Saturday, December 18, 2021

Simulation of 100 000 years of evolution in hunter-gatherers: Evolutionary shifts in disgust as polygenic trait occurred (consequence of germ-cell mutations), but cultural transmission between generations operated more quickly & at greater magnitude

The human behavioural immune system is a product of cultural evolution. Edwin S. Dalmaijer, Thomas Armstrong. arXiv Dec 17 2021,

Abstract: To avoid disease, humans show far greater contamination sensitivity and avoidance than their closest living relatives. This is driven by an increased propensity to experience disgust. There is broad agreement that uniquely sensitive disgust in humans is an evolutionary adaptation, which was previously thought to be fuelled by both cultural and genetic inheritance. However, current theories have centred biology and sidelined culture, despite surprisingly little empirical evidence to support this claim. Here, we simulated 100 000 years of evolution in human hunter-gatherers to directly compare genetic and cultural inheritance in a variety of scenarios. We modelled disgust avoidance as a trait that governed the extent to which individuals forewent potentially contaminated nutrition to avoid risking gastrointestinal illness. Our results confirmed natural selection for disgust, particularly as the level and cost of contamination in an environment increased. Evolutionary shifts in disgust as polygenic trait occurred as a consequence of germ-cell mutations, but were more prominent in populations with high initial genetic variance. Crucially, cultural transmission between generations operated more quickly and at greater magnitude, even if parental modelling was eliminated. Our computational work supports the hypothesis that cultural evolution outpaced its biological counterpart to select health-improving behaviours that benefited survival. This study serves not only as evidence of cultural evolution shaping the behavioural immune system, but is also an illustration of emerging theories that paint affective and cognitive mechanisms as socially transmitted rather than biologically determined functions.

Meat consumption: Health or environmental information has no main effect on attitude and no effect on intention or behavior

Can information influence meat consumption behaviour? An experimental field study in the university canteen. Nina Weingarten et al. Food Quality and Preference, December 17 2021, 104498.


• The study combines an online survey with a field study in a university canteen.

• Aim of the study is to investigate the role of information on meat consumption.

• Health information has no main effect on attitude, intention, or behavior.

• Environmental information has no main effect on attitude, intention, or behavior.

• Subjective knowledge moderates the effect of environmental information on attitude.

Abstract: The present study investigates the effectiveness of health and environmental information provision as an intervention to reduce meat consumption behaviour. In an experimental online survey (n = 194), we tested how information about the negative effects of meat consumption on health or the environment influence attitude and intention to reduce meat consumption. In the following two weeks, we measured participants’ meat consumption behaviour in the university canteen, which we accessed through an individual purchase card. Contrary to our hypotheses, our results show that there is no direct effect of health or environmental information on attitude, intention, or meat consumption behaviour compared to the control group. However, our results indicate that for participants with low subjective knowledge, environmental information is effective in influencing attitude. Neither attitude nor intention mediates the relationship between information and behaviour. Our findings highlight that information provision has limited effectiveness in changing attitude, but does not influence intention or behaviour. We conclude that more research is needed that includes a direct measure of meat consumption behaviour to evaluate the effectiveness of information provision as an intervention.

Keywords: Meat consumptionBehaviourHealth informationEnvironmental informationUniversity canteenSubjective knowledge

Countries that became less wealthy and more morally polarized over time also became less trustful

Stavrova, O., Evans, A. M., & Brandt, M. J. (2021). Ecological dimensions explain the past but do not predict future changes in trust. American Psychologist, 76(6), 983–996. Dec 2021.

Abstract: Concerns about declining trust and rising cynicism are recurrent in academic research and the media. Yet, prior studies focused on explaining, rather than predicting, temporal changes in trust. We tested prediction models of trust change across (up to) 98 countries over six measurement waves (from 1981 to 2014). We tested whether different ecological predictors (e.g., pathogen prevalence, population diversity, inequality) explain the past and predict future trust levels across countries. We used societal growth curve models to disentangle between- from within-country effects and evaluated the accuracy of the models’ out-of-sample predictions using the train-test split method: We used data from 1981–2009 to “train” the models and obtain predictions of trust for the period of 2010–2014. None of our models was more accurate in predicting future trust than a simpler baseline model. Moreover, we did not observe a universal decline in trust. Instead, temporal changes in trust were country-specific, highlighting the locality of cultural change. Most ecological predictors were correlated with between-country differences in trust. Only resource availability and moral opinion polarization were associated with within-country changes in trust: Countries that became less wealthy and more morally polarized over time also became less trustful. These results highlight important differences between explanatory and predictive models and suggest that ecological theories of trust might be of limited use when predicting future cultural shifts.


