R2. What is ultrasociality?

There is no generally accepted definition of ultrasociality. We chose a modified version of one proposed by Donald Campbell because we wish to focus on the fact that the agricultural transition marked a sharp, clear, and radical break with the past – so much so that agricultural groups themselves, as well as group-level traits related to food production, comprise the units of selection. It is important to make a clear distinction between ultrasociality and sociality. We realize the difficulty in defining ultrasociality and clearly demarcating it from prosocial behavior. We also consider the objections to our claim that ants, humans, and termites that practice agriculture evolved productive configurations that made all three similarly ultrasocial. We define ultrasociality so as to place it in the context of economic life. We emphasize that ultrasociality has led to the social conquest of Earth, and an interdependence forged through the complex division of labor necessary for agriculture, and thus also led to the expansionary economic dynamic that remains with us today.

Our discussion of ultrasociality is grounded in theories of multilevel selection (MLS; see sect. R3), theories rejected by several commentators. We carefully discussed our definition of ultrasociality, recognizing the lack of consensus over the term. Yet Vranka & Bahník declare that “ultrasociality is reached by groups of autonomous individuals who are able and motivated to seek their own self-interest.” Likewise, Kovaka, Santana, Patel, Akçay, & Weisberg (Kovaka et al.) assert that “individualist models are better suited than the second type of multilevel selection [MLS2] to shed light on the puzzles associated with the human transition from foraging to farming.” These views reflect a reductionist philosophy, reflected in neoclassical economic theory, and apparently in contemporary psychology (Kesebir Reference Kesebir2012) that the group is never more than the sum of its individual parts. This is exactly what we are arguing against in our presentation of ultrasociality.

Several commentators (Carpendale & Frayn; Grotuss & Beard; Houdek, Petr, Novakova, & Stastny [Houdek et al.]; Krasnow; Levine; and Rusch & Voland) assert that we fail to acknowledge the sociality of pre-agricultural humans. In fact, in our target article, we fully appreciate the antecedents to ultrasociality in hunter-gatherer societies, such as the division of labor (sect. 3.2), cooperation with non-kin, and caring for others (sect. 5.2) present in the Pleistocene if not earlier. We more extensively discuss the pre-adaptations that facilitated ultrasociality in two earlier papers (Gowdy & Krall Reference Gowdy and Krall2013; Reference Gowdy and Krall2014). In particular, see Gowdy and Krall (Reference Gowdy and Krall2014), section 4, “The co-opting of cooperation.” Were hunter-gatherers exceptional in their degree of sociality? Of course, as we state repeatedly in our work. Humans became compassionate and empathetic, employed a division of labor, lived with non-kin, and so forth, before agriculture. But we argue that the ability to cooperate and share with unrelated individuals was co-opted with agriculture and became a matter of almost mechanistic coordination and subjugation to authority, with limited room for individual agency compared to hunter-gatherer social organization.

We are puzzled by the failure of several commentators to appreciate the difference between hunting and gathering and agricultural state societies. Individual humans were “social” as members of hunter-gatherer bands and “social” in large-scale state empires. Why does this imply that the economic and social characteristics of these two radically different forms of social organization, and the place of individuals within them, were the same? Krasnow errs when he simplistically asserts that because “the social world of … our hunting and gathering ancestors was complex” our argument is refuted. Again, our point is not to deny the sociality of pre-agricultural peoples but rather to point out that the nature of sociality changed profoundly with the onset of agriculture. With agriculture, human economic structure took a form strikingly similar to that of agricultural insects. Humans became more materially interdependent, and it became necessary to support a greater non–food-producing population. Production of surplus was an inherent aspect of the altered configuration of society.

A basic confusion on the part of several commentators is a failure to recognize the difference between individual behavioral characteristics (e.g., altruism, cooperation) and group behavioral characteristics, which we deem ultrasocial (e.g., extremely complex division of labor and extensive interdependency around an “internalized” system of food production, ecosystem domination). The extent of differentiation and cohesion around food production created a qualitatively unique “group” having an evolutionary force of its own. The productive reconfiguration of society that came with agriculture is an important matter, and little attention has been paid to this radical change in the evolution of human society.

Levine maintains that our definition of ultrasociality “obviates the possibility of comparing human sociality with that of chimps, and draws an excessive dichotomy between human foragers and agriculturalists.” We obviously do not agree with Levine that “comparisons of shared (homologous) and derived characteristics among closely related species would be far more relevant and instructive for understanding the issues at hand.” Having said that, our discussion of ultrasociality in no way prevents comparisons of sociality in humans and other primates.

Studies of primate behavior have greatly enriched our understanding of human behavior. But consider this thought experiment: Suppose we discovered, deep in the Congo, a chimpanzee society with complex agriculture, including the sophisticated use of antibiotics and monoculture, social classes, highly organized warfare with other agricultural chimp groups, cities, a sophisticated communications network, and so on. Such a discovery would shake the foundations of the human sciences. Why are ants and termite societies with these similar characteristics relegated to the category of mildly interesting analogies with little relevance to human society?

We fail to understand the logic beyond Vranka & Bahník's blanket assertion that, because we acknowledge the difference between humans and social insects, “any knowledge of ultrasocial insects cannot be reliably applied to humans.”

A final point in this regard: Several of the commentators assert that the similarities between ants and humans are merely coincidental and not much more. Levine comments: “The problem with the analogies presented here is that they do nothing more than illustrate the general point that very different organisms may develop more or less similar solutions to the contingencies of life.” His comment is also repeated in one way or another by Houdek et al. who claim our analogy is merely “coincidental.” The most concrete manifestation of our sociality is found in the way we configure ourselves to alter the external world in order to meet our material needs. It is not clear to us why there is a tendency to discount the importance of this matter in the evolutionary matrix. Radically different species developing similar solutions to the contingencies of productive life means that they all have a capacity to do so. This is not to deny that the mechanisms for reconfiguring productive life might be unique for different species. Nonetheless, the configuration of productive life is an intimate and significant expression of the social life of a species, and the fact that diverse species come to configure themselves so similarly with agriculture cannot be a mere coincidence. In fact, it illustrates the importance of the productive configuration of a species in the determination of species life.

