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.

Can Behavior and Personality Traits Signal Underlying Physiological Function?

by Nicholas Grebe


One of the most basic decisions facing organisms of all kinds concerns how to spend limited resources. Given that energy and effort—which encompasses both physiological and psychological processes—draw from a finite budget, how should an individual partition its investments between the fundamental activities of life? For instance, upon reaching maturity, to what extent should an organism prioritize attracting and retaining mates, versus engaging in maintenance processes necessary to stay alive? We know this is a devilishly complicated question that depends on (at least) the evolutionary history, current environmental conditions, and developmental background of the organism in question. However, biologists are nevertheless keenly interested in identifying unifying mechanisms—conserved biological systems that may help explain why individuals differ so much in how they achieve evolutionary fitness outcomes.

One popular candidate mechanism stems from a physiological system common to all aerobic organisms. An inevitable consequence of creating cellular energy, whether you’re a nematode or a human, comes in the form of reactive oxygen species: by-products of oxygen metabolism that can damage DNA, cell membranes, and proteins. Naturally, organisms must counteract these “free radical” molecules, which they do via a number of elegant anti-oxidant mechanisms. (Interestingly, controlled amounts of reactive oxygen species help organisms carry out adaptive responses to events like infection or aerobic exercise. Problems arise when regulation of these molecules goes awry.) The dynamic balance between an individual’s production of reactive oxygen species and anti-oxidant neutralization—their state of oxidative stress—was the focus of our study.

Biologists have proposed that levels of oxidative stress, as a fundamental reflection of an organism’s state of energetic functioning, should be related to the expression of sexually selected signals. How and why this covariation occurs is a matter of serious debate, but let’s consider two simple alternative possibilities. On one hand, if an individual is better able to regulate oxidative stress, then perhaps that frees up a greater share of the energetic budget to spend on traits that are attractive to the opposite sex and/or beneficial for intrasexual competition: think brighter plumage, richer scent-marks, or more dominant personalities. Some even venture that these kinds of traits are attractive because they signal effective regulation of oxidative stress, though there could be other reasons for such an association. On the other hand, individuals who elect to devote more energy to sexual signaling, for whatever reason, might incur greater oxidative damage simply by virtue of expending more energy. These scenarios entail two opposing predictions: in the former, oxidative stress should be negatively related to indices of mating effort; in the latter, the two dimensions should be positively correlated.

Most of the background summarized above has concerned physical traits in non-human animals, but we wanted to investigate how oxidative stress might be implicated in human mating effort, broadly conceived. To do that, we explored associations between a biomarker of oxidative stress (8-OHdG, collected at two different time points per participant), psychological traits, and measures of health/athleticism in two Western university samples: one of 98 men, and one of 75 heterosexual couples. We focused on aspects of one’s personality and health that have established links to success in obtaining and keeping mates. Personality traits included social dominance (sample item: “I am quite good at convincing others to see my way”), non-submissiveness (“When other men/women cross the line with me, I’m not afraid to enter into a conflict with them”), and extraversion (“I often feel as if I’m bursting with energy”). Health traits included self-reports of athleticism, muscularity, and frequency of illness (all relative to others of the same age and sex). In our sample of couples, we also had partners rate each other on these same dimensions and found strong agreement in ratings, suggesting that these reports reflect apparent traits.

Our results were remarkably consistent in some aspects, but notably variable in others. In the consistent camp, we found that men’s 8-OHdG levels upon awakening—which we believe represents a relatively stable composite of oxidative stress—were negatively related to their social dominance, extraversion, and athleticism. However, on the variable side, these negative associations did not generalize to men’s oxidative stress several hours after waking, nor to women’s oxidative stress at any time. In fact, while not as consistent as patterns for men, women’s social dominance and athleticism were actually positively related to their oxidative stress levels.

