While ultrasocial insects are genetically closely related, contemporary human societies are not. Gowdy & Krall (G&K) suggest that it was the economic requirements of their agricultural subsistence regimes which led to a convergent evolution towards ultrasociality in all of these species. In humans, they propose, the irreversible transition from independently foraging groups of closely related, mobile hunter-gatherers to large, sedentary pre-state and state societies characterized by low relatedness and high levels of division of labor, enabled the evolutionary subjugation of individual (fitness) interests to the benefit of the respective subsistence groups through multilevel selection.
If this were the case, we wonder, why do we then find that human agricultural production is, and has likely always been, largely based on kinship? The European Union (EU) farm structure survey from 2010, for example, reports that 94.8% of all farms in the EU operate exclusively through the work of a single family (Eurostat 2015). In the United States, farms with 50% or more ownership interest held by the operator and/or his or her relatives accounted for 96.7% of all farms in 2012 (National Agricultural Statistics Service 2014). Furthermore, the Food and Agriculture Organization of the United Nations (FAO) estimated that in 2014 more than 90% of all farms worldwide were family farms (FAO 2014). While these estimates vary to some extent with the respective definitions of “family farm” employed (Garner & de la O Campos Reference Garner and de la O Campos2014), they still show that family labor is central to agricultural production even in contemporary industrialized countries. In addition, historical research clearly indicates that this is not a new phenomenon (Gasson et al. Reference Gasson, Crow, Errington, Hutson, Marsden and Winter1988; Hanson Reference Hanson1999; White Reference White1970). Recent anthropological research even suggests that the transition from hunter-gatherer subsistence to horticulturalism, that is, the earliest form of agriculture, was accompanied by an increase, and not a decrease, in genetic relatedness (Walker Reference Walker2014; also see: Dyble et al. Reference Dyble, Salali, Chaudhary, Page, Smith, Thompson, Vinicius, Mace and Migliano2015).
In G&K's deliberations, we urgently miss an explanation for this global prevalence of family farming and its vast temporal extent throughout human (pre)history. Although we do not think that their entire argument is rebutted by this observation, we do think that their claim that kin selection is “challenged to explain the extreme interdependence and coordination that occurs with agriculture” (target article, sect. 2, para. 1) has to be revisited in the light of this evidence.
In contrast to G&K, we suppose that the human capacities required for “extreme interdependence and coordination” did not occur with agriculture but evolved (long) before it (also see Sterelny Reference Sterelny2014; Tomasello et al. Reference Tomasello, Melis, Tennie, Wyman and Herrmann2012). Following Hrdy (Reference Hrdy2009), we think, instead, that the transition to a cooperative breeding system and the cognitive adaptations that came along with it (Burkart et al. Reference Burkart, Hrdy and van Schaik2009) are key to understanding the evolution of human pro- and ultrasociality. Recent comparative studies have established, for example, that, compared to non-cooperatively breeding species, cooperative breeders show higher levels of unsolicited prosociality (Burkart et al. Reference Burkart, Allon, Amici, Fichtel, Finkenwirth, Heschl, Huber, Isler, Kosonen, Martins, Meulman, Richiger, Rueth, Spillmann, Wiesendanger and Van Schaik2014) and solve collective action problems better, including cooperative resource defense (Willems et al. Reference Willems, Hellriegel and van Schaik2013; Willems & van Schaik Reference Willems and van Schaik2015), which is a necessary precondition for the advent of agriculture (see, e.g., Gat Reference Gat2008, for a detailed account of the importance of working group defense for sedentariness in humans). Cooperative breeding is closely associated with living in family groups in many animals (Hatchwell Reference Hatchwell2010; Hughes et al. Reference Hughes, Oldroyd, Beekman and Ratnieks2008; Sharp et al. Reference Sharp, Simeoni, McGowan, Nam and Hatchwell2011), and humans here are no exception (Hill et al. Reference Hill, Walker, Božičević, Eder, Headland, Hewlett, Hurtado, Marlowe, Wiessner and Wood2011; Walker Reference Walker2014). We therefore hold that this earlier phylogenetic phase is a better candidate for the evolutionary stage during which the suppression of individual fitness interests for the benefit of the respective subsistence groups was promoted by natural selection. In the case of humans these subsistence groups consisted of cooperatively breeding families. Therefore, kin-selection (with due regard to parent–offspring conflict dynamics; see Trivers Reference Trivers1974), in our view, suffices to explain why we evolved a readiness to bend to the interests of our families (Voland Reference Voland2014) and our extended in-groups, even if this entailed substantial individual fitness costs (Rusch Reference Rusch2015) potentially even as high as one's own life (Rusch Reference Rusch2014).
