October 2014




Evolution of the human sense of fairness

Humans have evolved a sense of other-directed inequity aversion, and this, from a self-interested point of view, is an evolutionary puzzle.  In other words, why do we selfish creatures so strongly protect and care about the needs of others in a sharing situation?  This issue lies at the heart of the human sense of responsibility to others, or “ought”.  

There are many theories about how the human sense of fairness evolved (see, for example, Baumard 2013; Tomasello 2016).  

We propose a similar evolutionary scenario here: cooperation with: 1) interdependence and helping, mutual respect and deservingness; 2) partner choice and partner control.  


Humans are forced to cooperate together to obtain their food, or run a great risk of starvation.  Therefore, for humans, a high degree of cooperation is obligatory.  


The joint agent “we” and joint self-governance

When two people agree to collaborate, their agreement forms a commitment to each other and they become a “joint agent” with a joint goal, joint attention, and joint thinking; and individual roles, sub-goals, and perspectives.  Each identifies with and partially hands over self-control to this governing joint agent, which may be described by the formula “we > me”.  


Roles, role ideals, self-other equivalence, and impartiality

Within a cooperative venture, there are fixed roles to be played, and fixed, ideal standards by which they must be performed if success is to be achieved.  The crucial realisation is that people are interchangeable within these roles – in principle, anyone with the right skills can do the job – and that any person, no matter who they are, has to submit to the same ideal standards or “role ideals”.  Therefore, humans have a sense that we are 1) fundamentally equal in some way; 2) somewhat interchangeable, “just one among many” rather than a unique isolated universe, which is more like the worlds of our other great ape relatives.  This leads to a sense that we are in some sense equivalent with others, and a sense of impartially having to live up to role ideals: hence, impartiality.  

The role ideals of early humans have become, in our present day, social and moral norms.  Role ideals and social norms –  for the role of being a good cooperator – include acting fairly and helping where needed.  


Interdependence and mutual respect

In the evolutionary scenario we are describing, perhaps in the context of collaborative hunting, good partners are valuable.  I cannot go hunting without good partners.  Therefore, together with the sense of self-other equivalence, early humans developed a sense of mutual respect within their collaborative partnerships.  I have the standing to demand respect as a valuable partner, and I respect my own valuable partners.  


Were the human species so framed by nature as that each individual possessed within himself every faculty, requisite both for his own preservation and for the propagation of his kind ... it seems evident, that so solitary a being would be as much incapable of justice, as of social discourse and conversation. ... Where mutual regards and forbearance serve to no manner of purpose, they would never direct the conduct of any reasonable man.  

David Hume – “An enquiry concerning the principles of morals”


The recognition of interdependence is a necessary condition for fairness.  If A does not need B, why should A be fair to B?  And vice versa.  


The interdependent “we”, mutual deservingness, and free riders

Within the members of the interdependent joint agent “we”, “we” agreed to work together to look after each other, but we didn't agree to work together to look after “you”, an outsider.  Again, together with self-other equivalence, and as a result of interdependence (see stakeholder principle), by which the work of each member of the team is valuable to every other, there arose in early humans a sense of the mutual deservingness of all other team members.  “You are helping me, and so you deserve for me to help you.”  

Free riders were not part of the team and therefore contributed no effort and receive no “affection” in the form of rights to a share of the proceeds.  



Proportionality – dividing proceeds strictly proportionally to the contributions made to the effort used to obtain them – may well have evolved later in history as it is a more businesslike and less personal way of distributing goods and burdens.  It is more at home in large anonymous populations where people are not so personally interdependent with each other, and where after an exchange, two partners may have no further opportunity for reciprocity.  Proportionality may be thought of as a form of “partner control” that effectively prevents partners from exploiting us or being exploited themselves.  It is a form of reciprocity or contingent cooperation (my cooperation depends on your cooperation).  

See also: reciprocity; unconditional love


Sharing in early humans

Many modern hunter gatherer societies practice a high degree of sharing “on demand” (Gurven 2004, Smith 2018, Smith 2019).  We are certain that the earliest humans, from around 2 million to 0.5 million years ago, were cooperatively breeding scavengers.  Scavenging requires sharing peacefully between all those present at the carcase, because a coalition of individuals is needed to scare off scavengers of other species, and plausibly, any dominants and food hogs among the people would have been rejected.  We also believe that self-domestication had taken place by this stage, following the invention of stone tools and the arising of pair-bonding leading to the removal of the great ape dominance hierarchy.  Cooperative breeding would have required a high degree of sharing on demand.  With evidence of early hunting, from around 5 hundred thousand years ago, there is also evidence of bringing large game back to a central location for on-demand sharing (Stiner 2009): for example, many of the cut-marks on the bones are haphazard and amateurish, suggesting something of a free-for-all.  


