Why We Keep Choosing Strongmen as Leaders: A Global Experiment Reveals an Evolutionary Secret

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– by Lasse Laustsen & Mark van Vugt

Across the globe and throughout history, people have repeatedly turned to dominant, authoritarian leaders—figures like Julius Caesar, Vladimir Putin, and Donald Trump. While democracy advocates may scratch their heads, evolutionary psychology offers a compelling explanation: during times of intergroup conflict—war, terrorism, or intense rivalry—our ancestral instincts kick in, prompting us to prefer tough, dominant personalities to lead us.

In our recent study, published in Evolution and Human Behavior, we put this theory to a rigorous global test. Partnering with a diverse group of researchers from 25 countries, we gathered data from over 5,000 individuals to explore whether the preference for dominant leaders spikes when intergroup conflict is perceived.

Our Study

Participants from a wide range of cultures and political contexts were presented with hypothetical scenarios involving war, peace, or neutral conditions. Afterward, they selected preferred leaders from pairs of faces subtly manipulated to appear more or less dominant. The results were clear and consistent across cultures: participants exposed to war scenarios significantly preferred more dominant-looking leaders. Importantly, we didn’t stop there. We also assessed participants’ explicit preferences for leader traits, revealing that during conflicts, dominance traits—like toughness, strength, and assertiveness—were prioritized over warmth and even competence.

Why Does Conflict Favor Dominance?

This finding aligns closely with an evolutionary perspective of leadership. Human survival historically depended heavily on group cohesion and effective defense against rival groups. A dominant leader would have likely been more effective in rallying a rapid, coordinated response against external threats, thus increasing a group’s chances of survival. Our ancestors, therefore, evolved psychological mechanisms attuned to selecting dominance when facing danger. In the modern world, however, such instincts may misfire—an evolutionary mismatch. While dominant leaders appear advantageous in ancestral intertribal conflicts, they often bring problematic governance and strained international relations today.

Dominance: A Universal Preference?

One might wonder whether these preferences were culturally determined or universally innate. Our comprehensive dataset—encompassing affluent democracies, developing nations, Western and non-Western societies—supports universality. Even with educational and economic diversity between the sampled countries, the conflict-driven preference for dominance was remarkably consistent. This suggests an innate basis for our leadership psychology that transcends cultural boundaries.

Individual Differences Also Matter

Beyond situational contexts, individual psychological traits also play a role. People predisposed to seeing the world as dangerous or hierarchical—those higher in authoritarianism or social dominance orientation—consistently showed stronger preferences for dominant leadership. This indicates how deeply ingrained psychological worldviews reinforce these leadership preferences, suggesting that dominant leaders may actively exploit or amplify threats to maintain power.

Implications for Modern Politics

Our findings have some implications for contemporary politics and international relations. Recognizing the evolutionary underpinnings of leader preferences can explain why, during crises, voters often choose leaders who exude strength and dominance—even if those leaders might not be optimal for democratic governance or long-term peace. Moreover, politicians themselves might strategically use this psychology by heightening public awareness of threats—real or perceived—to solidify their power base. Recent examples abound: Putin’s rhetoric around Western hostility or Trump’s campaign messages emphasizing global dangers illustrate how leaders can exploit evolutionary preferences.

Takeaway

Understanding our evolutionary psychology provides powerful insights into political behavior. Our study emphasizes the need for awareness: when conflict looms, our ancestral brains may push us towards dominant leaders, sometimes against our better democratic judgment. By recognizing this bias, societies can better guard against manipulative leadership tactics and consciously strive for balanced, cooperative and compassionate leadership—even amidst challenges and uncertainties.

Read the original article (here): Laustsen, L., Sheng, X., Ahmad, M. G., Al-Shawaf, L., Banai, B., Banai, I. P., … & Van Vugt, M. (2025). Cross-cultural evidence that intergroup conflict heightens preferences for dominant leaders: A 25-country study. Evolution and human behavior, 46(3), 106674.

HBES 2025 conference report

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HBES 2025 was a success!

From June 4-7, we gathered at Stockton University in Atlantic City, NJ, for 3.5 fantastic days of presentations, posters, and discussions. Thanks to Josh Duntley & the other organizers (Bobbi Hornbeck, Margaret Lewis, Liz Shobe), the Program Committee, the volunteers, the competition judges, the speakers & presenters, the sponsors, and everyone else who made it great!

