Do Local Sex Ratios Approximate Subjective Partner Markets? There is a need for more fine-grained, age-specific sex ratios

Do Local Sex Ratios Approximate Subjective Partner Markets? Evidence from the German Family Panel. Andreas Filser & Richard Preetz. Human Nature, Jun 19 2021. https://link.springer.com/article/10.1007/s12110-021-09397-6

Abstract: Sex ratios have widely been recognized as an important link between demographic contexts and behavior because changes in the ratio shift sex-specific bargaining power in the partner market. Implicitly, the literature considers individual partner market experiences to be a function of local sex ratios. However, empirical evidence on the correspondence between subjective partner availability and local sex ratios is lacking so far. In this paper, we analyzed how closely a set of different local sex ratio measures correlates with subjective partner market experiences. Linking a longitudinal German survey to population data for different entities (states, counties, municipalities), we used multilevel logistic regression models to explore associations between singles’ subjective partner market experiences and various operationalizations of local sex ratios. Results suggest that local sex ratios correlated only weakly with subjective partner market experiences. Adult sex ratios based on broad age brackets, including those for lower-level entities, did not significantly predict whether individuals predominantly met individuals of their own sex. More fine-grained, age-specific sex ratios prove to be better predictors of subjective partner market experiences, in particular when age hypergamy patterns were incorporated. Nevertheless, the respective associations were only significant for selected measures. In a complementary analysis, we illustrate the validity of the subjective indicator as a predictor of relationship formation. In sum, our results suggest that subjective partner availability is not adequately represented by the broad adult sex ratio measures that are frequently used in the literature. Future research should be careful not to equate local sex ratios and conscious partner market experiences.

Discussion

Imbalanced sex ratios have been linked to a wide range of social consequences, including family formation, economic decision-making, gender roles, partnership formation, fertility, personality, and sexuality (Bauer & Kneip, 2013; Feingold, 2011; Griskevicius et al., 2012; Harknett, 2008; Merli & Hertog, 2010; Pollet & Nettle, 2008; Schacht & Smith, 2017; Trent & South, 2012; Uggla & Mace, 2017). Sociodemographic and evolutionary mating market approaches have explained these findings by shifts in bargaining power based on differential mating opportunities for men and women in an imbalanced sex ratio environment (Filser & Schnettler, 2019; Guttentag & Secord, 1983; Kokko & Jennions, 2008; Pedersen, 1991; Schacht & Kramer, 2016). Individual partner market experiences might play a crucial role in these behavioral adaptations to local sex ratios given that subjective experiences provide critical guidelines for human behavior (Gilbert et al., 2016; Gintis, 2006; Kroneberg & Kalter, 2012). Yet, empirical evidence has been lacking on how closely individual experiences of partner market opportunities correspond to sex ratios of their local environment. To fill this gap, we analyzed associations between a variety of local sex ratio measures and subjective partner market experiences of female and male singles in a German panel survey.

In sum, the expected association between subjective partner market experiences and local sex ratios only held for selected, age-specific sex ratio measures. In particular, adult sex ratios based on broad age ranges as are commonly used in the literature did not prove to be significant predictors of subjective partner market experiences. This result was consistent across operationalizations of adult sex ratios as the proportion of men in the adult population (PMA) based on different age brackets at the level of states, counties, and municipalities. None of the adult sex ratio variants correlated with either men’s or women’s subjective experiences of surplus encounters with individuals of their own sex in a meaningful way. More granular, age-specific sex ratio measures (ASPM) that include only individuals of adjacent age cohorts were closer approximations of subjective partner market experiences. In particular, age-specific measures that also incorporated age shifts to reflect age hypergamy patterns proved to be better predictors of subjective partner market experiences. Nevertheless, only selected state-level, age-shifted sex ratios correlated with women’s surplus encounters with other women in a statistically significant way. The corresponding county-level age-shifted sex ratios yielded similar, yet smaller coefficients, which have to be interpreted with caution given that they did not reach statistical significance. For men, only county-level, age-shifted sex ratios significantly predicted associations with men’s subjective partner market experiences. Coefficients for state-level age-shifted sex ratios were similar in size but did not reach statistical significance. Overall, some reservations regarding the state-level findings seem warranted because the German states might be too large in geographic terms (with all but four being larger than 15,000 km2) to be considered a single partner market. Lengerer (2001:142) reports that 85% of future partners in Germany live within a 20 km radius of each other. Recent publications suggest that earlier recommendations to rely on smaller entities when operationalizing local partner markets continue to apply in the age of Internet dating (Bruch & Newman, 2019; Fossett & Kiecolt, 1991). Therefore, results for state-level sex ratios should be treated with caution.

In sum, the results of this study suggest that previous findings regarding the social consequences of imbalanced sex ratios are unlikely to be mediated by conscious adaptations to partner scarcities or oversupplies. Adult sex ratios for fixed age brackets, such as the population aged 16–49 or 16–64, constitute the standard operationalization of local sex ratios in the literature (see Schacht et al., 2014; Pollet et al., 2017 for reviews). Our findings suggest that sex ratios for fixed adult age ranges are unlikely to correspond closely to subjective partner market experiences. Previous research has demonstrated that sex ratios correlate only moderately with each other when different age cutoffs are used (see Fossett & Kiecolt, 1991 for a discussion using US census data). Therefore, adult sex ratios are unlikely to be a well-suited summary measure of age-specific sex ratios. This is also supported by our dissimilar results for adult and age-specific sex ratios. In contrast to adult ratios, selected age-specific and age-shifted operationalizations significantly predicted subjective partner market experiences. In particular, the integration of age hypergamy into the sex ratio measures yielded significant results for predicting subjective partner market experiences. Future research should therefore consider focusing on age-specific, age-shifted sex ratio measures. Yet, although age-shifted sex ratios predicted men’s subjective partner market experiences, we only find weak evidence for a similar association for women. This difference between men and women might be due to a smaller sample size of women in our models. A further explanation could be related to sex differences in sexual strategies guiding partner market behavior. In particular, sexual strategies theory suggests that sexual selection favored antagonistic mating competition and preferences for multiple short-term mating in men (Buss, 1999; Schmitt, 2015; Trivers, 1972). This could also entail that men are more aware of marriage squeezes than women are.

