Mate preferences among the Shuar of Ecuador: trait rankings and peer evaluations

The sound symbolism of food: the frequency of initial /PA-/ in words for (staple) food

In different languages around the world, morphemes representing the (cooked form of) staple food or food in general tend to begin with a [+labial] phoneme followed by a [+low] phoneme (/pa-/, /ma-/, /fa-/, /wa-/, etc.). This article provides evidence for this phonological similarity by analyzing 66 sample languages' morphemes representing the staple food within the society where each language is spoken. About a fourth of the morphemes referring to staple food begin with a [+labial] first phoneme followed by a [+low] second phoneme, which is a much higher proportion compared to another list of basic morphemes in the same 66 languages. I further argue that the motivation for this crosslinguistic tendency is the iconic association between the mouth-opening gesture and the concept of eating.

The effect of mating market dynamics on partner preference and relationship quality among Himba pastoralists

Relative mate value has long been believed to be a critical component of mate choice in humans. However, most empirical work focuses on preferences rather than actual pair formation, and data connecting partner preferences, partnership formation, and relationship quality remain rare. Here, we estimate mate value using >12,000 ratings by opposite-sex, in-group members to understand both hypothetical partnership preferences and actualized relationship dynamics. When evaluating hypothetical partnerships, people generally prefer individuals whose mate value is higher than their own, indicating an aspirational matching strategy. However, mate value comparisons of individuals in marital and nonmarital relationships show a positive correlation, suggesting that individuals tend to pair up with similarly desirable individuals. Furthermore, despite aspirational preferences, couples who are more closely matched reported greater relationship quality, measured through frequency of interactions, reported sexual histories, and partnership length.

Vocal communication across cultures: theoretical and methodological issues

The study of human vocal communication has been conducted primarily in Western, educated, industrialized, rich, democratic (WEIRD) societies. Recently, cross-cultural investigations in several domains of voice research have been expanding into more diverse populations. Theoretically, it is important to understand how universals and cultural variations interact in vocal production and perception, but cross-cultural voice research presents many methodological challenges. Experimental methods typically used in WEIRD societies are often not possible to implement in many populations such as rural, small-scale societies. Moreover, theoretical and methodological issues are often unnecessarily intertwined. Here, I focus on three areas of cross-cultural voice modulation research: (i) vocal signalling of formidability and dominance, (ii) vocal emotions, and (iii) production and perception of infant-directed speech. Research in these specific areas illustrates challenges that apply more generally across the human behavioural sciences but also reveals promise as we develop our understanding of the evolution of human communication. This article is part of the theme issue 'Voice modulation: from origin and mechanism to social impact (Part II)'.

When marital institutions break down: Impact and adaptation among the Enga of Papua New Guinea

Institutions to regulate marriage and sexual mores are nearly universal across human societies to assure production and reproduction and weave the fabric of society. The stakeholders are many. What happens when marital traditions break down in times of rapid change? Taking a long-term perspective, we will first look at developments in marital institutions that occurred after the arrival of the sweet potato (ca. 400 BP) among the Enga of Papua New Guinea. Next, we will document changes in recent marital practices of 402 Enga women collected in 2007. With data from 270 public forums in customary courts applying restorative justice between 2008 and 2019, we will consider (a) the impact of the breakdown of marital institutions and (b) responses to adapt norms to new practices. In the absence of regulation by 'traditional' institutions, individuals pursue their own interests and passions with negative outcomes for families and communities. Communities, non-governmental organisations, churches and government throughout Papua New Guinea are seeking to adapt norms to new conditions. We consider both norm change resulting from community action via customary courts and what communities strive to preserve. Cultural institutions and accompanying norms are important factors in assuring production and reproduction; however, they can instill attitudes that inhibit adaptation.