R3. Group selection is essential to explain the origin of ultrasociality

Several commentators focused on why they think group selection does not exist or is of no use in explaining human ultrasociality (Kovaka et al.; Krasnow; Stith & Vigil; and Sheskin, Lambert, & Baumard [Sheskin et al.]). Models of individual selection are thought by these critics to be more incisive in explaining it. We are convinced that social evolution cannot be understood without considering groups and group traits as units of selection (see commentaries by Ainsworth, Baumeister, & Vohs [Ainsworth et al.]; Farley; Goodnight; and Wilson; also see studies by Baumeister et al. [2016]; Richerson et al. [2016]; Smaldino [2014]; Wilson et al. [2014]).

We agree with Goodnight that the arguments for evolutionary mechanisms beyond the level of the gene are convincing. We are convinced that the rapid growth of state societies after the onset of agriculture was the result of competition between groups.

Group selection (and MLS) has been extensively debated in the pages of this journal at least since the seminal article by Wilson and Sober (Reference Wilson and Sober1994), a paper instrumental in resurrecting the group selection debate (see, e.g., Baumeister et al. Reference Baumeister, Ainsworth and Vohs2016; Richerson et al. Reference Richerson, Baldini, Bell, Demps, Frost, Hillis, Mathew, Newton, Naar, Newson, Ross, Smaldino, Waring and Zefferman2016; Smaldino Reference Smaldino2014; Wilson et al. Reference Wilson, Hayes, Biglan and Embry2014). We see no need to repeat the extensive discussion from the previous BBS articles and commentaries. Our work demonstrates that the argument that individual fitness is the sole currency of natural selection is a misleading simplification. For a detailed discussion of the current state of the multilevel selection debate, see Jablonka and Lamb (Reference Jablonka and Lamb2014) and D. S. Wilson (Reference Wilson2010).

It is important to be wary of frameworks that eliminate any possibility of considering a level of selection apart from the individual. For example, Stith & Vigil want to focus on “individual optimization models.” They say the focus should be competition among humans, whereas we stress the evolution of the whole system, not just isolated parts. They assert that it is “unclear which convergent evolutionary selection forces would have resulted in both complex human behaviors and behaviors found in a select handful of insect species.” By contrast, our target article is clear that the convergence in these species resulted from the similar economic forces driving the expansion of surplus production.

Likewise, Kovaka et al. accuse us of misusing MLS2 and claim that individualistic models are more appropriate. Their assertion is that units of selection must exhibit reproductive specialization in members of those units. Clearly, we do not agree with this requirement.

Sheskin et al. argue that “biological markets” explain the formation of large-scale societies. According to these authors, “Large-scale societies spread not because they contain individuals whose prosocial behaviors entail sacrificing their own welfare for the benefit of the group, but because they contain individuals whose prosocial behaviors entail access to cooperative opportunities that increase their own fitness” (emphasis Sheskin et al.'s). For this reason they claim that “individuals in large-scale societies have higher average fitness.” This is a variation of inclusive fitness: the idea is that individuals selfishly maximize their own well-being by being prosocial because prosocial behavior increases their chance of survival. The problem with this explanation is that it begins with the assumption that the individual is the only proper unit of analysis and that humans voluntarily engage in productive activity together – it is a matter of rational individual choice. Our analysis takes a more critical look into the black box of agricultural production.

We are baffled by Kovaka et al.'s assertion that “The rate of migration between human groups is high enough to prevent sharp genetic or cultural demarcation of one group from another, which reduces the potential for them to act as distinct evolutionary units.” There are obviously sharp cultural distinctions between human groups, and there exists a vast literature on group trait differences and their evolutionary impacts. (The work of Peter Turchin is one example: see Turchin Reference Turchin2006a; Reference Turchin, Richerson and Christiansen2013; and his project on “cliodynamics” available at:http://peterturchin.com/cliodynamics/.)

The commentaries on “fitness” and “well-being” clearly illustrate the importance of D. S. Wilson's (Reference Wilson2014) admonishment to be clear about the hierarchical level of the functional analysis. Darwinian fitness applies to a population, while “well-being” is a human construct applying to individuals.

Kovaka et al. erroneously claim that we conflate the distinction between fitness and well-being. Contrary to their misreading of our target article, we clearly distinguish between Darwinian fitness and individual well-being. Agriculture gave ants, humans, and termites a tremendous advantage in Darwinian fitness because it gave them the ability to produce their own food. Once agriculture was established, other derivative forms of complex social organization, like raiding agricultural societies for food and slaves, became possible (see Lyon & Caporael's commentary). We focus our discussion on changes in human individual well-being and not Darwinian fitness. A group can become more “fit” and still leave the average individual in the group worse-off. Of course, we recognize that “well-off” and “worse-off” are human judgment calls. But most people would agree that a decline in individual health and physical fitness makes a person worse-off. Individuals in agricultural groups have less productive autonomy with regard to food provisioning than individuals living as hunters and gatherers. Whether this bothers ants or not, we cannot say. But for humans, it is problematic because the engagement with the external world to reproduce material life is a creative activity demanding skills and executive functions that became more limited for most people. In this sense, the autonomy and integrity of the individual human is greatly compromised with agriculture; humans became creatures fighting thistles and weeds and working like draft animals for many hours a day. With agriculture, we became inured to a diminished life. None of this was likely apparent at the time-scale of the individual as things were unfolding. The transition was not a matter of rational choice, and neither did it diminish fitness in a biological sense.

Historically, social scientists have been shut off from the benefit of evolutionary thinking because of the justifiably bad reputation of crude socio-biology (Wilson). We intend to reclaim the domain of evolution in social science, and our thesis is that economic configuration can be a target of selection. We do not claim that there is a loss of Darwinian fitness in the transition to agriculture. On the contrary, we point out that the active management of food supply gives a species a tremendous evolutionary advantage that leads to ultrasociality. It might still be the case that the percentage of males who reproduce could decline with the onset of agriculture as more men are relegated to defense and subordination to those in authority (Betzig Reference Betzig2014).