Taking these considerations into account, we suggest that only after cooperative family units had eventually become the fundamental building blocks of our species' social organization, larger societies became possible, that is, functional collaborations of multiple extended families. In line with G&K's deliberations again, we also think that the Neolithic transition marks an important later phase in which coalitions of families that were able to collaboratively cultivate and successfully defend their resources began to reap the benefits of agricultural economy allowing for surplus production, high levels of division of labor, and, eventually, large pre-state and even larger state societies. For this late phase of human prehistory, we agree with G&K that our evolved nepotistic preferences alone might not suffice to explain why these larger societies held together. It is indeed very puzzling, for example, why almost every historical agricultural population readily fought their societies' wars, which were often started by remote chiefs, kings, or governments. The economic constraints highlighted by G&K, we think, will certainly prove to be important parts of a successful explanation of this phenomenon (see, e.g., Turchin et al. Reference Turchin, Currie, Turner and Gavrilets2013).
In summary: We think that G&K correctly identify the requirements of agricultural production as an important component of the last part of the human evolutionary trajectory towards ultrasociality. We would like to add, however, that not only in eusocial insects, but also in humans, genetic relatedness likely has played a decisive role in the evolution of the social structure allowing for this new form of economy. There is an important intermediate level between the individual and “society” in humans: the (extended) family. Thus, we suggest that G&K's outline of the evolution of human ultrasociality would benefit from incorporating the family-level of human social organization – particularly because the importance of kinship is so obvious in the organization of agricultural production even today.
While ultrasocial insects are genetically closely related, contemporary human societies are not. Gowdy & Krall (G&K) suggest that it was the economic requirements of their agricultural subsistence regimes which led to a convergent evolution towards ultrasociality in all of these species. In humans, they propose, the irreversible transition from independently foraging groups of closely related, mobile hunter-gatherers to large, sedentary pre-state and state societies characterized by low relatedness and high levels of division of labor, enabled the evolutionary subjugation of individual (fitness) interests to the benefit of the respective subsistence groups through multilevel selection.
If this were the case, we wonder, why do we then find that human agricultural production is, and has likely always been, largely based on kinship? The European Union (EU) farm structure survey from 2010, for example, reports that 94.8% of all farms in the EU operate exclusively through the work of a single family (Eurostat 2015). In the United States, farms with 50% or more ownership interest held by the operator and/or his or her relatives accounted for 96.7% of all farms in 2012 (National Agricultural Statistics Service 2014). Furthermore, the Food and Agriculture Organization of the United Nations (FAO) estimated that in 2014 more than 90% of all farms worldwide were family farms (FAO 2014). While these estimates vary to some extent with the respective definitions of “family farm” employed (Garner & de la O Campos Reference Garner and de la O Campos2014), they still show that family labor is central to agricultural production even in contemporary industrialized countries. In addition, historical research clearly indicates that this is not a new phenomenon (Gasson et al. Reference Gasson, Crow, Errington, Hutson, Marsden and Winter1988; Hanson Reference Hanson1999; White Reference White1970). Recent anthropological research even suggests that the transition from hunter-gatherer subsistence to horticulturalism, that is, the earliest form of agriculture, was accompanied by an increase, and not a decrease, in genetic relatedness (Walker Reference Walker2014; also see: Dyble et al. Reference Dyble, Salali, Chaudhary, Page, Smith, Thompson, Vinicius, Mace and Migliano2015).