Male Mating Expectations in Brazilian and American Samples

This study aims to investigate assortative mating based on mate value from male perspective. Male participants (132 Brazilian and 106 American) evaluated hypothetical “stimulus” males described in terms of physical attractiveness, social skills, and social status (each varied in high or low levels). Participants rated each stimulus and each stimulus' preferred mating partner on nine traits. The results showed that (1) positive assortative mating was expected in romantic relationships; (2) the stimulus ratings did not vary independently, suggesting that mate value is the result of the interaction of the characteristics of individuals; and (3) that participants expected physically attractive and healthier female partners to pair with high-status male stimuli. The American and Brazilian mating expectations were similar, minor differences indicate that Brazilian participants considered men with high levels of social skills to be more ambitious and intelligent; American participants expected men of high status to be healthier; Brazilians expect men of high status to have more attractive faces, while Americans expected these men to possess more attractive bodies; and Brazilian participants assigned more attractive bodies to men of lower status. These differences reflect the influence of economic and cultural factors on the local environment. The study contributes to the understanding of the construction of market value and reveals that male expectations are in line with human mating preferences. The investigation of mating expectations can be a rich approach to investigate socio-cultural aspects that are related to mating in different cultures

Resource demands reduce partner discrimination in Himba women

Where autonomy for partner choice is high, partner preferences may be shaped by both social and ecological conditions. In particular, women's access to resources can influence both the type and number of partnerships she engages in. However, most existing data linking resources and partner choice rely on either priming effects or large demographic databases, rather than preferences for specific individuals. Here we leverage a combination of demographic data, food insecurity scores and trait and partner preference ratings to determine whether resource security modulates partner preferences among Himba pastoralists. We find that while food insecurity alone has a weak effect on women's openness to new partners, the interaction of food insecurity and number of dependent children strongly predicts women's openness to potential partners. Further, we show that women who have more dependants have stronger preferences for wealthy and influential men. An alternative hypothesis derived from mating-market dynamics, that female desirability affects female preferences, had no effect. Our data show that women who face greater resource constraints are less discriminating in the number of partners they are open to, and have stronger preferences for resource-related traits. These findings highlight the importance of ecological signals in explaining the plasticity of mate preferences.

Evolutionary Mismatch in Mating

Evolutionary mismatch concepts are being fruitfully employed in a number of research domains, including medicine, health, and human cognition and behavior to generate novel hypotheses and better understand existing findings. We contend that research on human mating will benefit from explicitly addressing both the evolutionary mismatch of the people we study and the evolutionary mismatch of people conducting the research. We identified nine mismatch characteristics important to the study of human mating and reviewed the literature related to each of these characteristics. Many of the people we study are: exposed to social media, in temporary relationships, relocatable, autonomous in their mating decisions, nulliparous, in groups that are socially segmented, in an educational setting, confronted with lots of options, and young. We applied mismatch concepts to each characteristic to illustrate the importance of incorporating mismatch into this research area. Our aim in this paper is not to identify all potential mismatch effects in mating research, nor to challenge or disqualify existing data. Rather, we demonstrate principled ways of thinking about evolutionary mismatch in order to propel progress in mating research. We show how attending to the potential effects of mismatch can help us refine our theoretical and methodological approaches and deepen our understanding of existing patterns in the empirical record. We conclude with specific recommendations about how to include consideration of evolutionary mismatch into research on human mating.

Assortative Mating by an Obliquely Transmitted Local Cultural Trait Promotes Genetic Divergence: A Model

The effect of learned culture (e.g., birdsong dialects and human languages) on genetic divergence is unclear. Previous theoretical research suggests that because oblique learning allows phenotype transmission from individuals with no offspring to an unrelated individual in the next generation, the effect of sexual selection on the learned trait is masked. However, I propose that migration and spatially constrained learning can form statistical associations between cultural and genetic traits, which may allow selection on the cultural traits to indirectly affect the genetic traits. Here, I build a population genetic model that allows such statistical associations to form and find that sexual selection and divergent selection on the cultural trait can indeed help maintain genetic divergence through such statistical associations, while selection against genetic hybrids does not affect cultural trait divergence. Furthermore, I find that even when the cultural trait changes over time due to drift and mutation, it can still help maintain genetic divergence. These results suggest the role of obliquely transmitted traits in evolution may be underrated, and the lack of one-to-one associations between cultural and genetic traits may not be sufficient to disprove the role of culture in genetic divergence.