So, we found some evidence consistent with each of the scenarios presented above. Regarding the former scenario, men who experience lower costs to energy production, in the form of oxidative stress, appear to invest more heavily in socially dominant and athletic traits. Regarding the latter, women who report greater investment in intrasexual competition, rather than paying a lower marginal cost, appear to simply generate more oxidative damage. Unexpectedly, however, these patterns were restricted to samples collected first thing in the morning. While providing preliminary data that speaks to some established questions, we think our study introduces just as many additional complexities, and it furthermore suggests we have much to refine in our understanding of oxidative stress and human mating effort.

A brief afterword: This blog-length outline presents a necessarily simplified narrative about the theory and findings regarding sexual signaling and oxidative stress. For instance, while this piece only briefly touches on sex differences, there are a number of interesting implications for oxidative stress – trait associations that differ between the sexes. Here, we think readers might be interested in a small window into our peer-review experience with this paper. While both referees found things to like in our original submission, one reviewer in particular was quite skeptical of our theorizing and interpretations. But, in a model of constructive criticism, this reviewer didn’t act to gatekeep publication of our study; rather, they pushed us to present a fuller picture of the diverse, even contradictory findings pervading the literature upon which we relied, and to embrace greater epistemic humility regarding what our findings can and cannot tell us. We did our best to heed this call, and we encourage readers to check out the full paper for a more complete discussion of this corner of scientific research. Maybe Reviewer #2 isn’t so bad, after all.


Welcome (Back) to Detroit for #HBES2022!

Welcome to Detroit for HBES 2022!

We are back!!! And we are thrilled to announce that we are planning for an in-person HBES 2022 conference in Detroit, Michigan! Aside from the invited and submitted program, there are numerous formal and informal opportunities for networking and learning about the latest developments within the human evolutionary sciences. As in years past, we expect HBES 2022 top notch, exciting, and of course, fun! The conference website will provide you with all the information you need to enjoy #HBES2022 in Detroit. Be sure to mark important dates on your calendar, including when abstract submissions open on January 28.

HBES 2022 planning committee will be following the CDC’s coronavirus safety guidelines, along with state and local guidelines for Michigan and the city of Detroit to ensure a safe event for attendees. Please visit this site often for updates as they will be added periodically or you can email us with any questions or concerns at via hbes2022@gmail.com.



Multimodal attractiveness: How important our sight, sound, and scent are for first date impressions.

by Tom S. Roth & Iliana Samara


Maybe you still cherish vivid memories of your first date with your partner. Maybe you remember what they looked like, the sound of their voice, or even their scent! During first encounters, we are confronted with multiple sources of information, encompassing a range of modalities. It is well known that this information shapes our opinion about potential partners. However, what remains unknown is which of these sources is most important for partner choice. In an article that recently appeared in Evolution and Human Behavior, we examined this by exploring how attractiveness on different modalities relates to speed-date outcome.

A plethora of studies has investigated the role of visual attractiveness in partner choice. For example, when people go on a date with a visually attractive partner, they are more likely to seek another date with them. However, it has recently been suggested that when studying attractiveness we should look further than visual information, and include scent and sound as well. Even though some studies have investigated the attractiveness of scent and sound, their effect on actual partner choice remains unclear. Therefore, in our study, we combined multimodal attractiveness ratings with a natural paradigm to study partner choice, namely speed-dating. Speed-dates strongly reflect natural partner choice situations, and are therefore great tools to study partner choice in humans.

To study the role of multimodal attractiveness in partner choice, we invited a group of 67 heterosexual participants (34 women and 33 male), between the ages of 18 and 26 years old, to the lab. These participants were divided over 4 groups, that were each tested in a different time slot. Every group had approximately the same number of men and women. The experiment consisted of three stages: a sample collection stage, a sample rating stage, and a speed-dating stage.

