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Introduction: The Male Warrior Hypothesis (MWH) proposes that sex-specific selective pressures have promoted male cooperation with the ingroup members to outcompete rival groups. However, intergroup conflicts do not occur in isolation and the outcomes of previous competitions may influence group cooperativeness. Since this phenomenon is not well understood, we aimed to shed light on the effect of previous competition outcome on later cooperative behavior under intergroup conflicts. Based on the MWH, we hypothesized that repeated contests between groups could enhance ingroup cooperation, regardless of the outcome of the previous contest because status is at risk, but when competition is not present, participants would move to the symmetric equilibria. Methods: To test this hypothesis, we recruited 246 individuals organized in groups of 6 and measured cooperation using a threshold public good game over two rounds, manipulating the outcome in the first round to create groups of winners and losers. Results: Our results show that intergroup conflict scenarios promoted cooperation in both victory and defeat conditions, whereas, in the control scenario only losers increased their cooperation. Discussion: We argue that winners under the presence of an external threat may enhance in-group cooperation in order to assure their status; whereas, losers may be attempting to regain it.

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Testosterone plays an important role as a social hormone. Current evidence suggests that testosterone is positively related to sociosexuality increasing the psychological attitudes toward investing in short-term versus long-term mating and promotes status-seeking behaviors both by dominance and prestige. In addition, the social environment may play an important role in the expression of mating effort through changes in sociosexuality and status-seeking behaviors. However, the causal relationships among the mentioned variables are still debated. We employed a double-blind, placebo-controlled within-individual design, in order to test and integrate the proposed causal relationships between testosterone and social environment over short-term and long-term mating orientation and dominant and prestigious status-seeking behaviors in a sample of 95 young Chilean men. We did not find evidence that the administration of exogenous testosterone increased short-term or decreased long-term mating orientation as expected. Moreover, exogenous testosterone did not affect either aggressive or cooperative behavior failing to support the social status hypothesis. We also did not find any relationship between short or long-term mating orientation with status-seeking behaviors. Finally, we found support for the effect of social environment on sociosexual attitudes but not over status-seeking behaviors. Thus, men reported higher levels of short-term mating orientation in the presence of a woman compared to a man and no differences were found for long-term mating orientation. We argue that sociosexuality may be expressed flexibly, but contextual factors such as the presence of women seem more important than changes in testosterone levels.

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Intergroup conflict has been a persistent aspect of human societies since the emergence of our species. Various researchers have proposed that competition between groups has acted as a key selective force throughout human evolutionary history. Such intergroup competition for limited resources exacerbated the expression of intergroup aggression and intragroup cooperation. Furthermore, it would have a sexual dimorphism, with men demonstrating increased sensitivity to conflict threats-in order to maximize reproductive opportunities-, while women generally reject from active engagement in intergroup conflict. In the present study, we conducted behavioral experiments under controlled laboratory conditions to measure cooperation and aggression from using virtual games, specifically the Public Good Games and the Point Subtraction Aggression Paradigm, in a sample of 541 participants. We created control and experimental intergroup competition scenarios, where aggression and cooperation were necessary to increase monetary rewards. Our results shows that men modulate aggression and cooperation in the presence of intergroup conflict. In addition, our data also reveals that women cooperate more than men and display heightened levels of cooperation and aggression when confronted with intergroup conflict. These findings prompt a reevaluation of current functional theoretical models concerning the role of women in intergroup conflict and suggest that the dynamics of human aggression and cooperation may be more nuanced than previously believed.

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Dominance hierarchies vary between species and possess particular characteristics depending on the distribution and abundance of food resources that affect the competitive regime. Bonobos have been described as having female intersexual dominance, based mainly on female coalitionary support against males, and more egalitarian hierarchies than chimpanzees. In this study, we tested whether female intersexual dominance is dependent on female coalitions or whether it still arises when only dyadic interactions are considered. We also examined the role of food abundance in shaping dominance style in a wild population of bonobos in Wamba, Democratic Republic of Congo. We found partial support concerning our first prediction in which we expected a male dominance over females when only dyadic agonistic interactions were considered because females were not systematically dominant over males, finding instead an intersexual codominance pattern. We failed to find support for our second prediction that hierarchies become more despotic under low fruit abundance, in fact, we found the opposite pattern. We discuss that codominance based on dyadic interactions in this group may arise as a consequence of male deference rather than females winning conflicts against males and that more despotic hierarchies during high fruit season may arise as a consequence of competition for high-quality resources or variation in party size.