A further finding of this paper is that subjective surpluses of same-sex encounters significantly predicted relationship formation. For both sexes, a subjective surplus of encounters with individuals of one’s own sex was significantly associated with a lower probability of entering a relationship. We are aware that survey questions on subjective partner market experiences may represent an excessive demand for respondents. However, the fact that the subjective indicator correlates with this specific partner market outcome supports the idea that the analyzed reports of surplus encounters with same-sex individuals constituted a valid approximation of individual partner market experiences. Concerning the local sex ratio measures, age-specific and age-shifted variants proved to be advantageous over adult sex ratios also when predicting relationship formation. None of the adult sex ratios significantly predicted relationship formation. Moreover, age-specific local sex ratios only yielded significant coefficients when incorporating age shifts. Specifically, relationship formation for women was significantly predicted by state- and county-level age-specific and age-shifted sex ratios. Yet, the probability of men entering a relationship was not predicted by local sex ratios, replicating similar asymmetric findings by Uggla and Mace (2017). With regard to the link to subjective partner market experiences, our findings suggest that subjective partner market experiences and local sex ratios should be considered distinct context variables rather than equivalent indicators. This is even true for detailed measures of local sex ratios. For instance, age-specific county-level sex ratios with a two-year age shift were a significant predictor of women’s relationship formation. Yet, we do not find conclusive evidence that these measures were correlated with women’s subjective partner market experiences. Consequently, these findings suggest that subjective and local sex ratios are not interchangeable operationalizations. Rather, they appear to be two separate dimensions of partner market circumstances. Researchers should be aware of this distinction when offering theoretical interpretations of results based on local sex ratios.

The subjective partner market indicator used in this study is not equivalent to the situational perception of the sex proportions in a group. Instead, it approximated the everyday interactions of individuals and therefore should not be interpreted as indicative of an inability to perceive sex ratios in set groups. Both Alt et al. (2017) and Neuhoff (2017) demonstrated that participants are able to give accurate sex ratio estimations based on short-term exposure to visual and auditory cues. Against the backdrop of these previous studies, one potential explanation for our findings could be that individual partner market experiences are not a direct representation of macro-structural conditions, i.e., local sex ratios (Blau, 1977; Rapp et al., 2015; Schwartz, 1990). Instead, individual partner markets may be structured in different “foci of activity,” such as workplaces, voluntary associations, or hangouts (Feld, 1981; Rapp et al., 2015). With this in mind, studying the consequences of sex ratios in interactive spheres such as workplaces (Åberg, 2009; Barclay, 2013; Svarer, 2007), industries (Uggla & Andersson, 2018), bars (Lycett & Dunbar, 2000), or colleges (Harknett & Cranney, 2017) would have the advantage of assuming that the individuals are actually interacting with one another. This is much more plausible than the same contention would be for local sex ratios. Consequently, individuals’ foci-specific sex ratios might give a more accurate impression of partner supply and demand within the respective foci rather than sex ratios of the local population, even for their specific age cohort.

This paper used a combination of administrative population information and survey data, which is crucial to this analysis. Studies relying on such data face a trade-off between the scope of the data and the ability to link survey data with survey-based partner market measures. The pairfam survey data constitute a unique combination of both ends of this spectrum. However, adult sex ratios in Germany may not have sufficient variation to allow for identifying a clear effect. This is particularly true for adult sex ratios at the state level, which only range between 96 and 108 men per 100 women (see Table 2). Consequently, nonsignificant findings for state-level sex ratios could also be due to the lack of variation at this level of aggregation. Internationally, local adult sex ratios may vary more substantially in selected regions, most notably in the male-skewed populations of China and India (Guilmoto, 2012). However, the county-level variation in adult sex ratios in the analyzed data was consistent with that of recent studies from other Western countries (e.g., Schacht & Kramer, 2016), and the ranges of age-specific sex ratios exceeded the ranges of adult sex ratios in our data.

A further limitation is that the findings are contingent on the validity of the subjective partner market indicator. While our complementary analysis demonstrated the predictive validity of the subjective indicator with respect to relationship formation, limitations persist. The directional verbalization of the indicator question introduced ambiguity, resulting in imprecise measurement of undecided and disagreeing answers. Specifically, respondents who met an equal number of men and women either might have reported disagreeing with the statement of predominantly meeting individuals of their own sex or might have given an undecided answer to express their experience of a balanced sex ratio. We explored this issue via fitting linear and multinomial models for different variants of the original indicator scale. These auxiliary results confirmed that the difference in probabilities for undecided and disagreeing answers was not significantly correlated to local sex ratios. However, agreement with the surplus same-sex contacts scale was related to selected local sex ratio measures (Fig. S6-S8, in the ESM). We therefore focused on the dichotomized indicator that summarized disagreeing and undecided responses. Nevertheless, our logistic regression results do not persist when taking a linear modeling approach, most likely because of measurement noise in disagreeing and undecided responses. Furthermore, the current analysis was limited to one global subjective indicator of opposite-sex encounters. A detailed survey of foci-specific sex ratios might give a closer approximation of subjective partner market experiences (cf. Rapp et al., 2015). This could reveal whether partner markets in specific foci actually correspond to local sex ratios, whereas partner markets in other foci do not. In particular, detailed information on job location could be of particular relevance, given that 60% of German employees cross municipality borders when commuting (Pütz, 2017). Consequently, adding sex ratios based on the place of work could yield a higher correspondence to subjective partner markets.

In conclusion, the sex ratio literature should be cautious regarding the assumption that individuals are consciously aware of local sex ratio skews. In particular, subjective and conscious partner market experiences do not appear to be a direct function of broad-range adult sex ratios but instead are correlated only with selected, age-specific measures. Researchers should consider this when interpreting findings based on local sex ratios. Although our findings shed some doubt on a direct link between conscious experiences and local sex ratios, this does not necessarily imply that local sex ratios do not capture partner markets. So far, very little is understood about how humans experience, remember, and process contextual sex ratios (Dillon et al., 2017). In particular, the relative importance of immediate interaction partners, local communities, and broader social contexts is yet to be explored (Maner & Ackerman, 2020).

This paper explored the relationship between a general indicator of subjective partner market experiences and local sex ratio measures. In sum, general sex ratio measures that are based on broad age ranges do not seem to capture conscious partner market experiences in a meaningful way. Future research will have to establish the role of unconscious factors, including endocrinal or network effects mediating contextual local sex ratios and adaptations in individual behavior.

People often complain that their romantic partner spends money foolishly; & tightwads (who find spending money very painful) and spendthrifts tend to attract, which leads to arguments and financial infidelity

“You Spent How Much?” Toward an Understanding of How Romantic Partners Respond to Each Other’s Financial Decisions. Jenny G. Olson, Scott I. Rick. Current Opinion in Psychology, June 21 2021. https://doi.org/10.1016/j.copsyc.2021.06.006

Abstract: How people choose to spend money is often observable to others (e.g., based on their clothes, accessories, and social media pages), but there is a whole universe of financial decisions that are essentially unobservable (e.g., how people handle their debts, taxes, and retirement planning). We explore one context where people have an up-close-and-personal view of someone else’s financial decision-making process: romantic relationships. We discuss how the endless opportunities for financial observation in romantic relationships influence a range of behaviors, including spending habits, decisions about bank account structure, and financial infidelity. Our review highlights the need for more research on the ways in which financial decisions are made, communicated, and observed within romantic relationships.

