Shifting from foraging to farming, beginning ~12,000 years ago, changed everything.

A special Feature section in the Jan. 17 issue of PNAS offers a series of perspectives on the past 12,000 years of human behavior, adaptation, and evolution that shaped who we are today. An introduction to the special section by Larsen does an overview and brief summary of each of perspectives presented. I pass on the last paragraph (Conclusions) of that summary:

In evolutionary terms, the transition at the Pleistocene–Holocene boundary was extraordinary, especially in consideration of the beginning of a fundamental shift in dietary focus and the downstream effects of diets based on domesticated plants and animals. The transition provided the context for a remarkable increase in population. However, the costs for that success—elevated levels infectious diseases, undernutrition, and conflict—are still with us today. Our species will continue to adapt, to develop strategies for success, and to mitigate challenges. That is what we do. Once we began the shift to and intensification of farming, the remarkable changes seen in humans became critically important developments in recent human evolution. In view of conditions today, including climate change, overpopulation, and the rise in prevalence of infectious diseases, both old and newly emerging, it should come as no surprise that dependence on a few staple crops and shift to sedentary behavior will be with us for the foreseeable future. They are, after all, a legacy of our past, and forming and sharing of the dietary framework, behavioral patterns, and outcomes in health and well-being for all eight billion of us that occupy the world today.

The Evolution of Peace

I pass on the abstract of an article by Luke Glowacki that has been submitted to the network of Behavioral and Brain Science reviewers who might offer commentary on its arguments. Motivated readers can obtain a copy of the article from me.

Abstract: While some species have affiliative and even cooperative interactions between individuals of different social groups, humans are alone in having durable, positive-sum, interdependent relationships across unrelated social groups. Our capacity to have harmonious relationships that cross group boundaries is an important aspect of our species' success, allowing for the exchange of ideas, materials, and ultimately enabling cumulative cultural evolution. Knowledge about the conditions required for peaceful intergroup relationships is critical for understanding the success of our species and building a more peaceful world. How do humans create harmonious relationships across group boundaries and when did this capacity emerge in the human lineage? Answering these questions involves considering the costs and benefits of intergroup cooperation and aggression, for oneself, one's group, and one's neighbor. Taking a game theoretical perspective provides new insights into the difficulties of removing the threat of war and reveals an ironic logic to peace—the factors that enable peace also facilitate the increased scale and destructiveness of conflict. In what follows, I explore the conditions required for peace, why they are so difficult to achieve, and when we expect peace to have emerged in the human lineage. I argue that intergroup cooperation was an important component of human relationships and a selective force in our species history in the past 300 thousand years. But the preconditions for peace only emerged in the past 100 thousand years and likely coexisted with intermittent intergroup violence which would have also been an important and selective force in our species' history.

How modern human brains are different from those of other hominids and chimps.

Work pointed to in the previous post continues to add to the list of behaviors once presumed to be unique to humans that have now been found in other animals (morality, having a ‘self’, etc.) Previous MindBlog posts (list, von Economo neurons etc. do search..) have noted emerging evidence for brain features unique to - or much more pronounced in - humans than other primates. Now Pinson et al. have found that a single amino acid change in the transketolase-like 1 (TKTL1) protein on production of basal radial glia, the workhorses that generate much of the neocortex, appears that the modern human has more neocortex to work with than the ancient Neanderthal did. Here is their abstract:

Neanderthal brains were similar in size to those of modern humans. We sought to investigate potential differences in neurogenesis during neocortex development. Modern human transketolase-like 1 (TKTL1) differs from Neanderthal TKTL1 by a lysine-to-arginine amino acid substitution. Using overexpression in developing mouse and ferret neocortex, knockout in fetal human neocortical tissue, and genome-edited cerebral organoids, we found that the modern human variant, hTKTL1, but not the Neanderthal variant, increases the abundance of basal radial glia (bRG) but not that of intermediate progenitors (bIPs). bRG generate more neocortical neurons than bIPs. The hTKTL1 effect requires the pentose phosphate pathway and fatty acid synthesis. Inhibition of these metabolic pathways reduces bRG abundance in fetal human neocortical tissue. Our data suggest that neocortical neurogenesis in modern humans differs from that in Neanderthals.