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From an evolutionary perspective, phenotypic, social, and environmental factors help to shape the different costs and benefits of pursuing different reproductive strategies (or a mixture of them) from one individual to another. Since men's reproductive success is mainly constrained to women's availability, their mating orientations should be partially calibrated by features that women prefer in a potential partner. For long-term relationships, women prefer traits that signal access to resources, protection skills, and the willingness to share them. Using generalized linear models with laboratory data taken from a Chilean population (N = 197), this study aimed to test whether real and potential resources (measured as self-reported socioeconomic status), protection skills (measured as handgrip strength), and the willingness to provide resources and protection (measured as their disposition toward parenthood) are related to mating orientation in men. Our predictions were: (1) socioeconomic status would be positively associated with long-term and short-term mating orientation but for long-term-oriented individuals, this would be enhanced by having a more favorable parenthood disposition and (2) strength would be positively related to long-term mating orientation in men with higher socioeconomic status and a favorable disposition toward parenthood and it would have a positive and direct association with short-term mating orientation. Our results partially supported the first hypothesis, since men with higher socioeconomic status were more long-term oriented, but parenting disposition did not moderate this effect. Contrary to our expectations, socioeconomic status was not related to short-term mating orientation. Strength appeared not to be significant for long-term mating orientation, even interacting with other traits. However, strength by itself was powerfully linked with a short-term mating orientation. Our results suggest that only some individuals that are attractive for long-term relationships are indeed long-term oriented and may reflect the overall conflict of interests between mating strategies among sexes.

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In both sexes, aggression has been described as a critical trait to acquire social status. Still, almost uniquely in men, the link between aggressiveness and the genetic background of testosterone sensitivity measured from the polymorphism in the androgen receptor (AR) gene has been previously investigated. We assessed the relevance of the AR gene to understand aggression and how aggressiveness affects social status in a cross-sectional study of 195 participants, for the first time in both young men and women. We estimated polymorphism sequences from saliva and measured aggression and self-perceived social status. Unfortunately, the results did not support our prediction because we did not find any of the expected relationships. Therefore, the results suggest that the genetic association between aggressive mechanisms and polymorphism of the AR gene is less straightforward than expected, at least in men, and seems to indicate that aggression is not usually used to gain social status in our population.

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The decision to allocate time and energy to find multiple sexual partners or raise children is a fundamental reproductive trade-off. The Strategic Pluralism Hypothesis argues that human reproductive strategies are facultatively calibrated towards either investing in mating or parenting (or a mixture), according to the expression of features dependent on the individual's condition. This study seeks to test predictions derived from this hypothesis in a sample of 242 young men (M ± SD = 22.12 ± 3.08) from Chile's 5th Region (33Ö¯ south latitude). Specifically, two predictions were considered that raise questions about the relationship between traits related to physical and psychological attractiveness (fluctuating facial asymmetry and self-perception of attractiveness) and competitive skills (baseline testosterone and self-perception of fighting ability) with short-term reproductive strategies. Our results indicate that psychological features related to the self-perception of physical attractiveness are related to short-term reproductive strategies. However, no evidence was found that fluctuating facial asymmetry, basal levels of testosterone and self-perception of fighting ability were related to short-term reproductive strategies. These results support the existing evidence of the importance of physical attractiveness in calibrating men's reproductive strategies but cast doubts about the role of fluctuating facial asymmetry. They also suggest that traits related to physical attractiveness, in comparison to competitive capabilities, play a more important role in calibrating men's short-term reproductive strategies.

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OBJECTIVES: Strategic Pluralism Theory contends that human mating strategies are calibrated toward short-term (ST) or long-term (LT) mating according to the expression of condition-dependent traits and characteristics of the social and physical environment. Traits reflecting the effects of testosterone have been considered condition-dependent traits that provide information about the calibration of male mating strategy. We investigated the relationship of muscle mass and facial masculinity with attitudes and behaviors reflecting ST and LT mating tactics. METHODS: We measured skeletal muscle mass (SMM) through bioelectrical impedance and facial width-to-height ratio (fWHR) in a sample of Chilean men (n = 206; mean age = 22.52 ± 4.65 SD), and collected information about sociosexual attitudes and past sexual behavior. RESULTS: Our results showed an interaction effect of SMM and fWHR on unrestricted (but not restricted) sociosexual attitudes and past sexual behavior. Individuals with a consistent expression of both traits (ie, high SMM and fWHR or low SMM and fWHR) reported higher levels of unrestricted sociosexual attitudes and a greater number of lifetime and previous-year sexual partners. CONCLUSIONS: These findings suggest that the intensity and consistency of expression of body and facial masculinity is important in signaling male mating tactics and sociosexual attitudes.

