Fertility of Czech Gay and Straight Men, Women, and Their Relatives: Testing the Sexually Antagonistic Gene Hypothesis.

One proposal for the persistence of homosexuality in the human population is the sexually antagonistic gene hypothesis, which suggests that the lower fertility of homosexual individuals, especially men, may be compensated by higher fertility of their relatives of the opposite sex. To test this hypothesis, we have collected data from 7,312 heterosexual men, 459 gay men, 3,352 heterosexual women, and 79 lesbian women mainly from Czechia. In an online survey, participants answered questions regarding their own as well as their parents' and grandparents' fertility. For men, we obtained no significant results except for higher fertility of gay men's paternal grandmothers, but the magnitude of this effect was very small. For the female sample, we recorded lower fertility of lesbian women's mothers and fathers. In line with our expectations, both gay men and lesbian women had lower fertility rates than their heterosexual counterparts. Our results are consistent with recent studies which likewise do not support the sexually antagonistic gene hypothesis.

Kamasutra in Practice: The Use of Sexual Positions in the Czech Population and Their Association With Female Coital Orgasm Potential.

INTRODUCTION: A limited number of scientific studies explore the frequency with which various sexual positions are used in human populations and the potential of particular sexual position to facilitate female coital orgasm. AIM: The aim of this study was to provide data about the prevalence and frequency of various sexual positions, their rated pleasurability, and their association with female coital orgasm consistency (COC). METHODS: A sample of Czech heterosexual population (11,225 men/9,813 women) were presented with a list of 13 sexual positions in black-and-white silhouettes. For each position, they indicated frequency and pleasurability. COC was assessed as the proportion of penile-vaginal intercourse with a current partner which led to orgasm. MAIN OUTCOME MEASURE: Participants reported the frequency of use of sexual positions and rated their pleasurability. Using ordinal logistic regression, association between the COC and frequency of use of coital positions was tested. RESULTS: In both men and women, the most commonly used sexual positions were face to face/male above, face to face/female above, and kneeling/rear entry. Nonetheless, there emerged some gender differences in the rating of pleasurability of various positions (all P < .001). We found that a higher proportion of female coital orgasms are positively associated with the frequency of use of face to face/female above (odds ratio [OR] = 1.005, P < .001) and sitting/face-to-face positions (OR = 1.003, P < .001) and negatively associated with the frequency of kneeling/rear entry position (OR = 0.996, P < .001). CONCLUSIONS: Our findings suggest that there are no gender differences in the frequency of use of sexual positions, but their rated pleasurability differs between men and women, and higher frequency of use of face-to-face positions with female above increases the likelihood of achieving coital orgasm during penile-vaginal intercourse. Most results, however, were of small effect sizes, and more research is needed to further explore this issue. Krejcová L, Kuba R, Flegr J, et al. Kamasutra in Practice: The Use of Sexual Positions in the Czech Population and Their Association With Female Coital Orgasm Potential. Sex Med 2020;8:767-776.

Rhesus-minus phenotype as a predictor of sexual desire and behavior, wellbeing, mental health, and fecundity.

BACKGROUND: Since its discovery in the 1930s, the effects of Rh phenotype on human health and wellbeing, with the exception of the effects of Rh-negativity of a mother on the risk of hemolytic anemia of Rh-positive children, has only rarely been studied. In the last few years, however, several studies have shown that Rh-negative subjects have worse health and performance in certain tests than their Rh-positive peers. Nothing is known about the effect of Rh phenotype on the quality of life of subjects as measured by a standard instrument. METHODS: We hereby analyzed the data of 1768 male (24% Rh-negative) and 3759 female participants (23% Rh-negative) of an anonymous internet study using the partial Kendall test with the age and the population of the hometown of subjects controlled. RESULTS: The results showed that the Rh-negative women, but not men, scored worse in wellbeing measured with the WHO-BREFF. The Rh-negative men scored worse in mental health-related variables and in their reported economic situation and the Rh-negative women scored better in physical health-related variables. Both the Rh-negative men and women reported higher sexual activity than their Rh-positive peers. CONCLUSIONS: The effects of the Rh phenotype were significant after the correction for multiple tests. However, they were usually weaker and less numerous than those of smoking, consuming alcohol, and high body mass index, which were used as a sort of internal control.

Losing stinks! The effect of competition outcome on body odour quality.

Dominance hierarchy is often established via repeated agonistic encounters where consistent winners are considered dominant. Human body odour contains cues to psychological dominance and competition, but it is not known whether competition outcome (a marker of a change in dominance hierarchy) affects the hedonic quality of human axillary odour. Therefore, we investigated the effect of winning and losing on odour quality. We collected odour samples from Mixed Martial Arts fighters approximately 1 h before and immediately after a match. Raters then assessed samples for pleasantness, attractiveness, masculinity and intensity. We also obtained data on donors' affective state and cortisol and testosterone levels, since these are known to be associated with competition and body odour quality. Perceived body odour pleasantness, attractiveness and intensity significantly decreased while masculinity increased after a match irrespective of the outcome. Nonetheless, losing a match affected the pleasantness of body odour more profoundly, though bordering formal level of significance. Moreover, a path analysis revealed that match loss led to a decrease in odour attractiveness, which was mediated by participants' negative affective states. Our study suggests that physical competition and to some extent also its outcome affect the perceived quality of human body odour in specific real-life settings, thus providing cues to dominance-related characteristics. This article is part of the Theo Murphy meeting issue 'Olfactory communication in humans'.

Predictors of Fighting Ability Inferences Based on Faces.

Facial perception plays a key role in various social interactions, including formidability assessments. People make relatively accurate inferences about men's physical strength, aggressiveness, and success in physical confrontations based on facial cues. The physical factors related to the perception of fighting ability and their relative contribution have not been investigated yet, since most existing studies employed only a limited number of threat potential measures or proxies. In the present study, we collected data from Czech Mixed Martial Arts (MMA) fighters regarding their fighting success and physical performance in order to test physical predictors of perceived fighting ability made on the basis of high-fidelity facial photographs. We have also explored the relationship between perceived and actual fighting ability. We created standardized 360° photographs of 44 MMA fighters which were assessed on their perceived fighting ability by 94 raters (46 males). Further, we obtained data regarding their physical characteristics (e.g., age, height, body composition) and performance (MMA score, isometric strength, anaerobic performance, lung capacity). In contrast to previous studies, we did not find any significant links between the actual and the perceived fighting ability. The results of a multiple regression analysis have, however, shown that heavier fighters and those with higher anaerobic performance were judged as more successful. Our results suggest that certain physical performance-related characteristics are mirrored in individuals' faces but assessments of fighting success based on facial cues are not congruent with actual fighting performance.