Third-party punishment by preverbal infants

From Kanakogi et al.:

Third-party punishment of antisocial others is unique to humans and seems to be universal across cultures. However, its emergence in ontogeny remains unknown. We developed a participatory cognitive paradigm using gaze-contingency techniques, in which infants can use their gaze to affect agents displayed on a monitor. In this paradigm, fixation on an agent triggers the event of a stone crushing the agent. Throughout five experiments (total N = 120), we show that eight-month-old infants punished antisocial others. Specifically, infants increased their selective looks at the aggressor after watching aggressive interactions. Additionally, three control experiments excluded alternative interpretations of their selective gaze, suggesting that punishment-related decision-making influenced looking behaviour. These findings indicate that a disposition for third-party punishment of antisocial others emerges in early infancy and emphasize the importance of third-party punishment for human cooperation. This behavioural tendency may be a human trait acquired over the course of evolution.

Cognitive and Evolutionary Foundations of Puritanical Morality

MindBlog receives articles for commentary from the Cambridge University Journal of Behavioral and Brain Sciences. I will pass on the following abstract of an article by Fitouchi et. al. Motivated readers can email me to request a copy.

Why do many societies moralize apparently harmless pleasures, such as lust, gluttony, alcohol, drugs, and even music and dance? Why do they erect temperance, asceticism, sobriety, modesty, and piety as cardinal moral virtues? According to existing theories, this puritanical morality cannot be reduced to concerns for harm and fairness: it must emerge from cognitive systems that did not evolve for cooperation (e.g., disgust-based "Purity" concerns). Here, we argue that, despite appearances, puritanical morality is no exception to the cooperative function of moral cognition. It emerges in response to a key feature of cooperation, namely that cooperation is (ultimately) a long-term strategy, requiring (proximately) the self-control of appetites for immediate gratification. Puritanical moralizations condemn behaviors which, although inherently harmless, are perceived as indirectly facilitating uncooperative behaviors, by impairing the self-control required to refrain from cheating. Drinking, drugs, immodest clothing, and unruly music and dance, are condemned as stimulating short-term impulses, thus facilitating uncooperative behaviors (e.g., violence, adultery, free-riding). Overindulgence in harmless bodily pleasures (e.g., masturbation, gluttony) is perceived as making people slave to their urges, thus altering abilities to resist future antisocial temptations. Daily self-discipline, ascetic temperance, and pious ritual observance are perceived as cultivating the self-control required to honor prosocial obligations. We review psychological, historical, and ethnographic evidence supporting this account. We use this theory to explain the fall of puritanism in WEIRD societies, and discuss the cultural evolution of puritanical norms. Explaining puritanical norms does not require adding mechanisms unrelated to cooperation in our models of the moral mind.

Questioning common claims about human brain evolution

From DeCasien et al.:

Highlights

New research has questioned or contradicted multiple long-standing claims about human brain evolution.

Contrary to the social brain hypothesis, new work suggests that ecological factors, rather than social complexity, best predict relative brain size across primate species.

Brain size does not have similar effects or cognitive implications in different phylogenetic lineages since it is associated with different mosaic structural changes.

Although the human prefrontal cortex is proportionally large, this may not represent an adaptive specialization and research emphasis on this region has distracted attention from the importance of wider neural networks.

Functional and anatomical integration, rather than developmental constraints, may primarily explain patterns of brain region size covariation across species.

Abstract

Human brains are exceptionally large, support distinctive cognitive processes, and evolved by natural selection to mediate adaptive behavior. Comparative biology situates the human brain within an evolutionary context to illuminate how it has been shaped by selection and how its structure relates to evolutionary function, while identifying the developmental and molecular changes that were involved. Recent applications of powerful phylogenetic methods have uncovered new findings, some of which overturn conventional wisdom about how and why brains evolve. Here, we focus on four long-standing claims about brain evolution and discuss how new work has either contradicted these claims or shown the relevant phenomena to be more complicated than previously appreciated. Throughout, we emphasize studies of non-human primates and hominins, our close relatives and recent ancestors.

The authors dispute the following common claims about human brain evolution: (Motivated readers can obtain the whole text with their detailed arguments from me.)