Keywords: consumer financial decision-makingromantic relationshipsmarriageperson perception

Higher levels of men’s family carework were associated with lower suicide mortality, especially among men and under high-unemployment conditions, wich points to the suicide-protective potential of men’s family carework

Caregiving as suicide-prevention: an ecological 20-country study of the association between men’s family carework, unemployment, and suicide. Ying-Yeh Chen, ZiYi Cai, Qingsong Chang, Silvia Sara Canetto & Paul S. F. Yip. Social Psychiatry and Psychiatric Epidemiology, May 5 2021. https://doi.org/10.1007/s00127-021-02095-9

Abstract

Purpose: Suicide rates are generally higher in men than in women. Men’s higher suicide mortality is often attributed to public-life adversities, such as unemployment. Building on the theory that men’s suicide vulnerability is also related to their private-life behaviors, particularly men’s low engagement in family carework, this ecological study explored the association between men’s family carework, unemployment, and suicide.

Methods: Family-carework data for twenty Organization for Economic Co-operation and Development (OECD) countries were obtained from the OECD Family Database. Sex-specific age-standardized suicide rates came from the Global Burden of Disease dataset. The association between men’s engagement in family carework and suicide rates by sex was estimated, with OECD’s unemployment-benefits index and United-Nations’ Human Development-Index (HDI) evaluated as controls. The moderation of men’s carework on the unemployment-suicide relationship was also assessed.

Results: Overall and sex-specific suicide rates were lower in countries where men reported more family carework. In these countries, higher unemployment rates were not associated with higher male suicide rates. In countries where men reported less family carework, higher unemployment was associated with higher male suicide rates, independent of country’s HDI. Unemployment benefits were not associated with suicide rates. Men’s family carework moderated the association between unemployment and suicide rates.

Conclusion: This study’s findings that higher levels of men’s family carework were associated with lower suicide mortality, especially among men and under high-unemployment conditions, point to the suicide-protective potential of men’s family carework. They are consistent with evidence that where gender equality is greater, men’s and women’s well-being, health, and longevity are greater.

55 traditional cultures: Experts with observable motor skills like toolmaking were often generous teachers, but specialists with conceptual know-how for uncommon problems (health) used secretive knowledge to help clients

Ethnoscientific expertise and knowledge specialisation in 55 traditional cultures. Aaron D. Lightner, Cynthiann Heckelsmiller and Edward H. Hagen. Evolutionary Human Sciences, accepted manuscript, pp. 1 - 52, Jun 14 2021. https://doi.org/10.1017/ehs.2021.31

Abstract: People everywhere acquire high levels of conceptual knowledge about their social and natural worlds, which we refer to as ethnoscientific expertise. Evolutionary explanations for expertise are still widely debated. We analysed ethnographic text records (N=547) describing ethnoscientific expertise among 55 cultures in the Human Relations Area Files to investigate the mutually compatible roles of collaboration, proprietary knowledge, cultural transmission, honest signalling, and mate provisioning. We found relatively high levels of evidence for collaboration, proprietary knowledge, and cultural transmission, and lower levels of evidence for honest signalling and mate provisioning. In our exploratory analyses, we found that whether expertise involved proprietary vs. transmitted knowledge depended on the domain of expertise. Specifically, medicinal knowledge was positively associated with secretive and specialised knowledge for resolving uncommon and serious problems, i.e., proprietary knowledge. Motor skill-related expertise, such as subsistence and technological skills, was positively associated with broadly competent and generous teachers, i.e., cultural transmission. We also found that collaborative expertise was central to both of these models, and was generally important across different knowledge and skill domains.

Social media summary: In a cross-cultural study we found that experts with observable motor skills like toolmaking were often teachers, but specialists with conceptual know-how for uncommon problems like illness used secretive knowledge to help clients.

Keywords: Ethnoscience, Expertise, Cultural transmission, Conceptual knowledge, eHRAF

Animals also hold beliefs and there are some aspects that underly the formation of beliefs which are shared with other animal species, namely the relationship between causality, predictability and utility of beliefs

An Evolutionary Approach to the Adaptive Value of Belief. Anabela Pinto. Chapter in Evolutionary Psychology Meets Social Neuroscience, June 14th 2021. DOI: 10.5772/intechopen.97538

Abstract: The word “belief” evokes concepts such as religious or political beliefs, however there is more to belief than cultural aspects. The formation of beliefs depends on information acquired through subjective sampling and informants. Recent developments in the study of animal cognition suggest that animals also hold beliefs and there are some aspects that underly the formation of beliefs which are shared with other animal species, namely the relationship between causality, predictability and utility of beliefs. This review explores the biological roots of belief formation and suggests explanations for how evolution shaped the mind to harbour complex concepts based on linguistic structures held by humans. Furthermore, it suggests that beliefs are shaped by the type and process of information acquisition which progresses through three levels of complexity.

Keywords: Biology of beliefutility of beliefsacquisition of information meaning causality predictability utility bias

5. The adaptive value of beliefs

Thinkers, scientists and philosophers reach their own conclusions through methodological approaches specific to their field of expertise. In the process, they innovate, discover new methodologies, suggest theories. In summary, they gain insights into the problems they are addressing. When creating testable hypotheses, they make assumptions held as true, testing them for inconsistencies, flaws, mistakes, illogicality, etc. Hopefully, after a certain amount of time and painstaking testing, some of these assumptions, become a ‘truth’ in the mind of the thinker and her followers even though it is only a hypothesis. This truth will only survive until new evidence refutes it. A new paradigm replaces the former and the cycle restarts. This paradigm shift was thoroughly discussed by the American philosopher and physicist Thomas Kuhn in his 1962 book The Structure of Scientific Revolutions.

Many of our present social and personal beliefs result from cultural inheritance, our reliance on other people and sources we trust. Our survival depends on a large number of “specialised believers” telling us what to think.

We believe in the insights of others that preceded us and adopt them as truths. The teachings of the Buddha and the Middle Eastern religions, the insights of Classical Greek philosophers about the mind and nature, the discoveries of the Enlightenment and the progress of the industrial revolution, all are examples of personal insights that spread in space and time. Some insights are independently arrived at in different cultures and time frames, their common aspects suggesting that they may be intuitive across humankind. Similar social norms and recommendations based on an awareness of human nature that ensure that social order is upheld are found in tribal societies that never had contact with each other. Some of these rules have deep roots in biology, such as those aimed at controlling female behaviour to ensure the paternity of the offspring. Many of these norms passed on from generation to generation become enshrined in our present cultural norms and are still held as unquestionable dogmas. Similarly, questioning religious and scientific dogmas is still frowned upon by members of the groups that hold such doctrines. Individuals become emotionally attached to such beliefs and express anxiety and defensive reactions when such beliefs are challenged. This begs the question by which processes do beliefs operate to induce such strong emotional attachment?

There are aspects of the content of the belief that tap deeply into our biology [1]. When the information content of a belief aligns in some way with processes that provide survival strategies, that information perceived as meaningful is ardently protected and any challenge to its truth is aggressively repelled.

Which attributes make up the mind is much debated; however, their common features include the integration of a sensorial mechanism which contributes to make sense of an individual’s external and internal world. Whether or not the individual is conscious of that sense or meaning is irrelevant to definition, since proving presence of awareness in most animals empirically is impossible due its subjective nature. In the Descent of Man, Darwin laid out the case for believing that the difference between the minds of humans and other animals was ‘certainly one of degree and not of kind’.