Plenaries

We enjoyed plenaries from the following researchers:

Michael Platt kicked off #HBES2025 with a tour de force plenary in the neuroscience and consequences of social behavior! In wild monkeys on Cayo Santiago, social ties buffer against the health consequences of the devastating hurricane Maria. He used cutting edge neuroscience to challenge sparse coding models of brain activity in which individual neurons control specific behaviors, and instead show that neurons tend to be recruited for the regulation of multiple behaviors. Plenaries like this are what’s great about HBES: from data on the fundamental importance of social bonds to questions about the nature of computation in the brain all in one talk!

Beverly Strassmann provided a stunning testament to the power of long-term field studies and the human behavioral ecology perspective, with data from 40 years of research among the Dogon of Mali. Her research shows how individual reproductive interests can explain phenomena from the widest scale of religious conversation, to men’s control of women’s sexuality, to conflict among kin, and zooming all the way in to genomic imprinting. Fantastic work!

Jim Roney declared war on the “parsimony-based” approach that he claims dominates hormone research, i.e., attempts to find the “one” true effect of a hormone, which leads to imbalances in research on inputs vs outputs, obscures functions & creates confusion. He argued that we need to adopt a “theoretical frameworks” approach: study how hormones connect situational inputs with coordinated outputs. This reveals how hormones serve as physiological codes for adaptively-relevant situations. His plenary showed how this perspective yields fresh insights. He provides the 1st evidence of estradiol & progesterone coordinating to suppress sexual desire during the “implantation window”, & shows how this makes sense of seemingly conflicting effects of the famously mercurial hormone oxytocin”

Oliver Scott Curry took us on an interstellar tour through the universe of morality. He argued morality is fundamentally about promoting cooperation toward promoting the common good, which lets game theory model “What is good?” as a scientific question. He identified 7 types of cooperation that people around the world find morally good, showed how individual differences in moral intuition arise from variations on these themes, and demonstrated how culturally variable moral norms arise as combining these seven more basic elements.

Norm Li applied a life history framework to declines in fertility worldwide. He reviewed several known sources of fertility decline but called attention to a potentially underappreciated factor: evolutionary mismatch. He presented a series of experiments providing evidence that exposure to some modern challenges –climbing modern status ladders, economic uncertainty, & population density–induces shifts toward slower reproductive strategies.

Siobhán Cully’s plenary gave recommendations on “managing patriarchy in the evolutionary behavioral sciences”. She marshalled a range of evidence on the inadequacy of a “male-centered” view of evolution, i.e., that men hunting is the central driver of human life history evolution. According to Dr. Cully, men don’t exclusively use their caloric surpluses for provisioning, and are often less reliable caregivers. In addition, women’s contributions to culture, provisioning, and technology are underrepresented in the archeological record. She made a number of recommendations to paint a more accurate picture, including being more cautious in our inferences about sex and gender, to be more creative in our methods to capture variation, to focus on knowledge gaps, and to continue engaging in healthy debate.

Elizabeth Cashdan’s keynote surveyed the power of an evolutionary, cross-cultural, and comparative perspective for illuminating the nature and origin of sex differences in spatial cognition. Dr. Cashdan showed evidence that sex differences in spatial cognition are cross-culturally universal but flexible and ecologically contingent, underscoring the importance of experience in shaping cognition.

Conference Awards

Every HBES conference has three Conference Awards: the New Investigator Award to the best graduate student paper/presentation, the Postdoctoral Award to the best paper/presentation by a recent graduate (<5 years post-PhD), and the Poster Award (best poster by anyone). Here are the winners of the 2025 HBES Conference Awards:

  • New Investigator Award: Marco Balducci for “The Gender-Equality Paradox in Intraindividual Academic Strengths: A Cross-Temporal Analysis”
  • Postdoctoctdoral Award: Ahra Ko for “Politics, Pathogens, and Perception: Tracking Adaptive Shifts in the Behavioral Immune System in Real Time”
  • Poster Award: Angela Vasishta, Karthik Panchanathan, & Hannah Rubin for “The Effects of Reputation and Fairness on Homophily and Discrimination in Academic Collaboration Networks”

Society Awards

HBES also announces the Society Awards: the Early Career Award for Distinguished Scientific Contribution (best researcher <10 years post-PhD), the HBES Fellows (multiple awardees >10 years post-PhD), the Rising Stars (multiple awardees <8 years post-PhD), and the Lifetime Achievement Award for Distinguished Scientific Contribution. Here are the winners of the 2025 HBES Society Awards:

Paper Awards

And finally, there are the Paper Awards: the Margo Wilson Award for the best paper published the previous year in Evolution and Human Behavior (the official HBES journal), and the Don Symons Adaptationism Award for the best paper in the previous three years in any journal that best exemplifies the adaptationist program (this award is privately sponsored). The 2025 winners of the HBES Paper Awards are:

Announcing HBES 2025

Next year’s HBES will be held from May 13-16 at University Mohammad VI Polytechnique in Rabat, Morocco. They have a huge team of evolutionary researchers and brand new facilities in an international tourist destination. This will be a joint meeting with the Cultural Evolution Society (CES): CES meets May 11-13, HBES meets May 13-16, with one day of joint talks (May 13). For more details and an FAQ by the hosts, see our conference announcement. See you there!

Three australopithecines interacting peacefully

When Our Ancestors Stopped Being Bullies: The First Great Social Revolution of Early Humans

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– by Michael McBride

Imagine a world where the biggest, strongest individual gets to eat first, mate first, and make decisions while everyone else cowers in submission. This was the reality for our ancient ancestors millions of years ago, just as it is for many animals today. It was a social life dominated by bullies—mostly male but also female—who used brute force to control resources and social order. Yet, somewhere along our evolutionary journey, we flipped the script entirely.

In my recent study published in Evolution and Human Behavior, I investigated this pivotal transition in human evolution—the shift from a dominance hierarchy in which bullies rule to a reversed dominance hierarchy in which bullies are suppressed by coalitions of cooperating individuals. This transformation didn’t just change how our ancestors organized themselves socially; it fundamentally shaped what it means to be human.

Dominance Hierarchy and its Reversal

To understand this transition, we need to look back roughly 6-7 million years ago to our last common ancestor with chimpanzees and bonobos. As other scholars have explained, these ancient ancestors lived in societies where physical dominance determined social rank. The strongest individuals controlled access to food, mates, and territory through intimidation and violence, while everyone else fell in line.

This pattern of social interactions, while brutal, had its evolutionary logic. Strong individuals passed on their genes more successfully, and clear hierarchies reduced constant fighting. At the same time, this social arrangement also hindered the successful emergence of life-improving developments. For example, dominance hierarchy hindered more advanced forms or social cooperation and collective problem-solving.

Yet, sometime between that ancient ancestor and the emergence of modern humans, our hominin ancestors reversed the dominance hierarchy. Instead of submitting to bullies, individuals actively suppressed them, and bullying declined.

How and when this transition happened is still a mystery because many factors worked against coalition formation among the earliest hominins. Early hominins had limited cognition and communication abilities, which restricted their capacity to plan and coordinate complex group actions against bullies. Challenging a bully also meant taking on the huge risk of extreme physical harm. It probably wasn’t worth it to try to suppress bullies.

The Model and Key Findings

To study this transition, I developed a formal mathematical and game-theoretical model that tracks the evolution of different behaviors in early hominin populations. In each period of the evolutionary game, actors in a large population are randomly matched into trios to interact in what I call the Bullying Game. The strongest actor of the three can undertake bulling or not. If bullying occurs, then a second actor can challenge the bully or let the bully go challenged. If there is a challenge, then the third actor either helps in the challenge or does not help; helping means forming a coalition with the second actor. The bully’s reproductive fitness is highest after unchallenged bullying, but is lowest after a challenging coalition. Conversely, the victims suffer fitness losses after bullying, but a coalitional challenge minimizes those losses.

When matched in the Bullying Game, each actor acts according to their behavioral type which is inherited from their parent. The model identifies several distinct behavioral types, ranging from pure bullies who never help others to cooperative challengers who challenge bullies and help others who challenge bullies. Evolutionary selection determines the distribution of behavioral types in the population such that parents with higher fitness reproduce children of their same type at higher rates.

The analysis reveals how the evolution of types in the population depends on both the initial distribution of types in the population and on several key parameters. For example, evolutionary selection favors bullies when there are relatively few challengers because bullying goes unchecked, and selection disfavors challenging when there are few helpers because a solitary challenge against a strong bully yields a large fitness loss to the challenger. At the same time, challenging and helping have relatively higher returns when the fitness costs of being bullied are large because there is less to lose and more to gain from the challenge.