Responsibility to others  

A sense of fairness carries with it a sense of “ought”.  We feel that we “ought” to be fair.  

Responsibility to others is commanded by a larger governing body than the self: i.e. the joint agent “we”.  Cooperating with others is a risky business – the others might let me down – and trust comes in two forms: 1) “strategic” trust where each partner knows what is rational for each other to do, in order to achieve success; 2) “normative” trust where each partner makes an explicit agreement or commitment to cooperate, and is then bound by this commitment.  If I fail to stick to the commitment, my cooperative identity (both social and personal) is at stake.  

The agreement to cooperate generates a joint agent “we” that has a joint goal, joint intentions, joint thinking, individual coordinated roles, and individual perspectives.  I identify with “we” because this is in keeping with my cooperative identity.  It makes sense for me to at least partly relinquish personal control to the governing “we”, so I internalise a feeling of “we > me”.  As “we” is made up of “me” and “others”, I interpret this as a responsibility to others.  The responsibility is to fulfill the role ideals of the task (see above) and to be a good cooperator all the way through the collaboration until the end.  


The original supraindividual entity that early humans were able to create was the "we" established by a joint commitment between two collaborative partners.  ... Each individual intentionally invites the other, in the open, to make plans, even risky plans, around the fact that she will do X – to trust that she will persist in pursuing X, ignoring fatigue and outside temptations, until both of them are satisfied with the result [1]; to believe that she may proceed without fear of failure due to his lassitude or negligence [2]; and in general, to depend on him.  And crucially, joint commitments can be terminated only by some kind of joint agreement as well.  One partner cannot just decide she is no longer committed; she must ask the other to end the commitment, and the partner must accept [3].  Joint commitments are joint all the way down.  

Michael Tomasello – “A Natural History of Human Morality”


Original references:  

[1]  Friedrich, D and N Southwood.  2011.  Promises and trust.  In H Sheinman, ed., Promises and agreement: Philosophical essays (pp. 275-292).  New York: Oxford University Press.  

[2]  Scanlon, T M.  1990.  Promises and practices.  Philosophy and Public Affairs, 19(3), 199-226.

[3]  Gilbert, M.  2011.  Three dogmas about promising.  In H Sheinman, ed., Promises and agreement: Philosophical essays (pp. 80-109).  New York: Oxford University Press.  


Social norms and the social contract

As groups grew larger, and cooperation and interdependence became more widespread throughout human social life, it is possible that these original commitments to uphold collaborative role ideals became culturally, over time, the social contracts to uphold moral and social norms that we see today.  


Partner choice and partner control

In order for someone to choose me and be able to trust me as a cooperator, I need to have a good cooperative identity: a good track record of cooperating well.  My social cooperative identity, how I am seen by others as a cooperator, is my reputation.  If I am not a good cooperator, including behaving fairly, then my personal and public cooperative identities will suffer.  

On behalf of the governing “we”, we all monitor ourselves and others in order to check that we/they are fulfilling cooperative norms and role ideals.  An atheist might say that this is externalised as God, and internalised as the conscience and moral sense.  


“Ought” and the logic of interdependence

Because we are interdependent with others, and therefore I need the help of others, it is “cooperatively rational” (Tomasello 2016) for me to help those others upon whom I depend.  Therefore, helping others when needed has become a human “ought”.  

If we examine the map of cooperation (small groups) then we can see a clear “association of normativity” stretching from “obligate interdependence” through “joint goal”, “joint commitment” and “upholding role ideals” to “governing self and others”.  



A study of Agta hunter-gatherers in the Philippines found experimentally that a quarter of sharing in this group is done in response to need.

From: Jaeggi, Adrian V and Michael Gurven – “Natural Cooperators: Food Sharing in Humans and Other Primates”:  Evolutionary Anthropology 22: 186-195 (2013)


Many modern hunter-gatherer groups are known to have a fiercely egalitarian ethos, with food, and the few portable possessions, being shared on demand (Gurven 2004, Woodburn 1982), and “levelling mechanisms” employed to cut dominant, aggressive, assertive or competitive people down to size, including public ridicule, desertion, or even assassination (Boehm et al. 1993).   

Egalitarianism means the ethos of treating one’s fellows as equals.  (see also: self-other equivalence)  


Were there a species of creatures, intermingled with men, which, though rational, were possessed of such inferior strength, both of body and mind, that they were incapable of all resistance, and could never, upon the highest provocation, make us feel the effects of their resentment; the necessary consequence ... is that we ... should not, properly speaking, lie under any restraint of justice with regard to them.  ... Our intercourse with them could not be called society, which supposes a degree of equality; but absolute command on the one side, and servile obedience on the other.  