Contrary to Sheskin et al., we do not argue that agriculture resulted in “evolutionary costliness to an individual.” Individuals do not evolve; populations evolve. Sheskin et al. claim that separating quality-of-life costs from fitness cost is important and that we have conflated them. They maintain that only fitness costs matter for natural selection. The former is an inaccurate reading of our target article, and the latter is confused. They claim that our over-reading of the cost to the individual (by conflating fitness and quality of life) leads us to invoke group selection. This too is not a correct reading of our nuanced argument. We are well aware that fitness, as it is defined by biologists, refers to reproduction of genes, and that in humans, with agriculture, we get the successful reproduction of genes, but the quality of life goes down on average. Superficially, it seems odd that cultural practices are adopted make life more difficult for most individuals, but our point is that individual decision making is not the driving force in the evolution of the ultrasocial group. Again, with multilevel selection the analysis should focus on the level of the phenomenon being examined. The structure of economic life (that changed dramatically with agriculture) is not properly understood as a matter of individual decision, but it does provide an altered context in which decisions are made. Once again, our purpose in invoking group selection is to demonstrate that an altered group formation took hold with agriculture. Of course, it is based on the potential of the species to be altered (e.g., the preexistence of prosocial behavior). But the alteration that took hold with agriculture is a case of emergent characteristics that coalesced to make a new system. The extensive division of labor, economies of scale, coevolutionary success with annual grains, and a huge stock of soil carbon, in addition to the Holocene warming and all of the prosocial traits that had already evolved in humans, are all ingredients that mix together to emerge with an altered configuration of food production that makes the species expansionary and interdependent in a way that it had not been before.

R4. The false allure of human exceptionalism

Perhaps the most contentious part of our target article for the commentators is our claim that the evolution of human ultrasociality is a consequence of the same mechanistic (i.e., not consciously directed) evolutionary forces that govern other species. It is disturbing to consider that “mindless” creatures like ants can duplicate complex aspects of human social structure. We began with the observation that the configuration of ant and human agricultural societies are very similar and then focused on outcomes (ecosystem domination, complex division of labor, the subjugation of individuals for the group goal of surplus production), rather than individual intentionality. Similar outcomes in insect and human ultrasocial systems suggest common drivers of social evolution independent of intentional behavior and planning. Ultrasociality challenges the notions of human exceptionalism and intentional behavior at the individual level, and at the level of society.

Darwin's heretical idea was that humans are subject to the same evolutionary forces and natural laws that govern the evolution of other species. As economists, we have throughout our careers challenged the notion of many of our fellow economists that human ingenuity and the human institution of markets will solve any environmental or social problem. The notion that humans are unique should not overshadow the simultaneous reality that the similarities between humans and other unrelated species have amounted to something significant in the course of evolution. Sheskin et al. assert that humans have a “moral psychology … not present in even our closest evolutionary relatives.” Williams & Bliss-Moreau make a case that human emotions are unique in the animal kingdom. Carpendale & Frayn argue that humans are unique in their ability to consider their patterns of interactions with others. It is easy to see human history as a story of progress and perfectibility based on individual initiative and the ability to plan for the future (Kovaka et al.; Ross; Sheskin et al.). But others argue that our moral capacity often makes the world worse, through, for example, “righteous violence” (Fiske & Rai Reference Fiske and Rai2015).

The strong cultural belief in western societies in the primacy of individual choice leads to an exaggeration of the ability of individual humans to control their own destiny and the destiny of human society. This is expressed in technological utopianism (Ross) and in an exaggerated belief in social mobility (Sheskin et al.; Vranka & Bahník). Sheskin et al. fail to grasp the meaning of “totipotency” as discussed in our target article. There are more ways in which a person can make a living in large-scale societies but the opportunity for a particular individual to choose an occupation is severely constrained, particularly in the highly stratified early state societies (Betzig Reference Betzig2014). The ability of individuals to choose occupations, even in modern western democracies, is greatly exaggerated in the popular imagination. In a study of social mobility, the economist Gregory Clark found that societies as different as communist China, the United States, and Japan, are characterized by low social mobility rates and these rates are resistant to social policies. Clark (Reference Clark2014, p. x) writes: “Having for years poured scorn over my colleagues in sociology for their obsessions with such illusory categories as class, I now had evidence that individuals' life chances were predictable not just from the status of their parents but from that of their great-great-great grandparents.” Contrary to Vranka & Bahník's confusing assertion that people are able to “choose the group to which they want to subjugate themselves,” social mobility is limited even in progressive Western societies, and much more so in the rigid caste systems that prevailed for most of the past 10,000 years.

The uniqueness of human intentionality is also being challenged by another line of research stretching the notion of “intentionally” to include not only non-human sentient species, such as the other primates, whales, dolphins, and elephants, but also plants. Schull (Reference Schull1990, p. 63), quoted in Trewavas (Reference Trewavas and Morris2008), writes: “Plant and animal species are information processing entities of such complexity, integration and adaptive competence that it may be scientifically fruitful to regard them as intelligent.” Trewavas (Reference Trewavas and Morris2008) makes a strong case that plants exhibit intelligence in the sense of adaptive behavior in response to signals. To focus only on aspects of intelligence peculiar to humans is biased and subjective because it is based on the prejudices of the observer (Warwick Reference Warwick2001).

Above the level of the individual, the notion of intelligent action has been extended to include group behavior (Baumeister et al. Reference Baumeister, Ainsworth and Vohs2016). Evidence for some sort of collective consciousness exists in humans as well as in non-human species. This again points to the need for a multilevel perspective and an awareness of the need to focus sharply on the particular level (gene, individual, group) being examined (see Wilson).

The prevailing mythology is that humans before agriculture were savage brutes, and life was nasty, brutish, and short (Hobbes). Humans then became clever enough to invent agriculture (V. G. Childe; see, e.g., Childe Reference Childe1936). Civilization made us more human, less violent, cooperative, and democratic (Pinker Reference Pinker2011). Evidence based on contemporary or historical hunter-gatherers suggests that people living in mobile, small-scale foraging societies rarely or never engage in “warfare” (Culotta Reference Culotta2013; Fry & Söderberg Reference Fry and Söderberg2013). Lethal conflicts are rare and are usually the result of personal disputes, not “tribal warfare.” Pinker's “decline in violence” story has been widely accepted because it plays into the myth of linear progress in the human condition and overcoming our animal nature to become civilized (Ryan & Jethá Reference Ryan and Jethá2010).

The question raised by ultrasociality, as commentators Crespi, Hou, and Wilson variously discuss, is: Can we intentionally take control of our destiny as an ultrasocial species? How do we get away from the dystopic implications of our target article? We believe that intentional change is possible, even a radical redirection of society. An example of an intentional radical change in an entire culture is the case of Tikopia, a small island in the South Pacific with a culture headed down the same path as Easter Island and many other Polynesian cultures – massive deforestation, extinction of native species, soil erosion, and rapid population growth. But Tikopia managed to change course and achieve a stable existence. Archaeological evidence indicates that, sometime around 1700 C.E., all pigs and dogs were eliminated from the island, and slash and burn agriculture was replaced with a “complex system of fruit and nut trees forming an upper canopy, with aroids, yams, and other shade tolerant crops under these” (Kirch & Yen Reference Kirch and Yen1982, p. 353). Tikopians adopted a variety of customs to ensure zero population growth, and the island's culture was apparently sustainable until missionaries arrived in the 1900s (McDaniel & Gowdy Reference McDaniel and Gowdy2000).

