HBES membership fees are increasing starting September 15

/in ,

Membership fees will increase starting September 15 (see below for details). If you are currently on a one-year membership, you can upgrade to a three-year plan at the current prices. You have until September 15 to upgrade your one-year membership.

  • Extend Regular One Year to Three Year ($102)

  • Extend Student One Year to Three Year ($51)

To renew or upgrade your membership, click here.


New membership pricing starting September 15, 2026

One-year rates:

  • Full/Associate professor (or equivalent):  $100

  • Early career (postdocs, assistant-level, or equivalent):  $80

  • Retired:  $70

  • Students:  $50

Three-year rates:

  • Full/Associate professor (or equivalent):  $240

  • Early career (postdocs, assistant-level, or equivalent):  $190

  • Retired:  $170

  • Students:  $120

One-year rates for residents of low- and middle-income countries:

  • Professional: $50

  • Student: $25

  • Three-year Qualifying Countries

  • Professional: $120

  • Student: $60

Citizens of countries not listed as “high income” qualify for the reduced membership cost. For a list of qualifying countries, click here.

Sex-Specific Vulnerabilities

/in ,

– by David C. Geary

Sex differences are common across species and often related to sexual selection, that is, they are found for traits that influence intrasexual competition for mates and intersexual discriminative mate choices (Andersson, 1994). Sexually selected traits are often exaggerated in size or are physiologically demanding (e.g., of cardiovascular fitness) and thus are more sensitive to stressor exposure than other traits. For instance, sex differences in armament or coloration (e.g., plumage) are often driven by male-male competition or female choice, but these sex differences become smaller when males are exposed to stressors. This is because stressor exposure affects the exaggerated male trait more strongly than the same trait in females, although the same differential sensitivity should occur for traits showing a female advantage. The key, universal stressors are well captured by the Horsemen of the Apocalypse – poor or inadequate nutrition (famine), disease (plague), and intense social competition (war; or predation for prey species).

The same principles apply to humans and can be used to identify age-, sex-, and trait-specific vulnerabilities (Geary, 2015). The basic idea can test tested for populations and individuals: Evolved sex differences are larger in healthy populations, and the magnitude of these differences becomes smaller as living conditional deteriorate. My colleagues and I tested this hypothesis using data from two large multi-national studies. The first was a British Broadcasting Corporation (BBC) study that included two spatial measures that typically favor men and the second was a study that included an emotion recognition measure (The Eyes Test) that typically favors women (Greenberg et al., 2022; Lippa et al., 2010). We confirmed the originally reported sex differences and then plotted their magnitude across countries that varied on the Human Development Index (HDI). Individuals living in low HDI countries are more likely to suffer from infectious diseases, poor nutrition and a larger overall disease burden than are individuals living in high HDI countries (Emadi et al., 2021).

In a prior study, we showed that men’s advantage in height and weight – both sexually selected traits related to male-male competition and female choice – increased with increases in HDI scores (Giofrè et al., 2025). Thus, sex differences in height can be used as a proxy for national differences in developmental health, with smaller differences indicating that large portions of the population are exposed to nutritional and disease stressors. Within low HDI countries, the sex difference in height is larger for wealthier individuals than for individuals growing up in poorer contexts. Using this pattern and height data from the BBC, we showed that the BBC data are biased toward healthier samples in lower HDI countries and thus will underestimate cross-national sex differences in spatial cognition.

Despite biased samples, we found that the magnitude of men’s advantage in spatial cognition increased with national increases in HDI scores, just as men’s advantage in height and weight increase with improvements in living conditions; women’s advantage in lifespan increases in these same countries and thus the effects are sex- and trait-specific (Medalia & Chang, 2011). However, women’s advantage in emotion recognition was stable across countries. It could be that men’s spatial abilities are more sensitive to poor early and current living conditions than women’s competence at recognizing emotions, but this is unlikely. Other studies suggest that women’s advantages in social cognition are compromised by extreme nutritional deficits and are smaller when they grow up in contexts with poor general living conditions (Bora & Köse, 2016). Our null finding for the Eyes Test could have been due to biased samples for lower HDI countries, but we were not able to assess this possibility due to the lack of height data in the corresponding study.