A key insight from the analysis is that populations can still get “stuck” in dominance hierarchies unless some specific conditions are met. First, potential helpers must also suffer significant fitness losses when they witness bullying. If the cost of living in a society with unchecked bullies is high enough to motivate helping in a challenge, then helpers emerge and challenges become successful. Second, the cost of challenging a bully must be relatively low. Finally, there must be just the right amount of genetic drift, which is random changes in population composition that aren’t based on fitness advantages. If there is too little drift in a dominance hierarchy, then challengers are driven to extinction before helpers can gain a foothold and make challenging a viable strategy. If there is too much drift, then the drift prevents a full reversal of dominance hierarchy because the evolutionary system has too much randomness. I argue in the paper that this right kind of drift was likely present, thus making the transition possible when the other key conditions were present.

Another striking finding is that societies undergoing this transition must go through an extremely violent phase. As conditions for helping improve, the rate of helping increases, which in turn drives an increase in challenging. Then, violence replaces submission as the common response to bullying, and conflict peaks as bullies who continue their violent ways are actively suppressed by coalitions. Our hominin ancestors had to navigate this dangerous period just before the transition’s completion.

Timing the Transition

But when did this momentous change occur? As previous scholars have noted, Homo erectus (about 1.8 million years ago) undertook large-game hunting and was the first hominin to spread across continents. These activities are both unlikely in a dominance hierarchy because they required new forms of social cooperation. For example, large-game hunting likely required new forms of meat sharing and a suppression of bullying to make it worthwhile for group members to undertake the danger and risks associated with hunting large animals. So, the transition must have happened sometime between 7 to 2 million years ago.

Here, the model helps again. By interpreting how the key evolutionary developments among our hominin ancestors would affect coalition formation and bully suppression in the model, I narrow down the possible window of time for the transition. Consider these developments:

  • Bipedalism: Walking on two legs enabled longer travel, opened new forms of hunting, and freed hands for weapons. These developments increased the returns from many activities, but also increased the stakes from bullying and challenging bullies.
  • Tools: Wood and stone tools increased access to new food sources, thereby also raising the bullying stakes. Stone tools first emerged 3.3 million years ago, but wood tools likely predated them.
  • Cognition: As our ancestors’ cognition improved, they became smarter about social dynamics, including the ability to recognize potential allies and coordinate group actions that would increase the chance of success against bullies,
  • Weapons: When anyone can kill with a weapon, physical size becomes less important than intelligence and cooperation. The emergence of weapons could have even been the ultimate trigger of the transition by making challenging coalitions more effective, though my analysis reveals that a weapons-free transition was also possible.

I conclude that the most likely time frame for the reversal of dominance hierarchy is during the late Pliocene or early Pleistocene epoch (roughly 3.5 to 2 million years ago), when bipedalism, cognitive abilities, and tool use had meaningfully developed and the Homo genus first emerged. This timing places the transition right before or near the emergence of the genus Homo, but also well before other important developments in human social life such as the emergence of more advanced forms of morality.

The Ongoing Legacy

The reversal of dominance hierarchy represents a seminal step in our evolutionary journey toward unprecedented cooperation. This transition built upon earlier developments like bipedalism, basic tool use, and improved cognitive abilities that had already begun distinguishing our lineage from other great apes. As new cooperative opportunities emerged, the costs of dominance hierarchy increased, and the transition could begin. However, the reversal of dominance hierarchy also paved the way for other critical innovations that would further transform human society. For example, the suppression of reproductive bullying would make cooperative breeding a more viable reproductive strategy. Understanding how the reversal of dominance hierarchy is part of a larger evolutionary sequence helps illuminate how our ancestors gradually assembled the building blocks of modern human cooperation, with each development creating conditions that made the next breakthrough possible.

This ancient revolution in bully suppression also reminds us that cooperation isn’t weakness—it’s one of our species’ greatest strengths, forged in the crucible of evolutionary pressure and refined over millions of years of social innovation. The specific conditions required for this transition to succeed make it all the more remarkable that our ancestors managed to navigate this complex evolutionary challenge, ultimately giving rise to the uniquely cooperative yet competitive species we are today.

Read the original paper here: McBride, M. (2025). Early hominins and the reversal of dominance hierarchy. Evolution & Human Behavior, 46(3), 106688.

Announcing HBES 2026

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Dear HBES Community,

Now that HBES 2025 in Atlantic City is over, it’s time to start thinking towards 2026. Hosting HBES shows dedication to the society, so thanks to Josh Duntley and the hosts of HBES 2025 for a successful conference. What’s in store for HBES 2026?