R5. The division of labor, interdependence, and class

The division of labor is the most important economic driver in the march to ultrasociality. We are well aware that the division of labor predates agriculture (Gowdy & Krall Reference Gowdy and Krall2014). We do not doubt that the reproductive division of labor in ants originated in the Cretaceous, and that this may have given ant society cohesion before the advent of agriculture (Godzińska; Kovaka et al.). We argue that the division of labor innately increases efficiency, and that it was necessary for agriculture to become a viable strategy because it requires a large number of interconnected tasks. Humans and certain species of ants and termites were capable of employing an elaborate division of labor and were therefore positioned to make the transition to agriculture. Humans, ants, and termites thereby became much more highly interdependent and almost mechanistically structured in food production. And each individual role in the execution of agricultural tasks was more circumscribed, thereby rendering individuals less capable of independent survival. Thus, the division of labor specific to agriculture is central to ultrasociality because it sets up a profound interdependence where individuals essentially become part of a “superorganism.” This becomes obvious with large-scale “institutional agriculture,” which evolved very rapidly after the onset of agriculture (Shepard Reference Shepard1973).

Hunters and gatherers had a simple division of labor but it did not come close to the complexity of labor differentiation in ultrasocial societies. We agree with Noles & Danovitch that a “division of cognitive labor” may be a preadaptation to ultrasociality. We do not claim that societies that adopt agriculture always reach a high level of complexity, nor do we deny that pre-agricultural societies can have some complexity as indicated by hierarchy. As we mentioned in our target article, the northwest coast Indians had settled communities and the beginnings of a hierarchical society without agriculture due to the unique natural bounty in the northwest coast. Salmon could be stored (surplus production), and the best salmon areas could be monopolized. This strengthens our case of the importance of surplus production leading to hierarchies. Control of surplus cannot be separated from the control of capital (Woodburn Reference Woodburn1982).

We fully recognize the problem of class conflict and power in human societies. The combination of the division of labor and the existence of surplus created an opening for institutional mediation in the specific allocation of jobs and command of surplus. But we want to stress interdependence. Hierarchy in itself is not a defining attribute of ultrasociality. The most advanced social insect societies are not hierarchical (Gordon Reference Gordon2007). It is the rigid interdependence in food production that initially defines ultrasociality. No matter what role or which class one occupies, all have a vested interest in the stability and smooth functioning of a system in which they all participate and indeed must participate if they are to survive.

McCain points to the importance of class and power, characteristics that distinguish arthropod and human societies. But the issue of hierarchy and class involves more than power. It is also the acquiescence to power that comes from the interlocking coordination of classes in complex production. We fully recognize that this acquiescence is incomplete in humans. This difference was discussed at length by Georgescu-Roegen (Reference Georgescu-Roegen1977a), who pointed out that insect societies are organized into castes according to the endosomatic (within the body) attributes. Doorkeeper ants have large heads to block entrances, and soldiers have large mandibles for fighting. Humans, on the other hand, have become dependent on the exosomatic (outside of the body) instruments of our material culture. Because there are no genetic reasons why a particular person or group of persons should have control of these instruments, they become a source of social conflict.

McCain accuses us of neglecting the role of class systems based on threat. We recognize the role of coercion and threat. But we focus on something more basic to ultrasociality – with ultrasocialty, even the most oppressed classes have a vital stake in preserving the system. We chose to conceptualize our current ecosphere/economy challenges in an evolutionary framework rather than to use an evolutionary game theory model as McCain suggests. Our research has led us to conclude that there is an evolutionary story to the transition to ultrasociality and to our present set of circumstances. The prisoner's dilemma highlights the relationship between individuals and cooperative behavior, including the division of labor, but leaves us with limited insight about the social context of these behaviors.

Crespi claims that in humans, divisions of labor are not primarily cooperative but competitive. He argues that the presence of surplus and the division of labor gives way to hierarchy in humans and interprets this as “competitive” when it leads to enhanced reproduction and consumption rates for city-state rulers. The more important issue with regard to cooperation is the unbridled interdependence of agricultural society, which rigidly structures productive life and turns cooperation into coercion. As for the reproductive division of labor, while it is true humans do not have the same division of labor in reproduction as social insects, for most of human history it was clearly not true that “human groups almost certainly benefit at the cultural group level from high fecundity of their female members” (Crespi). But in agriculture, high fecundity of female members meant that the division of labor by gender became more pronounced, and this was not a positive change for women. By contrast, the imperative for hunter-gatherers was to keep population rates low. Agriculture and the ensuing 10,000 years has been the exception.

Crespi states that the “human reproductive division of labor” is precluded. This is too strong a statement. A large literature exists about the long period of post-menstrual life in human females. Another interesting phenomenon here is the replacement of human workers by robots, a non-reproducing class of workers. Is this another example of the human transition to an ant-like production system?

R6. Energy and complexity

Our analysis of the evolution of ultrasociality with agriculture cannot be reduced to a matter of energy, although there are clearly energy implications to this change in social organization. Given that the species that practice agriculture are expansionary and come to dominate ecosystems, the relationship of these species to energy is obviously important. The relationship between energy and expansion is approached in a nuanced and systemic way in our analysis. Expansion is seen through the lens of the complex evolutionary process of group formation specific to agriculture, and energy is obviously part of that process.

One of our claims is that the formation of ultrasociality was boosted with agriculture as humans were able to tap into the stocks of carbon. We make a similar claim for ants that practice agriculture. But the energy story is further complicated for these species because tapping into stocks was only one aspect of their relationship with energy. Agriculture allowed for a redirection of solar energy to the species that were able to redirect it through cultivation, thus providing more food. Humans and species of ants and termites were able to manage agriculture by virtue of a social reconfiguration of their relations of production. In other words, it was necessary to implement a more elaborate division of labor to engage agriculture, and these species were able to do so. The altered division of labor with agriculture enabled the species that practiced it to tap into certain economies of scale in energy use, which in turn reinforced the expansionary dynamic.