In each group, we started by collecting samples. After arriving at the lab, we took a standardized portrait picture of each participant, recorded their voice while they were reading out a standardized Dutch text, and we asked them to bring a t-shirt that they had worn during the night. In this way, we had a sample that could be rated for visual, auditory, and olfactory attractiveness from each participant. In the sample-rating part of the experiment, participants rated the attractiveness of all the samples that we gathered from the opposite-sex participants on a 1 to 7 scale, with 1 meaning very unattractive and 7 meaning very attractive. Thus, the men rated the attractiveness of the picture, voice recording and t-shirt scent of the women in their timeslot, while the women rated the samples of the men in their timeslot. Finally, after completing all the rating tasks, participants took part in the speed-dating part of the experiment. Each participant had a maximum of 10 speed-dates, depending on the number of opposite-sex participants in their timeslot. At the end of each date, participants indicated whether they would like to go on another date with their partner, and how attractive they found their partner. Furthermore, people that both indicated that they wanted to meet their partner again, received each other’s contact information, so that they could meet up again after the experiment.

We investigated how well the ratings of the different modalities predicted the date outcome, in this case, how likely participants were to seek another date with their partner. We found that, as would be expected, visual information was the most important predictor of the willingness to date again for both men and women. Regarding the auditory information, we found that vocal attractiveness seemed to have a small positive influence on willingness to meet again in men, but not women. For olfactory information, we found the opposite pattern. There was no clear effect in men, but in women there was a surprising negative association. In other words, the more pleasant an odor was rated before the speed-dating paradigm, the less likely women were to indicate that they would go on another date with their partner.

This study is the first one that distinguishes between visual, auditory and olfactory attractiveness, and compares their importance in partner choice. In line with previous studies, we found that facial attractiveness was the strongest predictor for willingness to go on another date. This finding is not surprising, given that humans are visually well-equipped, and strongly inclined to pay more attention to visual information than other modalities.

When it comes to sound, auditory attractiveness seemed to be somewhat important for men, but not women. Nonetheless, this could be due to naturally occurring voice fluctuations during the date, for example people might tend to modulate their pitch when speaking to someone that they consider attractive. Importantly, this finding could be due to the noise in the room, as all group dates were hosted at the same time. This might have led to the voice of the partner being perceived as different compared to the recording.

Regarding the olfactory attractiveness, we found no discernible pattern for men, and a small but surprising negative association for women. This finding could be due to people wearing perfumed hygienic products before putting on the t-shirt (e.g., deodorant). Even though participants were instructed not to use such products before and while wearing the t-shirt, they might have wanted to mask their natural body odor. Therefore, it could be that the smell samples represent diplomatic odor (i.e., combination of natural body odor and hygienic products), thereby obscuring the effect of scent attractiveness on partner choice.


Visual attraction seems to be most important during first dates, while voice and scent seem to have little to no effect.


An interesting theoretical explanation for the fact that auditory and olfactory attractiveness seem to have little to no effect on mate choice compared to visual attractiveness could be that visual, auditory, and olfactory information become important in different stages of the relationship. In other words, upon meeting a new partner, visual information could act as a filter, ensuring that a sufficiently attractive partner is selected. Following this stage, auditory information and olfactory gradually might become more decisive for partner selection and maintenance. Future research can investigate whether this is indeed the case.

In sum, visual attraction seems to be most important during first dates, while voice and scent seem to have little to no effect. Thus, while attractiveness might indeed be multimodal, when it comes to first encounters it seems that the eyes have it.

Does disgust change during the menstrual cycle?

by Karolina Milkowska


In periods when the body’s immunity is lowered or the risk of infection rises, people should show increased prophylactic behavior. It is assumed that the feeling of disgust is a mechanism that should protect against contact with the source of infection. The increased susceptibility of the organism to infections can be compensated by recognizing the potential threat and by avoiding or eliminating the identified threats thanks to preventive actions.

In women, the functioning of the immune system may be influenced by progesterone levels, a sex hormone that is produced in the luteal phase of the menstrual cycle, following the rupture of the Graaf follicle (ovulation). Progesterone causes immunosuppressive stimulation of the immune system, by reducing inflammatory immune responses. Such modification of the immune response i) prevents the female immune system from attacking the genetically half-foreign blastocyst, ii) enables implantation and development of the embryo, iii) but also makes women more susceptible to infections.

