Roundtable Seminar on Evolving Solutions to Global Climate Change and Sustainability on April 25

We hope you will join us for the Roundtable Seminar Series event Monday, April 25th 2021 at 12:30 – 1:45 pm EDT where Drs. Talbot Andrews, Daniel Kelly, Anne Pisor, and Gonzalo Palamo-Vélez will engage in discussion, moderated by Dr. Tim Waring on the topic, “Evolving Solutions to Global Climate Change and Sustainability”. We’re looking forward to engaging with our members on important discussions happening in this area.

This series is an opportunity for HBES members to engage with experts on topics in the evolutionary behavioral sciences. Each virtual session will feature a panel of speakers answering questions from a moderator and live audience. Join us each month to discuss the big questions facing our field. Live sessions on the HBES ohyay space are open to registered HBES members only, but a recording will be made publicly available on Youtube after the event.

Please check your email for instructions to set up your ohyay account an access the HBES ohyay space that will be sent out on the week before the event.

Which Factors Best Explain Variance in Human Reproduction and Mating?

By Martin Fieder

 

Evolutionary biology has always been interested in the question, which individual traits influence how many children we have, and how much each of these traits contributes to it. As nearly every trait has to some extent a genetical basis, together with the progeny also the genes that are associated with any favorable trait are spreading – in evolutionary terms “the trait is under positive selection”.

 

It is meanwhile known that several traits influence how many children a person has, at which age a person becomes mother or father, or what the chances are that a person finds a mate. It is also established that the effects of those traits may differ whether the person is a woman or a man. Moreover, for some of these traits their genetical basis in terms of so-called polygenic risk scores has been determined, which enables us to estimate the liability of an individual for a certain trait. What has been largely neglected so far is the question, how much each trait contributes (in statistical terms how much variance is explained) to the number of children or the probability of finding a mate/being ever married. We therefore aimed to explore that issue and analyzed how much each single trait contributes to the individual variance of number of children and ever being married. As we used the Wisconsin Longitudinal study (WLS) for that analysis, ever being married is a rather good proxy for mating in general because participants in that data set are born between 1937 and 1940, as marriage was very common at that time in the US.

 

Among these analyzed traits are religious intensity (as it is known for its pro-fertile effect in both men and women), facial attractiveness as well as social status because social status in terms of income is also known to foster number of children in men though not in women. Our analyses showed that among men, this positive effect of social status on a man’s number of children can simply be explained by mating. Being married was by far the most important factor of having children in this data set. And the factor that contributed most to the fact, whether or not a person was ever married or not, was income (~18% in men and ~7% in women). The direction of that effect, however, differed between men and women. In men, higher wages were associated with a higher chance of ever being married. Accordingly, female preference for high social status in terms of high income predicted a man’s chances of marriage and hence, his number of children. In women, on the other hand, higher wages were associated with a lower chance of being married. We do not have a final explanation for the negative effect of income on ever being married in women, but likely the problem of combining family issues and career plays a role.

 

The effect of education, another indicator of social status, on marriage and reproduction was less straightforward. In both men and women of our data set, higher education predicted a lower number of children, which is in line with the literature and, due to postponing of reproduction, is particularly expected in women. Interestingly, in men but not in women, the genetic predisposition towards higher education (polygenetic score for general cognitive ability) had a small positive effect on the number of children. A more detailed analysis revealed, that in men, a higher predisposition for education/general cognitive ability was associated with higher income, which in turn predicted a higher number of children.

 

“Our data show that in men, social status in terms of income has by far the strongest effect on marriage and as a result on reproduction as well. This is a finding which is clearly in line with evolutionary assumptions, predicting that women should prefer men of higher social status for their own and the sake of their progeny”

 

The effect of all other analyzed traits on the number of children or ever being married was much weaker. Only facial attractiveness explained 6% of ever being married in women and 2% in men, which, however, is still lower than expected as facial attractiveness has always been reported to be an important determinant for mating.