There are at least four basic conditions that make a belief meaningful. First the belief must offer an explanation for causal events, secondly it must offer a sense of predictability, thirdly, the information received must be reliable and correspond to what is believed to be fact and finally, that belief must have some utility providing survival advantages [40]. But before each one of these conditions is addressed, it is necessary to understand the notion of meaning.

5.1 A biological approach to the concept of meaning

The concept of meaning can be approached through a philosophical point of view such as ‘what is the meaning of life’, a psychological cognitive approach, such as ‘what you are telling me makes no sense in my mind’ and through a linguistic approach which begs for definitions such as in ‘what is the meaning of this word?’. The linguistic description of meaning plays an important role in communication and spread of beliefs. A sound, a word, a sentence, all have meaning when they contribute to the comprehension of the message. But comprehension or understanding is also a function of the subjective experiences of the receiver. If I say “table” it induces different mental images in the receiver. It can be a word that simply categorises objects with four legs and a surface high enough to allow our legs under it. But there are many variations of the concept table. Is it in wood or metal and glass? Is it unassuming with straight lines or convolutedly decorated with arabesques? The word table may confer a limited number of characteristics that are common to most people that have experienced the shape and function of furniture but its meaning varies accordingly to function. Is it a dining table, a coffee table or a desk? Whereas descriptive words for objects may be easy to define by just pointing at it or simply describing its function, abstract concepts may have different meanings to different people. For example, what is the meaning of the concept of freedom of speech? Does it mean I can say whatever I feel like or does it encompass a certain level of censorship to prevent incitement to harm others? What is the meaning of friendship? Does it require unconditional loyalty or does it give room for compassionate lies?

Frequently, what gives meaning to some of these abstract concepts is the level of emotion associated with them. People who believe in freedom, or God, or homoeopathy may feel threatened when their beliefs are challenged because such beliefs define the individual, her nature, his cultural identification, her expectations. Holding strongly to beliefs provides a sense of security and predictability. Such emotions are defined by neurological processes that transduce the sound of words, to their meaning and to their emotional valence; e.g. whereas to some people the word spider evokes fear and the word mouse evokes of cuteness, to others the word mouse may evoke feelings of fear and anxiety. A thing has meaning when its description aligns with our preconceived mental models. If I am learning statistics, a t-test only has meaning if I have a prior knowledge of means and other arithmetic calculations. Asking someone to do a t-test on a set of numbers without previous understating of basic concepts, renders the requirement meaningless. Furthermore, it may induce a state of anxiety due to acknowledgement of ignorance about that subject.

The informational content of a message acquires meaning, when it is compared with a mental database of previously learnt units of knowledge and it aligns or provides incremental increases to that knowledge. It follows that meaningful information is more useful than meaningless information. It functions as a tool of survival, based on which we can induce and deduce further knowledge. It is therefore reasonable to assume that an emotional connection between pieces of meaningful information is formed. On the other hand, meaningless information triggers a sense of discomfort and rejection. Meaningful information comes associated with an emotional protective layer to challenge. This explains the strong tendency to confirmation bias and rejection of new sources of knowledge that disconfirms our beliefs.

Individuals develop an emotional attachment to familiar information to the point of suffering great anxiety when that information is deemed false.

Festinger [41] defined meaning as the perception of coherence between one’s beliefs and the real world. “When these things align, we are left with the sense that the world is ordered, controlled, and understandable. When this coherence is disrupted, however, meaning is threatened and we feel distressed and anxious as a result”.

The sense of meaning could then be seen as an adaptive feature derived and supporting beliefs. Adaptive beliefs are those which contain information that contribute to individual survival. A belief is adaptive if the information about what caused an event is reliable, predictable and useful. Beliefs shaped in this context are very likely to be strong which means, they are upheld in the mind with vehemency and any challenge to the belief is perceived as a threat to constancy. Some mental processes are common across species because they are built on neural structures that have roots in common ancestors. Perhaps the most primitive processes are those that refer to identifying the causes of what happens around oneself. The next step consists in an ability to predict future events and prediction can only be successful if it relies on the accuracy and reliability of previously stored information.

5.2 Causality: understanding causes and sequences of events

As discussed above the establishment of associations between cause and effect is perhaps the most ancient form of learning. Such associations provide the organisms with opportunities to test and improve its tactics during the acquisition of resources essential for their survival. Beliefs about the cause of events are perhaps one of the most important factors for survival. When we know what caused an event, we can somehow predict the outcome next time a similar cause is enacted. The concept of causality is coupled with the perception of agency. An agent is a living or inanimate cause which triggers an event, but very often humans attribute intentionality to the agent.

Detection of the cause-effect association is quite powerful and the motivation to find an explanation for the cause sometimes disregards rational thinking. If the explanation satisfies, then it is likely to be promptly accepted as true.

Explanation of causes are often associated with the presence of an agent. In humans, when the cause is unknown because there is no direct observation of the causal event, there is a tendency to create an invisible agent and attribute human characteristics such as intentionality. This is an important component of magical thinking and is the origin of animistic religions which created a backcloth to religions with deities. Animism attributes intentionality to forces of nature without anthropomorphic representations of entities. In animism, the believer appeals to the forces and energy of nature. They refer to the spirit of the elements such as the wind, the water, the earth as if they were fuzzy undelimited agents with consciousness and aims. Religion with gods is built on this principle where the agent is no more the forces of nature, but some invisible figure that concentrates those forces. These agents can be represented as animals whose characteristics identify with the natural phenomenon or humans.

The assumption that we are hardwired to discern relationship between cause and effect induces us to pay more attention to events that coincide, or are salient especially when they support our beliefs, thus reinforcing confirmation bias and often supporting beliefs in the paranormal.

5.3 Predictability

Assuming predictability is a strategy for coping with uncertainty. It helps in planning future decision making. Uncertainty leads to anxiety and stress and, as such, beliefs that promote a false impression of predictability are naturally easier to accept. Observations of animal behaviour and historical narratives have shown evidence that safe environments promote co-operation and trust among the members of a social group, whereas instance of resource shortage and unpredictable social settings are conducive of social instability often expressed in varied forms of aggression [1].

Predictability is intrinsically associated with pattern detection. The perception of patterns, even when they are absent in reality, confers a sense of control. Patternicity equates constancy and repeatability [1].

The perception of patterns and the need for predictability underpin the onset of superstitious behaviours present in humans and animals [42]. A pursuit of predictability is yet more pronounced in situations marked by environmental social instability. For example, studies on political preferences suggested that the way humans perceive insecurity and unpredictable events may have some influence on their political beliefs. Research revealed that helping people imagine they are completely safe from harm can make them (temporarily) hold more liberal views on social issues [43, 44] and that a perception of threat can make liberals lean more towards conservative views [45].