In any case, these results and others like them have theoretical and practical implications. Theoretically, these studies show that evolved human sex differences are not fixed, but rather their magnitude varies systematically with current living conditions and conditions during development, just like with other species (Geary, 2015). As living conditions improve and societies become more liberal and gender equal, sex differences for many traits become larger (Halsey & Geary, 2025; Herlitz et al., 2025). This pattern is now well documented and refutes strong social-constructivist theories on the origin of sex differences.

More practically, sex differences in trait-specific sensitivity can be used to identify at-risk populations and could be used diagnostically at the individual level (Geary, 2015). For instance, women have advantages in verbal memory, but these competencies decline more rapidly in women than men with the onset of dementia. Men’s well-developed visuospatial abilities are more severely compromised than their verbal abilities with exposure to various toxins. In other words, evolutionary theory and sex-specific vulnerabilities could be used to develop assessments that are more sensitive to various stressors or cognitive declines than assessments based on the assumption that deficits are equally diagnostic for women and men. By analogy, we would not identify growth deficits using height or weight charts averaged across boys and girls. Rather, any such diagnosis needs to be based on sex-specific norms and same may apply to many more traits that show sex differences.

Geary, D. C, Giofrè, D., Collaer, M., Lippa, R. A., & Halsey, L. (2026). The vulnerable male brain: Men’s spatial abilities are condition-dependent, sexually selected traits. Evolution and Human Behavior, 47(4), 106901.

References

How Function Shapes Form

/in ,

– by Murillo Pagnotta

Symbolic artefacts as tools of the mind

In the study of human evolution, evidence of symbolic behaviour is often taken to indicate when the mind of our deep past relatives became equivalent to ours. While language is the ultimate yardstick of symbolic behaviour, in a broad sense this also includes other meaning-making practices such as drawing, sculpting, making ornaments, singing, and dancing. And while language does not fossilise, the production of materials laden with symbolic meaning can leave traces in the archaeological record.

Some of the oldest evidence of symbolic behaviour come from two well-known archaeological sites in South Africa. These are the engraved markings found in the ochre pieces from the Blombos Cave and the ostrich eggshell pieces from the Diepkloof Rock Shelter. These materials date back as far as ~100 thousand years ago and hint at a practice spanning tens of thousands of years. The engravings are widely interpreted as intentional markings. They are certainly not accidental—but what function did they actually serve? This has been a matter of debate among archaeologists and three main hypotheses have been proposed: the markings served i) a decorative purpose, ii) as markers of group identity, or iii) as denotational symbols (similar to a proto-writing system).

The basic motivation for our recent article published in Evolution and Human Behaviour is to generate experimental evidence for or against these competing hypotheses. Looking closely at the engraved patterns, they appear to have changed over time: earlier (older) patterns are simpler configurations of roughly parallel lines, while later (more recent) ones show complex patterns such as cross-hatching. We believe the structural properties of these engravings—and especially how they changed over time—might provide clues about their function. This work is actually the third in a series, so let’s view it in its proper context.

The cognitive profile of the Blombos and Diepkloof engravings.

In the first study in the series, the late Kristian Tylén and colleagues (2020) argued that symbolic artefacts such as the Blombos and Diepkloof engravings might be seen as ‘tools of the mind’—they can shape our thinking. The analogy is with instrumental tools, such as the stone cleavers, handaxes, and flakes our deep past relatives produced. Instrumental tools act on the physical environment and are often refined over time to better serve their function—stone flakes, for instance, became increasingly efficient cutting tools, and their structure reveal their basic function. Symbolic artefacts, by contrast, primarily act on perceptual and cognitive processes, facilitating reasoning, communication, and aesthetics in senders and receivers—and like instrumental tools, they too may be incrementally refined as they are repeatedly produced for the same purpose across generations. Our underlying hypothesis is that structural changes in symbolic artefacts can likewise reveal their function, all with cognitive implications that we can measure in the lab.

How can structural changes inform us about function? Tylén and colleagues hypothesised that each candidate function should map onto a distinct cognitive profile: decoration (hypothesis 1) predicts later patterns becoming more salient and purposeful-looking; group identity (hypothesis 2) predicts them becoming easier to remember and more stylistically distinct; denotational communication (hypothesis 3) predicts them becoming easier to discriminate within a set, so as to carry specific meanings efficiently.