David Hume – “An enquiry concerning the principles of morals”


For a human sense of fairness to evolve, it was necessary to remove the great ape dominance hierarchy based on fighting ability.  See: domestication of the human race.  “Might is right” is the opposite of fairness.  Fairness requires a lack of force, bullying or coercion: each person has to be happy with what they have received, that their right to thrive ethically has been respected impartially, just because they are a human being.  

Fairness is possible within the dominance hierarchies we see in society today (Baumard et al.).  People do not have to lose their human rights, no matter where they are in the hierarchy.  

If fairness is about distributive justice, it is also about respect.  Equality of rights – distributing respect, and recognising dignity, so that all concerned may be satisfied – is a counterpart to distributive fairness that emphasises helping in response to the need to thrive.  


Rights do not exist in a vacuum.  They are the creation of law, which is a product of social organisation, and is therefore necessarily a matter of political choice.  So, when we speak of some rights as being inherent in our humanity, we are not really saying anything about the nature of humanity.  We are making a personal moral judgement that some rights ought to exist because they are so fundamental to our values, and so widely accepted, as to be above legitimate political debate.  Almost all of us believe that there are some rights in that category.  But the idea only works if the rights in question are truly fundamental and generally accepted.  If there is room for reasonable people to disagree about them, then we need a political process to resolve that disagreement.  In that case, they cannot be above legitimate political debate, except in a totalitarian state.  

There are probably only two categories of right that are truly fundamental and generally accepted.  First, there are rights which are fundamental, because without them life is reduced to a crude contest in the deployment of force.  So we have rights not to be arbitrarily detained, injured or killed.  We have equality before the law, and recourse to impartial and independent courts.  Secondly, there are rights without which a community cannot function as a democracy.  So there must at least be freedom of thought and expression, assembly and association, and the right to participate in fair and regular elections.  Of course, democracies should confer many more rights than these.  But they should confer them by collective political choice, and not because they are thought to be inherent in our humanity, or derived from some higher law.  

Jonathan Sumption – Reith Lectures 2019, BBC Radio 4, 4 June 2019 – 3/5: “Human Rights and Wrongs”




Fairness and cooperation

Sharing fairly after a collaborative activity provides motivation for further cooperation.  People do not want to collaborate with a bully or a hog who takes a disproportionate amount of the fruits of a collective labour for themselves.  Instead, they expect to be rewarded fairly.  

Humans are the only great apes that collaborate to any great degree in order to obtain food.  In experiments, it has been found that three year old children share resources equally with each other much more easily (75% of the time) after earning them through a joint collaboration, than through an unearned windfall (25% of the time) (Hamann et al.).  In contrast, chimpanzees are equally likely to (not) share under either condition (Melis et al. 2011).  Chimpanzees do not collaborate in order to obtain food, except in the case of hunting for monkeys, in which case the largest shares go to whoever is nearest to the kill, or begs the hardest; or some sharing is done reciprocally with coalition partners (Tomasello).

These results make it plausible to say that fairness, as distributive justice, may well have evolved within the context of sharing the spoils after collaboration in such a way that all the partners were satisfied.  This makes sense if we consider that each partner has contributed an appropriate amount of effort, resources, skill, commitment etc. to the process of reaching the joint goal, and therefore wants to see the best possible return on their investment.  

Each person wants to maximise the benefits for themselves, but through a combination of mutual respect (as interdependent, necessary, competent partners), mutual deservingness (as fellow helpers and non-free riders), self-other equivalence and impartiality (through interchangeability of persons within fixed roles, with ideal standards that must be performed by anyone), and joint self-governing by the joint agent "we", partners with a well developed sense of fairness will want to maximise the benefits all round and prevent self- and other-directed inequity aversion.  

Fairness can be seen as a cooperative distribution of benefit and harm.  




Reducing competition

Fairness is a way to reduce competition – and reducing competition is one of the primary challenges of a cooperatively social species.  Inequality tends to increase competition (including in the form of hierarchy) because one person has control of more resources than another: there is an imbalance from the point of view of natural selection, and natural selection works on the advantage of the individual organism relative to its peers.  




John Rawls, justice as fairness, and the veil of ignorance  

Distributive justice in this case refers to a nation state dividing resources among its subjects.  

Rawls defined primary goods as: 1) liberties; 2) opportunities; 3) income and wealth.  

John Rawls' theory takes the form of a thought experiment, and states that the fairest way to divide resources in an ideal state would be from behind an impartial "veil of ignorance" whereby each of us does not know anything about what we would be like in the hypothetical society, or what position we may occupy – rich or poor, high or low, fortunate or unfortunate.  So he imagines that it is rational for each of us to want the worst off to be taken care of, and consequently, that rational people would design a "floor constraint" – a restriction on how little people would receive, so that nobody has to be too poor.  The point of view is therefore that of the worst off.  (Shapiro)

Here we see a (hypothetical) implementation of the Golden Rule – “I will treat others as I would wish to be treated”.  