In G&K's deliberations, we urgently miss an explanation for this global prevalence of family farming and its vast temporal extent throughout human (pre)history. Although we do not think that their entire argument is rebutted by this observation, we do think that their claim that kin selection is “challenged to explain the extreme interdependence and coordination that occurs with agriculture” (target article, sect. 2, para. 1) has to be revisited in the light of this evidence.
In contrast to G&K, we suppose that the human capacities required for “extreme interdependence and coordination” did not occur with agriculture but evolved (long) before it (also see Sterelny Reference Sterelny2014; Tomasello et al. Reference Tomasello, Melis, Tennie, Wyman and Herrmann2012). Following Hrdy (Reference Hrdy2009), we think, instead, that the transition to a cooperative breeding system and the cognitive adaptations that came along with it (Burkart et al. Reference Burkart, Hrdy and van Schaik2009) are key to understanding the evolution of human pro- and ultrasociality. Recent comparative studies have established, for example, that, compared to non-cooperatively breeding species, cooperative breeders show higher levels of unsolicited prosociality (Burkart et al. Reference Burkart, Allon, Amici, Fichtel, Finkenwirth, Heschl, Huber, Isler, Kosonen, Martins, Meulman, Richiger, Rueth, Spillmann, Wiesendanger and Van Schaik2014) and solve collective action problems better, including cooperative resource defense (Willems et al. Reference Willems, Hellriegel and van Schaik2013; Willems & van Schaik Reference Willems and van Schaik2015), which is a necessary precondition for the advent of agriculture (see, e.g., Gat Reference Gat2008, for a detailed account of the importance of working group defense for sedentariness in humans). Cooperative breeding is closely associated with living in family groups in many animals (Hatchwell Reference Hatchwell2010; Hughes et al. Reference Hughes, Oldroyd, Beekman and Ratnieks2008; Sharp et al. Reference Sharp, Simeoni, McGowan, Nam and Hatchwell2011), and humans here are no exception (Hill et al. Reference Hill, Walker, Božičević, Eder, Headland, Hewlett, Hurtado, Marlowe, Wiessner and Wood2011; Walker Reference Walker2014). We therefore hold that this earlier phylogenetic phase is a better candidate for the evolutionary stage during which the suppression of individual fitness interests for the benefit of the respective subsistence groups was promoted by natural selection. In the case of humans these subsistence groups consisted of cooperatively breeding families. Therefore, kin-selection (with due regard to parent–offspring conflict dynamics; see Trivers Reference Trivers1974), in our view, suffices to explain why we evolved a readiness to bend to the interests of our families (Voland Reference Voland2014) and our extended in-groups, even if this entailed substantial individual fitness costs (Rusch Reference Rusch2015) potentially even as high as one's own life (Rusch Reference Rusch2014).
Taking these considerations into account, we suggest that only after cooperative family units had eventually become the fundamental building blocks of our species' social organization, larger societies became possible, that is, functional collaborations of multiple extended families. In line with G&K's deliberations again, we also think that the Neolithic transition marks an important later phase in which coalitions of families that were able to collaboratively cultivate and successfully defend their resources began to reap the benefits of agricultural economy allowing for surplus production, high levels of division of labor, and, eventually, large pre-state and even larger state societies. For this late phase of human prehistory, we agree with G&K that our evolved nepotistic preferences alone might not suffice to explain why these larger societies held together. It is indeed very puzzling, for example, why almost every historical agricultural population readily fought their societies' wars, which were often started by remote chiefs, kings, or governments. The economic constraints highlighted by G&K, we think, will certainly prove to be important parts of a successful explanation of this phenomenon (see, e.g., Turchin et al. Reference Turchin, Currie, Turner and Gavrilets2013).
In summary: We think that G&K correctly identify the requirements of agricultural production as an important component of the last part of the human evolutionary trajectory towards ultrasociality. We would like to add, however, that not only in eusocial insects, but also in humans, genetic relatedness likely has played a decisive role in the evolution of the social structure allowing for this new form of economy. There is an important intermediate level between the individual and “society” in humans: the (extended) family. Thus, we suggest that G&K's outline of the evolution of human ultrasociality would benefit from incorporating the family-level of human social organization – particularly because the importance of kinship is so obvious in the organization of agricultural production even today.