Claim 1. Social complexity is the primary driver of non-human primate and human brain evolution

Claim 2. Brain size has similar effects and cognitive implications across a wide range of species

Claim 3. The proportionally large human PFC reflects selection on PFC-specific functions

Claim 4. Developmental constraints play a major role in the evolution of brain structure

The human fear paradox: Affective origins of cooperative care

On the same morning last week that I read a NYTimes essay by Thomas Edsall "The Politics of Fear Show No Sign of Abating" I received an email from the journal Behavioral and Brain Science soliciting reviews on an upcoming article by Tobias Grossmann with an interesting hypothesis on why we humans are so fearful: "The human fear paradox: Affective origins of cooperative care." His 'fearful ape hypothesis' proposes that, in the context of the strong interdependence reflected in cooperative caregiving and provisioning unique to human great ape group life, heightened fearfulness was adaptive. Here I pass on the abstract of Grossmann's piece, and motivated readers can obtain the whole text from me.

Already as infants humans are more fearful than our closest living primate relatives, the chimpanzees. Yet heightened fearfulness is mostly considered maladaptive, as it is thought to increase the risk of developing anxiety and depression. How can this human fear paradox be explained? The fearful ape hypothesis presented herein stipulates that, in the context of cooperative caregiving and provisioning unique to human great ape group life, heightened fearfulness was adaptive. This is because from early in ontogeny fearfulness expressed and perceived enhanced care-based responding and provisioning from, while concurrently increasing cooperation with, mothers and others. This explanation is based on a synthesis of existing research with human infants and children, demonstrating a link between fearfulness, greater sensitivity to and accuracy in detecting fear in others, and enhanced levels of cooperative behaviors. These insights critically advance current evolutionary theories of human cooperation by adding an early-developing affective component to the human cooperative makeup. Moreover, the current proposal has important cultural, societal and health implications, as it challenges the predominant view in WEIRD societies that commonly construe fearfulness as a maladaptive trait, potentially ignoring its evolutionary adaptive functions.

The road to our larger brains

Bertrand et al. address the question of how and why mammals evolved large brain sizes relative to their body mass by characterizing the timing and pattern of mammal brain development across the Early Jurassic to the middle Cenozoic (∼200 million to 30 million years ago) when the ecological niches vacated by the extinction of large reptiles were being filled by large mammals. Here is their abstract:

Mammals are the most encephalized vertebrates, with the largest brains relative to body size. Placental mammals have particularly enlarged brains, with expanded neocortices for sensory integration, the origins of which are unclear. We used computed tomography scans of newly discovered Paleocene fossils to show that contrary to the convention that mammal brains have steadily enlarged over time, early placentals initially decreased their relative brain sizes because body mass increased at a faster rate. Later in the Eocene, multiple crown lineages independently acquired highly encephalized brains through marked growth in sensory regions. We argue that the placental radiation initially emphasized increases in body size as extinction survivors filled vacant niches. Brains eventually became larger as ecosystems saturated and competition intensified.

Humans don’t have culture because we’re smart, we’re smart because we have culture.

The title of this post is a sentence taken from the final paragraph of Henrich's Perspective article in Science on the work of Thompson et al. which notes that Thompson et al.'s results

...highlight a deeper point: Humans don’t have culture because we’re smart, we’re smart because we have culture. The selective processes of cultural evolution not only generate more sophisticated practices and technologies but also produce new cognitive tools—algorithms—that make humans better adapted to the ecological and institutional challenges that we confront. Thompson et al.’s results underline the need for the psychological sciences to abandon their implicit reliance on a digital computer metaphor of the mind (hardware versus software) and transform into a historical science that considers not just how cultural evolution shapes what we think (our mental contents) but also how we think [our cognitive processes].

Here I pass on the introductory paragraphs and then the abstract of the Thompson et al. article. Motivated readers can obtain the full text by emailing me.

Reading, counting, cooking, and sailing are just some of the human abilities passed from generation to generation through social learning... Complex abilities like these often depend on learned cognitive algorithms: procedural representations of a problem that coordinate memory, attention, and perception into sequences of useful computations and actions. Accumulation of complex algorithms—from ancient tool-making techniques to bread making, boat building, or horticulture—is central to human adaptation yet challenging to explain because algorithmic concepts can be difficult to discover, communicate, and learn from observation, making them vulnerable to loss. Theories of cultural evolution suggest that human social learning may help overcome this fragility. For example, mathematical models predict that choosing to learn from successful or prestigious individuals can prevent the loss of rare innovations. However, this potential link between sociality and complex abilities is challenging to establish.