The story of how cognition and fitness relate may not be simple, but simple stories and complex systems rarely go together

Cognition and reproductive success in cowbirds. David J. White, J. Arthur, H. B. Davies & M. F. Guigueno. Learning & Behavior, Dec 16 2021.

Abstract: Understanding the relationships between cognitive abilities and fitness is integral to an evolutionary study of brain and behavior. However, these relationships are often difficult to measure and detect. Here we draw upon an opportunistic sample of brown-headed cowbird (Molothrus ater) subjects that had two separate research experiences: First, they engaged in a large series of cognitive tests in David Sherry’s Lab in the Advanced Facility for Avian Research (AFAR) at Western University, then subsequently moved to the Field Avian Research Megalab (FARM) at Wilfrid Laurier University where they lived in large breeding flocks in aviaries with other wild-caught cowbirds. Thus, we had extensive measures of cognitive abilities, breeding behavior, and reproductive success for these birds. We report here, for the fist time, the surprisingly strong connections we found among these different measures. Female cowbirds’ spatial cognitive abilities correlated positively with how intensely they were courted by males, and with their overall egg production. Males’ spatial cognition correlated positively with their ability to engage in singing contests (“countersinging”) with other males. In addition, a separate non-spatial cognitive ability correlated positively with the attractiveness of the songs they sung. In sum, these results suggest the cognitive skills assessed in the lab were strongly connected to breeding behavior and reproductive success. Moreover, since certain cognitive abilities related to different aspects of breeding success, it suggests that cognitive modules may have specialized adaptive value, but also that these specialized skills may interact and influence fitness in surprising ways.


Despite the small sample size, the different cognitive scores correlated with several aspects of breeding behavior and reproductive success in both males and females.


Those females who reliably scored highest on spatial tests in the lab received the most courtship song from males. The number of songs sung to females is an important variable associated with pairbond strength and copulation success, and thus is integral to reproduction (White et al., 2010abc). It is unclear what drives this correlation. It is possible that there is something about these females that makes them more attractive to males. Results of past work, however, would suggest that something about the females’ behavior is important in stimulating the males to sing to them more often (Maguire et al., 2013). What females do to get males to sing to them more often is unknown – though one possibility is the use of chatter in response to males’ song (Maguire et al., 2013).

The other variable significantly associated with cognition for females was egg production. Females are often highly variable in egg production between and across groups and past work has been only marginally successful in explaining this variation. Most of those explanations have revolved around the idea that females invest more in egg production in circumstances where they have the most valuable information about the quality of males present (White et al., 2010abc). The cognition score used here is by far the strongest explanatory variable we have ever found for egg production. Perhaps females who have better cognitive abilities can best engage in the behaviors associated with selecting the highest quality, or most compatible mate, building the most successful pairbond, and therefore most likely to invest in egg production. An interesting aspect of this relationship is that laying more eggs leads to a higher spatial memory demand because it requires finding more nests. No matter what mechanism explains this relationship, the connection between spatial cognition and reproductive success suggests that sexual selection can be a driving force on spatial cognition in females.


We had the opportunity to examine how two measures of cognitive performance related to males’ fitness. First, we found that song attractiveness, as measured in playback tests related to the males’ performance on cognitive tasks that used color stimuli in delayed match-to-sample tests. That song attractiveness related to cognitive performance supports the theory that those males best able to learn are the ones who can produce the most attractive signal – a theory of the functional value of song that has been posited for songbirds in general (Nowicki et al., 19982002) and cowbirds specifically (West & King, 1988). These results connecting cognitive performance and song differ from work in song sparrows (Soha et al., 2019), where no connections between cognition and song could be detected (see also Templeton et al., 2014). Why song attractiveness should relate to cognition for color per se, is unclear. Perhaps song attractiveness and performance on the color tasks are linked by another unmeasured variable relating to male quality (health, “good genes”, or stress responsiveness). This would appear unlikely since past work has shown that song attractiveness is highly dependent on developmental (West & King, 1988) and immediate (Gersick & White, 2018) social experiences. Thus, the most likely route leading to variation in song attractiveness involves interacting and learning from the visual responses of females and other males to singing overtures. The color tasks were designed as a control for spatial memory performance and not designed specifically to examine an aspect of cognition hypothesized to be important to male breeding behavior. Thus, the color tasks may be measuring some more general aspect of visual acuity, attention, or learning. More work is needed to determine exactly what cognitive mechanism is driving color discrimination and song development. It is clear, however, that the cognitive ability measured using the color task was distinct from spatial memory skill because performance on spatial tasks did not relate to song attractiveness.