When the information is provided by an informant rather than through subjective sampling, the reliability of the message can vary in levels of accuracy since many factors may corrupt the informational content from the time it leaves the informant and arrives at the receiver. The type and intensity of these modifications affect the reliability of the message and may therefore provide misleading information. The occurrence of ambiguity in the message is frequently interpreted as satisfying the desired goals inducing a belief that the message offers predictions that satisfy their expectations. This process is open to behaviour manipulation. Corrupted informational content may be unintentional, deriving from random mistakes or misperception, but can also be intentional where the informer sends purposefully dishonest signals. Since dishonest signalling is widespread in nature, detection systems have co-evolved to counteract such signals.

Conveying truthful and fake information are processes that promote the survival of individuals but are not without trade-offs. While cheating can be advantageous to individuals that interact only once, it will work against the cheater once the interaction is repeated and detected. Then cheating does not pay anymore. In social groups where most individuals know one another, the cheater may collect immediate rewards but once it is detected, it is promptly punished by elements of the group. However, in human social groups when the cheating is propagated through words that meet the desires and expectations of the receivers, the cheater can get away with his lies for quite a long time. Humans seem to be open to accept lies, as long as they align with their wishful thinking. In evolutionary terms this seems to be a process that would eventually vanish from the population, given its negative impact. However, it is not all negative, for there is also a need to conform with the beliefs of the group as a means of gaining protection.

5.4 Utility

Group membership in mammals is usually established by sharing similar scents. In humans, scent identification is complemented by the sharing similar ideas where thinking like the tribe becomes the equivalent of smelling like the tribe and fitting in the same social group. Similar scents indicate a level of kin relations and, accordingly to kin selection theory based on mathematical models developed by George R. Price [46] and popularised by W.D.Hamilton [47], altruism and cooperation are more prevalent among individuals that share the highest number of genes. This implies that individuals are more likely to protect those who share genes with them, than those who do not.

Likewise, in human societies this rule could be applied to ideas in the sense that those individuals that share the same stances as me are more likely to protect one another. These ideas were popularised by Richard Dawkins [48] who coined the word memes, suggesting that the transmission of information from mind to mind follows similar rules like the transmission of molecular information through genes from parents to offspring.

This convergence towards homogenous ideas inside the group may explain the success of religion, political factions, belief in conspiracy theories, doomsday and other cults, reflecting a process of group cohesion previously regulated by scent similarity. This is reflected by what political scientists call elective affinities—the notion that there is mutual attraction between ‘the structure and contents of belief systems and the underlying needs and motives of individuals and groups who subscribe to them’ [49].

Many beliefs are not derived from personal experience, but from trusted sources or communities. So, giving up those beliefs may threaten ties with the community. When established beliefs have a useful function there is a tendency to conserve them since the sharing of common beliefs promotes group cohesion. On the other hand, homogenous group thinking prevents creativity which may result from a reluctance to conform with established rules. Rebels threaten the cohesion of the group and in order to keep them under control it is necessary to develop punitive mechanisms that discourage deviating from the status quo [50].

Thus, a strategy based on a hierarchical system of policing develops. But this strategy is not exclusive to humans, or mammalian social groups. It is also observed in groups of social insects such as ants and bees. Note that there is a difference between the evolutionary concepts of “strategies” and “tactics”. While strategies refer to a set of behavioural adaptations that evolved over time, tactics refer to the individual actions taken to pursue a strategy [50, 51]. The concept of utility can also be observed in individuals who believe in conspiracy theories. A conspiracy theory, however unlikely, represents an identification badge identifying that social group. In human societies the sharing of beliefs plays the same function as scent sharing in kin related animal groups. Common beliefs are the “intellectual scent” that unites a group. Conspiracy theories often offer theories that contradict the prevailing or official narrative of facts or events. They offer alternative explanations that appeal to those who believe they have a reason to distrust mainstream narratives. They usually refer to the existence of some hidden enemy and the individual finds safety in the confinements of their like-minded group. The belief in conspiracy theories relies on faith promoted by group think rather than evidence. The individual then finds a false sense of safety inside these ideological bubbles.

Perhaps one of the most puzzling aspects of beliefs which confer survival utility is the placebo effect which seems to have positive effects in healing of the mind and body. Perhaps one of the main characteristics of this effect is that it is grounded on the human’s tendency to magical thinking and embrace convictions rather than simple beliefs.

What Are Friends for in Russia Versus Canada?; the notions of trust and help in adversity emerged as defining features of friendship in Russia but were less clearly present in Canada

What Are Friends for in Russia Versus Canada?: An Approach for Documenting Cross-Cultural Differences. Marina M. Doucerain, Andrew G. Ryder, Catherine E. Amiot. Cross-Cultural Research, June 16, 2021. https://doi.org/10.1177/10693971211024599

Abstract: Most research on friendship has been grounded in Western cultural worlds, a bias that needs to be addressed. To that end, we propose a methodological roadmap to translate linguistic/anthropological work into quantitative psychological cross-cultural investigations of friendship, and showcase its implementation in Russia and Canada. Adopting an intersubjective perspective on culture, we assessed cultural models of friendship in three inter-related ways: by (1) deriving people’s mental maps of close interpersonal relationships; (2) examining the factor structure of friendship; and (3) predicting cultural group membership from a given person’s friendship model. Two studies of Russians (Study 1, n = 89; Study 2a, n = 195; Study 2b, n = 232) and Canadians (Study 1, n = 89; Study 2a, n = 164; Study 2b, n = 199) implemented this approach. The notions of trust and help in adversity emerged as defining features of friendship in Russia but were less clearly present in Canada. Different friendship models seem to be prevalent in these two cultural worlds. The roadmap described in the current research documents these varying intersubjective representations, showcasing an approach that is portable across contexts (rather than limited to a specific cross-cultural contrast) and relies on well-established methods (i.e., easily accessible in many research contexts).

Keywords: friendship, Russia, Canada, cultural models, intersubjective culture, methods

Discussion

The present studies showcased a three-pronged approach to quantitatively document cross-cultural differences in models of friendship in Canadian versus Russian cultural contexts. Our hypotheses were largely supported. Participants’ mental map of the interpersonal space around friend was different from that around droog (H1), the factorial structure of friendship characteristics differed across cultural settings (H2), and we could predict group membership from participants’ ratings of friendship characteristics (H3). We also found evidence of cultural consensus in people’s responses across studies and across cultural contexts. Further, the three aspects of our methodological approach relied on very different analytic strategies, yet yielded convergent results.