According to the Compensatory Prophylaxis Hypothesis (CPH), women in the luteal phase of the menstrual cycle should show stronger disgust and more increased prophylactic behavior than during the follicular phase, in order to avoid infections in periods of reduced immunity by avoiding potential sources of infection.

In a recent study, we explored whether disgust sensitivity differs between phases of the menstrual cycle in regularly cycling, healthy women of reproductive age, who performed ovulatory tests to determine the phases of the menstrual cycle and repeatedly assessed the disgust level using both questionnaires and photographs of potential sources of infections.

Disgust sensitivity was measured twice during one menstrual cycle among all participants:

1) 5th or 6th day of the cycle

2) and on the 5th day after a positive LH test, or on the 20th day of a cycle if the result of LH test was not positive (indicating that the cycle was anovulatory).

Disgust was assessed by the Pathogen and Moral domains of the Three-Domain Disgust Scale (TDDS) and a set of photographs depicting potential sources of infection. Moreover, we measured contamination sensitivity with the use of Contamination Obsessions and Washing Compulsions Subscale of Padua Inventory – Washington State University Revision.

During the luteal phase, compared to the follicular phase, women scored higher on the:
1) Pathogen Disgust of Three-Domain Disgust Scale,

2) Contamination Obsessions and Washing Compulsions Subscale of Padua Inventory,

3) and when rating their disgust level while watching photographs depicting sources of a potential infection.

Did other studies get the same results?

Our results are consistent with several previous findings. Among studies that measured progesterone levels when testing CPH, Fleischman and Fessler (2011) and Żelaźniewicz et al. (2016) have shown a positive correlation between progesterone and the feeling of disgust toward pathogenic factors. However, a recent study with a large study sample has shown a lack of association between progesterone and the pathogen disgust sensitivity. Studies comparing pathogen disgust sensitivity within the phases of the menstrual cycle also provided inconclusive findings. For example, a previous study has shown, contrary to our results, a lack of significant differences in the Pathogen Disgust domain of the TDDS. One other study found that only women who had an ongoing infection had higher scores on the Pathogen Disgust domain of the TDDS while being in the luteal phase than women in the follicular phase. Further, a study by Fessler and Navarrete (2003), contrary to our research, revealed no differences in the intensity of the feeling of disgust across the cycle – women in the luteal phase did not differ from women in the follicular phase. However, they did not conduct ovulatory tests or repeated measurements of disgust.

Similar to some of the previous research no statistically significant differences in the Moral Disgust domain of TDDS were observed across the menstrual cycle. This is consistent with predictions of the CPH that postulates changes in avoiding pathogens and sources of infections, as opposed to changes in disgust with socio-moral violations, such as theft.


We believe that understanding how the feeling of disgust varies in relation to phases of the menstrual cycle or to progesterone status could be useful in designing effective disease prevention strategies for women.


What are the practical implications of the obtained results?

The feeling of disgust can be used as a mechanism in strategies aiming to improve health, e.g., within public health programs in response to pandemics such as COVID-19. Moreover, as disgust is a basic symptom of many psychopathologies, it has important implications for psychological welfare. Hence, we believe that understanding how the feeling of disgust varies in relation to phases of the menstrual cycle or to progesterone status (e.g., in women using hormonal contraceptives, or in postmenopausal women) could be useful in designing effective disease prevention strategies for women. If indeed women are more sensitive to disgusting stimuli during the luteal phase, perhaps public health interventions focused on infections could be more effective during this time of a cycle. Additionally, public health interventions could also be focused on rising women’s awareness that their disgust levels might be narrowed in the follicular phase of the cycle resulting in potential disease as well. Also, post-menopausal women have very low progesterone levels, thus if progesterone is involved in disgust perception, it could be hypothesized that at an older age women need stronger stimuli to elicit this behavior.