To test these predictions, they designed five experiments measuring these cognitive implications: saliency, discriminability, style, intentionality, and memorability using drawings derived from early, intermediate, and late engravings as stimuli. They found that, over time, the engravings became more salient, more stylistically distinct, more intentional-looking, and easier to remember and reproduce—but no easier to discriminate within their own site and period. This cognitive profile points to decoration and/or group identity marking (hypotheses 1 and 2), but not denotational communication (hypothesis 3).

The cognitive profile of experimental transmission chain drawings—and back to the engravings.

This foundational analysis assumed that functional context constrains how artefacts change over time, with different functions producing distinct trajectories of structural change—and thus different cognitive profiles. Our two subsequent studies tested this assumption directly. Both studies followed a two-part approach. First, a transmission chain methodology generated lineages of related drawings: participants were assigned a position or ‘generation’ in a chain, shown drawings from the previous generation, and asked to reproduce them digitally after a short delay (the first participant in a chain saw drawings derived from the early engravings). In the second part of the study, a subset of these transmission chain drawings was used as stimuli in the same five cognitive experiments.

Our two transmission chain experiments different in the following way: One study implemented a simple delayed reproduction task to provide a baseline (Pagnotta, Tylén et al. 2026). We found that the drawings became increasingly regular, and this had cognitive consequences: they became easier to discriminate, looked more intentional, and became easier to remember—but their saliency did not change, and they became less stylistically distinct between chains. These changes appear to be shaped by working memory constraints, perceptual grouping, and other basic aspects of visual perception. In our latest study, we embedded the reproduction task within three functional contexts operationalising the three hypotheses: decoration, identity-marking, and denotative communication (Pagnotta, Wisher et al. 2026).

We found that different contexts indeed led to different cognitive profiles. For example, discriminability increased only under the denotative communication condition. Comparing the cognitive profiles of the transmission chain drawings with those of the original engravings, we found matching patterns suggesting that the original engravings were probably used for decorative or identity-marking functions—or, not inconceivably, a mix of these—but not denotative communication. These findings corroborate the conclusions from Tylén et al (2020).

In sum, these studies contribute to a growing corpus of experimental and quantitative evolutionary semiotics by showcasing how cognitive scientists and archaeologists can collaborate and use experiments to test competing hypotheses about ancient symbolic artefacts and the cognitive capacities they index.

This study was funded by the EU ERC (eSYMb, 101044626) and the Interacting Minds Centre (IMC) at Aarhus University.

Pagnotta, M., Wisher, I., Petersen, M. L., Riede, F., Tylén, K., & Fusaroli, R. (2026). The evolution of symbolic artefacts: How function shapes form. Evolution and Human Behavior, 47(5), 106902. https://doi.org/10.1016/j.evolhumbehav.2026.106902

References

Tylén, K., Fusaroli, R., Rojo, S., Heimann, K., Fay, N., Johannsen, N. N., Riede, F., & Lombard, M. (2020). The evolution of early symbolic behavior in Homo sapiens. Proceedings of the National Academy of Sciences, 117(9), 4578–4584. https://doi.org /10.1073/pnas.1910880117

Pagnotta, M., Tylén, K., Qvist, A.S., Kjeldsen, R.F., Rojo, S., Heimann, K., Fay, N., Johannsen, N.N., Riede, F., Lombard, M. and Fusaroli, R. (2026), Simulating Symbolic Evolution in the Lab: Potentials and Implications of Using Transmission Chains to Study Early Symbolic Behavior at the Emergence of Homo sapiens. Topics of Cognitive Science, 18: e70036. https://doi.org /10.1111/tops.70036

Pagnotta, M., Wisher, I., Petersen, M. L., Riede, F., Tylén, K., & Fusaroli, R. (2026). The evolution of symbolic artefacts: How function shapes form. Evolution and Human Behavior, 47(5), 106902. https://doi.org/10.1016/j.evolhumbehav.2026.106902

 

 

Why are humans so intelligent?