We are very pleased to announce that HBES 2026 will be held in Rabat, Morocco, at the University Mohammad VI Polytechnic (UM6P) from May 13-16, 2026. This will be a joint conference with the Cultural Evolution Society (CES).

Unique Benefits of HBES 2026 in Rabat

Having HBES 2026 at UM6P in Rabat is exciting for many reasons.

First, UM6P has a growing community of evolutionary social scientists, including HBES members and students thereof (Zach Garfield, Ed Seabright, Sarah Alami, Mathieu Charbonneau, Rebecca Koomen, Cody Moser, Dominique Guillo, Alejandro Erut, Nicolas Porot, Emmanuel Trouche, & Cathal O’Madagain). As many hosts can attest, a good team is important, rather than relying on just a single evolutionary person to host, and this is a big team who have put in a lot of work over the last year preparing to host HBES 2026.

Second, we’re excited about the venue itself. It’s a good place venue for hosting events, with brand new facilities. Our hosting team has negotiated with UM6P to provide a lot of support, which will help keep costs down for our attendees, including students. In addition to hotels, there will be student dorms available for those who want keep costs even lower.

Third, it’s a chance for a joint conference with another prominent evolutionary society: the Cultural Evolution Society (CES). The conferences will be back-to-back: CES from May 11-13, and HBES from May 13-16, with one day of overlapping talks (May 13). This opportunity will provide a lot of useful cross-pollination between these two societies.

Fourth, this is a unique opportunity to bring HBES and CES to Africa, allowing African scholars to attend and present their research (in addition to the rest of the world). Much research in Evolutionary Psychology and Human Behavioral Ecology is conducted in Africa, so this will strengthen ties to African research institutions involved in these areas. Many scholars in the Global South have trouble traveling to North America or Europe (e.g., visas), so this conference can attract researchers who normally can’t attend HBES. UM6P values socioeconomic, cultural, and religious diversity. At the School of Collective Intelligence, where many of the host faculty are based, half the student body are international students from across Africa, and half are women. At the conference, we will hear perspectives from many researchers we don’t normally hear from, and foster the HBES goal of being a truly global society for the evolution of human behavior.

Altogether, this is an exciting opportunity for a great location, hosted by a great team, with another great evolutionary society, and with voices we seldom get to hear.

Travel to Rabat

We’ve never held an HBES in Morocco, and many members have never been there. As such, we recognize that some HBES members might have questions about Morocco. The hosts have put together a FAQ to answer common questions – it’s attached at this link, and will be updated as new questions come in (the date gets updated as the file does). The hosts also have solicited a letter from a local LGBTQ+ organization specifically about LGBTQ+ issues, which is available at this link. Here’s a quick overview.

How to get there: Many cities in Europe and North America have direct flights to Rabat or to Casablanca (1h by high-speed train), so direct and connecting flights are available

Costs: We estimate that total costs will be equivalent to or lower than most HBES meetings, because the high support from UM6P will result in low registration fees. Flights from North America are roughly equivalent to a flight to Europe (like some HBES meetings), and flights from Europe are close to that of a within-Europe flight.

Safety: Rabat is the capital of Morocco and has long been an international tourist destination. It is a safe and modern city, with crime rates lower than many US or European cities, including a lower risk of terrorism and unrest. UM6P campus itself is particularly secure. The tap water is drinkable in large Moroccan cities. Safety is always a concern when traveling, so the hosts have provided relevant details in the FAQ.

Women’s safety: Rabat is the safest city in Morocco for women. In major Moroccan cities, women can dress as they would in North America or Canada – Rabat itself is a cosmopolitan city, and residents are used to diversity in dress, especially among foreigners. Morocco criminalized sexual harassment in public spaces in 2018, and sexual harassment has decreased dramatically. Anecdotally, HBES members who have traveled to Morocco and Rabat in both personal and professional capacities report positive experiences. See the FAQ for details.

LGBTQ+ rights: Although same-sex relations are illegal in Morocco, these laws are only enforced against Moroccan citizens. LGBTQ+ tourists typically report no issues. The hosts have partnered with community organizers and advocates for Queer rights in Morocco to draft a letter to HBES members, which addresses the safety issue, and argues against boycotting Moroccan academic institutions. Please see the attached letter and the FAQ.