Hou's remarks help disentangle the complex story of energy. Hou talks about this in the language of sublinear scaling (Bettencourt et al. Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007; Hou et al. Reference Hou, Kaspari, Vander Zanden and Gillooly2010) and points out that: “The similar economies of scaling in both ant and human societies reflect, as G&K point out for ants, that a larger group size is more energetically efficient.” Thus, the tendency (based on sublinear scaling) would be toward a larger colony size because larger size is able to capture scaling benefits. If this were all that was at work, the ultimate restriction on expansion would emerge when the species reached carrying capacity. Hou suggests that sublinear scaling is a matter of inequality in energy use owing to the “heterogeneity in the activity level of individuals in the network”; when “group size increases, relatively fewer individuals consume a lot, and more consume a little.” This interfaces nicely with our observation that agriculture demands and lends itself to a more elaborate division of labor, making it quite likely that there are differing energy demands between individuals involved in different roles.

Referring to the work of Bettencourt et al. (Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007), Hou further claims that, “Theoretical models predict that driving forces with different scaling powers will generate sharply different growth patterns.” In particular, “Bettencourt et al. (Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007) show that, besides the infrastructure properties that scale with the population size in the same way as in ant colonies [i.e., sublinearly], human society also has a suite of unique properties ‘reflecting wealth creation and innovation’ (p. 7301), which have no counterpart in ant society.” These properties scale superlinearly rather than sublinearly, making the relationship to energy and the growth cycle and its end different for humans. Specifically, humans are more inclined to collapse as sublinear energy scaling is not sufficient to counteract superlinear scaling, exacerbating the ever greater demand for energy as group size increases (Brown et al. Reference Brown, Burnside, Davidson, DeLong, Dunn, Hamilton, Mercado-Silva, Nekola, Okie, Woodruff and Zuo2011). Because humans exhibit both sublinear and superlinear scaling, Hou tells us that “superlinear scaling in a human society inevitably results in unbounded growth.” That is, of course, until the systems crash.

Hou does not analyze the superlinear scaling apparent in human societies, but if one interjects the overlay of economic structure, it is fairly easy to see what is happening. Surplus production and expansion in humans that begins in agriculture leads to markets (an institutional arrangement to redistribute surplus), and markets eventually evolve into market society. Market society (capitalism) is driven by the production of exchange value (and not the production of use value), but the production of exchange value is not directly linked to biophysical foundations. Exchange value is simply a term used to convey the idea that the purpose of production (or any economic activity) is not primarily to produce useful things, but to make money. With the advent of the use of fossil fuel, this non-organic aspect of economic evolution was supercharged, and the economic system became supra-organic. As well, in market capitalism fueled by fossil fuel, the cost of sublinear scaling was a tremendous increase in productivity, creating internal contradictions in the system. In the end, we are left with an ironic outcome – we have an economic system that has profound biophysical implications (take climate change as an example) but one that is nonetheless framed by an imperative that is not directly tied to biophysical limits. The probability of collapse is enhanced. But all of this begins with agriculture. We discuss this extensively in another paper (Gowdy & Krall Reference Gowdy and Krall2013).

Tainter maintains that we have done a “valuable service in helping to undermine historical narratives that underpin this ancestor myth” (the notion of the “heroic progress” of human society). Tainter has understood that our analysis gets into the “black box” of progress to examine the altered way society was differentiated and reconfigured with agriculture. Our analysis does not offer an ancestor myth (appealing to the special status of humans and their propensity for ingenuity), nor a simplistic energy interpretation of the transition to agriculture and human expansion. Tainter points out that before fossil fuel use the “cost of complexity would have inhibited its development.” This can be seen in the collapse of many large-scale state societies where the energy accommodation to complexity would have been limited primarily to agriculture. Were it not for the advent of the use of fossil fuel, it is likely that the evolution of market society (capitalism) would have been hampered. But with the advent of fossil fuel, the energy/complexity spiral continues to grow, or as Hou and Bettencourt et al. (Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007) claim, energy scales superlinearly. In some sense those limits will be determined by the interplay of the energy demands of complexity and the dual dynamic of sublinear and superlinear scaling.

Farley rightly points out that “fossil fuel use and monetary exchange have taken human ultrasociality and economic organization in new directions.” This claim is substantiated by Hou as well as the work of Bettencourt et al. (Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007) and Tainter. We would argue that Farley is not altogether correct in his claim that, “The modern capitalist economy emerged not with the transition to agriculture, but rather, simultaneously with our ability to tap fossil fuel stocks.” We talk more extensively about this in section R8.

Certainly, the energetics of society changed dramatically with agriculture. The framework of sublinear and superlinear scaling of human society in terms of energy and size seem potentially fruitful ways to understand the complex energy dynamic that clearly begins with agriculture. Superlinear scaling would have been greatly expanded with the advent of capitalism and the use of fossil fuel, or in Hou's words, “the expansion of a human society is probably … driven by innovation and wealth creation which scale superlinearly.” Infrastructure is a matter of sublinear scaling, but “‘wealth creation and innovation’ (Bettencourt et al. Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007, p. 7301), which have no counterpart in ant society” scale superlinearly.

The question that remains temporarily unanswered here is whether the energy used by hunter-gatherers scaled sublinearly and/or what the size constraints on the process of scaling might have been. Were they different than for humans who employed agriculture? Because these societies remained low in population, it is likely that there were no scaling dynamics pushing them in the direction of expansion. If this is true, then the case can be made that scaling in terms of size of group and energy might be considered one indicator of ultrasociality.

R7. Expansion and sustainability

We make the claim that the evolution of ultrasociality in humans, ants, and termites is a case of convergent evolution. More specifically, we claim that “in all three lineages similar patterns of economic organization emerge through similar selection pressures” (target article, sect. 1, para. 1). We do not deny the role of culture or institutions in reinforcing and interpreting the pattern of economic organization established with agriculture. We recognize that the “details of ultrasociality in humans play out in ways that are mediated by human intentionality and cultural norms” (sect. 1, para. 1). While the role of gene-culture coevolution has long been recognized (Richerson & Boyd Reference Richerson and Boyd2005; Wilson Reference Wilson1997), as has the validity of MLS and group selection, little work has been done on the organization of economic life as a particularly significant component of social evolution. Wilson recognizes that we move “beyond human genetic evolution to include human cultural evolution, while remaining fully biological in [our] comparison with insect societies.” We use MLS and group selection fully recognizing that insects and humans may have different mechanisms of inheritance. We identify economic structure and economic drivers that are unique and significant in determining the commonalities of ants, termites, and humans. Economic structure and its drivers are intentionally highlighted in the matrix of the social evolution of the species we explore.