We conducted large-scale simulations of cultural evolution with human participants to assess how selective social learning influenced the evolution of cognitive algorithms. Prior research shows that social learning can improve decisions in multiple-choice tasks, perceptual judgments, and search problems and can improve artifacts such as physical structures or computer programs. However, the evolution of cognitive algorithms at the population level has been difficult to study. We developed custom software to recruit large numbers of participants online and organize them into evolving societies facing a common problem. Twenty populations tackled a sequential decision problem... Presented with six images, participants attempted to establish hidden arbitrary orderings using pairwise comparisons. Out-of-order pairs swapped positions when compared. Participants were rewarded for establishing the ordering using fewer comparisons. This task poses a sorting problem, requiring a strategy for executing appropriate sequences of actions, analogous to culturally evolved strategies for making tools or food.

Abstract:

Many human abilities rely on cognitive algorithms discovered by previous generations. Cultural accumulation of innovative algorithms is hard to explain because complex concepts are difficult to pass on. We found that selective social learning preserved rare discoveries of exceptional algorithms in a large experimental simulation of cultural evolution. Participants (N = 3450) faced a difficult sequential decision problem (sorting an unknown sequence of numbers) and transmitted solutions across 12 generations in 20 populations. Several known sorting algorithms were discovered. Complex algorithms persisted when participants could choose who to learn from but frequently became extinct in populations lacking this selection process, converging on highly transmissible lower-performance algorithms. These results provide experimental evidence for hypothesized links between sociality and cognitive function in humans.

Neurons in the brain that respond mainly to singing

New work from Norman-Haignere et al. describes a population of cells in our auditory cortex, located between the music and speech-selective areas, that is responsive to singing, but not to instrumental music or speech. (Their experiments were done on patients who were in hospital with electrodes implanted into their heads for epilepsy treatment, allowing more precise location data than can be obtained from fMRI scans.) Their result is consonant with a popular theory that singing has an important role in the evolution of music and language. Their abstract:  

Highlights

• Neural population responsive to singing, but not instrumental music or speech 

• New statistical method infers neural populations from human intracranial responses 

• fMRI used to map the spatial distribution of intracranial responses 

• Intracranial responses replicate distinct music- and speech-selective populations

Summary

How is music represented in the brain? While neuroimaging has revealed some spatial segregation between responses to music versus other sounds, little is known about the neural code for music itself. To address this question, we developed a method to infer canonical response components of human auditory cortex using intracranial responses to natural sounds, and further used the superior coverage of fMRI to map their spatial distribution. The inferred components replicated many prior findings, including distinct neural selectivity for speech and music, but also revealed a novel component that responded nearly exclusively to music with singing. Song selectivity was not explainable by standard acoustic features, was located near speech- and music-selective responses, and was also evident in individual electrodes. These results suggest that representations of music are fractionated into subpopulations selective for different types of music, one of which is specialized for the analysis of song.

Expression unleashed: The evolutionary & cognitive foundations of human communication

I'm passing on the abstract of a dense but interesting article by Christophe Heintz and Thom Scott-Phillips that will be published in Behavioral and Brain Science and is now being circulated for comment by reviewers. Motivated readers can request a PDF of the article from me.

Human expression is open-ended, versatile and diverse, ranging from ordinary language use to painting, from exaggerated displays of affection to micro-movements that aid coordination. Here we present and defend the claim that this expressive diversity is united by an interrelated suite of cognitive capacities, the evolved functions of which are the expression and recognition of informative intentions. We describe how evolutionary dynamics normally leash communication to narrow domains of statistical mutual benefit, and how they are unleashed in humans. The relevant cognitive capacities are cognitive adaptations to living in a partner choice social ecology; and they are, correspondingly, part of the ordinarily developing human cognitive phenotype, emerging early and reliably in ontogeny. In other words, we identify distinctive features of our species’ social ecology to explain how and why humans, and only humans, evolved the cognitive capacities that, in turn, lead to massive diversity and open-endedness in means and modes of expression. Language use is but one of these modes of expression, albeit one of manifestly high importance. We make cross-species comparisons, describe how the relevant cognitive capacities can evolve in a gradual manner, and survey how unleashed expression facilitates not only language use but novel behaviour in many other domains too, focusing on the examples of joint action, teaching, punishment and art, all of which are ubiquitous in human societies but relatively rare in other species. Much of this diversity derives from graded aspects of human expression, which can be used to satisfy informative intentions in creative and new ways. We aim to help reorient cognitive pragmatics, as a phenomenon that is not a supplement to linguistic communication and on the periphery of language science, but rather the foundation of the many of the most distinctive features of human behaviour, society and culture.