Causes and consequences of adult sex ratio imbalance in a historical U.S. population

The responsiveness of individuals to partner availability has been well-documented across the literature. However, there is disagreement regarding the direction of the consequences of sex ratio imbalance. Specifically, does an excess of males or females promote male-male mating competition? In an attempt to clarify the role of the adult sex ratio (ASR) on behaviour, here we evaluate both competing and complimentary expectations derived from theory across the social and biological sciences. We use data drawn from a historical, nineteenth century population in North America and target several life-history traits thought to be affected by partner availability: age at first birth, relationship status, completed fertility and longevity. Furthermore, we assess the role of various contributors to a population's ASR. We find that both the contributors to and consequences of sex ratio imbalance vary over time. Our results largely support predictions of greater male pairbond commitment and lesser male mating effort, as well as elevated bargaining power of women in response to female scarcity. After reviewing our findings, and others from across the literature, we highlight the need to adjust predictions in response to ASR imbalance by the: (i) culturally mediated mating arena, (ii) variable role of demographic inputs across time and place, (iii) constraints to behavioural outcomes across populations, and (iv) ability and accuracy of individuals to assess partner availability.This article is part of the themed issue 'Adult sex ratios and reproductive strategies: a critical re-examination of sex differences in human and animal societies'.

Multiple reputation domains and cooperative behaviour in two Latin American communities

Reputations are a ubiquitous feature of human social life, and a large literature has been dedicated to explaining the relationship between prosocial reputations and cooperation in social dilemmas. However, humans form reputations in domains other than prosociality, such as economic competency that could affect cooperation. To date, no research has evaluated the relative effects of multiple reputation domains on cooperation. To bridge this gap, we analyse how prosocial and competency reputations affect cooperation in two Latin American communities (Bwa Mawego, Dominica, and Pucucanchita, Peru) across a number of social contexts (Dominica: labour contracting, labour exchange and conjugal partnership formation; Peru: agricultural and health advice network size). First, we examine the behavioural correlates of prosocial and competency reputations. Following, we analyse whether prosocial, competency, or both reputation domains explain the flow of cooperative benefits within the two communities. Our analyses suggest that (i) although some behaviours affect both reputation domains simultaneously, each reputation domain has a unique behavioural signature; and (ii) competency reputations affect cooperation across a greater number of social contexts compared to prosocial reputations. Results are contextualized with reference to the social markets in which behaviour is embedded and a call for greater theory development is stressed.

Additional Psychometric Data for the Mate Value Scale

We administered a revised version of the Mate Value Scale that focuses on individuals’ perception of their romantic partner's mate value. Students (N = 330) from four universities completed surveys. The measure demonstrated good internal consistency reliability. Multiple regression analyses indicate that those who perceive their mates as possessing a higher value tended to compromise more when faced with conflict with their partners, had less anxiety in close relationships, and had more passionate love attitudes. We argue that this pattern of associations provides additional validity data in support of the Mate Value Scale.

Intra-sex Variation in Human Mating Strategies: Different People, Different Tactics

Several studies have demonstrated that men and women exhibit different romantic preferences, which align with the patterns predicted by sexual strategies theory. It is also assumed that the mate's value is a central factor in determining an individual's sexual strategy. Thus, the current study was developed to investigate whether intra-sex variation exists in the ideal romantic preferences of both genders and whether these preferences are associated with self-perception. To investigate these questions, cluster analyses were performed on the descriptions of ideal mates for short- and long-term relationships given by 366 Brazilian undergraduates (145 men and 221 women). Subsequently, comparisons were made between the lists of self-perceived attributes related to reproduction generated by the resulting groups. The results suggest that males and females use different mating tactics for short-term mating and that males use different tactics for long-term mating. Among men, the mating tactics observed seem to be related to male mate value and their tactics changed when they described ideal short- and long-term partners. Women's results showed different preference patterns in short-term assessments but minor differences were observed between them in terms of female mate value. For long-term relationships, female patterns were less distinct, indicating a single preference pattern. These findings indicate that a number of different tactics may be clustered together in investigations that address ideal preferences, and that studies of mate preferences must consider individual self-perceptions.

A bioeconomic approach to marriage and the sexual division of labor

Children may be viewed as public goods whereby both parents receive equal genetic benefits yet one parent often invests more heavily than the other. We introduce a microeconomic framework for understanding household investment decisions to address questions concerning conflicts of interest over types and amount of work effort among married men and women. Although gains and costs of marriage may not be spread equally among marriage partners, marriage is still a favorable, efficient outcome under a wide range of conditions. This bioeconomic framework subsumes both cooperative and conflictive views on the sexual division of labor. We test hypotheses concerning marriage markets, assortative mating, and men’s labor motivations among Tsimane forager-horticulturalists of Bolivia and find that: (1) men and women both value work effort in marital partners, (2) marital labor contributions are complementary, (3) work effort is correlated between spouses, (4) total production is correlated with total reproduction, and (5) better hunters have higher fitness gains within marital unions.