/in ,

– by Jonathan Egeland, Leif Edward Ottesen Kennair, and Thomas Haarklau Kleppestø

A central puzzle in the evolutionary behavioral sciences, studied since Darwin, is how to explain our uniquely human intelligence. Why did it evolve? What made it useful enough to be favored by selection? And what is the proximate explanation for how it works? Our recent paper in Evolution and Human Behavior argues that reciprocal cooperation holds the key to answering these questions.

Over the second half of the twentieth century, many researchers came to think that human intelligence has to be understood in light of the social environments our ancestors lived in. Humans evolved in groups, and surviving in those groups meant dealing with a great many kinds of social interaction throughout development. That basic idea is widely accepted. The harder part has been turning it into a clear, plausible, and testable explanation.

Our paper was an attempt to make progress on this issue. We focus both on what intelligence is for (its function), and on how this kind of explanation can be made consistent with relevant findings from personality research, psychometrics, and comparative psychology. We began by highlighting a simple coordination problem: how can the pursuit of individual fitness-related advantages be made compatible with social cooperation between members of the same coalition or group? In many other primate species, social life is characterized by dominance hierarchies. But in humans, cooperation is often the norm. A lot of research suggests that the coordination problem was solved by instituting a system of social exchange where individuals gain status by providing benefits to other group members. This is a form of reciprocity in which cooperation is established and maintained by repeated mutually beneficial interactions. In such a system, status will typically take the form of prestige rather than dominance, as voluntary deference is shown to individuals with traits or competencies indicative of what we call “coalitional value” (i.e., social partner value).

Our main claim is that intelligence­—or its behavioral effects, to be more specific—is one of the traits that signals this kind of value. Our Coalitional Intelligence Hypothesis proposes that the behavioral effects of intelligence reliably signal an individual’s ability to benefit others. Intelligence allows people to solve problems, generate useful ideas, coordinate activities, and provide other kinds of benefit to their group, and it grants prestige in return. This leads to several predictions, one of which is that intelligence should be positively related to prestige, and this relationship should be mediated by the extent to which individuals actually benefit their social partners. In slightly technical terms, intelligence enables reciprocal exchanges of status and cognitive-computational services.

Although there are many studies whose results are consistent with this prediction, few, if any, provide direct tests of it. For example, research from psychometrics and personality psychology shows that intelligent individuals achieve higher status, in part because they provide social benefits. However, status in these studies is operationalized in terms of socio-economic status (i.e., income, education, and occupation), rather than prestige. On the other hand, there are many findings from anthropology linking the relevant variables, but intelligence is usually measured subjectively and not in terms of actual cognitive performance. Future tests of the hypothesis should therefore focus on whether cognitive performance leads to higher prestige, mediated by ability to benefit one’s social group.

In addition to discussing what the hypothesis predicts and how it compares to other, established hypotheses from the literature, we also focused on whether human intelligence can be studied meaningfully as an evolved trait. Some researchers have argued that there is a single intelligence mechanism or system, while others see it as a loose collection of many different cognitive mechanisms; and the debate between these camps goes back more than a hundred years. However, we suggest that this may be a false dichotomy. At the level of underlying mechanisms, there is clearly a lot of heterogeneity. Human intelligence involves many different systems—there is no such thing as the intelligence algorithm—and claims to the contrary risk becoming incoherent. However, at the same time, research from comparative psychology and animal cognition suggests that human intelligence is made possible by increased computational capacity across a variety of underlying cognitive mechanisms. From this we draw two inferences: first, that intelligence can be “many” at the mechanistic level, while still for certain purposes being meaningfully conceptualized as “one” functional, higher-order trait; and second, it may be plausibly conjectured that individual differences in intelligence also are reflective of patterns of covariance in computational capacity across different cognitive mechanisms.

Taken together, our paper suggests that uniquely human intelligence evolved, at least in part, because it enabled reciprocal exchanges of status and social benefits. If people voluntarily defer to social partners providing them with useful services, then there can be selection for traits and competencies indicative of social partner value. As Richard Alexander once noted, ancestral humans living in such social environments had to “cooperate to compete”. One way of competing in this manner is to provide cognitive services to others, which intelligent individuals are better able to do.

