We congratulate authors Richerson et al. on the scope and scale of the wide-ranging literature they have brought to bear on their thesis. This offers an impressive scholarly review of evidence bearing on the nature of human cultural evolution. Nevertheless, we find it difficult to judge yet how compelling is the resulting case for cultural group selection (CGS) specifically, because of a lack of clarity on some core issues. Here we focus on two.
The first concerns the period of human evolution that Richerson et al. aspire to address, which remains surprisingly ambiguous in the target article. Much of the article focuses on recent times, notably the Holocene. At one point they speculate that CGS may have been important “as far back” as symbolic evolution developments, at around 160 k.y.a. But given that the authors start their article by taking the distinctiveness of human cooperation as the remarkable phenomenon they wish to explain, it seems to us that they should be more seriously addressing the earlier periods of hunting and gathering, including necessarily highly cooperative big-game hunting, which a variety of evidence suggests was already significant between 500 k.y.a. and 1 m.y.a. at least (Whiten & Erdal Reference Whiten and Erdal2012). This is important not only because of its relevance to the authors' central concerns, but also because the socio-cognitive processes selected for over this vast timescale are likely to have left a significant legacy in the architecture of the human mind, including its cooperative and cultural dispositions.
The ethnographic, archaeological, and comparative evidence that over the years we (Erdal & Whiten Reference Erdal, Whiten, Mellars and Gibson1996; Whiten & Erdal Reference Whiten and Erdal2012) and others have marshalled indicate that this long hunter-gatherer era was already marked by unprecedented egalitarianism, generalized sharing, and coupled, enhanced levels of cooperation – the core phenomenon the authors profess to wish to explain – of various kinds. These have included cooperation in each of the enterprises of hunting (including manufacturing the weapons and traps utilized) and gathering, but also the ways in which these activities, typically undertaken through division of labour between separately foraging parties, are integrated over space and time and coordinated to permit generalized sharing of spoils at campsites, coupled with information exchange between hunters and gatherers that enhances subsequent foraging effectiveness. Among the many other forms of enhanced cooperation are shared child care and inter-band marriage arrangements. The result is that interdependence in hunter-gatherers displays unique levels and forms among primates, such that through the exploitation of its socio-cognitive niche, the band effectively acts like a unified predatory organism, able to outcompete such “professional predators” as the large social carnivores of Africa. It is thus the earlier evolution of these distinctive cooperative and other characteristics, in small bands numbering about 30 individuals, that begs explanation. Given these were surely already enmeshed in complex cumulative cultures, shouldn't the analysis of Richerson et al. be focused more on the social dynamics and selective regimes that have operated in tens of thousands of generations of hunting and gathering?
The unique forms and degree of interdependence among the members of a human hunter-gatherer band – which mean that the inclusive fitness of individuals is highly contingent on their contributions to the effectiveness of the group as a whole – could perhaps be argued to provide an unusually supportive context for the operation of genetic group selection. However, we are here talking instead of cultural group selection, and this leads us to the second issue we wish to raise, which is the more general one of what exactly are the replicating (even if with varying fidelity) entities that are proposed to be exposed to differential selection in the CGS theory? We feel this remains surprisingly unclear in this article. At times the authors write as if it is cultural “groups” of people, with some groups outcompeting or absorbing others. But should not the unit of replication instead be a cultural entity, more along the lines of (although not necessarily isomorphic with) – what have earlier been called “memes” or “meme-complexes” (e.g., Aunger Reference Aunger2000)? The latter concept of a set of co-adapted cultural elements (Dawkins Reference Dawkins1976, pp. 212–213) is presumably where the “group” aspect of CGS would get purchase? And for CGS to occur, these meme-complexes would somehow need to spread preferentially across populations, as when cultural complexes such as religions like Catholicism, or even national cultures in the case of large scale invasions like that of the Roman Empire, spread through new populations. Selection involving the differential reproductive success of cultural entities (group-level selection where “group” is akin to “meme-complex”) is a very different phenomenon to selection involving differential reproductive success of groups of individuals. The two are not mutually exclusive but it needs to be clearer whether CGS is conceptualized as involving both types of competition or one in particular?
If the focus of the “group” term in CGS is cultural complexes, perhaps such phenomena have indeed characterized only the relatively recent phases of human cultural evolution that the authors focus on, particularly the Holocene. But is such a conclusion based only on the fact that we have rich, relevant evidence about cultural change across this recent period? We know all too little about the processes that characterized the earlier and vastly longer period of our hunter-gatherer history we alluded to earlier. Indeed, we know all too little about the nature of cultural change from all the studies undertaken in the recent ethnographic past. From what we do know (e.g., Hewlett et al. Reference Hewlett, Fouts, Boyette and Hewlett2011; Jordan Reference Jordan2015), it is far from apparent that “group” needs inserting in “cultural selection” to characterize the processes at work.