Children universally across societies enforce conventional norms but in culturally variable ways

From Kanngiesser et al. in PNAS:

Humans, as compared with other animals, create and follow conventional norms that determine how we greet each other, dress, or play certain games. Conventional norms are universal in all human societies, but it is an open question whether individuals in all societies also actively enforce conventional norms when others in their group break them. We investigated third-party enforcement of conventional norms in 5- to 8-y-old children (n = 376) from eight diverse small-scale and large-scale societies. Children learned the rules for playing a new sorting game and then, observed a peer who was apparently breaking them. Across societies, observer children intervened frequently to correct their misguided peer (i.e., more frequently than when the peer was following the rules). However, both the magnitude and the style of interventions varied across societies. Detailed analyses of children’s interactions revealed societal differences in children’s verbal protest styles as well as in their use of actions, gestures, and nonverbal expressions to intervene. Observers’ interventions predicted whether their peer adopted the observer’s sorting rule. Enforcement of conventional norms appears to be an early emerging human universal that comes to be expressed in culturally variable ways.

The active grandparent hypothesis

Lieberman et al. suggest that selection in humans for lifelong physical activity, including during postreproductive years to provision offspring, promoted selection for energy allocation pathways which synergistically slow senescence and reduce vulnerability to many forms of chronic diseases. Here is their abstract (motivated readers can obtain a copy of the article from me):

The proximate mechanisms by which physical activity (PA) slows senescence and decreases morbidity and mortality have been extensively documented. However, we lack an ultimate, evolutionary explanation for why lifelong PA, particularly during middle and older age, promotes health. As the growing worldwide epidemic of physical inactivity accelerates the prevalence of noncommunicable diseases among aging populations, integrating evolutionary and biomedical perspectives can foster new insights into how and why lifelong PA helps preserve health and extend lifespans. Building on previous life-history research, we assess the evidence that humans were selected not just to live several decades after they cease reproducing but also to be moderately physically active during those postreproductive years. We next review the longstanding hypothesis that PA promotes health by allocating energy away from potentially harmful overinvestments in fat storage and reproductive tissues and propose the novel hypothesis that PA also stimulates energy allocation toward repair and maintenance processes. We hypothesize that selection in humans for lifelong PA, including during postreproductive years to provision offspring, promoted selection for both energy allocation pathways which synergistically slow senescence and reduce vulnerability to many forms of chronic diseases. As a result, extended human healthspans and lifespans are both a cause and an effect of habitual PA, helping explain why lack of lifelong PA in humans can increase disease risk and reduce longevity.

What is a DAO? Who needs humans?

A DAO is a Decentralised Autonomous Organisation. My son pointed out this intriguing and also somewhat terrifying video to me. Like Mark Zuckerberg's corporate "Meta" fantasies another step towards tearing our evolved biolgical bodies and social brains away from the organic tactile contacts with each other for which they were designed.

 

What the mind is - similarities and differences in concepts of mental life in five cultures

From Weisman et al., who do a fascinating study of cognitive structures 'from the bottom up', allowing data to give rise to ontological structures, rather than working 'from the top down' by using a theory to guide hypothesis-driven data collection. :

How do concepts of mental life vary across cultures? By asking simple questions about humans, animals and other entities – for example, ‘Do beetles get hungry? Remember things? Feel love?’ – we reconstructed concepts of mental life from the bottom up among adults (N = 711) and children (ages 6–12 years, N = 693) in the USA, Ghana, Thailand, China and Vanuatu. This revealed a cross-cultural and developmental continuity: in all sites, among both adults and children, cognitive abilities travelled separately from bodily sensations, suggesting that a mind–body distinction is common across diverse cultures and present by middle childhood. Yet there were substantial cultural and developmental differences in the status of social–emotional abilities – as part of the body, part of the mind or a third category unto themselves. Such differences may have far-reaching social consequences, whereas the similarities identify aspects of human understanding that may be universal.

