The theories of Darwin and Wallace were similar, both seeing evolutionary change coming about as a function of a differential reproduction fueled by the pressure to succeed in the struggle for existence.  Darwin and Wallace came to their thinking independently.  The behavior of both men, in what could have been a tense situation, was exemplary.  Wallace sent his paper to Darwin, a postal journey from the Far East to England that took far longer than people expect.  This has led to beliefs that Darwin sat unfairly on the paper, perhaps using it to burnish his own work.  In truth, upon its receipt, Darwin quickly contacted his senior friends Lyell and Herschel, offering to let Wallace have full priority.  Lyell and Hooker arranged for Wallace’s paper and unaltered, pertinent abstracts of Darwin’s earlier writings to be published together in the journal of the Linnaean Society.  Both Darwin and Wallace always felt that matters had been dealt with speedily and honorably.  That said, there were significant differences in the thinking of Darwin and Wallace.  The latter was never comfortable with the metaphor of selection, he always embraced group selection in opposition to Darwin’s determined individual selectionist thinking, and most famously – notoriously – Wallace turned to spiritualism to explain human evolution, spurring Darwin to give an entirely naturalistic explanation is his Descent of Man.

Humans are complexly social and exceptionally cooperative. Human behavioral ecology has been successful by explaining small-scale dyadic cooperative interactions like food sharing using standard theoretical perspectives of kin selection and reciprocity. Such models have been enhanced with additional ideas including mutualism, partner choice, costly signaling, competitive altruism, and biological market theory. Concepts such as stake, interdependence, and need-based support have provided additional predictive power. While these tools have been effective at explaining face-to-face cooperative relationships, their inability to explain the large, complex social groupings typical of human societies has led researchers to look to new models of multilevel and cultural group selection theory for solutions. Culture plays a key role in structuring human sociality and facilitating group selection by reducing behavioral variation within groups while increasing variation among groups. Gene-culture coevolution can favor psychological propensities like conformist bias that assort people into symbolically marked groups of trusted partners with shared identities and normative ways of organizing cooperative life. Societies whose cumulative culture maintain institutions that encourage magnanimity and coordination between members achieve collective action benefits unobtainable otherwise and outcompete other groups whose institutions fail to organize their members in ways that lead to cooperative outcomes at scale.

● Darwin invented the concept of group selection to explain the evolution of traits that lead individuals to improve the fitnesses of others at a fitness cost to self. Such traits are now called “altruistic.” ● Understanding Simpson’s paradox is key to understanding how natural selection can cause altruism to increase in frequency in a meta-population. ● A criterion is derived for when altruism is fitter than selfishness in a meta-population in which there are groups of size 2. The relevance of correlation and genealogical relatedness to the evolution of altruism is discussed, as is the question of whether reciprocal altruism is really a form of selfishness. ● The concepts of cultural group selection and species selection require further refinements in how group fitness needs to be understood. ● In addition to individual selection and group selection, there is a third unit of selection – intragenomic conflict. Meiotic drive is a classic example. ● The reductionist thesis that group and individual selection reduce to selection on genes is criticized, as are conventionalist theses that assert that it is a matter of convenience, not biological fact, whether group selection occurs in a population.

This chapter argues that Darwin's thought plays a central role in the history of the conscience and that the history of the conscience plays a central role in Darwin's thought. A core project of his later works is to show how the human moral faculties could have evolved, since such a faculty seemed to pose a decisive objection to the theory of natural selection. But the theory of group selection Darwin developed to explain the origins of morality had the inadvertent effect of inducing skepticism about instinctive moral feeling. Such skepticism transformed Western moral thought: although appeals to moral “intuitions” and naturalistic theories of ethics would return, after Darwin's analysis of the conscience never again could the bare fact of moral feeling offer evidence of the divine design of humanity. In ways thinkers are still considering, Darwin forced moral philosophy to confront its fundamental earthliness.

The term ultrasocial refers to those complex human and social insect societies that actively manage the cradle-to-grave production of the food they depend on. Contemporary theoretical concepts in evolutionary biology – including group selection, epigenetics, and social evolution – help to understand the transition to ultrasociality. Twentieth-century biology was dominated by a gene-centric view of evolution and natural selection. Today, biologists and social scientists are applying the basic principles of Darwinian evolution – selection, variation, and inheritance – at multiple levels. The recognition that Darwinian natural selection need not be gene based opens the door for a rigorous analysis of the common factors in the transformative evolution of humans and social insects that came with agriculture. Concepts of group selection can be successfully applied to understand how and why differentiated social structure and social complexity evolved. For humans and other ultrasocial animals, the evolution of complexity was propelled by their ability to produce surplus food. Basic economic laws drove the evolution of this major evolutionary transition.

Some 10,000 years ago, agriculture arose independently in several areas across the world. The causes of the agricultural transition are still debated, but it is likely that the unprecedented warmth and stability of the Holocene climate made agriculture possible and that the climate instability of the Pleistocene made it impossible. As the weather became more predictable, people began to more intensively manage wild plants and began to store the grain they collected. Because of the unpredictability of harvests, people cultivated more crops than they thought they would need, and in most years, there was a surplus of food, leading to larger and more concentrated populations. By 5,000 years ago, small-scale agriculture had led to large-scale state-managed economies and total dependence on agriculture. Competition between city-states gave us full-blown ultrasocial economies and hierarchical, repressive states. Other consequences of agriculture for individuals include a marked decline in physical health, a reduction in brain size, and a loss of individual autonomy.

This chapter offers some suggestions on how reciprocity might be used to justify specific policy directions. For instance, so long as salaries remain the predominant form of remuneration for public sector employees, performance incentives – both positive and negative – might be beneficial so long as all parties accept that the chosen indicators of good and bad performance are appropriate and deem the corresponding performance-related compensation/penalties as fair. Moreover, insofar as reciprocity is entwined with reputational concerns, a reputational model of governance that threatens to punish bad absolute performance and that supports the implementation of good practice is recommended. Relatedly, group selection theory implies that providing the conditions for reputational competition across regions in relation to public sector services may incentivise cooperation and more innovation within each region, generating lessons that could be shared across regions. Furthermore, given that people naturally reciprocate, framing messages with this fundamental motivational force is worthy of consideration when trying to secure individual behaviour change.

This chapter aims to consider how deep reciprocity lies in humans, by looking at some of the evidence on how tribal communities live. Although extant tribal communities have invariably been touched by the modern world, they perhaps offer a reasonable approximation of the practices conducted in human hunter-gather societies for tens of thousands of years. Reciprocity – in both its positive and negative forms – is of fundamental importance to the functioning of tribal communities. Here, people reciprocate over almost everything – e.g. through sharing meat, childcare responsibilities, wisdom etc. – and within and between communities, gifts are used to bind and obligate. Moreover, the threat of negative reciprocity discourages the transgression of social norms and attempts to exert power. In tribal communities, it is likely that reciprocity evolved organically for the good of the group, but as societies became larger and more atomised, creating opportunities for people to act on egoistic motivations with less fear of detection, a form of social contract was perhaps needed to nurture and sustain the socially beneficial norm of reciprocity.