Romantic partners in a market perspective: expectations about what ensures a highly desirable partner

This study used the biological market perspective and influential statistical models from the marketing field to investigate males' and females' expectations regarding which combination of characteristics are most relevant in ensuring desirable partnerships for same-sex individuals. Thus, 358 Brazilian undergraduates assessed eight descriptions of same-gender stimulus targets (formulated with different levels of physical attractiveness, social skills, and current or prospective social status) and evaluated the overall desirability of the targets' expected or probable partners. From the possible combinations, three groups emerged: for one group, mainly composed of men, status characteristics were the most important attributes; for the others, mostly composed of women, social skills or physical characteristics were identified as most important in appealing to a desirable partner. This work expands the understanding of variability in male and female romantic expectations, and its implications are discussed from an evolutionary perspective.

The development of children's prelife reasoning: evidence from two cultures

Two studies investigated children's reasoning about their mental and bodily states during the time prior to biological conception-"prelife." By exploring prelife beliefs in 5- to 12-year-olds (N = 283) from two distinct cultures (urban Ecuadorians, rural indigenous Shuar), the studies aimed to uncover children's untutored intuitions about the essential features of persons. Results showed that with age, children judged fewer mental and bodily states to be functional during prelife. However, children from both cultures continued to privilege the functionality of certain mental states (i.e., emotions, desires) relative to bodily states (i.e., biological, psychobiological, perceptual states). Results converge with afterlife research and suggest that there is an unlearned cognitive tendency to view emotions and desires as the eternal core of personhood.

Successful hunting increases testosterone and cortisol in a subsistence population

Controversy over the adaptive significance of male hunting in subsistence societies hinges on the relative importance of familial provisioning and mate-quality signalling. This paper examines the proximate and ultimate motivations of hunting behaviour from a neuroendocrine perspective, using salivary testosterone and cortisol data collected before, during and after hunting focal follows from 31 Tsimane hunters aged 18-82 years. Despite circadian declines in hormone levels, testosterone and cortisol of Tsimane hunters increased at the time of a kill, and remained high as successful hunters returned home. Previous studies of hormonal changes during competitions find that high-stakes and success in the presence of relevant audiences result in increased neuroendocrine arousal. If men hunt primarily to provision their families, then an additional audience would not be expected to impact testosterone or cortisol, nor would the size of the animal killed. However, if signalling male quality by 'showing off' was a larger relative driver of men's hunting behaviour, one would expect greater hormonal response in cases where men returned with large sharable kills, especially in the presence of community members. Consistent with provisioning models of male hunting motivation, neither kill size nor encountering an audience of villagers while returning from hunting was associated with hormonal changes for successful hunters.

Access to resources shapes maternal decision making: evidence from a factorial vignette experiment

The central assumption of behavioral ecology is that natural selection has shaped individuals with the capacity to make decisions that balance the fitness costs and benefits of behavior. A number of factors shape the fitness costs and benefits of maternal care, but we lack a clear understanding how they, taken together, play a role in the decision-making process. In animal studies, the use of experimental methods has allowed for the tight control of these factors. Standard experimentation is inappropriate in human behavioral ecology, but vignette experiments may solve the problem. I used a confounded factorial vignette experiment to gather 640 third-party judgments about the maternal care decisions of hypothetical women and their children from 40 female karo Batak respondents in rural Indonesia. This allowed me to test hypotheses derived from parental investment theory about the relative importance of five binary factors in shaping maternal care decisions with regard to two distinct scenarios. As predicted, access to resources--measured as the ability of a woman to provide food for her children--led to increased care. A handful of other factors conformed to prediction, but they were inconsistent across scenarios. The results suggest that mothers may use simple heuristics, rather than a full accounting for costs and benefits, to make decisions about maternal care. Vignettes have become a standard tool for studying decision making, but have made only modest inroads to evolutionarily informed studies of human behavior.