Some commentators object that we did not emphasize the roles of hierarchy (class), warfare, and institutions in the formation of complex societies (Houdek et al.; Levine; McCain). Houdek et al. assert that institutions, not agriculture, are responsible for ultrasociality. They confuse proximate and ultimate causation. What we say is that agriculture resulted in institutional arrangements reinforcing surplus production and expansion. For example, there is no question that the institution of property rights was important in the cultural configuration of agriculture. We fully recognize that defense is necessary to protect the sites of agricultural production and storage, and that warfare can take on a life of its own, particularly when wedded to hierarchy. These are particular human institutional interpretations of the demands of agriculture, and there is no question that the presence of augmenting institutions reinforced the system. In fact, we argue that those early post-hunter-gatherer societies that had institutions favorable to surplus production were able to out-compete others. The transition to agriculture, like other major transitions, is a complex evolving process depending on myriad interacting phenomena. But our perspective is that economic structure provides foundational material conditions that frame and direct institutional possibilities. We fully acknowledge that in humans, cultural mediation of economic structure is possible and can influence the direction of economic evolution. But cultural mediation is unlikely to fundamentally alter the dynamic and structure of the economic system unless the contradictions of the system become so great that they simply are no longer workable. Interdependence is profound in agricultural societies whether they are ruled by kings or not. And the presence – indeed, the imperative – of surplus in agricultural societies gives rise to institutional accommodations, like markets, which, as we have argued, may take on a life of their own without fundamentally changing the essential aspects of ultrasocial economic society: division of labor, interdependence, expansion, domination of ecosystems, and loss of autonomy (Gowdy & Krall Reference Gowdy and Krall2013).

Houdek et al. state that, “There is nothing about human agriculture … that makes it inherently and inescapably unsustainable in terms of inequality, environmental degradation, or violence. In all of these aspects, the effect of development is not necessarily negative.” First of all, we do not argue that agriculture is “inescapably unsustainable,” but we do assert that: “The basic problem is that ultrasocial societies are expansionary …; and because of their tremendous interdependence, they are particularly difficult to disengage before they reach the point of collapse” (target article, sect. 5.1, para. 1). Houdek et al. refer to the Kuznets curve and the environmental Kuznets curve as evidence for their assertion that we are not correct. These curves refer to evidence for an inverted U relationship between inequality and economic growth, and between pollution and economic growth. Both have been thoroughly discredited as general relationships. As Piketty (Reference Piketty2014, pp. 13–160) points out, the Kuznets curve for inequality, the idea that as an economy develops inequality first increases then decreases, was a product of the Cold War and the desire to keep underdeveloped countries within the sphere of influence of the free world. The empirical evidence behind the inequality bell curve was shaky, according to Kuznets himself (Kuznets Reference Kuznets1953, pp. 24–26, quoted in Piketty, p. 581): “This is perhaps 5 percent empirical information and 95 percent speculation, some of it possibly tainted by wishful thinking.” The sharp reduction in income inequality after WWI until the end of WWII, the period of Kuznets's evidence, was an aberration, not a general law of development. Piketty (Reference Piketty2014, p. 15) summarizes: “The sharp reduction in income inequality that we observe in almost all of the rich countries between 1914 and 1945 was due above all to the world wars and the violent economic and political shocks they entailed (especially for people with large fortunes). It had little to do with the tranquil process of intersectoral mobility described by Kuznets.” An alternative is that inequality increases over time, and this eventually leads to a point where it is not sustainable in a capitalist economy.

Evidence for the environmental Kuznets curve, that with development and economic growth, pollution increases then decreases, is at least as discredited (Stern Reference Stern2004). The history of development in advanced Western countries shows a negative relationship between some kinds of pollution and economic growth (urban air quality for example), but a positive relationship between other kinds of pollution and economic growth (climate change for example). And given the mounting evidence on climate change, rates of extinction, deforestation, decline in fisheries, and so on, we think it is safe to say the current rendition of ultrasociality (globalized monopoly finance capital), or rather the current assault on the rest of the natural world, is not sustainable.

We hope that Ristau is correct in her optimism about the possibility of radical intentional change. We acknowledge the exciting new field of study of “directed evolution” and intentional change (Wilson et al. Reference Wilson, Hayes, Biglan and Embry2014).

Ross accuses us of being neo-Malthusians and asserts that individual initiative and technology will solve our environmental and social problems. Malthus wrote his “Principles of Population” essay in 1798. It was immediately criticized by William Godwin, who argued that the “perfectibility of mankind” would overcome any scarcity. Ross echoes this 200-year-old argument: “But it is at least as plausible to predict that incentives operating at the scale of individuals will produce the technology that delivers planetary salvation.” Fortunately, the Malthusian debate about technology versus exponential growth has matured considerably during the last 200 years (see, e.g., Nekola et al. Reference Nekola, Allen, Brown, Burger, Davidson, Fristoe, Hamilton, Hammond, Kodric-Brown, Mercado-Silva and Okie2013).

We do not mention Malthus in our target article, nor do we defend doomsday population scenarios. Whether or not Malthus will be proven correct in the coming decades, remains to be seen. Economists are notoriously optimistic about the ability of technology to overcome any resource scarcity or pollution problem. The widely quoted economist Julian Simon wrote: “We now have in our hands – really in our libraries – the technology to feed, clothe, and supply energy to an ever-growing population for the next seven billion years” (http://www.azquotes.com/quote/808123). It may be possible to feed the projected human population of 9.6 billion in the year 2050 (see United Nations, Department of Economic and Social Affairs, Population Division 2013). But unlike Ross, we do not assume that technology will automatically solve the food production problem, or the problems of destabilizing climate change, ocean acidification, and biodiversity loss. Will population growth continue unabated or will the human global society collapse? Will the benefits of technology outpace the destabilizing effects of increased complexity (Tainter), social instability (Nephew & Pittet; Ristau), and environmental degradation (Farley)? The human population is expected to peak at about 10 billion around the year 2100 and decline after that. If we are to survive the bottleneck of the 21st century, we need more than a blind faith in technology and individual initiative.

According to Ross, individual initiative is the key to innovation, and the more individualistic humans are, the better: “Modern humans are likely more individualistic, not less so, than pre-ultrasocial hunter-gatherers.” As Farley points out, markets and money make people more selfish and less sociable. But is this good? Surely, getting control of common destiny depends on more cooperation, not more selfish behavior (Wilson & Gowdy Reference Wilson and Gowdy2015).