Experimental results

There is evidence that in situations where different values of fairness conflict, people make a trade-off between them on a case-by-case basis.  In experimental games simulating distributive justice, it has been found that people prefer to maximise the average income while maintaining a good level for the worst off.  (Frohlich)




Forms of justice

Justice comes in a number of forms:  




Fairness and respect

To treat someone with respect means to treat them as an equal, i.e. as as much a person as you are, i.e. as much deserving of empathic concern and their own ethical thriving as you are.  Therefore it means to respect and value their need to thrive, and the way in which this thriving matters to them.  See: the Healing Principle, personhood.  Therefore, to treat someone with respect means that they are to receive the maximum benefit and minimum harm available to them.  In what circumstances?  At least, when my action affects them.  In effect, this is helping in response to the need to thrive.  In turn, this means that helping has to be proportionate to need: the more in need someone is, the more helping they require in order to thrive as much as someone less in need.  

If I treat someone a certain way, then it logically follows that my action(s) affect(s) them.  It also is often the case that more than one person is affected by my action(s).  If we take the set of people affected by my actions(s), and treat each one with respect, it means that each person, including myself, is to receive the maximum benefit and minimum harm available to them.  Therefore each person in a given situation can reasonably be satisfied with their allotment of goods and burdens, and this is one definition of fairness.  

Being treated fairly is to feel that one has been treated impartially and with respect.  To be treated unfairly means to feel that one has been shown a lack of respect.  





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Brosnan, Sarah F and Frans B M de Waal – “Evolution of responses to (un)fairness”: Science vol 346, issue 6207, 17 October 2014

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

Haidt, Jonathan – “The Righteous Mind – why good people are divided by politics and religion”

Hamann, Katharina; Felix Warneken, Julia R. Greenberg and Michael Tomasello – “Collaboration encourages equal sharing in children but not in chimpanzees”: Nature vol 476, 18 August 2011

Jaeggi, Adrian V and Michael Gurven – “Natural Cooperators: Food Sharing in Humans and Other Primates”:  Evolutionary Anthropology 22: 186-195 (2013)

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Kaplan, Hillard; Kim Hill – “Food Sharing among Ache Foragers: Tests of Explanatory Hypotheses” – Current Anthropology Vol. 26, No. 2, April 1985

Lewis, Hannah M; Lucio Vinicius, Janis Strods, Ruth Mace, and Andrea Bamberg Migliano – “High mobility explains demand sharing and enforced cooperation in egalitarian hunter-gatherers” – Nature Communications, 16 December 2014

Melis, Alicia P; Anna-Claire Schneider, Michael Tomasello – “Chimpanzees, Pan troglodytes, share food in the same way after collaborative and individual food acquisition” – Animal Behaviour (2011), doi:10.1016/j.anbehav.2011.05.024

Niemi, Laura; Emily Wasserman and Liane Young – “The behavioral and neural signatures of distinct conceptions of fairness”: Social Neuroscience 2017

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Shaffer, Leah – “Is a More Generous Society Possible?”: sapiens.org, 21 Feb 2019  https://www.sapiens.org/culture/ik-people-generosity/

Shapiro, Ian – “The Rawlsian Social Contract” lecture from the Yale University course “Moral Foundations of Politics” (PLSC 118)  https://youtu.be/6uV3p9bMD4I

Smith, Daniel; Mark Dyble; Katie Major; Abigail E Page; Nikhil Chaudhary; Gul Deniz Salali; James Thompson; Lucio Vinicius; Andrea Bamberg Migliano; Ruth Mace – “A friend in need is a friend indeed: Need-based sharing, rather than cooperative assortment, predicts experimental resource transfers among Agta hunter-gatherers”: Evolution and Human Behavior 40 (2019) 82-89

Smith, Kristopher M; Tomás Larroucau; Ibrahim A Mabulla; Coren L Apicella – “Hunter-Gatherers Maintain Assortivity in Cooperation despite High Levels of Residential Change and Mixing”:  Current Biology 28, 1-6, October 8, 2018

Spikins, Penny – “How Compassion Made Us Human – the evolutionary origins of tenderness, trust and morality”

Starmans, Christina; Mark Sheskin, and Paul Bloom – “Why people prefer unequal societies”: Nature Human Behaviour vol 1, article number 0082

Stiner, Mary C; Ran Barkai; Avi Gopher – “Cooperative hunting and meat sharing 400-200 kya at Qesem Cave, Israel”: PNAS, August 11 2009, vol. 106, no. 32, 13207-13212

Tomasello, Michael – “A Natural History of Human Morality”: Harvard 2016

Tomasello, Michael (2018) – “Response to commentators”, Philosophical Psychology, 31:5, 817-829

Wilson, Edward Q – “The Moral Sense”  

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