We congratulate authors Richerson et al. on the scope and scale of the wide-ranging literature they have brought to bear on their thesis. This offers an impressive scholarly review of evidence bearing on the nature of human cultural evolution. Nevertheless, we find it difficult to judge yet how compelling is the resulting case for cultural group selection (CGS) specifically, because of a lack of clarity on some core issues. Here we focus on two.
The first concerns the period of human evolution that Richerson et al. aspire to address, which remains surprisingly ambiguous in the target article. Much of the article focuses on recent times, notably the Holocene. At one point they speculate that CGS may have been important “as far back” as symbolic evolution developments, at around 160 k.y.a. But given that the authors start their article by taking the distinctiveness of human cooperation as the remarkable phenomenon they wish to explain, it seems to us that they should be more seriously addressing the earlier periods of hunting and gathering, including necessarily highly cooperative big-game hunting, which a variety of evidence suggests was already significant between 500 k.y.a. and 1 m.y.a. at least (Whiten & Erdal Reference Whiten and Erdal2012). This is important not only because of its relevance to the authors' central concerns, but also because the socio-cognitive processes selected for over this vast timescale are likely to have left a significant legacy in the architecture of the human mind, including its cooperative and cultural dispositions.
The ethnographic, archaeological, and comparative evidence that over the years we (Erdal & Whiten Reference Erdal, Whiten, Mellars and Gibson1996; Whiten & Erdal Reference Whiten and Erdal2012) and others have marshalled indicate that this long hunter-gatherer era was already marked by unprecedented egalitarianism, generalized sharing, and coupled, enhanced levels of cooperation – the core phenomenon the authors profess to wish to explain – of various kinds. These have included cooperation in each of the enterprises of hunting (including manufacturing the weapons and traps utilized) and gathering, but also the ways in which these activities, typically undertaken through division of labour between separately foraging parties, are integrated over space and time and coordinated to permit generalized sharing of spoils at campsites, coupled with information exchange between hunters and gatherers that enhances subsequent foraging effectiveness. Among the many other forms of enhanced cooperation are shared child care and inter-band marriage arrangements. The result is that interdependence in hunter-gatherers displays unique levels and forms among primates, such that through the exploitation of its socio-cognitive niche, the band effectively acts like a unified predatory organism, able to outcompete such “professional predators” as the large social carnivores of Africa. It is thus the earlier evolution of these distinctive cooperative and other characteristics, in small bands numbering about 30 individuals, that begs explanation. Given these were surely already enmeshed in complex cumulative cultures, shouldn't the analysis of Richerson et al. be focused more on the social dynamics and selective regimes that have operated in tens of thousands of generations of hunting and gathering?
The unique forms and degree of interdependence among the members of a human hunter-gatherer band – which mean that the inclusive fitness of individuals is highly contingent on their contributions to the effectiveness of the group as a whole – could perhaps be argued to provide an unusually supportive context for the operation of genetic group selection. However, we are here talking instead of cultural group selection, and this leads us to the second issue we wish to raise, which is the more general one of what exactly are the replicating (even if with varying fidelity) entities that are proposed to be exposed to differential selection in the CGS theory? We feel this remains surprisingly unclear in this article. At times the authors write as if it is cultural “groups” of people, with some groups outcompeting or absorbing others. But should not the unit of replication instead be a cultural entity, more along the lines of (although not necessarily isomorphic with) – what have earlier been called “memes” or “meme-complexes” (e.g., Aunger Reference Aunger2000)? The latter concept of a set of co-adapted cultural elements (Dawkins Reference Dawkins1976, pp. 212–213) is presumably where the “group” aspect of CGS would get purchase? And for CGS to occur, these meme-complexes would somehow need to spread preferentially across populations, as when cultural complexes such as religions like Catholicism, or even national cultures in the case of large scale invasions like that of the Roman Empire, spread through new populations. Selection involving the differential reproductive success of cultural entities (group-level selection where “group” is akin to “meme-complex”) is a very different phenomenon to selection involving differential reproductive success of groups of individuals. The two are not mutually exclusive but it needs to be clearer whether CGS is conceptualized as involving both types of competition or one in particular?
If the focus of the “group” term in CGS is cultural complexes, perhaps such phenomena have indeed characterized only the relatively recent phases of human cultural evolution that the authors focus on, particularly the Holocene. But is such a conclusion based only on the fact that we have rich, relevant evidence about cultural change across this recent period? We know all too little about the processes that characterized the earlier and vastly longer period of our hunter-gatherer history we alluded to earlier. Indeed, we know all too little about the nature of cultural change from all the studies undertaken in the recent ethnographic past. From what we do know (e.g., Hewlett et al. Reference Hewlett, Fouts, Boyette and Hewlett2011; Jordan Reference Jordan2015), it is far from apparent that “group” needs inserting in “cultural selection” to characterize the processes at work.