Our results documented some similarities between the two cultural contexts. Both friend and droog were located close to relationship terms with connotations of fun and good times (Study 1), and items referring to stimulating companionship clearly loaded on a single factor in both countries (Study 2a). This is consistent with existing research on the classical Aristotelian model of friendship, where enjoyment is an important feature of friendship (Bukowski et al., 1987; Hall, 2012). However, across studies, the notions of trust and help in adversity emerged as defining features of friendship in the Russian context, whereas they were less clearly present in the Canadian context. Relationship terms with connotations of “brother-in-arms” were located very close to droog (Study 1), and higher ratings of trust and not fearing negative consequences from a friend’s actions were related to a greater likelihood of being Russian (Study 2b). Trust is also seen as a friendship characteristic in the Western literature (Hall, 2012; Hartup & Stevens, 1997; Wright, 2006), but in addition to being particularly salient for Russian participants, trust may also be represented differently in the Russian context. Indeed, trust and esteem for one’s friend formed a single factor among Russians, whereas trust items were associated with instrumental help (or tended to not load very highly on their respective factor) among Canadians (Study 2a). This is consistent with Russia’s 20th century historical events. In a totalitarian regime where self-disclosure could have life threatening consequences, trust, and help in adversity may well have emerged as paramount features of friendship.

The results also indicated that friendship is seen as a closer and more intimate relationship in the Russian group than in the Canadian group. Droog and luchshiy-droog were located very close together, whereas friend and best-friend were in different clusters (Study 1), and seeing friendship as entailing very frequent interactions was related to a greater likelihood of being Russian (Study 2b). As mentioned earlier, Western research on friendship regularly distinguishes between “casual” and “close” friendships. In Western/North-American cultural worlds, a generic friendship may be mentally represented as a not a very deep relationship, and qualifiers such as “close” are necessary to account for a broader range of social ties. It was also noteworthy that endorsing more strongly the idea that having friends is a reflection of one’s social skills (Study 2b) was related to a greater likelihood of being Canadian. This is consistent with the Western interpersonal literature, whereby friendships index one’s interpersonal abilities (Jerrome, 1984) and personal characteristics (Walther et al., 2008). This notion is also encoded in the English language, where “‘making friends’ appears to be seen as an art and a skill” (Wierzbicka, 1997, p. 45).

Overall, our results echo Wierzbicka’s (1997) linguistic analyses and the qualitative findings that friendship is a very involved and demanding relationship in the Russian cultural context (Doucerain et al., 2018). Collectively, these results also support the notion that different intersubjective representations of friendship, or friendship models, are prevalent in these two cultural worlds. Although these results encourage confidence in our methodological approach, several limitations should be noted. First, we used gender-neutral names to elicit representations of as generic a friendship as possible, but this decision may have introduced noise into the results. Gender differences in friendship patterns are well documented (Aukett et al., 1988), and whether participants had a male or female generic friendship in mind when completing the study might have influenced their answers. Second, both Russian and Canadian samples were fairly young (in their thirties on average), and it is possible that older participants would have characterized friendship differently. This is particularly problematic for the Russian sample, given the profound social changes that Russia experienced over the last decades. In a related vein, North American products are increasingly prevalent in Russia, like in many other parts of the world. These globalization forces (Cowen, 2009) may influence people’s friendship representations—particularly among younger people, just like they contribute to reshaping a number of psychological constructs and processes (Kirmayer, 2006; Watters, 2011). Finally, so far, we have tacitly assumed a complete overlap between nation-state and cultural group, which is problematic. Cultural/cross-cultural psychologists routinely rely on such correspondences, but they are over-simplifications that can unfortunately reify and essentialize cultural differences (Morris et al., 2015). Our goal here was to propose and document an approach to characterize cultural models of friendship—and our results suggest that our approach was adequate—but future research should take these limitations into consideration.

We showcased our three-pronged methodological approach by contrasting Russian versus Canadian friendship models, but future research could employ a similar approach in other cultural contexts. For example, some preliminary qualitative work suggests that Japanese friendship models may also differ from North American ones (Cargile, 1998). It would be interesting to examine where friend’s translation equivalent tomodachi (友達) stands in relation to other relationship terms such as mikata, nakama, shinyuu, or tsukiai, and how the factor structure of a generic tomodachi’s characteristics compares to the factor structures derived here.

However, rather than being an end in itself, documenting cross-cultural differences in friendship models should serve as a base for subsequent “unpackaging” studies: namely, studies clarifying what mechanisms account for the observed cultural differences (Dere et al., 2012; Matsumoto et al., 2008). In other words, what sociocultural characteristics, historical circumstances, prevalent practices or core concerns of Russian versus Canadian worlds can explain the differences in friendship models we observed here? For example, the high premium placed on trust in the Russian model may stem from decades of Soviet rule where self-disclosure entailed significant risk to one’s safety, and future research should test such a hypothesis.

More broadly, focusing on the mechanisms underlying cross-cultural differences in friendship patterns may stimulate work on how culture shapes ways of relating to each other. Cultural/Cross-cultural psychologists have usually focused on individual-level constructs, such as values (Schwartz, 2012), self-construal (Markus & Kitayama, 1991), or emotional experience (Matsumoto et al., 2008), but much less on relational constructs (Morris et al., 2000). The present work took a step toward addressing this paucity of research by proposing a methodological road map for studying cross-cultural differences in friendship models and by documenting these differences across Canadian and Russian cultural contexts. Many quantitative investigations of cross-cultural differences build on initial qualitative, anthropological, or linguistic evidence. We hope to have demonstrated here one approach to negotiating this transition step in a systematic way.

Mask-wearing improved wearers’ sense of the attractiveness of faces, which were rated as less attractive when a mask was not worn after the onset of the COVID-19 epidemic

Effects of masks worn to protect against COVID-19 on the perception of facial attractiveness. Miki Kamatani, Motohiro Ito, Yuki Miyazaki, and Jun I. Kawahara. Accepted at i-Perception (2021) DOI: 10.1177/20416695211027920. Jun 2021

Abstract: Wearing a sanitary mask tended, in the main, to reduce the wearer's sense of perceived facial attractiveness before the COVID-19 epidemic (Miyazaki & Kawahara, 2016). This phenomenon, termed the sanitary-mask effect, was explained using a two-factor model involving the occlusion of cues used for the judgment of attractiveness and unhealthiness priming (e.g., presumed illness). However, these data were collected during the pre-COVID-19 period. Thus, in the present study, we examined whether the COVID-19 epidemic changed the perceived attractiveness and healthiness when viewing faces with and without sanitary masks. We also used questionnaires to evaluate beliefs regarding mask wearers. We found that the perception of mask-worn faces differed before versus after the onset of the COVID-19 epidemic. Specifically, mask-wearing improved wearers’ sense of the attractiveness of faces, which were rated as less attractive when a mask was not worn after the onset of the COVID-19 epidemic. Further, mask-worn faces were rated as healthier post-COVID-19. The proportion of respondents with negative associations regarding mask-wearing (e.g., unhealthiness) decreased relative to before the epidemic. We suggest that the weakening of this association altered the sanitary-mask effect with a relative emphasis on the occlusion component, reflecting the temporal impact of a global social incident (the COVID-19 epidemic) on the perception of facial attractiveness.