 

Our data show that in men, social status in terms of income has by far the strongest effect on marriage and as a result on reproduction as well. This is a finding which is clearly in line with evolutionary assumptions, predicting that women should prefer men of higher social status for their own and the sake of their progeny. However, as income is a very recent indicator of social status we are not able to make any final conclusions on ongoing selection pressures in modern societies. On the basis of our data, we can just argue that men in modern societies seem to be under pressure to “earn money” if they aim to find a mate and to have children.

 

Read the paper: Contemporary selection pressures in modern societies? Which factors best explain variance in human reproduction and mating?

Men and Women Desire Some Different Features in Their Friends

By Jessica Ayers, Jaimie Krems, & Keelah Williams

 

We often focus our finite time, interest, and even research energy on mating and kin relationships rather than friendships. But across evolutionary history, friends have provided important benefits and helped us solve recurrent adaptive problems. For example, our ancestors’ friends helped them acquire resources, gain status, win social conflicts, attract and retain mates, and so forth. Further, friends help us when we are in need (and unlikely to receive help from strangers). As our time and energy to devote to these relationships is finiteit takes some 200 hours to make a close friend—we must choose in which friend(s) to invest our time and energy.

 

The qualities possessed by various friends can help us make these prioritization decisions. We invest in friends who have the qualities we most like. But what qualities do we look for in our friends?

 

Past work suggests that both men and women seek friends who are trustworthy, similar, familiar, generous, and who like us. Just as in work on romantic relationships, then, the qualities that men and women most want in partners are the same—even if there are some predicted, notable sex differences. But because there’s been much less of a research focus on friendship, we know less about the predicted, possibly notable sex differences in what people want in friends. That’s where we focused.

 

Building on previous work investigating evolved friend preferences, we reasoned that the nature and priority of the adaptive challenges (that friends help to solve) have been somewhat different for men and for women, and so some of the qualities that men and women value in friends might also be differently prioritized—again, even as many of the qualities men and women cherish in friends are the same.

 

In a series of three studies, we investigated (1) people’s preferences for ideal friends, (2) the actual qualities possessed by people’s real-life best friends, and (3) people’s prioritization when given a limited “friend budget” to spend on different qualities.

 

In Study 1, we asked 213 U.S. undergraduates to imagine an ideal same-sex friend and rate how important it was that this ideal friend possessed various qualities—qualities we created to reflect eleven different categories of adaptive problems. Men, as compared to women, more so reported that they wanted their ideal friend to be wealthy, have high status, provide access to potential mates, and be physically formidable. Women, as compared to men, more so reported that they wanted their ideal friend to provide emotional support, prioritize the friendship, help protect their romantic relationships, be an ally during conflicts, and provide useful social information. (We found no sex difference in the extent to which men and women valued ideal friends who actively tried to build their friendship networks or had unique skills/expertise.)

 

In Study 2, we aimed to assess how these preferences changed when participants reported on their actual same-sex best friend. We asked 306 U.S. adults to report the extent to which their real-life best friend possessed these traits. We largely replicated the results of Study 1. Men reported that their same-sex best friends were more likely to be wealthy, provide access to potential mates, and be physically formidable compared to women’s same-sex best friends. Women reported that their same-sex best friends were more likely to provide emotional support, help protect their romantic relationships, and be an ally during conflicts compared to men’s same-sex best-friends. (We again found no sex differences in the extent to which men and women reported that their same-sex best friend actively tried to build their friendship network or had unique skills/expertise.) However, we did not replicate the sex differences in status, prioritizing the friendship, and providing useful social information found in Study 1.

 

“We find that whereas men and women both benefit from friends with certain qualities (e.g., trustworthiness, intelligence), there have also been some recurrent, sex-specific challenges that men’s and women’s same-sex friendships helped to solve.”