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Objective: There is evidence that competitive conflicts are the main form of intrasexual competition among men. The capacity to recognize visual cues of fighting ability in competitors is thought to be an important characteristic that allows men to avoid the costs of contest competition. However, for an accurate comparison to take place, individuals need to compare the fighting ability of their competitors to their own to assess this asymmetry. Methods: In order to improve our understanding of this self-assessment process, here we study the relationship between visual fighting ability cues, namely (i) muscularity, as measured with a bioimpedance device, (ii) the real capacity to inflict cost to a rival based on strength, as measured with a hand grip dynamometer (HGS), and (iii) self-perceived fighting ability, as determined with a questionnaire. The study sample was 364 men between 18 and 38 years of age (M ± SD = 22.27 ± 3.99). Results: Our results confirm the expected positive relationship between upper-body muscularity and strength, while controlling for body mass index (BMI). However, muscularity explained only around 30.2% of the variance in strength. In addition, muscularity was related to self-perception of fighting ability in our sample, its effect being partially mediated by strength. Conclusion: The more muscular men perceive their fighting ability as being greater, and not only because they are stronger (at least in the HGS task). Accordingly, it seems that men take into account the overestimation the robustness of the relationship between strength and muscularity that prevails within his peers.

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Durante los últimos años en Chile se ha detectado una masificación en el uso de anticonceptivos orales. Sin embargo, en Chile y al igual que en casi todos los países latinoamericanos prácticamente no se han investigado sus implicancias sobre la conducta humana. Específicamente, este estudio evaluó el impacto del uso de estos anticonceptivos sobre la conducta de emparejamiento en un grupo de 164 mujeres jóvenes universitarias, con una media de edad igual a 19 años y provenientes de cuatro universidades chilenas. Para ello se utilizó la adaptación chilena del Cuestionario de Componentes del Valor de Pareja que está compuesto por 22 ítems que se responden en una escala Likert de siete valores. Los resultados señalan diferencias entre las mujeres que consumen píldoras anticonceptivas (PA) y las que no lo hacen. Las consumidoras presentan los mayores valores del índice general del cuestionario sobre los componentes del valor de pareja y las subescalas de historia de relaciones de pareja, apreciación desde el sexo opuesto y apariencia. Estos resultados indican que las mujeres consumidoras de la PA se autoperciben y creen que el sexo contrario las evalúa como atractivas y muestran una vida sexual más diversificada, no mostrando diferencias en los otros aspectos relevantes para el valor de pareja no vinculados centralmente al atractivo físico. En definitiva, los resultados parecen indicar que el consumo de anticonceptivos hormonales no modifica la conducta social y parental de las mujeres, aunque su uso parece estar asociado con una mayor autopercepción de atractivo y mayor diversidad sexual.

Oral contraceptives, also known as birth control pills (PAs from now on), have been available on the world market for five decades. At present, the use of PA is massifier worldwide, being consumed by more than 100 million women on the planet. In recent years, in Latin America has been detected a dramatic increase in the use of oral contraceptives, and Chile is not the exception. In this sense, it is probable that the increase in the consumption of PAs in Chile is linked to the increase of women who decide to pursue higher studies and to develop professional careers. Concurrently, a wide field of research has been focused on the physiological and psychological effect of the consumption of oral contraceptives on human behavior, being mating behavior one of the main topics of research. However, in Chile as in most Latin American countries there is a lack of studies on the implications of the consumption of oral contraceptives on human behavior. In the present study, we investigated in a group of 164 university young women (Mean ± Standard Deviation: 19.27± 2.88 years) of Chile the impact of the use of oral contraceptives on mating behavior. Accordingly, we have applied a validated psychometric test to assessed mate value, one of the more relevant components of mating behavior i.e., the Mate Value Questionnaire. Mate value can be defined as a construct that incorporates a number of physical, psychological, and social dimensions that are related to an individual's ability to find, attract, and successfully retain a partner. This questionnaire is composed by 22 items and 7 subscales that are answered in a Likert Scale of 7 values. The Mate Value Questionnaire showed a high reliability (α = .85). According with previous studies that showed a decrease in sexual satisfaction and desire on women that consume oral contraceptives, we predicted a decrease of mating behavior and, then, a decrease on Mate Value for those women that use oral contraceptives. This effect was expected for all subscales of this questionnaire with the exception of relationship history subscale since women that consume oral contraceptives reported to have more diverse sexual partners on previous studies. The results show differences between women who use oral contraceptives (n = 87 women: 19.60 ± 2.89 years) in comparison to those who do not (n = women: 18.90 ± 2.84 years). However, the differences were, in general, opposed to our expectations being the consumers of oral contraceptives who presented the highest values of the general index of the Mate Value Questionnaire, and, concretely, for the subscales of relationship history, views of the opposite sex, and looks. In addition, we have failed into found any differences between groups in subscales that were not associated to physical appearance, such as wealth, sociality and fear of failure. The results suggest that the use of hormonal contraceptives does not modify the social and parental behavior of the women, although their use seems to be associated with a greater self-perception of attractiveness and greater diversity in sexual life. This study provides new information that will increase the understanding and discussion about the hypothetical effect that would or would not, the consumption of the PA on the pairing behavior. It is important to point out that the field of research on changes in the sexual preferences of women, derived from hormonal states, is in an important discussion process. Therefore, we believe that it is critical to carry out research in the future in order to elucidate the real robustness of this phenomenon, improving our understanding about the behavioral effects of consuming oral contraceptives.