Long-term gene–culture coevolution and the human evolutionary transition: There is strong evidence that culture is a major adaptive force in the evolution of many animal species

Long-term gene–culture coevolution and the human evolutionary transition. Timothy M. Waring and Zachary T. Wood. Proceedings of the Royal Society B: Biological Sciences, June 2 2021. https://doi.org/10.1098/rspb.2021.0538

Abstract: It has been suggested that the human species may be undergoing an evolutionary transition in individuality (ETI). But there is disagreement about how to apply the ETI framework to our species, and whether culture is implicated as either cause or consequence. Long-term gene–culture coevolution (GCC) is also poorly understood. Some have argued that culture steers human evolution, while others proposed that genes hold culture on a leash. We review the literature and evidence on long-term GCC in humans and find a set of common themes. First, culture appears to hold greater adaptive potential than genetic inheritance and is probably driving human evolution. The evolutionary impact of culture occurs mainly through culturally organized groups, which have come to dominate human affairs in recent millennia. Second, the role of culture appears to be growing, increasingly bypassing genetic evolution and weakening genetic adaptive potential. Taken together, these findings suggest that human long-term GCC is characterized by an evolutionary transition in inheritance (from genes to culture) which entails a transition in individuality (from genetic individual to cultural group). Thus, research on GCC should focus on the possibility of an ongoing transition in the human inheritance system.

2. The role of culture in human evolution

[...]

(a) Adaptive capacity

Cultural inheritance may hold greater adaptive potential than genetic inheritance due to its mechanistic differences. Indeed, the primary explanation for the emergence of the human cultural inheritance system itself is that it provides a more flexible and rapid system of behavioural evolution than genetics alone allow. Evidence [28] and theory [29] support the assertion that cultural evolution is more rapid than genetic evolution [27,28,30,31], even when measured on comparable scales [30,31]. One simple reason for this difference is that the ‘generation time’, G, of cultural transmission can be orders of magnitude shorter than that of genetic transmission [30]. In humans, the average time between the birth of parents and the birth of their offspring, genetic G, ranges from roughly 2 to 3 decades, while cultural G, the average time between learning a piece of information and transmitting it, ranges from seconds to decades. Thus, it is reasonable to presume that cultural inheritance may provide greater adaptive capacity than genetic inheritance.

Indeed, there is strong evidence that culture is a major adaptive force in the evolution of many animal species, among which humans show both the strongest evidence and the greatest impacts of GCC [32]. Human culture is by far the most complex and extensive form of culture, and its impact on human genetics is correspondingly profound [33,34]. Humans are thought to have acquired significant genetic changes as a result of long-term GCC, including dramatic digestive changes, the emergence of docility and reduced aggression [35], modified vocal tracts [36], the cognitive apparatus for social learning [22,37] and norm internalization [38]. Apparent genetic accommodation of cultural evolution in humans supports the proposal that cultural evolution may be more adaptive than genetic evolution. It is still further supported by the correspondence between the growth in the scale and complexity of our social systems, and emergence of our species as the dominant ecological force on Earth [39]. Far beyond simply altering human evolution, this evidence suggests that human cultural inheritance is of global evolutionary significance.

Uncontrollable mortality creates selective advantages for families with many “cheap” offspring; declining mortality and medical progress facilitate the transition towards growth-promoting “low-fertility-high-quality” phenotypes

Darwin beats Malthus: evolutionary anthropology, human capital and the demographic transition. Katharina Mühlhoff. Cliometrica, Jun 16 2021. https://link.springer.com/article/10.1007/s11698-021-00234-5

Abstract: Declining mortality seems a natural explanation for the demographic transition. However, many economists have discarded improved infant survival as a causal trigger. Moreover, certain currents in Neo-Malthusian economics point to potentially beneficial side-effects of population shocks. Based on historical demography and evolutionary science, I challenge these views. The argument is that uncontrollable (“extrinsic”) mortality creates selective advantages for families with many “cheap” offspring, whereas stable environments favor child “quality”. Combining “life-history-theory” and a unified growth model, I demonstrate that declining mortality and medical progress facilitate the transition towards growth-promoting “low-fertility-high-quality” phenotypes. As it will turn out, this framework produces qualitatively and quantitatively closer predictions of the historical fertility decline than standard models of the Barro–Becker type. Moreover, evolutionary mechanisms provide a parsimonious explanation for diverse demographic transition patterns. Thus, evolved adaptations add a new and culture-free mechanism to older theories. Moreover, regarding sustainable growth, they suggest that natural selection eventually offsets the benefits from population shocks claimed by Malthusian theories.

Connecting with others makes people happier, but strangers in close proximity often ignore each other; we may avoid pleasant conversations with strangers because of miscalibrated concerns about starting them

Hello, stranger? Pleasant conversations are preceded by concerns about starting one. Juliana Schroeder, Donald Lyons, & Nicholas Epley. Accepted Journal of Experimental Psychology: General. Jun 2021. https://static1.squarespace.com/static/5c171ac1710699e060ed3d94/t/60c43987d485fc055656c1ca/1623472521485/Hello+Stranger+-+June+2021.pdf

Abstract: Connecting with others makes people happier, but strangers in close proximity often ignore each other. Prior research (Epley & Schroeder, 2014) suggested this social disconnection stems from people misunderstanding how pleasant it would be to talk with strangers. Extending these prior results, in a field experiment with London-area train commuters, those assigned to talk with a stranger reported having a significantly more positive experience, and learning significantly more, than those assigned to a solitude or control condition. Commuters also expected a more positive experience if they talked to a stranger than in the solitude or control conditions. A second experiment explored why commuters nevertheless avoid conversation even  when it is generally pleasant. Commuters predicted that trying to have a conversation would be less pleasant than actually having one because they anticipated that others would be uninterested in talking. These experiments clarify the precise aspects of social interaction that may be  misunderstood. People may avoid pleasant conversations with strangers because of miscalibrated  concerns about starting them.

Keywords: conversation; communication; social cognition; social motivation; wellbeing

Individuals rated their past relationship quality more negatively in retrospect than they had actually reported at the time

Peetz, Johanna, Aidan Smyth, and Adreinne Capaldi. 2021. “Ex-appraisal Bias: Negative Illusions in Appraising Relationship Quality Retrospectively.” PsyArXiv. June 18. doi:10.1177/0265407520907150

Abstract: Cognitive biases are prevalent within the context of romantic relationships. The present research investigated biases about relationships after they have ended. In a longitudinal design (N = 184), individuals reported relationship quality at two time points, as well as rated relationship quality retrospectively. Results supported an ex-appraisal bias: individuals rated their past relationship quality more negatively in retrospect than they had actually reported at the time. This bias was present across participants who stayed together and those who broke up but was three times larger for those whose relationships had ended. This bias may be a motivated cognition that helps individuals let go of their ex-partners after a breakup.