A debate over stewardship of global collective behavior

In this post I'm going to pass on the abstract of a PNAS perspective piece by Bak-Coleman et al., a critique by Cheong and Jones and a reply to the critique by Bak-Coleman and Bergstrom. First the Bak-Coleman et al. abstract:

Collective behavior provides a framework for understanding how the actions and properties of groups emerge from the way individuals generate and share information. In humans, information flows were initially shaped by natural selection yet are increasingly structured by emerging communication technologies. Our larger, more complex social networks now transfer high-fidelity information over vast distances at low cost. The digital age and the rise of social media have accelerated changes to our social systems, with poorly understood functional consequences. This gap in our knowledge represents a principal challenge to scientific progress, democracy, and actions to address global crises. We argue that the study of collective behavior must rise to a “crisis discipline” just as medicine, conservation, and climate science have, with a focus on providing actionable insight to policymakers and regulators for the stewardship of social systems.

The critique by Cheong and Jones:

In vivid detail, Bak-Coleman et al. describe explosively multiplicative global pathologies of scale posing existential risk to humanity. They argue that the study of collective behavior in the age of digital social media must rise to a “crisis discipline” dedicated to averting global ruin through the adaptive manipulation of social dynamics and the emergent phenomenon of collective behavior. Their proposed remedy is a massive global, multidisciplinary coalition of scientific experts to discover how the “dispersed networks” of digital media can be expertly manipulated through “urgent, evidence-based research” to “steward” social dynamics into “rapid and effective collective behavioral responses,” analogous to “providing regulators with information” to guide the stewardship of ecosystems. They picture the enlightened harnessing of yet-to-be-discovered scale-dependent rules of internet-age social dynamics as a route to fostering the emergent phenomenon of adaptive swarm intelligence.

We wish to issue an urgent warning of our own: Responding to the self-evident fulminant, rampaging pathologies of scale ravaging the planet with yet another pathology of scale will, at best, be ineffective and, at worst, counterproductive. It is the same thing that got us here. The complex international coalition they propose would be like forming a new, ultramodern weather bureau to furnish consensus recommendations to policy makers while a megahurricane is already making landfall. This conjures images of foot dragging, floor fights, and consensus building while looking for actionable “mechanistic insight” into social dynamics on the deck of the Titanic. After lucidly spotlighting the urgent scale-dependent mechanistic nature of the crisis, Bak-Coleman et al. do not propose any immediate measures to reduce scale, but rather offer that there “is reason to be hopeful that well-designed systems can promote healthy collective action at scale...” Hope is neither a strategy nor an action.

Despite lofty goals, the coalition they propose does not match the urgency or promise a rapid and collective behavioral response to the existential threats they identify. Scale reduction may be “collective,” but achieving it will have to be local, authentic, and without delay—that is, a response conforming to the “all hands on deck” swarm intelligence phenomena that are well described in eusocial species already. When faced with the potential for imminent global ruin lurking ominously in the fat tail (5) of the future distribution, the precautionary principle dictates that we should respond with now-or-never urgency. This is a simple fact. A “weather bureau” for social dynamics would certainly be a valuable, if not indispensable, institution for future generations. But there is no reason that scientists around the world, acting as individuals within their own existing social networks and spheres of influence, observing what is already obvious with their own eyes, cannot immediately create a collective chorus to send this message through every digital channel instead of waiting for a green light from above. “Urgency” is euphemistic. It is now or never.

The Bak-Coleman and Bergstrom reply to the critique:

In our PNAS article “Stewardship of global collective behavior”, we describe the breakneck pace of recent innovations in information technology. This radical transformation has transpired not through a stewarded effort to improve information quality or to further human well-being. Rather, current technologies have been developed and deployed largely for the orthogonal purpose of keeping people engaged online. We cannot expect that an information ecology organized around ad sales will promote sustainability, equity, or global health. In the face of such impediments to rational democratic action, how can we hope to overcome threats such as global warming, habitat destruction, mass extinction, war, food security, and pandemic disease? We call for a concerted transdisciplinary response, analogous to other crisis disciplines such as conservation ecology and climate science.

In their letter, Cheong and Jones share our vision of the problem—but they express frustration at the absence of an immediately actionable solution to the enormity of challenges that we describe. They assert “swarm intelligence begins now or never” and advocate local, authentic, and immediate “scale reduction.” It’s an appealing thought: Let us counter pathologies of scale by somehow reversing course.