In conclusion, our study provides support for the CPH, showing increased pathogen disgust sensitivity and contamination sensitivity in the luteal phase among healthy women of reproductive age. To the best of our knowledge, we present the first study that used ovulatory tests, repeated measurements of disgust, and both questionnaires and photographs of potential sources of infections to test the CPH. We suggest that future studies testing the CPH should adopt these methods.



Read the paper: Pathogen disgust, but not moral disgust, changes across the menstrual cycle

The Evolution of Human Personality Roundtable Seminar Event on Sep. 27

We hope you will join us for the Roundtable Seminar Series event Monday, September 27th 2021 at 3:00 – 4:15 pm EST where Drs. David Schmitt, Aaron Lukaszewski, Julia Stern, & Alexander Weiss, will engage in discussion, moderated by Dr. Dario Maestripieri on the topic, “The Evolution of Human Personality”. 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 Monday September 20 2021.

The State of Evolution and Human Behavior: Potential for Future Collaborations Between Evolutionary Anthropologists and Psychologists

by Rebecka K. Hahnel-Peeters


There are many disciplines, subdisciplines, and paradigms through which to understand human behavior – two of which are evolutionary anthropology (EA) and evolutionary psychology (EP). At its core, the goal of EP is to understand the design features of the human mind shaped by natural selection to solve adaptive problems produced over evolutionary time (for review see Buss, 1995; Daly & Wilson, 1997). In a similar manner, EA uses the lens of evolutionary theory to analyze human behavior (both past and present; Fessler et al., 2016). Both EA and EP use the environment of evolutionary adaptiveness (Tooby & Cosmides, 1990) to inform theories of possible psychological mechanisms. However, EA and EP were founded on differing assumptions, and competition between these disciplines was motivated by (1) the differences in assumptions, (2) empirical methodology, and (3) limited time and resources to establish each discipline as serious scientific pursuits (Alden Smith, 2000)—all of which I review in depth here.

What are the similarities and differences between Evolutionary Anthropology and Evolutionary Psychology?

Similarities between the two disciplines include the study of human behavior, emotion, and cognition informed by adaptationist thinking; using comparative animal behavior to understand our behavior; and recognizing the importance of testing hypotheses in environments more like those of our ancestral past (Fessler et al., 2016).  Notably, researchers in both disciplines hold adaptive behavior resulting from mechanisms shaped by selective pressures reliably linked to distinct adaptive challenges (Barrett, 2015; Fessler, 2006).

Differences between the two fields have been characterized most heavily by  methodology. In many subdisciplines of EA, the focus of study has been on behavioral variance rather than the design features of the psychological mechanisms which produce our behavior (Alden Smith, 2000). Therefore, the main difference between EA and EP are their differing focal points (i.e., behavioral variation in different ecologies vs. the structure of cognitive mechanisms). This led to the differences in methodologies that characterize the fields today (e.g., anthropological field work and psychological lab experiments).

Evolutionary Anthropology and Psychology Are Complimentary

Since Alden Smith (2000) argued that EA and EP shouldn’t be considered competing disciplines and the recent 10th anniversary of Henrich et al.’s (2010) “the WEIRDEST people in the world” paper presented good reason to assess the state of the evolutionary social sciences, I conducted a content analysis of articles published in our society’s flagship journal. Henrich et al. (2010) highlighted a problem that most psychological research was based on WEIRD societies; because of this, we may expect increased collaborations between EA’s and EP’s in tests of evolutionary theories cross-culturally following the article’s publication.

Have Evolutionary Anthropologists and Evolutionary Psychologists become more collaborative?

Based on publications in EHB: not really (Figure 1). Across the 737 articles published between 2009 and 2020 there doesn’t seem to be an increase in collaborations between anthropologists and psychologists. In 2009, collaborations between anthropologists and psychologists accounted for 15.8% (n = 6) of the publications. The following years included between 2% and 18% of the publications with the mean rate of collaborations being 9.68% (n = 5.8).