Those who believe crime is caused by a single gene believe that punishment should be weakened, are less supportive of rehabilitation efforts, and believe that offenders are less capable of redemption

Beyond a Crime Gene: Genetic Literacy and Correctional Orientation. Amanda Graham, J.C. Barnes, Hexuan Liu & Francis T. Cullen. American Journal of Criminal Justice, Jan 9 2021. https://link.springer.com/article/10.1007/s12103-020-09595-5

Abstract: Is there a “crime gene”? This question has been answered by the scientific community, and the response is a definitive “no.” Yet, it is unclear whether this information has been communicated to the general public. Furthermore, it is unclear whether people’s views about the genetics of crime influence their perceptions of the way offenders should be treated. This study uses attribution theory to understand how perceptions of the role of genetic factors in criminal behavior influence beliefs about the punishment, redeemability, and rehabilitation of offenders. Drawing on a national sample of White respondents (N = 392), this study finds that only a small proportion believe there is a single crime gene. Compared to other respondents, those who believe crime is caused by a single gene believe that punishment should be weakened, are less supportive of rehabilitation efforts, and believe that offenders are less capable of redemption. Implications of these findings are discussed.

Studies of females with congenital adrenal hyperplasia show how prenatal androgens affect behavior across the life span; large effects on interest and engagement in gendered activities, moderate effects on spatial abilities

Evidence and Implications From a Natural Experiment of Prenatal Androgen Effects on Gendered Behavior. Sheri A. Berenbaum, Adriene M. Beltz. Current Directions in Psychological Science, June 18, 2021. https://doi.org/10.1177/0963721421998341

Abstract: Sex and gender are key to people’s lives, and are the focus of scientific and popular interest and controversy. Sex-related psychological characteristics reflect more than socialization; they are influenced by sex hormones present during sensitive periods of development, particularly androgens that are present prenatally. Studies of females with congenital adrenal hyperplasia (CAH) show how prenatal androgens affect behavior across the life span; these hormones have large effects on interest and engagement in gendered activities, moderate effects on spatial abilities, and relatively small (or no) effects on gender identity, gender cognitions, and gendered peer involvement. In addition to showing the complexity of androgens’ effects on gendered behavior, studies of females with CAH provide an opportunity to test theories of gender development, gain insight into how nature and nurture work together, and examine mechanisms of development. The implications of this work have often been misunderstood, so we consider what it means—and does not mean—for biology to influence gender-related behavior.

Keywords: congenital adrenal hyperplasia, differences of sex development, gender development, gender identity, interests, natural experiments, peers, prenatal androgens, spatial abilities

New Research Claims Darwin Made an Error About Sexual Selection: Evolution of large males is associated with female-skewed adult sex ratios in amniotes

Evolution of large males is associated with female-skewed adult sex ratios in amniotes. András Liker, Veronika Bókony, Ivett Pipoly, Jean-Francois Lemaître, Jean-Michel Gaillard, Tamás Székely, Robert P. Freckleton. Evolution, May 22 2021. https://doi.org/10.1111/evo.14273

Abstract: Body size often differs between the sexes (leading to sexual size dimorphism, SSD), as a consequence of differential responses by males and females to selection pressures. Adult sex ratio (ASR, the proportion of males in the adult population) should influence SSD because ASR relates to both the number of competitors and available mates, which shape the intensity of mating competition and thereby promotes SSD evolution. However, whether ASR correlates with SSD variation among species has not been yet tested across a broad range of taxa. Using phylogenetic comparative analyses of 462 amniotes (i.e., reptiles, birds, and mammals), we fill this knowledge gap by showing that male bias in SSD increases with increasingly female-skewed ASRs in both mammals and birds. This relationship is not explained by the higher mortality of the larger sex because SSD is not associated with sex differences in either juvenile or adult mortality. Phylogenetic path analysis indicates that higher mortality in one sex leads to skewed ASR, which in turn may generate selection for SSD biased toward the rare sex. Taken together, our findings provide evidence that skewed ASRs in amniote populations can result in the rarer sex evolving large size to capitalize on enhanced mating opportunities.

Popular version Darwin Made an Error About Sexual Selection, New Research Reveals (sciencealert.com):

In a new study, my colleagues and I have confirmed a link between sexual selection and sex ratios, as Darwin suspected. But surprisingly, our findings suggest Darwin got things the wrong way round. We found that sexual selection is most pronounced not when potential mates are scarce, but when they're abundant – and this means looking again at the selection pressures at play in animal populations that feature uneven sex ratios."

[...]

This in no way invalidates Darwin's theories of natural selection and sexual selection. Our finding simply shows that a different mechanism to the one Darwin proposed is driving mating competition for animals living in sex-skewed populations.

Darwin's assumption was based on the idea that the most intense competition for mates should occur when there's a shortage of mating partners. But more recent theories suggest this logic may not be correct, and that sexual selection is actually a system in which the winner takes all.

That means that when there are many potential partners in the population, a top male – in our study, the largest and heaviest – enjoys a disproportionately high payout, fertilizing a large number of females at the expense of smaller males, who may not reproduce at all.

Autism diagnosis and symptoms were associated with greater brain maleness, but the effects appeared to be driven by differences in brain size; brain maleness may be due to he same factors that influence brain size

Testing the extreme male brain hypothesis: Is autism spectrum disorder associated with a more male-typical brain? Liza van Eijk, Brendan P. Zietsch. Autism Research, May 19 2021. https://doi.org/10.1002/aur.2537

Abstract: Autism spectrum disorder (ASD) is more common in males than females and has been linked to male-typical behavior. Accordingly, the “Extreme Male Brain” hypothesis suggests that ASD is associated with an exaggeratedly male-typical brain. To test this hypothesis, we derived a data-driven measure of individual differences along a male–female dimension based on sex differences in subcortical brain shape (i.e., brain maleness) by training our algorithm on two population samples (Queensland Twin IMaging study and Human Connectome Project; combined N = 2153). We then applied this algorithm to two clinical datasets (Autism Brain Imaging Data Exchange I and II; ASD N = 1060; neurotypical controls N = 1166) to obtain a brain maleness score for each individual, representing maleness of their brain on a male–female continuum. Consistent with the Extreme Male Brain hypothesis, we found a higher mean brain maleness score in the ASD group than in controls (d = 0.20 [0.12–0.29]), parallel to higher scores for control males than control females (d = 1.17 [1.05–1.29]). Further, brain maleness was positively associated with autistic symptoms. We tested the possibility this finding was driven by the ASD group's larger brains than controls (d = 0.17 [0.08–0.25]), given that males had larger brains than females (d = 0.96 [0.84–1.07]). Indeed, after adjusting for differences in brain size, the brain maleness difference between the ASD group and controls disappeared, and no association with autistic symptoms remained (after controlling for multiple comparisons), suggesting greater maleness of the autistic brain is driven by brain size. Brain maleness may be influenced by the same factors that influence brain size.

Lay Summary: A popular theory proposes that individuals with autistic spectrum disorder (ASD) have an “extreme male brain”, but this has not been subject to rigorous, direct tests. We developed a measure of individual differences along a male–female dimension and then derived this measure for 1060 individuals with ASD and 1166 neurotypical controls. Individuals with ASD had slightly more male-type brains. However, this difference is accounted for by males and individuals with ASD having relatively larger brains than females and controls, respectively.