 

In Study 3, we conducted a complementary assessment of friendship preferences using a self-report paradigm adapted from behavioral economics—the budget allocation paradigm, wherein participants are given finite budgets to spend on friendship qualities to create their ideal same-sex friend. When men and women are given large budgets from which to create their friends, we hypothesized that they would create similar ideal friends: When there is no constraint on the positive qualities an ideal friend can possess, people should want it all. When budgets are constrained, however, men and women are forced to prioritize the qualities they deem most important. We asked 250 U.S. adults to create their ideal friend using this paradigm. Looking at those choices under constrained budgets, we found that women, compared to men, (again) prioritized having a friend who provided emotional support and that men, compared to women, prioritized having a friend who had high status and provided access to potential mates.

 

We find that whereas men and women both benefit from friends with certain qualities (e.g., trustworthiness, intelligence), there have also been some recurrent, sex-specific challenges that men’s and women’s same-sex friendships helped to solve. By considering these pressures, future research can begin to investigate aspects of friendship—and, here, what we want in friends—that we can reasonably expect to be somewhat sex differentiated, such as the similarities and differences in how men and women maintain or terminate their friendships.

 

 

Read the paper: Sex differences in friendship preferences

The High Price of Low Status in Human Rituals

By Dimitris Xygalatas

 

What do peacocks and humans have in common? I suppose there may be other possible answers to this question, but one feature they do share is the use of extravagant, apparently senseless traits as a means of transmitting important information. When such transmission is beneficial to both senders and receivers, those traits will be favored by the forces of selection, even if at first glance they appear to be wasteful. In a nutshell, this is the core claim of costly signaling theory.

 

In the case of the peacock, the signal is built into its body. Its disproportionately long, iridescent tail is calorically expensive to produce, maintain, and carry around. It reduces agility, adds drag during flight, and makes its bearer a flashing target for predators. But as Darwin already noted, there is a method to this evolutionary madness. Although the tail itself may have no utility, the effort that goes into growing and maintaining it can still pay off. As only a fit peacock could afford to carry such a costly ornament and still be alive, peahens use this ornament as a reliable indicator of the male’s prowess. By selectively mating with males that carry extravagant tails, they are investing in good genes for their offspring, inadvertently pushing the males to grow ever more grandiose tails.

 

The same logic can also apply to behavioral traits. In humans, some of the best-known examples come from the domain of ritual.  Signaling theories of ritual argue that costly ceremonies help solve important coordination problems: for any group that requires cooperation among its members, information on people’s levels of commitment is crucial. But declaring one’s loyalty to the group is cheap. Paying a hefty membership price provides more compelling evidence of commitment to the group and its values. Actions speak louder than words.

 

There is mounting evidence in support of this view. For instance, empirical research shows that people who participate in costly rituals are more committed to group causes. This is not lost on community members, who perceive participation as a signal of prosocial qualities. However, unlike the indexical nature of the peacock’s tail (what you see is what you get), human signals are embedded in complex sociocultural contexts.

 

For the sake of simplicity, formal models of signaling typically assume that the intensity of the signal varies while all else being equal. But in reality, all else is never equal. Social inequalities may influence default perceptions of a sender’s quality, impacting the signal’s cost-benefit ratio. While previous research treated this variation as noise, we designed a study to quantify it.

 

Our study, reported in Evolution and Human Behavior, took place in the island of Mauritius during the Thaipusam Kavadi, a Tamil Hindu festival held in honor of Lord Murugan. Performed by millions of Hindus in India and around thew world, it involves several days of activities that culminate with a pilgrimage to the god’s temple. Before embarking on the day-long procession under the scorching tropical sun, devotees have their bodies pierced with metal needles, hooks, and skewers. They also carry large portable shrines called kavadi. Those are built on a wooden, bamboo, or metal frame supported on the shoulders and are decorated with flowers and peacock feathers (in serendipitous but seemingly emblematic fashion, the peacock is Murugan’s symbol). The word kavadi, which in Tamil means “burden”, is what gives this ritual its name – aptly, as those structures can often weigh as much as a person.

