Chater and Christiansen’s (C&C) general claim that human cultural evolution is undesigned yet generated through cognitive problem-solving, and particularly cognitive tinkering with social problems, offers a useful corrective to accounts that propose random generation of behavioral patterns for selection. An important feature of their account is its emphasis on how shared features of the evolved human cognitive apparatus allow such tinkering to be compatible with mutual legibility and therefore with rich coordination dynamics. Their general argument that local social tinkering, without central design or general hierarchy, has produced the cascading complexity of human culture and dynamical niche reconstruction that in turn explains our global ecological dominance, is persuasive. However, they are vague on the implications of this account for the stability of this distinctive human ecological strategy.
C&C say explicitly that “there is no expectation that spontaneous order through social tinkering leads inexorably to ‘progress’ in any sense.” The meaning of this disavowal is ambiguous in the context of their paper. It is a core feature of their story that the elements of deliberation and foresight in both parametric and social tinkering generate progress in the sense of solving problems. Furthermore, the cumulative conservation of solutions resulting from human record keeping ensures that, with occasional exceptions, these solutions are not forgotten (though, as stressed by Henrich (Reference Henrich2015), their rationales frequently are). C&C are not similarly explicit about the sense in which this process is not progressive: its tendency to generate at least temporary general equilibria degrades with increasing complexity and increasing scale. C&C say near the end that social tinkering focuses pragmatically and intelligently on “the immediate challenge of keeping ‘the ship’ afloat.” But at large population scales, there is not one ship that successful tinkering successively repairs; there is rather a flotilla of ships with tendencies to collide, and some of them exchange canonfire.
I suggest that the main generator of this ambiguity is C&C’s correct focus on the importance of tinkering with norms. Normative evolution is functionally shaped by selection for social stability. Furthermore, norms support increasing complexity in part because their institutionalization allows for larger populations to be coordinated. However, C&C do not comment on whether this tendency for the scope of norms to expand and thereby generate larger-scale stability also generates increasing fragility, as system interdependencies multiply beyond what anyone’s local tinkering can control.
If there is a blind spot here, its roots may lie in overly one-sided emphasis on the relationship between human cognition and self-control. C&C appeal to evolutionary neuroscience to claim that Baldwin effects in human brain evolution, in selecting for unique neural and synaptic density in the frontal cortex, in turn selected for the self-control that makes humans “supercooperators.” It is true that the imaginative capacity delivered by the dense frontal cortex allows humans to be constrained by more complex social norms. But it promotes the opposite of reliable normative control. Some other large-brained and long-lived social animals, including elephants and cetaceans, appear to be more reliably governed by learned social expectations than humans (Ross, Reference Ross2025). There has been a tendency in cultural evolutionary studies to minimize human tendencies to disruptive conflict (including within cultural groups) because humans are more docile with non-relatives than chimpanzees. But here we may be comparing ourselves with the least socially orderly high-intelligence animals.
An alternative picture emphasizes a different special power generated by massive frontal cortical density. Yes, powerful imaginative capacity has allowed humans to collectively reengineer their own ecological arenas, and in particular to fill their environments with cognitive scaffolding that enhances their effective intelligence at both individual and collective scales. This shared scaffolding then massively contributes to the coordinated intentionality that C&C emphasize. But this scaffolding, especially as it becomes more integrated at larger scales, can eclipse physical and biological reality.
As a result of their hyperactive imaginations, even individual humans are prone to disconnection from reality. This vulnerability becomes far harder to overcome when collectively constructed artificial and information-saturated environments become the primary arena of selection – and tinkering. Human history is replete with large-scale commitments to solving self-invented problems that were not genuine threats to ecological success as a species, and indeed this history has often led populations to undermine – until recently only locally, but now globally – the conditions for maintenance of their ecosystems (Harrison & Ross, Reference Harrison and Ross2025).
C&C’s framework provides a useful logic for expressing this problem. Myopic and distributed tinkering should be expected to generate relatively stable population-scale structures to the extent that the tinkering responds to generally shared problems. Problems will tend to be generally legible when they arise from the real environment. To the extent that they arise from imagined problems in false models of reality, we should expect two tendencies that undermine equilibrium dynamics: normative fracturing among sub-populations and generation of large-scale risks that cannot be managed through distributed tinkering.
None of this is unfriendly to C&C’s basic thesis. They take themselves to be explaining the evolution of social complexity. But some of their examples and sub-generalizations suggest complex stability. We should more reasonably expect increasingly unstable complexity and local-scale tinkering that amplifies problems at larger scales.