Figure 1. Rates of collaborations between anthropologists and psychologists in EHB between the years 2009 and 2020.


How do evolutionary anthropologists and psychologists study phenomena?

Both use behavioral data and a variety of methods. Evolutionary anthropologists and psychologists do not appear to differ much in their use of behavioral data; however, the methods used to get these data were statistically different. There were significant differences in the methods used by anthropologists and psychologists. Anthropologists were more likely to use survey methods and field work than psychologists, and psychologists were more likely to use experiments in artificial environments (e.g., labs). Interestingly, it appears that psychologists started utilizing more methods to test their hypotheses after 2010. The variation in methodology started looking more like that of anthropologists (Figures 2 & 3).

Figure 2. Percentage of methods appearing in articles published by anthropologists in EHB between the years 2009 and 2020.



Figure 3. Percentage of methods appearing in articles published by psychologists in EHB between the years 2009 and 2020.



In the preprint, I discuss this project more in depth – including methodology, limitations, and future directions to understand the state of the evolutionary social sciences.

Interdisciplinary research—especially between complimentary disciplines—can strengthen our understanding of the world around us. EA and EP are uniquely positioned for collaboration, but the current state of EHB doesn’t show high levels of explicit collaboration between anthropologists and psychologists. It is possible that these two disciplines are becoming more collaborative implicitly; that is, they may be citing each other more, influence each other’s research questions and hypotheses, or evolutionary anthropologists may be training evolutionary psychologists (or vice versa).

Finally, we should continue to consider a roadmap for future collaboration suggested by Fessler et al. (2016). These four steps are attainable and could result in meaningful contributions to the field:

  1. Take advantage of existing literature within paleoanthropology and comparative animal behavior
  2. Read, cite, and understand ethnographic depictions of small-scale societies
  3. Utilize the electronic Human Relations Area Files
  4. Increase collaborations between evolutionary anthropologists and psychologists

Gendered Fitness Interests: Why people can hold political views that disadvantage their own sex

by Rob Brooks and Khandis R. Blake


The views of women and men can differ on important issues such as abortion, gender equity and government spending priorities. Surprisingly, however, average differences in sex on this front are often small. Many women adopt social and political positions that favour men and many men favour women-friendly positions.

In a recent paper in Evolution and Human Behavior we tried to make sense of this apparent paradox. We did so by understanding how people’s politics and practices don’t just track what’s good for them, but also what’s good for their relatives.

Election campaign games

A mere three days after his 2016 inauguration, US President Donald Trump reinstated the Mexico City policy, also called the “global gag rule”. The rule denies US health funding to foreign non-governmental organisations that provide abortions, refer patients for abortions, offer abortion-related counselling or advocate for more liberal abortion laws.

It wasn’t just Trump’s haste to reinstate the rule that galled pro-choice Americans. It was also the supporting cast of men Trump lined up for the photo-op.

Access to abortion is seen – and often spoken about – as a “women’s issue” as it impinges on women’s bodily autonomy and reproductive rights. But had Trump not been appealing to male voters, he could have gathered several prominent anti-choice women to stand behind him instead. Like Charmaine Yoest, former president of Americans United for Life, and soon-to-be appointed by Trump as Assistant Secretary of Health and Human Services for Public Affairs. Despite expectations and rhetoric, support for abortion is far more complicated than a simple tussle between the interests of women and men.


One of the first executive orders that Donald Trump signed was to reinstate the Mexico City Policy (also called the ‘global gag order’), concerning non-governmental organisations and abortion access. Donald J. Trump/Facebook


Think of the children

Polling conducted in the US by Gallup between 2018 and 2020 found 49% of men and 46% of women identified as “pro-life”. A similar gap was observed between “pro-choice” men and women, at 46% and 48% respectively.

“Pro-choice” policies give women options to control their own reproduction and, therefore, an important part of their lives. It would seem rational then for women to support these policies more than men.