 

In this setting, we recruited 80 adult participants of various ages. We measured the size of the kavadis they carried and the number of piercings they endured. After they completed their pilgrimage, we also asked them questions about their religious beliefs and practices and gave them a survey to assess their socioeconomic status.

 

We found great variation in both the intensity and form of signaling: the number of piercings ranged from zero to 600, and kavadis varied from petite to gargantuan. The festival provides different signaling opportunities and, as it turns out, participants harness them according to their means. High-status individuals carried larger and more flamboyant kavadis — for those at the top third of the socioeconomic ladder, almost three times larger than those at the bottom third.

 

Why would that be? Quite simply, because they could afford to. Building and decorating a kavadi can be expensive: the most elaborate structures can cost the equivalent of three months’ salary of an unskilled worker. And those larger kavadis are not necessarily heavier (at least not proportionally), as the affluent can purchase better and more lightweight materials (e.g. aluminum in place of iron), which allows them to amplify their signals even further.

 

“During the ritual, low-status individuals on average put almost four times more needles into their bodies compared to the upper classes. Lacking the material capital to compete with the elites, those of low status turned to whatever other means were available to them: quite literally, their own blood, sweat, and tears.”

 

On the other hand, there was a negative relationship between socioeconomic status and frequency of participation: across their lifespan, low status individuals carried the kavadi over four times more often. But it was not just a matter of frequency: during the ritual, low-status individuals on average put almost four times more needles into their bodies compared to the upper classes. Lacking the material capital to compete with the elites, those of low status turned to whatever other means were available to them: quite literally, their own blood, sweat, and tears.

 

It is worth noting that across all these metrics, there was a large effect of gender. While most women had only one piercing, the median number for men was 79. Men also participated in the ritual more times over their lifetime and carried kavadis that were on average over twice as large. Unsurprisingly, then, the associations with socioeconomic status were even stronger when we looked at the male-only portion of our sample.

 

While the physically demanding aspects of the festival are mostly a male affair, this does not mean that women do not engage in commitment signaling — far from it. For instance, they are more likely to fall into trance, which can be a hard-to-fake signal of devotion. Moreover, women play key roles in parts of the ritual that are seemingly peripheral but socially important nonetheless, such as hosting and organizing elaborate family feasts at the conclusion of the festival — a laborious and time-consuming activity.

 

Our study was the first to quantify the multi-layered costs of an extreme ritual and their variation along socioeconomic lines. Our findings are in support of a costly signaling view of ritual. Needless to say, cultural practices are complex and cannot be reduced to monocausal explanations. Our study has merely scratched the surface of one of the most widely performed rituals in the world.

 

 

Read the paper: Social inequality and signaling in a costly ritual

The Evolution of Mental Health Disorders Roundtable Event on Feb 28th

We hope you will join us for the Roundtable Seminar Series event Monday, February 28th 2021 at 12:00 – 1:15 pm EST where Drs. Simon Baron-Cohen, Kristen Syme, Matthew Keller & Bernard Crespi will engage in discussion, moderated by Dr. Ed Hagen on the topic, “The Evolution of Mental Health Disorders”. We’re looking forward to engaging with our members on important discussions happening in this area.

This series is an opportunity for HBES members to engage with experts on topics in the evolutionary behavioral sciences. Each virtual session will feature a panel of speakers answering questions from a moderator and live audience. Join us each month to discuss the big questions facing our field. Live sessions on the HBES ohyay space are open to registered HBES members only, but a recording will be made publicly available on Youtube after the event.

Please check your email for instructions to set up your ohyay account an access the HBES ohyay space that will be sent out on the week before the event.