Jonathan Egeland, Leif Edward Ottesen Kennair, and Thomas Haarklau Kleppestø. 2026. Coalitional Psychology and the Evolution of Intelligence. Evolution and Human Behavior 47(3): 106839.

Do the damaging effects of the Epstein Barr virus, the cause of the Kissing Disease, weaken the idea that kissing is an adaptation favored by sexual selection?

/in ,

– by Paul Ewald

In modern societies kissing is a widespread and important aspect of social interactions. It appears to be a sexually selected adaptation that facilitates mate evaluation, pair bonding, and/or sexual activity. This evolutionary explanation is paradoxical because kissing seems unnecessary for mate selection and is associated with transmission of diseases, which might outweigh the evolutionary advantages of kissing. The most widely recognized of these diseases is infectious mononucleosis, commonly known as the Kissing Disease. Although people with mononucleosis experience fever, body aches, and extreme fatigue, the illness itself is almost never life-threatening. People generally recover within a few weeks without any specific treatment. If that were the whole story, suffering infectious mononucleosis as a consequence of kissing would not be compelling evidence against the hypothesis that kissing is a sexually selected adaptation. However, the mounting knowledge about EBV-associated diseases indicates that kissing has more serious consequences.

The Epstein Barr virus was first accepted as the primary cause of infectious mononucleosis in 1968. About a decade later its major route of transmission in affluent populations was generally recognized to be salivary exchange during intimate kissing. Over the past half-century, EBV has been associated with severe diseases such as cancers, multiple sclerosis and systemic lupus erythematosus. Together with infectious mononucleosis, these diseases would seem to generate fitness costs that could offset or even completely negate the mating advantages of kissing, and make an adaptive explanation of kissing questionable.

If these diseases were not present during the evolutionary history of humans, this concern would disappear.

Comparisons across populations help clarify whether intimate kissing has been associated with these diseases during our evolutionary history and therefore with a high fitness cost. Specifically, if these diseases tend to occur only in modern populations with particular attributes, then their presence would not weaken the hypothesis that kissing evolved as a sexually selected adaptation.

The existing evidence indicates that infectious mononucleosis occurs primarily in modern affluent populations in which environmental disinfection is emphasized. In areas with poor hygiene, EBV infections tends to occur prior to adolescence and rarely causes infectious mononucleosis. When infectious mononucleosis does occur, it tends to be more mild than when it occurs in affluent populations. The general explanation for this difference is that kids tend to be exposed to low doses of EBV in areas with poor hygiene and therefore develop some immunity that protects them from the high doses that are associated with intimate kissing. Comparative evidence therefore indicates that infectious mononucleosis has been largely a recent consequence of EBV infection resulting from hygienic activities that increase the probability of severe infections from kissing. This conclusion has ramifications for understanding the fitness costs of kissing that arise from the more serious EBV-associated diseases.

EBV has been strongly associated with breast cancer. Comparisons of EBV positivity in breast cancers relative to control breast tissue together with effects of EBV on cellular proliferation indicate that EBV plays a causal role in about 20% of breast cancer. EBV is also now generally accepted as a cause of multiple sclerosis. The associations of EBV with breast cancer and multiple sclerosis are statistically significant only among patients who had experienced infectious mononucleosis. Because mononucleosis is a modern disease associated with delayed EBV infection, the associations of these diseases with mononucleosis indicates that they too are modern diseases associated with delayed EBV infection.

EBV is now a generally accepted cause of about half of Hodgkin’s lymphoma. Breast cancer is associated with young adult Hodgkin’s lymphoma, which tends to occur within two to three years after infectious mononucleosis in EBV positive tumors. EBV-negative tumors show no association with time since infectious mononucleosis. Like breast cancer, Hodgkin’s lymphoma therefore is associated with the more severe EBV infections in modern affluent populations.

EBV is now generally accepted as a cause of systemic lupus erythematosus. Although studies have not assessed whether lupus is restricted to individuals who have had infectious mononucleosis, lupus, like multiple sclerosis, tends to occur in affluent modern populations. The main genetic risk factor for EBV-associated multiples sclerosis is also a risk factor for lupus. It codes for a protein that EBV uses as a receptor to enter cells and became prevalent about 5000 years ago. This information suggests that lupus, like multiple sclerosis, would not have been a factor disfavoring kissing during the broader span of human evolution.