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Chater and Christiansen’s (C&C) general claim that human cultural evolution is undesigned yet generated through cognitive problem-solving, and particularly cognitive tinkering with social problems, offers a useful corrective to accounts that propose random generation of behavioral patterns for selection. An important feature of their account is its emphasis on how shared features of the evolved human cognitive apparatus allow such tinkering to be compatible with mutual legibility and therefore with rich coordination dynamics. Their general argument that local social tinkering, without central design or general hierarchy, has produced the cascading complexity of human culture and dynamical niche reconstruction that in turn explains our global ecological dominance, is persuasive. However, they are vague on the implications of this account for the stability of this distinctive human ecological strategy.
C&C say explicitly that “there is no expectation that spontaneous order through social tinkering leads inexorably to ‘progress’ in any sense.” The meaning of this disavowal is ambiguous in the context of their paper. It is a core feature of their story that the elements of deliberation and foresight in both parametric and social tinkering generate progress in the sense of solving problems. Furthermore, the cumulative conservation of solutions resulting from human record keeping ensures that, with occasional exceptions, these solutions are not forgotten (though, as stressed by Henrich (Reference Henrich2015), their rationales frequently are). C&C are not similarly explicit about the sense in which this process is not progressive: its tendency to generate at least temporary general equilibria degrades with increasing complexity and increasing scale. C&C say near the end that social tinkering focuses pragmatically and intelligently on “the immediate challenge of keeping ‘the ship’ afloat.” But at large population scales, there is not one ship that successful tinkering successively repairs; there is rather a flotilla of ships with tendencies to collide, and some of them exchange canonfire.
I suggest that the main generator of this ambiguity is C&C’s correct focus on the importance of tinkering with norms. Normative evolution is functionally shaped by selection for social stability. Furthermore, norms support increasing complexity in part because their institutionalization allows for larger populations to be coordinated. However, C&C do not comment on whether this tendency for the scope of norms to expand and thereby generate larger-scale stability also generates increasing fragility, as system interdependencies multiply beyond what anyone’s local tinkering can control.
If there is a blind spot here, its roots may lie in overly one-sided emphasis on the relationship between human cognition and self-control. C&C appeal to evolutionary neuroscience to claim that Baldwin effects in human brain evolution, in selecting for unique neural and synaptic density in the frontal cortex, in turn selected for the self-control that makes humans “supercooperators.” It is true that the imaginative capacity delivered by the dense frontal cortex allows humans to be constrained by more complex social norms. But it promotes the opposite of reliable normative control. Some other large-brained and long-lived social animals, including elephants and cetaceans, appear to be more reliably governed by learned social expectations than humans (Ross, Reference Ross2025). There has been a tendency in cultural evolutionary studies to minimize human tendencies to disruptive conflict (including within cultural groups) because humans are more docile with non-relatives than chimpanzees. But here we may be comparing ourselves with the least socially orderly high-intelligence animals.
An alternative picture emphasizes a different special power generated by massive frontal cortical density. Yes, powerful imaginative capacity has allowed humans to collectively reengineer their own ecological arenas, and in particular to fill their environments with cognitive scaffolding that enhances their effective intelligence at both individual and collective scales. This shared scaffolding then massively contributes to the coordinated intentionality that C&C emphasize. But this scaffolding, especially as it becomes more integrated at larger scales, can eclipse physical and biological reality.
As a result of their hyperactive imaginations, even individual humans are prone to disconnection from reality. This vulnerability becomes far harder to overcome when collectively constructed artificial and information-saturated environments become the primary arena of selection – and tinkering. Human history is replete with large-scale commitments to solving self-invented problems that were not genuine threats to ecological success as a species, and indeed this history has often led populations to undermine – until recently only locally, but now globally – the conditions for maintenance of their ecosystems (Harrison & Ross, Reference Harrison and Ross2025).
C&C’s framework provides a useful logic for expressing this problem. Myopic and distributed tinkering should be expected to generate relatively stable population-scale structures to the extent that the tinkering responds to generally shared problems. Problems will tend to be generally legible when they arise from the real environment. To the extent that they arise from imagined problems in false models of reality, we should expect two tendencies that undermine equilibrium dynamics: normative fracturing among sub-populations and generation of large-scale risks that cannot be managed through distributed tinkering.
None of this is unfriendly to C&C’s basic thesis. They take themselves to be explaining the evolution of social complexity. But some of their examples and sub-generalizations suggest complex stability. We should more reasonably expect increasingly unstable complexity and local-scale tinkering that amplifies problems at larger scales.
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This research received no specific grant from any funding agency.
Competing interests
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