Age-independent increases in male salivary testosterone during horticultural activity among Tsimane forager-farmers

Testosterone plays an important role in mediating male reproductive trade-offs in many vertebrate species, augmenting muscle and influencing behavior necessary for male-male competition and mating-effort. Among humans, testosterone may also play a key role in facilitating male provisioning of offspring as muscular and neuromuscular performance are deeply influenced by acute changes in testosterone. This study examines acute changes in salivary testosterone among 63 Tsimane men ranging in age from 16-80 (mean 38.2) years during one-hour bouts of tree-chopping while clearing horticultural plots. The Tsimane forager-horticulturalists living in the Bolivian Amazon experience high energy expenditure associated with food production, have high levels of parasites and pathogens, and display significantly lower baseline salivary testosterone than age-matched US males. Mixed-effects models controlling for BMI and time of specimen collection reveal increased salivary testosterone (p<0.001) equivalent to a 48.6% rise, after one hour of tree chopping. Age had no effect on baseline (p=0.656) or change in testosterone (p=0.530); self-reported illness did not modify testosterone change (p=0.488). A comparison of these results to the relative change in testosterone during a competitive soccer tournament in the same population reveals larger relative changes in testosterone following resource production (tree chopping), compared to competition (soccer). These findings highlight the importance of moving beyond a unidimensional focus on changes in testosterone and male-male aggression to investigate the importance of testosterone-behavior interactions across additional male fitness-related activities. Acutely increased testosterone during muscularly intensive horticultural food production may facilitate male productivity and provisioning.

Why do the Karo Batak prefer women with big feet? Flexible mate preferences and the notion that one size fits all

Men may find women with small feet relative to body size more attractive because foot size reliably indexes nubility-i.e., age and parity. I collected judgments of attractiveness in response to drawings of women with varying foot sizes from a sample of 159 Karo Batak respondents from North Sumatra, Indonesia, as part of a collaborative project on foot size and attractiveness. The data revealed a contrarian preference among the Karo Batak for women with big feet. The judgments were compared with the results of an existing cross-cultural study that found a preference for women with small feet in aggregate, but a mix of small- and large-foot preferences in the societies taken individually. Using contingency table analysis, I found that ecology and less exposure to Western media were associated with a preference for women with big feet; patriarchal values were not. The findings suggest that human mating preferences may arise in response to local ecological conditions, and may persist and spread via cultural transmission. This has implications for the concept of universality espoused in some versions of evolutionary psychology.

Romantic preferences in Brazilian undergraduate students: from the short term to the long term

A number of studies have described different preference patterns typically found for men and women when choosing romantic mates. These vary according to the involvement level expected in the relationship. Despite the number of investigations on the topic, one must be careful not to generalize because most studies use samples composed of North American university undergraduates. This study sought to determine if the preference patterns typically found in other countries also occur among Brazilian undergraduates. The importance of characteristics and modifications in preference patterns under gradually restrictive conditions was also investigated. In general, the results obtained suggest that the preferences found in a number of countries also occur in Brazil. In short-term relationships, men prioritize physical attributes, whereas personal traits gain importance when involvement increases. Women in short-term relationships value physical and personal traits, whereas in the long term, they emphasize personal characteristics and their mate's desire to acquire resources. Resource-related traits were less important than the other traits, and were more important for women than for men.

The weirdest people in the world?

Behavioral scientists routinely publish broad claims about human psychology and behavior in the world's top journals based on samples drawn entirely from Western, Educated, Industrialized, Rich, and Democratic (WEIRD) societies. Researchers – often implicitly – assume that either there is little variation across human populations, or that these “standard subjects” are as representative of the species as any other population. Are these assumptions justified? Here, our review of the comparative database from across the behavioral sciences suggests both that there is substantial variability in experimental results across populations and that WEIRD subjects are particularly unusual compared with the rest of the species – frequent outliers. The domains reviewed include visual perception, fairness, cooperation, spatial reasoning, categorization and inferential induction, moral reasoning, reasoning styles, self-concepts and related motivations, and the heritability of IQ. The findings suggest that members of WEIRD societies, including young children, are among the least representative populations one could find for generalizing about humans. Many of these findings involve domains that are associated with fundamental aspects of psychology, motivation, and behavior – hence, there are no obviousa priorigrounds for claiming that a particular behavioral phenomenon is universal based on sampling from a single subpopulation. Overall, these empirical patterns suggests that we need to be less cavalier in addressing questions ofhumannature on the basis of data drawn from this particularly thin, and rather unusual, slice of humanity. We close by proposing ways to structurally re-organize the behavioral sciences to best tackle these challenges.