Spatial task performance did, however, relate to one important aspect of singing in males: countersinging. Countersinging is a skill that males must learn in order to attain and maintain dominance among males and to stimulate the reproductive output of females (White et al., 2010abc). Past work has shown that countersinging is learned by juveniles over their first year of life as they approach and sing with adult males (White, King, & West, 2002a). This ability to get close to other males, sing with them in duetting bouts, and temper aggression leads to a cascade of learning other breeding skills and is highly variable among males (White et al., 2007ab; White, King, & West, 2002a).

No other variables for males or females reached the large effect size necessary for statistical significance (other than chatter patterns in females). There is, however, a distinction that should be made between the correlation strength needed for statistical confidence and for biological relevance. Evolution can act on very small effects. Tables 1 and 2 show some of the effects that did not reach significance but will be the subject of future work, as many of them may inform us of the potential directions of effect occurring with other variables. For example, female chatter is highly stimulating and motivating to males (Burnell & Rothstein, 1994; Freed-Brown & White, 2009; Hauber et al., 2001; Lynch et al., 2017; Snyder-Mackler & White, 2011). Perhaps the production and use of chatter is a behavioral mechanism that females use to regulate males’ behavior, stimulate courtship effort, and strengthen the pairbond (Maguire et al., 2013), leading eventually to more egg output. Other interesting positive relationships with females’ spatial cognition include the song attractiveness of their pairmate, and the amount of courtship song they receive only from their pairmate (a measure of pairbond strength we have found in the past to be important for breeding success; Maguire et al., 2013).

The disclaimers here are most likely obvious: the frustratingly low sample size highlights the challenges for neuroecology and studies of animal cognition in general where the depth of understanding of individuals’ cognitive abilities trades off against testing large numbers of subjects and therefore against generalizability and statistical power. The low number of subjects precluded more detailed statistical analyses, and we could only rely on a small number of a priori comparisons requiring very strong relationships to reject a null hypothesis. Also, the birds in this study, while wild caught, experienced years of life in abnormal contexts, raising questions about generalizability to the wild (although in the aviaries they bred in patterns very similar to the resident birds). Finally, it was not the primary goal of the cognitive experiments to subsequently study fitness. Had it been, we would have ensured that we collected measures that were more directly comparable across subjects. As is, it is not clear what cognitive modules we are examining here. The color-discrimination tasks might be measuring visual acuity, attention, learning speed, etc. Spatial cognition here also includes tasks that were focused on numerical discrimination. Thus, this work should be considered an exploratory first step that, even with the limitation inherent in these data, was surprisingly successful in demonstrating relationships between different aspects of cognition and reproductive success. This discovery will drive experiments both in the lab and in aviaries for years to come.

What do these findings mean for the adaptive specialization hypothesis about cowbird spatial memory? We still have not been able to test directly whether spatial cognition abilities allow females to successfully find and select viable nests in the wild – the critical relationship posited by the adaptive specialization hypothesis that started the work with cowbirds. With modern advances in automated tracking technology and advances in neural manipulations, this relationship may be testable in the near future. The findings reported here – that different measures of cognition related to different aspects of effective breeding – support the idea that there are functionally distinct cognitive systems as proposed by Sherry and Schacter (1987). There do seem to be different cognitive domains at work here, similar to food-caching species that show different patterns of performance depending on whether a task is spatially based or color based (Olson et al., 1995). Females’ superiority in behavioral tasks and the hippocampal size evidence suggest that the potential exists for selection to act on spatial cognition through nest-finding abilities. The interconnections between these cognitive systems and diverse aspects of breeding revealed here, however, suggests some cooption, or exaptation of the cognitive system, which significantly complicates determining how selection has acted and may act (Gould & Vrba, 1982; Sherry & Schacter, 1987). Selection may be operating on spatial memory skills for both a specialized demand on the species (finding nests), and also a non-specialized demand (selecting a mate and reproducing). This suggests there are non-additive interactions among cognitive modules and fitness.

The story of how cognition and fitness relate may not be simple, but simple stories and complex systems rarely go together. The complexity of living systems presents many different routes and strategies leading to reproductive success and thus identifying how distinct memory systems relate to fitness can be challenging. Studying the wealth of links between memory systems, however – how they can work independently and together, how they react to different environments, to past experiences and to conspecifics – and ultimately lead to organizing adaptive behavior holds the promise to fully understand the evolution of the brain and intelligence.

Several adverse perinatal events were associated with an increased risk of violent and non-violent criminal convictions; low birth weight, smallness relative to gestational age and preterm birth with non-violent convictions were higher for men

Adverse perinatal events and offspring criminal convictions in men and women: A population-based study. Sofi Oskarsson et al. Journal of Criminal Justice, Volume 78, January–February 2022, 101879.