These findings indicate that the relationship between kissing transmitted EBV and these severe diseases is relatively recent, and that these diseases therefore did not generate fitness costs that would have selected against intimate kissing during the evolutionary history of Homo sapiens. The flip side of this conclusion is that intimate kissing is now more unsafe than it used to be during our evolutionary history, and humans have not evolved to be sufficiently wary of the present-day dangers of intimate kissing.

Paul W. Ewald. 2026. Epstein Barr virus, infectious mononucleosis and associated diseases as contributors to the costs of intimate kissing. Evolution and Human Behavior 47 (2): 106817.

Assistant Professor of Quantitative/Computational Psychology – Penn State

/in , ,

The Department of Psychology at The Pennsylvania State University, University Park, PA, invites applications for a full-time Assistant Professor of Quantitative/Computational Psychology. The position is co-funded by Penn State’s Social Science Research Institute.

We seek candidates who use cutting-edge methods to advance our understanding of complex social, cognitive, and behavioral phenomena–specifically in the areas of Cognitive Psychology, Cognitive Neuroscience, or Industrial-Organizational psychology.

Follow this link for more information on the job and how to apply.

Ed Hagen awarded the Evolution in the Public Eye Award

/in ,

HBES Members,

I am thrilled to announce that our HBES President, Ed Hagen, has just been awarded the inaugural Evolution in the Public Eye Award.

The EPE Award honors outstanding contributions to the public understanding of evolutionary perspectives on behavior. These contributions positively impact our perception and understanding of evolutionary science by communicating accurate, evidence-based information and/or exposing and countering misinformation and misleading claims. Through social media, community blogs, academic outreach, or other forms of science communication, honorees have helped foster more informed and nuanced public discourse about evolutionary science. This award recognizes those whose efforts strengthen the bridge between rigorous research and public understanding, helping ensure that evolutionary perspectives are represented accurately in broader societal discussions.

For more information including details on award ceremony and lecture on October 24, please follow this link. And if you are in the Ann Arbor, MI, area, consider attending the lecture!

Nominations for HBES elections 2025

/in , ,
Dear HBES Community,
2025 is an election year for the Executive Council. We are therefore seeking suggestions for nominees for the following positions:
  • President of HBES
  • Communications Officer
  • Member-at-Large (two positions available)
  • Student Representative (must be current graduate student through spring 2027)
Suggestions for Nominees are due by January 31, 2025.
Elections Process:
  1. HBES community submits suggestions for nominees of particular positions, listed above.
  2. The Elections Committee of the HBES Executive Council will consider the HBES community suggestions and internal suggestions for positions.
  3. The Elections Committee will contact all nominees to confirm their willingness to serve if elected.
  4. The final selection of nominees for all positions will be shared with the HBES community in February 2025.
  5. HBES members will vote during spring of 2025 with voting open for at least 30 days. Your membership MUST be active to be eligible to vote. You can join or renew here.
  6. Results will be announced by the President of HBES.
  7. New officers will assume their roles after the 2025 HBES conference.
Sincerely,
HBES Elections Committee
(President Clark Barrett, Past-President Dave Schmitt, Treasurer Jessica Hehman)

Assistant Professor position in Psychology at Knox College

/in

Knox College is seeking an Assistant Professor in Clinical or Social Psychology, and either way they’re interested in someone who takes an evolutionary approach. Review of applications begins Oct 18th 2024. See here for more details: https://apply.interfolio.com/154607

For more jobs in the evolutionary social sciences, check out our Evolutionary Social Science wiki, which is maintained by members like you. Know of a job in the evolutionary social sciences? Please post it on the wiki.

Archived videos from 2018

/in
Here are old videos from the website front page from 2018 – I’m trying to archive them somewhere (2024). This page looks like hell, but it’s not meant to be seen by anyone – it’s just a temporary holding page so I can make the front page look better without permanently deleting these links

Twins, virtual twins and other curious couples

 

 

On the Origin of the Evolution Revolution: Conversations with the Pioneers of Evolutionary Biology, Anthropology, and Psychology