Other policies relating to gender equity, sexual harassment, health-care spending and education also impact women and men differently. And while both genders’ views on these topics differ, the difference is quite small on average – in the order of 5%.

Variation of social and political views within a sex is actually far greater. While this is commonly thought to be due to differences in experience, we wanted to know whether the composition of a person’s family might change their views.

Our line of inquiry was inspired by a range of studies that have shown a child’s gender can change their parents’ views. For instance, firms led by male CEOs with daughters tend to adopt more socially and environmentally progressive corporate policies. They’re also more likely to appoint female directors and hire female partners, with positive effects on firm performance. On the other hand, male CEOs of Danish firms who fathered a son, rather than a daughter, paid their employees less generously and paid themselves more generously.

A similar pattern emerges in politics. In the US, legislators with daughters are more likely to vote for “pro-woman” laws than those with sons. And in both the US and Canada, parents with daughters favour gender equity more than those with sons.

Sometimes the effects become visible even before offspring have had much chance to experience the world. In one study, the birth of a son caused parents’ voting intentions to swerve immediately to the right, while a daughter prompted a swerve to the left. In another, the effects kicked in as soon as the parents learned their child’s sex at a prenatal ultrasound.

How your family’s composition can impact you

Research published by Laura Betzig and Lesley Hodgkins Lombardo in 1992 found people’s attitudes towards abortion varied depending on how many of their female relatives were in the age group considered “at risk” of unwanted pregnancy.

The more female relatives someone had aged between 15–50, the more likely they were to favour pro-choice policies. In turn, the more male relatives they had of a reproductive age, the more likely they were to support pro-life policies.

This study inspired us to consider whether gendered issues might depend not only on an individual’s own sex, but also the sex composition of their family. Humans, like other animals, are more invested in their close genetic relatives as a result of Hamiltonian kin selection.

We propose a new metric called “Gendered Fitness Interests”, or GFI. This not only looks at how many genetic relatives of each sex a person has, but also how closely related they are and how many potential reproductive years remain for them.

We built a simple model that confirmed out intuition that people with many close, younger female relatives (such as daughters and sisters) are expected to have a pro-female bias, while those with plenty of young brothers, sons or grandsons should have a bias that favours males.

In our model, sex differences in social and political attitudes are likely to be greatest in young adulthood, when a person’s own gender impacts them greatly. However, as an individual’s potential to have children diminishes, their current children and other relatives start to have a greater influence. Since most people have a balance of male and female relatives, this means a shift towards the centre.

Supporting Evidence

In the early stages of developing our model, long before we published it, a wonderful opportunity to test our ideas arose. For her PhD studies at UNSW, Maleke Fourati gathered data on attitudes towards Islamic veiling practices in Tunisia, specifically on mandatory veiling, which is one of those gendered issues on which we expect women and men might differ. Maleke’s data provided an early test of our idea of gendered fitness interests.

As we predicted, men were more likely than women to support mandatory veiling. But women with more sons (male-biased GFI) were more likely to wear veils themselves and to think other women should too. These mothers, we argued, also in Evolution and Human Behavior, take this position as it serves their sons over their daughters-in-law.

More recently, Nick Kerry, then busy finishing his PhD at Tulane University, led a study testing our prediction in an online American sample. Participants with more reproductive-age male kin held more conservative positions on gender-related issues like gender roles, women’s rights, and abortion.

Separating sex from identity

The web of conflicting interests that give shape to our social and political attitudes is never easy to trace and there are always multiple factors at play.

Perhaps the most interesting implication of our proposal is it undermines the idea that the interests of women and men sit at fixed odds with one another. Some individuals’ values will align more with the opposite sex than with their own, weakening the importance of gender as a distinct part of social and political identity.


This article is republished, with slight modifications, from The Conversation under a Creative Commons license. Read the original article.


Read the paper: Gendered fitness interests: A method partitioning the effects of family composition on socio-political attitudes and behaviors