• Adverse perinatal events were associated with an increased risk of violent and non-violent criminal offending

• Associations between some adverse perinatal events with criminal convictions were significantly higher for men than for women

•There was a dose-dependent association between adverse perinatal events with criminal convictions for both men and women


Background: We examined associations of adverse perinatal events with offspring violent and non-violent criminal convictions in men and women.

Methods: All singleton births between 1973 and 1995 (n = 1,146,570 men, n = 1,085,217 women) were identified through Swedish population-based registers. Information about adverse perinatal events was retrieved from the Medical Birth Register. Outcomes were criminal convictions collected from the National Crime Register. We estimated absolute and relative risks of being convicted of criminal convictions using the Kaplan-Meier method and survival analyses for men and women separately. We also tested for differences in magnitudes of associations for men versus women.

Results: Several adverse perinatal events were associated with an increased risk of violent and non-violent criminal convictions in both men and women. Associations between low birth weight, smallness relative to gestational age and preterm birth with non-violent criminal convictions were statistically significantly higher for men than for women. There was a dose-dependent association between adverse perinatal events with violent and non-violent criminal convictions for both men and women, indicated by the strengthened magnitude of HR estimates with exposure to an increasing number of adverse perinatal events.

Conclusions: Adverse perinatal events are associated with violent and non-violent criminal convictions in men and women, with some differences in risk estimates between sexes. Findings are compatible with theoretical accounts implicating disruption of the neurodevelopment during the perinatal period.

4. Discussion

In this large-scale population-based study, we found that several adverse perinatal events were associated with an increased risk of violent and non-violent criminal convictions. These results are not only in line with findings from previous research (Liu et al., 2009), but also extend these. Specifically, we add to the existing literature by showing that the exposure to adverse perinatal events increases the risk of violent and non-violent criminal convictions, in both men and women. Further, we found evidence for a dose-dependent relationship between adverse perinatal events and criminal behavior, whereby the exposure to an increasing number of adverse perinatal events elevated the risk for violent and non-violent convictions in both men and women. Additionally, our findings suggest that there may be different adverse perinatal events that heightened the risk of violent and non-violent criminal convictions for men compared to women, even though they are few. For example, observed associations for low birth weight and preterm birth with non-violent criminal convictions were significantly higher for men than for women. These findings build on the existing knowledge regarding the potential importance of early risk factors for criminal offending and point to a dose-dependent relationship.

We also found that small head circumference at birth was associated not only with violent criminal convictions as reported in earlier studies (Ikäheimo et al., 2007) but also with non-violent criminal convictions. These findings were evident for both men and women. Small head circumference has in the previous literature been referred to as a minor physical anomaly (Denno, 1990). From a biopsychosocial criminological perspective, minor physical anomalies have been viewed as reflecting physical and neural maldevelopment of the fetus during pregnancy, potentially due to both genetic and environmental influences (Raine, 2002b; Raine, 2019). Minor physical anomalies have long been a known correlate of male aggression (Waldrop et al., 1978) and criminality (Raine, 2013), but the current results indicate that this association extends to criminal offending among women.

One previous study using a sample that overlapped partly with the present study's, reported a reduced risk of any criminal conviction among offspring who were born preterm (D'Onofrio et al., 2013). This association remained even among discordant siblings, pointing to an independent association between being born preterm and later criminal offending. Being born preterm would thus serve as a protective factor for later criminality. We found that in models adjusted for birth year, preterm birth increased the risk for violent and non-violent criminal convictions among men, but not women. However, in mutually adjusted models, preterm birth was associated with violent criminal convictions but not non-violent convictions, among men, but not women. The discrepancy in findings may be due to the fact that the present study examined men and women separately, whereas the previous study (D'Onofrio et al., 2013) used a total population sample with an adjustment for offspring sex. Another explanation may relate to the different outcomes studied: whereas the present study utilized violent and non-violent criminal convictions as separate outcomes and D'Onofrio et al. (2013) employed any criminal conviction as the outcome.

Taken together, these findings highlight the importance of examining men and women separately when studying associations between adverse perinatal events and criminal convictions, as well as studying violent and non-violent criminal convictions as separate outcomes. The male brain has been suggested to be more susceptible to influences early in life that can disrupt normative neurological development (Golding & Fitzgerald, 2019), and it is well-known that preterm birth is associated with behavioral and psychological problems in later life (Bhutta et al., 2002). Our findings suggest that the association between preterm birth and criminal offending should be further investigated to better understand whether this is a factor contributing to the higher overall rate of criminal convictions for men as compared to women.