Perhaps the more critical consideration is not how many people can be technologically supported on this planet. One thing we know is that the more humans there are, the less diverse the ecosphere will be. We have a complex and essentially contradictory evolutionary history. The human ecologist Paul Shepard (Reference Shepard1982, p. 6) conjectured more than three decades ago that the ontogeny of tribal peoples (hunters and gatherers) is “more normal than ours and that it may be considered to be a standard from which we deviated.… Theirs is the way of life to which our ontogeny was fitted by natural selection.” Shepard does not discuss ultrasociality, but he extensively explores the abrupt change in the history of humankind marked by the transition to agriculture. We offer that this too was the result of natural selection but it was in conflict with the healthy ontogeny that had evolved in the Pleistocene. Our present circumstances should nudge us to critically consider this complex social evolution and its conflict with our Pleistocene genome. Psychologists might ask the question of whether we are better adapted to mature in a healthy manner in this world of profound interdependence and expansion with little of the natural impulse of the planet around us or whether our individual ontogeny is best adapted to a different world that was undermined when we turned to agriculture.

R8. The accelerating evolution of human ultrasociality

The analysis of the evolution of ultrasociality from agriculture to global capitalism is a natural extension of our work. We have previously begun that exploration in our paper “The Ultrasocial Origin of the Anthropocene” (Gowdy & Krall Reference Gowdy and Krall2013). We appreciate Farley's comments because he rightly acknowledges that the direction ultrasociality has now taken is distinct. But we raise a cautionary note – while global capitalism has its own distinct character it is nonetheless the direct descendant of agriculture so it is important to understand both its connection and its difference.

As we mention in section R6 (para. 7), Farley states: “The modern capitalist economy emerged not with the transition to agriculture, but rather, simultaneously with our ability to tap fossil fuel stocks.” At the start of his commentary he writes: “I would suggest, however, that fossil fuel use and monetary exchange have taken human ultrasociality and economic organization in new directions.” Later, Farley tells us, “A monetary fossil fuel economy is very different from a pre-monetary agricultural one.” No one would argue with the claim that the use of fossil fuels fundamentally altered market society, or what Farley refers to as “monetary exchange” (cf. Gowdy & Krall Reference Gowdy and Krall2014; Klitgaard & Krall Reference Klitgaard and Krall2012; Krall & Klitgaard Reference Krall and Klitgaard2011). It is important to understand that evolution is a continuous process yet there are major evolutionary transitions. We argue that the leap from hunting and gathering to agriculture was a major evolutionary transition. Global capitalism is the descendant of this transition.

A few points of clarification are in order. The term “monetary exchange” is vague. Monetary exchange took place in many state societies which also had markets, but no one would argue that these were equivalent to market society (capitalism). Thus, “monetary exchange” does little to help us distinguish capitalism from other societies that had markets and produced surplus. A more exact vocabulary must be used to distinguish between previous ultrasocial societies and global capitalism as an ultrasocial society. We have argued that capitalism is economically distinct, but in an evolutionary sense it is the continuation of the revolution in the biophysical dynamic of human society that took hold with the transition to settled agriculture. The parsing of capitalism requires accounting for its connection to previous ultrasocial system(s) and also identifying its unique rendering of ultrasociality. The extreme division of labor in productive life, interdependence, the production of surplus, and the dynamic of expansion distinguish ultrasocial economic systems from those of the hunter-gatherer past, which had only a rudimentary division of labor, limited interdependence in productive life, little or no surplus, and no expansionary dynamic. It is also the case that hierarchy did not dominate pre-agricultural societies but came to dominate the structure of society beginning with agriculture.

We posit that the uniqueness of capitalism can be understood by making the distinction between the evolution of “societies with markets” and the later development to “market society.” These are two different things. Although Farley's instinct that there is something unique about the era of fossil fuel and capitalism is appropriate, his terminology (referring to capitalism as “monetary exchange”) is vague and does not lead to a clear understanding of what makes capitalism stand apart. In market society the division of labor is further expanded, and the production of surplus takes on a distinct institutional structure. A market economy, as opposed to an economy with markets, “is an economic system controlled, regulated, and directed by markets alone; order in production and distribution of goods is entrusted to this self-regulating mechanism” (Polanyi Reference Polanyi1944, p. 68). And as we have argued in other papers, market society was a distinctive rendering of the dynamic of surplus production (Gowdy & Krall Reference Gowdy and Krall2013). In market society the purpose of production is not primarily to produce useful items, it is to produce profit – or put another way, the purpose of the economy is not the creation of use value, but the creation of exchange value. Surplus is obtained at the point of production and realized when goods are sold. Surplus ultimately takes the form of profit, which has the imperative of then finding further outlets for making even more profit. The advent of fossil fuels gave this altered structure of surplus production and expansion an added impulse. The production of exchange value, already institutionally disconnected from a biophysical basis, was given a seemingly unending supply of energy, giving capitalism an almost supra-organic dimension. Landes gives us some idea of the expansionary force when he tells us that coal use in the United Kingdom had increased to 100 million tons by 1870, which was “equivalent to 850 million calories of energy, enough to feed a population of 850 million adult males for a year (actual population was then about 31 million)” (Landes Reference Landes1969, p. 97). One can justifiably ask the question: What would capitalism have looked like without the use of fossil fuel? There is no question that it would have looked much different, as Farley clearly understands. But the roots of a new system had already been laid previously in the revolution that took place with agriculture. And, in fact, the evolution of markets to market society had already taken form before the advent of wide-spread use of fossil fuel technology.

Farley maintains that “current environmental challenges can all be characterized as prisoner's dilemmas: The best outcome for the individual is selfish behavior, regardless of what others do, but the best outcome for society is cooperation.” There is no question that what might be good for a person at one level is not good at another level (Wilson). But this approach leads us to believe that if we can only overcome individual selfish behavior (greed) through cooperation then we can see our way out of this mess. It may well be the case that it is important in the modern era to cooperate at a global level to solve some of our worst problems (like climate change), but we must acknowledge that our propensity for cooperation has been structured – it is embedded in the fabric of our economic system and is apparent in the division of labor, class formation, and the profound productive interdependence. An evolutionary approach to group formation and selection helps to highlight the significance of this fact. As Wilson points out, when “many lower-level traits” interact in a “complex fashion” multilevel selection theory steps in avoiding a “detailed reductionistic understanding of the traits.” The reason we concentrate on ultrasociality with agriculture is because it was evident that an altered system had taken hold that structured cooperation in a different way. We surely have the capacity for cooperation, but our more important challenge is to understand how our capacity for cooperation manifests itself in our present system. Cooperation (or greed for that matter) is socially and economically complex and embedded as part of the structure of productive life. Cooperation is but one of the traits that form a “group” with evolutionary significance. It cannot be reduced to an individual trait. In the same way, selfish behavior does not provide the cornerstone for understanding our present economic system. Corporations and individuals may be greedy, but they are supported in their greediness by institutions of property, rights of corporations, and the dynamic life of market society where the rewards of greediness serve the process of accumulation and expansion.