Religion: Morocco is a majority-Muslim country, but it is known for religious tolerance. Legal protections for religious beliefs are enshrined in the 2011 constitution, and major cities have active churches and synagogues. As one sign of tolerance: UM6P is very supportive of hosting two evolutionary conferences, which is something we cannot say about some campuses in North America and Europe.

The FAQ goes into more detail on each of these issues and more (e.g., travel details). The HBES exec has been working with the hosts for over a year, and we have been working together to ensure HBES 2026 will provide a safe and welcoming climate for all HBES members.

Overall: We’re Excited about HBES 2026 in Rabat!

HBES 2026 represents multiple unique opportunities, in addition to the usual quality experience of an HBES conference. We hope that the FAQ helps to answer any questions people have. If you have additional questions, please contact the hosts using the details found in the FAQ.

Looking forward to seeing you in Rabat!

Sincerely,

The HBES Team

PS: We start working with hosts a few years in advance, so if anyone is interested in hosting HBES in 2027 or beyond, please contact the HBES President.

Results of 2025 HBES Election

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We ran our 2025 elections this spring for the HBES executive, and are happy to announce the following winners:

President-Elect: David Puts

Student Representative: Nike (Yunsuh) Wee

Communications Officer: Karthik Panchanathan

Members-At-Large: Tania Reynolds (2031) & Zach Garfield (2031)

 

These incoming executive members will join the ongoing executive members:

President (formerly President-Elect): Ed Hagen

Past-President (formerly President): H. Clark Barrett

Treasurer: Jessica Hehman

Secretary: Lisa Welling

Members-At-Large: Jaimie Arona Krems (2027), Josh Tybur (2027), Dan Conroy-Beam (2029), Marco Del Giudice (2029)

 

We thank the departing executive members for their service:

Past-President: David Schmitt

Communications Officer: Pat Barclay

Student Representative: Nina Rodriguez

Members-At-Large: Coren Apicella (2025) & Chris von Rueden (2025)

 

A dense forest with multiple kinds of trees

Reconciling Our Three Traditions: Human Behavioral Ecology, Evolutionary Psychology, and Cultural Evolution

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– by Nicolas Baumard & Jean-Baptiste André

The evolutionary social sciences are grounded in the idea that evolutionary theory provides a unified framework to explain human behavior, including social norms, institutions, and cultural practices. Historically, the field emerged from the inclusive fitness revolution of the 1960s and developed into a powerful toolkit for analyzing strategic behavior. Yet over time, it has fractured into three dominant traditions—Human Behavioral Ecology (HBE), Evolutionary Psychology (EP), and Cultural Evolution (CE)—that often find themselves in tension, especially when addressing cultural phenomena.

In this article, we propose an ecological approach to culture that aims to reconcile these three traditions. Our proposal draws on their most robust insights while correcting the limitations that have led to fragmentation.

From Evolutionary Psychology, we adopt the foundational idea that humans are equipped with evolved cognitive mechanisms oriented toward adaptive goals such as survival, reproduction, social status, or cooperation. However, unlike traditional EP which emphasizes the universality and domain-specificity of these mechanisms, we emphasize their plasticity and generative nature. These mechanisms are not rigid modules but adaptive systems capable of producing flexible, context-sensitive responses—including entirely novel behaviors, institutions, and cultural artifacts—based on environmental inputs.

From Human Behavioral Ecology, we adopt the insight that adaptive strategies depend on context. Humans do not pursue fitness in a vacuum; they do so under particular ecological constraints and opportunities. As such, behavior cannot be understood apart from the ecology—broadly defined to include social, economic, and informational environments—that individuals inhabit.

From Cultural Evolution, we recognize that the human environment is not only natural, but also cultural—shaped by the accumulated actions of previous generations. Humans learn many of our behaviors by watching how others do things, whether how to forage, what tools to use, or how to achieve social status, i.e., we learn culturally. These are not “transmitted” in a genetic or replicative sense, but rather function as ecological legacies — modifications of the environment that constrain and enable future behavior, much like the trails left by elephants or the structures built by beavers shape the conditions of life for subsequent individuals. Individuals choose to adopt, build on, or ignore these cultural legacies based on the payoffs for doing so, including the social payoffs.

This perspective leads us to a key divergence from standard Cultural Evolution Theory: we see no need to posit a distinct inheritance system or an analogue of natural selection operating at the cultural level. Cultural change, in our view, does not depend on the replication and differential survival of cultural variants, but on how individuals, equipped with evolved psychological mechanisms, reuse and recombine the available cultural elements in ways that serve their current goals within a given ecology.