HBES 2022 is Going Virtual

Dear HBES community,

The HBES Council and HBES 2022 Host Committee have made the very difficult decision to move our 2022 conference to a fully online format. We have come to this decision based on the following:

  • Feedback from our members in our recent survey showing a 50/50 split of responding members reporting they were likely or unlikely to attend the conference in-person in Detroit.
  • 70% of our international members expressed significant concerns about being able to travel to attend the conference.
  • To break even on an in-person conference, we would have needed at least 400 in-person attendees, which seemed highly unlikely given that our typical conference attendance is around this number.
  • After repeated discussions with the Detroit hosting venue, it was determined a smaller in-person conference or a hybrid conference at the Detroit conference site would have resulted in a significant financial cost to the society, upwards of $100,000.
  • In addition, there were the continued uncertainties regarding COVID and the interest of health and safety for all our members, though the economic argument alone was sufficient.

We appreciate this is disappointing news, especially for our early career researchers. However, given the facts laid out above, we are convinced this is the appropriate decision to make at this time for both our members and our society.

We are currently in the process of finalizing plans for the online conference. We are looking at holding the virtual conference on OHYAY again this year given the highly positive feedback last year, and we are aiming for the same dates the in-person Detroit conference was to be held (June 22-25, 2022). We will provide a more definitive set of dates for submissions and other announcements in the very near future. 

Sincerely,

Dave Schmitt, HBES President on behalf of the HBES Council

Intelligence Can be Detected But is Not Found Attractive at First Sight

by Julie C. Driebe

 

Intelligence shapes many aspects of our everyday life. It is, for example, a robust predictor of health, income and social status. However, human brains seem too costly and complex to have evolved for mere survival. For example, our intelligence enables us to create art, literature, or engage in humorous wordplay. A well-known theory therefore proposed that our extraordinary intelligence could serve as an indicator of genetic quality and was therefore preferred in prospective partners, thus evolved not only through natural but also sexual selection. Moreover, the theory proposes that humour could function as an intelligence display. Supporting this theory, past research has established that, cross-culturally, intelligence is considered a highly attractive trait in hypothetical long-term mates. However, it is less clear whether actual, objectively assessed intelligence is indeed found attractive when evaluating prospective partners, particularly in face-to-face contexts.

The aim of the current study was to test whether measured intelligence is indeed perceived and found attractive in potential mates by members of the opposite sex and whether funniness could be an intelligence display. To answer our research questions, we used two complementary approaches: an elaborate rating design (study 1) and a more ecologically valid speed-dating study (study 2).

In study 1, we objectively measured the intelligence of 88 target men using eight intelligence subtests. Results of cognitive ability tests are substantially intercorrelated, yielding a latent, general factor of intelligence, referred to as the g factor. These target men were then rated on their intelligence, funniness, physical attractiveness and mate appeal by 179 women. Women in different sets rated different traits. One set of women rated men’s physical attractiveness, based on a facial and full-body photograph. Another set of women rated men’s funniness and intelligence after watching short video clips of men performing several tasks. These tasks were selected to include cues related to men’s intelligence. For example, one task was to read out newspaper headlines aloud, which has been found to enable accurate intelligence perception. In the most complex condition, women provided ratings of men’s mate appeal several times: First, after they saw a facial and full-body photograph, second after watching a video of men pronouncing vowels (which included information on vocal attractiveness but not intelligence), third, after men read out newspaper headlines and finally, a video, in which men were asked to make the experimenter laugh.

In study 2, 763 participants took part in 2-5 speed-dates and interacted with members of the opposite sex for 3 minutes. After each interaction, participants rated each other on their mate appeal, intelligence and funniness. Once all speed-dates and ratings had been completed, participants filled out the post-questionnaire including their assessment of their partner’s verbal intelligence.

Results of both studies suggested that intelligence can be accurately perceived after viewing short video clips, even net of attractiveness halo effects, and after participating in short interactions. However, only perceived intelligence, not measured intelligence, was associated with mate appeal. Similarly, only perceived and not measured intelligence was related to funniness. The main predictor of mate appeal was physical attractiveness.