But it’s not clear what this would entail by way of practical, safe, ethical, and effective intervention. Have there ever been successful, voluntary, large-scale reductions in the scale of any aspect of human social life?

Nor is there reason to believe that an arbitrary, hasty, and heuristically decided large-scale restructuring of our social networks would reduce the long tail of existential risk. Rather, rapid shocks to complex systems are a canonical source of cascading failure. Moving fast and breaking things got us here. We can’t expect it to get us out.

Nor do we share the authors’ optimism about what scientists can accomplish with “a collective chorus … through every digital channel”. It is difficult to envision a louder, more vehement, and more cohesive scientific response than that to the COVID-19 pandemic. Yet this unified call for basic public health measures—grounded in centuries of scientific knowledge—nonetheless failed to mobilize political leadership and popular opinion.

Our views do align when it comes to the “now-or-never urgency” that Cheong and Jones highlight. Indeed, this is a key feature of a crisis discipline: We must act without delay to steer a complex system—while still lacking a complete understanding of how that system operates.

As scholars, our job is to call attention to underappreciated threats and to provide the knowledge base for informed decision-making. Academics do not—and should not—engage in large-scale social engineering. Our grounded view of what science can and should do in a crisis must not be mistaken for lassitude or unconcern. Worldwide, the unprecedented restructuring of human communication is having an enormous impact on issues of social choice, often to our detriment. Our paper is intended to raise the alarm. Providing the definitive solution will be a task for a much broader community of scientists, policy makers, technologists, ethicists, and other voices from around the globe.

Seven nuggets on how we confuse ourselves about our brains and our world.

In a series of posts starting on Nov. 27, 2020 I attempted to abstract and condense the ideas in Lisa Feldman Barrett’s 2017 book “How Emotions Are Made: The Secret Life of the Brain”. That book is a hard slog, as was my series of posts on its contents. Barrett also did her own condensation in her followup book, “Seven and a Half Lessons About the Brain,” that appeared in late 2020 at the same time as my posts, and I’ve finally gotten around to scanning through it. I want to pass on her brief epilogue that extracts a few crisp nuggets from her lessons:

ONCE UPON A TIME, you were a little stomach on a stick, floating in the sea. Little by little, you evolved. You grew sensory systems and learned that you were part of a bigger world. You grew bodily systems to navigate that world efficiently. And you grew a brain that ran a budget for your body. You learned to live in groups with all the other little brains-in-bodies. You crawled out of the water and onto land. And across the expanse of evolutionary time - with the innovation that comes from trial and error and the deaths of trillions of animals - you ended up with a human brain. A brain that can do so many impressive things but at the same time severely misunderstands itself.

-A brain that constructs such rich mental experiences that we feel like emotion and reason wrestle inside us 

-A brain that’s so complex that we describe it by metaphors and mistake them for knowledge 

-A brain that’s so skilled at rewiring itself that we think we’re born with all sorts of things that we actually learn 

-A brain that’s so effective at hallucinating that we believe we see the world objectively, and so fast at predicting that we mistake our movements for reactions 

-A brain that regulates other brains so invisibly that we presume we’re independent of each other 

-A brain that creates so many kinds of minds that we assume there’s a single human nature to explain them all 

-A brain that’s so good at believing its own inventions that we mistake social reality for the natural world

We know much about the brain today, but there are still so many more lessons to learn. For now, at least, we’ve learned enough to sketch our brain’s fantastical evolutionary journey and consider the implications for some of the most central and challenging aspects of our lives.

Our kind of brain isn’t the biggest in the animal kingdom, and it’s not the best in any objective sense. But it’s ours. It’s the source of our strengths and our foibles. It gives us our capacity to build civilizations and our capacity to tear down each other. It makes us simply, imperfectly, gloriously human.

Cultural Evolution of Genetic Heritability

Behavioral and Brain Sciences has accepted an article from Uchiyama et al., whose abstract I copy below, and invites the submission of commentary proposals.