To take a specific image, we propose thinking of cultures as akin to forests (hence the picture!). A forest is the emergent product of countless interactions between organisms, their environment, and the phenotypic structures they (and their predecessors) build to pursue adaptive goals: trees anchoring themselves in the soil, fungi forming symbiotic networks, animals digging burrows or using tree canopies for shelter, and so forth.  Like cultures, forests persist across generations and precede the individuals living in them. They constrain and enable individual actions; vary in form and structure depending on local conditions; they exhibit historical contingency and path-dependence; result from myriad individual decisions without being reducible to any one of them; display emergent integration and functional organization; and accumulate structural and organic matter over time, which further shapes the environment and the behavior of future generations.

Yet in ecology, a forest is not treated as the output of a second inheritance system or as a group-level adaptation. Rather, it is seen as the aggregate result of individual organisms pursuing their adaptive goals—organisms whose actions transform the environment for others. This altered environment, in turn, constrains and enables new strategies in a continuous feedback loop. Likewise, cultural phenomena such as religious traditions, legal systems, or market economies may appear as autonomous forces acting on individuals. But in reality, they are the ecological residue of strategic behaviors shaped by individual adaptive goals in specific historical environments. Culture is not a transmitted substance; it is the structured context that emerges from repeated and overlapping individual actions.

This ecological approach allows us to make sense of both continuity and radical change in cultural forms. The same religious tradition, artistic style, or social institution can take on very different functions and meanings across time, not because it is faithfully transmitted, but because it is continually repurposed by individuals making strategic use of new ecological conditions. What we observe as “cultural continuity” often masks deep underlying plasticity and strategic adaptation.

By focusing on proximate cognitive mechanisms and the dynamic feedback loops between individuals and their modified environments, the ecological approach to culture offers a unified framework capable of integrating the strategic reasoning of HBE, the psychological realism of EP, and the cultural legacy emphasis of CE—while avoiding the problematic assumption of cultural replication. Culture, we argue, is not a second system of inheritance; it is the ecological residue of cumulative behavior from previous generations, to which our evolved minds respond with flexible, adaptive strategies.

In placing human agents—and their evolved interests—at the heart of cultural dynamics, the ecological approach to culture not only bridges the gap between behavioral ecology, evolutionary psychology, and cultural evolution; it also reclaims the original power of inclusive fitness theory that grounded the evolutionary study of behavior. The strength of inclusive fitness lies in its parsimony and constraint: it limits what evolution can plausibly produce and thereby yields genuine explanatory and predictive power. It treats cultural behaviors as ecological phenomena, shaped by the adaptive strategies of individuals operating in environments that include the material and informational legacies of the past. This perspective brings culture back under the umbrella of adaptationist reasoning, restoring the predictive power of evolutionary theory. It allows us to understand why some traditions persist while others vanish, why cultural change can be both rapid and conservative, and why individuals sometimes embrace cultural inputs and sometimes discard them. In doing so, it reaffirms that cultural behavior, no less than any other aspect of behavior, can be explained—not just described—by evolutionary principles, constrained by the logic of inclusive fitness.

Read the original paper (here): Baumard, N., & Jean-Baptiste André, J.-B. (2025). The ecological approach to culture. Evolution & Human Behavior, 46(3), 106686.

Two chimpanzees interacting peacefully

Blueprints of Language in Chimpanzee Interactions

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– by Bas van Boekholt & Simone Pika. Photo credit by Bas van Boekholt

The complexity of human language has no counterpart in the animal kingdom, even though some basic building blocks can be found in animal communication. However, there is not “one” human language, with great variability in languages across the world and cultures. Despite this, the way humans use their language in day-to-day conversations shows remarkable similarities. Human conversations tend to consist of short flexible alternating turns with very little overlap or gaps. Additionally, when interacting, we use our gaze and body posture to make clear who or what is part of the conversation (and who/what not). This underlying infrastructure of interactions has been termed “turn-taking” and extends beyond normal conversations into sign language as well as in interactions devoid of any language, such as for example, joint actions. Moreover, from the moment infants start to interact with the world around them, their interactions display precursors to this infrastructure and parts of this infrastructure have been found in the interactions of other primate species.