R9. Human biological evolution since agriculture

There have been significant physical and behavioral changes in individual humans with ultrasociality. Michod and Nedelcu (Reference Michod and Nedelcu2003, p. 64) pinpoint the basic problem in understanding major evolutionary transitions – how does a group of individuals become a new kind of individual having heritable variation in fitness? As we discuss in our target article and as mentioned by several commentators, a necessary precursor to a major transition is cooperative interactions among lower-level units. We argue that in the human transition to agriculture, the striking ability to cooperate that arose before agriculture paved the way for a radically different kind of cooperation, more properly called coordination, that was harnessed to facilitate the complex organization of food production. This involves the “co-option of lower-level processes for new functions at the higher level” (Michod & Nedelcu Reference Michod and Nedelcu2003, p. 64). With ants and termites, the transition to ultrasociality was accompanied by dramatic changes in the genotypes and phenotypes of individuals. Can we see biological changes in humans after the transition to agriculture?

Considerable evidence exists for the shrinking human brain after agriculture. The reasons for this are complex, but we know that the human brain is an expensive organ to maintain in terms of energy use. If a larger brain is no longer necessary for survival because survival is supported by high-density protective societies, then brains should become smaller. Moreover, our intellectual and emotional abilities are genetically fragile – between 2,000 and 5,000 genes are needed for intellectual and emotional function (Crabtree Reference Crabtree2013a) – implying that changes in these abilities can be quite rapid. The agricultural transition brought a new set of selection pressures unrelated to intelligence. Crabtree (Reference Crabtree2013b, p. 4) writes: “When might we have begun to lose these abilities? Most likely we started our slide with high-density living, which was enabled by the transformative invention of agriculture. Selection may have begun operating on resistance to diseases that naturally grow out of high-density living, switching the pressure from intelligence to immunity.”

Does the shrinking brain imply a loss of intellectual and emotional intelligence? Crabtree (Reference Crabtree2013a) is unequivocal on this question:

There exists a large and interesting literature about human domestication (see Leach Reference Leach2003). Characteristics of the domestication of wild animals include reduction in size and skeletal robustness, cranio-facial shortening, and reduction in cranial capacity. All of these changes have occurred in humans since the adoption of agriculture. Leach (Reference Leach2003, p. 349) makes a case for human domestication based on “the effects of the built environment, decreased mobility, and changes in diet consistency associated with increasing sedentism.” Behavioral changes highly relevant for the human transition to agriculture include submission to hierarchy, and “a reduction in environmental awareness” (translated from the German phrase Verarmung der Merkwelt). The impoverishment of the observed world that came with agriculture has been described by the human ecologist Paul Shepard (Shepard Reference Shepard1998, p. 57): “Stated simply the ‘civilized mind’ attempts to simplify and level the world whereas the ‘savage mind’ is not afraid to become enmeshed in its complexity.” A major reason for the environmental crises that threaten to eliminate the human species is the loss of “oneness” with the natural world.

Domestication and submission to hierarchy can be clearly seen in a comparison of dogs and wolves. Range and Virányi (Reference Range and Virányi2014) performed a controlled experiment testing the sociality of dog and wolf packs: They tested the tolerance of each species by pairing a high-ranking dog with a low-ranking one and gave them one bowl of food. They gave the same test to a pair of wolves. In every dog matchup, the higher-ranking dog monopolized the food, but with the wolves, both high-ranking and low-ranking animals had equal access. A report on the study summarized, “Wolves cooperate but dogs submit” (Morell Reference Morell2014). Human domestication should raise a red flag over “just-so” stories about the progressive evolution of cooperation and peacefulness. Rather than better angels, have we become better servants to those at the top of the hierarchy?

There have been changes in human reproduction patterns since agriculture. Hunter-gatherer societies had low reproductive variance, and dispersal possibilities were high. In state societies reproductive variance was high, and dispersal options were usually low. Betzig (Reference Betzig2014, p. 81) uses examples from early state societies and from ultrasocial and eusocial insect societies to argue that reproductive inequality goes up with settled life. In civilizations from the Near East, India, China, Greece, and Rome, kings collected thousands of females and guarded them with thousands of eunuchs. Genghis Khan fathered hundreds of children, and as a result, millions of Asian men have a similar Y chromosome linage. These cultural patterns have left a mark on the human genome (Aitken). According to Karmin et al. (Reference Karmin2015), the hoarding of females by high-ranking males led to a dramatic decline in male genetic lineages 4,000 to 8,000 years ago. The research suggests that the accumulation of wealth and power caused a genetic bottleneck in Y chromosomes lineages. The accumulation of wealth and power that came with agriculture produced a detectable reproductive skew in current human populations.

Hou discusses scaling laws with respect to ant and human “ultrasocieties.” His research has uncovered similar economies of scaling and found that in both societies a larger group size is more energetically efficient. The evidence is only suggestive, but it seems that the basic metabolism of human society changed dramatically with the transition to agriculture. Hamilton et al. (Reference Hamilton, Lobo, Rupley, Youn and West2014) found that residential mobility in hunter-gatherer societies is predicted by average human body size and by limits to the ability of mobile hunter-gatherers to store energy internally, that is, by the characteristics of individuals within a society. Hamilton (p. 2) writes: “Our results demonstrate that large-scale evolutionary and ecological processes, common to all plants and animals, constrain hunter-gatherers in predictable ways as they move through territories to effectively exploit resources over the course of a year.” The energetics of hunter-gatherer bands are no different from those of, say, a wolf pack or a chimpanzee group. The energetics of ultrasocial societies, however, point to a major evolutionary transition such that the metabolic characteristics of the society resemble those of an individual organism (Bettencourt et al. Reference Bettencourt, Lobo, Helbing, Kuhnert and West2007; Hou et al. Reference Hou, Kaspari, Vander Zanden and Gillooly2010; Shik et al. Reference Shik, Hou, Kay, Kasari and Gillooly2012).