Behavioral genetics and cultural evolution have both revolutionized our understanding of human behavior—largely independent of each other. Here we reconcile these two fields under a dual inheritance framework, offering a more nuanced understanding of the interaction between genes and culture. Going beyond typical analyses of gene- environment interactions, we describe the cultural dynamics that shape these interactions by shaping the environment and population structure. A cultural evolutionary approach can explain, for example, how factors such as rates of innovation and diffusion, density of cultural sub-groups, and tolerance for behavioral diversity impact heritability estimates, thus yielding predictions for different social contexts. Moreover, when cumulative culture functionally overlaps with genes, genetic effects become masked, unmasked, or even reversed, and the causal effects of an identified gene become confounded with features of the cultural environment. The manner of confounding is specific to a particular society at a particular time, but a WEIRD (Western, educated, industrialized, rich, democratic) sampling problem obscures this boundedness. Cultural evolutionary dynamics are typically missing from models of gene-to-phenotype causality, hindering generalizability of genetic effects across societies and across time. We lay out a reconciled framework and use it to predict the ways in which heritability should differ between societies, between socioeconomic levels and other groupings within some societies but not others, and over the life course. An integrated cultural evolutionary behavioral genetic approach cuts through the nature-nurture debate and helps resolve controversies in topics such as IQ.

Darwin’s insights: How the evolutionary perspective has come to permeate the social sciences.

I want to pass on a review article on human evolution by Richerson1,Gavrilets, and de Waal (open source) in a recent issue of Science Magazine. Here is the Editor's summary: 

150 years of The Descent of Man

Charles Darwin's The Descent of Man was published in 1871. Ever since, it has been the foundation stone of human evolutionary studies. Richerson et al. have reviewed how modern studies of human biological and cultural evolution reflect the ideas in Darwin's work. They emphasize how cooperation, social learning, and cumulative culture in the ancestors of modern humans were key to our evolution and were enhanced during the environmental upheavals of the Pleistocene. The evolutionary perspective has come to permeate not just

Can You Have More Than 150 Friends?

MindBlog has done more than 9 posts over the past 15 years (enter Dunbar in the search box in the left column of this web page) pointing to Robin Dunbar's work showing that for a large number of animal species brain size and social group size get larger together, with his curve predicting that the optimal group size for humans is about 150. The staus of this widely accepted number has been challenged by Lind and collaborators, whose article suggests that the number could be much higher. Here is their abstract and a few clips from their discussion:

A widespread and popular belief posits that humans possess a cognitive capacity that is limited to keeping track of and maintaining stable relationships with approximately 150 people. This influential number, ‘Dunbar's number’, originates from an extrapolation of a regression line describing the relationship between relative neocortex size and group size in primates. Here, we test if there is statistical support for this idea. Our analyses on complementary datasets using different methods yield wildly different numbers. Bayesian and generalized least-squares phylogenetic methods generate approximations of average group sizes between 69–109 and 16–42, respectively. However, enormous 95% confidence intervals (4–520 and 2–336, respectively) imply that specifying any one number is futile. A cognitive limit on human group size cannot be derived in this manner.

Ruiter et al. make the point that

Dunbar's assumption that the evolution of human brain physiology corresponds with a limit in our capacity to maintain relationships ignores the cultural mechanisms, practices, and social structures that humans develop to counter potential deficiencies...Human information process management, we argue, cannot be understood as a simple product of brain physiology. Cross-cultural comparison of not only group size but also relationship-reckoning systems like kinship terminologies suggests that although neocortices are undoubtedly crucial to human behavior, they cannot be given such primacy in explaining complex group composition, formation, or management.

An article by Jenny Gross quotes Dunbar's responses to the above.

The new analysis, he said, “is bonkers, absolutely bonkers,” adding that the Stockholm University researchers conducted a flawed statistical analysis and misunderstood both the nuances of his analyses and of human connections. “I marvel at their apparent failure to understand relationships.”

Dr. Dunbar defines meaningful relationships as those people you know well enough to greet without feeling awkward if you ran into them in an airport lounge. That number typically ranges from 100 to 250, with the average around 150...Around 6000 B.C., the size of Neolithic villages from the Middle East was 120 to 150 people, judging by the number of dwellings. In 1086, the average size of most English villages recorded in the Domesday Book was 160 people. In modern armies, fighting units contain an average of 130 to 150 people, he said...Dr. Dunbar contended that his theory is still viable, even in today’s hyper-connected world, since the quality of connections on social networks is often low. “These are not personalized relationships,” he said...“It’s fairly blatantly obvious to most people when they sit down and think about it that that’s how their social network is organized,” he said. Dunbar’s number, he said, is not going anywhere.