This evidence led Stephen Levinson to propose the interaction engine hypothesis, which suggests that our capacity to socially interact, and involved skills (e.g., intentionality, multimodality, turn-taking), paved the way for language to evolve in the first place. Specifically turn-taking has been suggested to be a very ancient mechanism with its building blocks appearing across the primate lineage. However, to systematically compare interactions across and within species, a comparative framework is needed. Pika and colleagues recently developed such a framework splitting human turn-taking into four key elements: (A) flexibility of turn-taking organization, (B) who is taking the next turn, (C) when do response turns occur, and (D) what should the next turn do. Following this framework, studies have shown some turn-taking elements in the interactions of other primate species, but they often focused on specific contexts or modalities (for example just looking at vocalisations). Additionally, very little is known about the development of these elements in the first few years of life. These biases have given us a limited perspective of the infrastructure underlying primate interactions and its ontogeny.

In this study, we wanted to address this gap by investigating whether interactions between young chimpanzee infants and their mother, involve two crucial elements of human turn-taking: temporal relationships (when do response turns occur) and participation frameworks (who is taking the next turn). Additionally, we investigated one more characteristic describing the infrastructure of interactions: the relative use of signals and actions. While most human interactions, such as conversations, consist of signal-signal exchanges with relatively little use of actions, this might not hold for interactions of other primate species, which are generally of a more imperative nature with individuals trying to achieve a physical goal. To investigate if these three characteristics are consistent in describing the infrastructure of chimpanzee interactions, we also determined if they were influenced by demographic and interactional factors such as the age and sex of the infant, the interactant class (infant or mother) or the context in which the interaction took place.

To answer these research questions, we filmed and analysed 360 interactions in 17 mother-infant dyads (infants: 0-5 year) over four different contexts of chimpanzees of the Ngogo population living in their natural environment in the Kibale National Park, Uganda over a two-year period.

Taking all interactions together, mother and infant chimpanzees used slightly more signals (N=1943) than actions (N=1704). Infants produced more signals and actions than their mothers, but the signal/action ration stayed the same. Moreover, the signal/action ratio did not change over development but was influenced by context, where, in the food-sharing context, there were relatively more signals produced and in the joint-travel context there were relative more actions. Most interactions (~86%) contained both signals and actions with less then 1% of the interactions consisting exclusively of signals. These results showcase the importance of both signals and actions in chimpanzee communication, and that, opposed to humans, chimpanzees do not have signal-only “conversations”.

For the temporal relationships we found that most responses fall within a zero to two second time window, with a threshold of three seconds. The timing of these response times was independent of the age of the infant, and did not differ between the infant and the mother or whether the response was to a signal or action. However, context had an influence with faster response times characterizing the joint-travel context. As we used slightly different methodologies, we cannot directly compare these response times to human studies, but the time window coincides with what previous studies have shown in adult chimpanzees.

Finally, throughout all interactions both mother and infant chimpanzees make frequent use of directed gaze and body direction to create and maintain a participation framework. Infants showed higher frequencies of directed gaze and body direction compared to their mother which might have been caused by dependence of young chimpanzee infants on their mother leading to a smaller social environment.

Concluding, we found that chimpanzee mother-infant interactions were characterized by an equal distribution of actions and signals, response times averaging around one second, and the establishment and maintenance of participation frameworks through high frequencies of directed gaze and body direction. These characteristics seem to be independent of distinct demographic and interactional factors, except for the influence of context. With a high occurrence of actions, chimpanzees of our study population did not seem to engage in signal-signal ‘conversations’. This could mean that the precursor of human conversational turn-taking was a complex system composed of interactions containing both signals and actions, similarly to interactions of human adults and infants. Subsequently, humans might have specialized in signal-signal conversations, that appear later in development.

Additionally, these interactional characteristics appear early in development, barely changing with aging infants, highlighting the consistent and fundamental nature of this infrastructure of mother-infant interactions. This is in line with the interaction engine hypothesis which suggests that this interactional infrastructure, together with other skills such as intentionality preceded the evolution of human language. However, future studies are needed to uncover if this infrastructure is present and comparable in other populations, species and age-classes across the primate lineage. Taking this comparative approach will help us to unravel the way ancient humans socially interacted, and if this infrastructure formed the blueprint from which language evolved.

Read the original paper: van Boekholt, B., & Pika, S. (2025). Infrastructure of mother-infant interactions across development in chimpanzees (Pan troglodytes) in the wild. Evolution & Human Behavior, 46(2), 106671.