These findings cast doubt on the theory that intelligence evolved as a fitness indicator through good genes sexual selection, since intelligence would have needed to be found attractive as soon as it can be perceived to effectively sift through many potential mates (i.e., providers of genetic benefits). Further, funniness does not seem to advertise intelligence since we found no association of funniness and measured intelligence. We found that only perceived intelligence and not measured intelligence predicted mate appeal. That perceived intelligence is found attractive could explain why intelligence is often listed as a desirable trait for hypothetical partners. Nevertheless, intelligence could play a role at later stages of long-term relationship formation, as intelligence is a potent predictor of direct mate choice benefits, including resource provision, social status, problem solving skills, and being a competent cooperation partner. We believe that we investigated the research question with complementing studies in which drawbacks of one study were addressed by strengths of the other study. In addition, an independent recent speed dating study found highly consistent results. However, future studies should follow courtships over longer timespans than initial contact.

 

Read the paper: Intelligence can be detected but is not found attractive in videos and live interactions

 

Evolutionary Health in Indigenous Populations Roundtable on December 6th

We hope you will join us for the Roundtable Seminar Series event Monday, December 6th 2021 at 12:00 – 1:15 pm EST where Drs. Abigail Page, Claudia Valeggia, Herman Pontzer & Theresa Gildner will engage in discussion, moderated by Dr. Michael Gurven on the topic, “Evolutionary Health in Indigenous Populations”. We’re looking forward to engaging with our members on important discussions happening in this area.

This series is an opportunity for HBES members to engage with experts on topics in the evolutionary behavioral sciences. Each virtual session will feature a panel of speakers answering questions from a moderator and live audience. Join us each month to discuss the big questions facing our field. Live sessions on the HBES ohyay space are open to registered HBES members only, but a recording will be made publicly available on Youtube after the event.

Please check your email for instructions to set up your ohyay account an access the HBES ohyay space that will be sent out on the week before the event.

The Evolution of Reputation Roundtable Event on Nov 5th

We hope you will join us for the Roundtable Seminar Series event Friday, November 5th 2021 at 9:00 – 10:15 am ET where Drs. Alex Shaw, Amanda Rotella, Erez Yoeli, & Esther Herrmann will engage in discussion, moderated by Dr. Felix Warneken on the topic, “The Evolution of Reputation”. We’re looking forward to engaging with our members on important discussions happening in this area.

This series is an opportunity for HBES members to engage with experts on topics in the evolutionary behavioral sciences. Each virtual session will feature a panel of speakers answering questions from a moderator and live audience. Join us each month to discuss the big questions facing our field. Live sessions on the HBES ohyay space are open to registered HBES members only, but a recording will be made publicly available on Youtube after the event.

Please check your email for instructions to set up your ohyay account an access the HBES ohyay space that will be sent out on the week before the event.

Sexual Jealousy and Intimate Partner Violence Roundtable Event on October 19th

We hope you will join us for the Roundtable Seminar Series event Tuesday, October 19th 2021 at 10:00 – 11:15 am EST where Drs. David Buss, Janet Howard, and Todd Shackelford will engage in discussion, moderated by Dr. Elizabeth Pillsworth on the topic, “Sexual Jealousy and Intimate Partner Violence”. We’re looking forward to engaging with our members on important discussions happening in this area.

This series is an opportunity for HBES members to engage with experts on topics in the evolutionary behavioral sciences. Each virtual session will feature a panel of speakers answering questions from a moderator and live audience. Join us each month to discuss the big questions facing our field. Live sessions on the HBES ohyay space are open to registered HBES members only, but a recording will be made publicly available on Youtube after the event.

Please check your email for instructions to set up your ohyay account an access the HBES ohyay space that will be sent out on the week before the event.