One previous study has demonstrated associations between adverse perinatal events and later self-reported violent behavior in a dose-dependent manner, among both men and women (Murray et al., 2015). Our results are in line with these findings and suggest that when adverse perinatal events accumulate in the same individual (up to four for men and up to three for women in the present study), the risk for criminal convictions in the offspring increases for both men and women. The dose-dependent association between adverse perinatal events and offspring criminality is in line with biopsychosocial criminological theory, which suggest that adverse perinatal events contribute to a disruption of neuropsychological development, which in turn can heighten the risk for criminal behavior (Raine, 2002c). It is possible that the accumulation of adverse perinatal events in the same individual index disruption of fetal development during pregnancy more effectively than exposure to a single event. This may further be why we see relatively weak associations between individual adverse perinatal events with offspring criminal convictions, as well as low cumulative incidences, even though there are some indications that certain adverse perinatal events are more important than others (e.g., smallness for gestational age). Further research is needed to clarify the nature and etiological basis of the dose-dependent association between perinatal events and later criminal behavior in offspring, which in turn can inform clinical practice and possibly prevention efforts.

Interestingly, the adverse perinatal events that evidenced an association with criminal offending in the mutually adjusted models differed for men and women. For men, the summative index encompassed extremely low and low birthweight, small for gestational age, small head circumference, and post-term birth for non-violent criminal convictions, with the addition of preterm birth for violent criminal convictions. For women, the summative index encompassed of low birth weight, small head circumference, and post-term birth. The implication is that certain adverse perinatal events, when accounting for all others, are more important for men than for women and vice versa. We opted for an empirically driven approach that allowed for different adverse perinatal events to be included in the summative indices for men and women respectively. Our results highlight the need to differentiate between men and women in the study of adverse perinatal events in relation to criminal convictions, since men and women likely are at different risk of experiencing adverse perinatal events (Zeitlin et al., 2002), as well as engage in criminality. This approach was further supported by the HR estimates for the summative index in the total population (Table S3 in Supporting Information), which in general were not significant or in most cases exhibited overlapping CIs. The dose-dependent relationship between adverse perinatal events and offspring criminal behavior should be explored more extensively in future research to better understand the differences between men and women.

Some unexpected findings in our study should also be noted. Certain adverse perinatal events were associated with a decreased risk of violent and non-violent criminal convictions (e.g., breech presentation, assisted vaginal delivery). Breech presentation, as well as other adverse perinatal events, have previously been related to a lack of oxygen to the fetus (i.e., anoxia), which in turn has been described as a risk factor for criminal offending (Tibbetts, 2011). No study thus far has specifically examined breech presentation in relation to criminal offending, let alone different types of breech positions (e.g., frank breech, complete breech). Further research using other samples is needed to explicate the role of different breech presentations and other aspects of delivery on risk for later criminality.

In our sensitivity analyses, we stratified the full sample including men and women based on levels of SES. Previous work has reported associations between exposure to adverse perinatal events in combination with psychosocial adversities, such as maternal rejection (Raine et al., 1994Raine et al., 1997) and a disadvantaged family environment (Piquero & Tibbetts, 1999) and later criminal behavior in the offspring. However, a few exceptions should be noted though (Murray et al., 2010Murray et al., 2015). In the current study, HR estimates were largely unaffected by stratifying the sample into levels of SES, if anything they were somewhat attenuated for all groups.

Findings from the present study should be considered in the light of certain limitations. Some of our reported associations, particularly those for the female portion of the sample, need to be interpreted with caution because of the small number of individuals being exposed to particular adverse perinatal events, as well as the small portion of criminal offenders among females. Owing to these factors, HR estimates for females were less precise than those for males, with wider confidence intervals.

Another limitation is that, although the great majority of births in Sweden are recorded in the MBR, there are still 1–3% of all births during each of the past 20 years that are missing from the register (the National Board of Health and Welfare, 2021). While the MBR contains information of varying quality, the adverse perinatal events included in the present study have previously shown high validity (Källén & Källén, 2003). It is also important to acknowledge that our criminal convictions data relied on official records, which may not be representative of all men and women who have engaged in criminal activity. While registry data reduces the risk of misclassification in one way by limiting recall bias that is often associated with interview data, the results in the present study assume the same level of misclassification of criminal convictions for men and women. While more research is needed on this specific topic, especially in relation to registry data, there is some evidence for a more lenient treatment of female offenders as compared to male offenders (Doerner & Demuth, 2014). Lastly, we performed sensitivity analyses in the total sample of men and women, stratified on levels of SES. Ideally, this would have been done in men and women separately but was not possible due to statistical power restrictions.