Contraception ends the genetic maintenance of human same-sex sexual behavior.

Because human same-sex sexual behavior (SSB) is heritable and leads to fewer offspring, it is puzzling why SSB-associated alleles have not been selectively purged. Current evidence supports the antagonistic pleiotropy hypothesis that SSB-associated alleles benefit individuals exclusively performing opposite-sex sexual behavior by increasing their number of sexual partners and consequently their number of offspring. However, by analyzing the UK Biobank, here, we show that having more sexual partners no longer predicts more offspring since the availability of oral contraceptives in the 1960s and that SSB is now genetically negatively correlated with the number of offspring, suggesting a loss of SSB's genetic maintenance in modern societies.

Does use of anal cytology as a triage test improve the performance of high-risk human papillomavirus screening in gay and bisexual men for anal cancer prevention?

Anal high-risk human papillomavirus (HRHPV) testing-based anal cancer screening gay and bisexual men (GBM) is associated with high sensitivity, but low specificity. We report the potential role of triage use of anal cytology with HRHPV testing in detecting 12-month persistent anal high-grade squamous epithelial lesions (HSIL) in a cohort of GBM in Sydney, Australia. Participants were GBM from the Study of the Prevention of Anal Cancer (SPANC) who underwent annual anal HPV testing, cytology, and high-resolution anoscopy (HRA)-guided histology. The sensitivity and specificity of five screening algorithms based on HRHPV test results with triage use of anal cytology (atypical squamous cells of undetermined significance (ASCUS) and atypical squamous cells, cannot exclude HSIL (ASC-H) used as referral thresholds) were compared to these of HRHPV testing and anal cytology alone. A total of 475 men who had valid HRHPV, cytological, and histological results at both baseline and first annual follow-up visits were included, median age 49 years (inter-quartile range: 43-56) and 173 (36.4%) GBM with human immunodeficiency virus. Of all triage algorithms assessed, two had comparable sensitivity with HRHPV testing alone in detecting persistent anal HSIL, but ~20% higher specificity and 20% lower HRA referral rates. These two algorithms involved the immediate referral of those with HPV16 and for those with non-16 HRHPV either immediate or delayed (for 12 months) referral, depending on cytology result at baseline. Triage use of anal cytology in GBM testing positive for anal HRHPV increases specificity and reduces referral rates while maintaining high sensitivity in detection of HSIL.

Still trouble with bleeding: Risk factors for HCV transmission in men who have sex with men and behavioural trajectories from 2019 to 2021.

OBJECTIVES: To identify sexual/sex-associated risk factors for hepatitis C transmission among men who have sex with men (MSM) and visualise behavioural trajectories from 2019 to 2021. METHODS: We linked a behavioural survey to a hepatitis C cohort study (NoCo), established in 2019 across six German HIV/hepatitis C virus (HCV) treatment centres, and performed a case-control analysis. Cases were MSM with recent HCV infection, and controls were matched for HIV status (model 1) or proportions of sexual partners with HIV (model 2). We conducted conditional univariable and multivariable regression analyses. RESULTS: In all, 197 cases and 314 controls completed the baseline questionnaire and could be matched with clinical data. For regression models, we restricted cases to those with HCV diagnosed since 2018 (N = 100). Factors independently associated with case status included sex-associated rectal bleeding, shared fisting lubricant, anal douching, chemsex, intravenous and intracavernosal injections, with population-attributable fractions of 88% (model 1) and 85% (model 2). These factors remained stable over time among cases, while sexual partner numbers and group sex decreased during COVID-19 measures. CONCLUSIONS: Sexual/sex-associated practices leading to blood exposure are key factors in HCV transmission in MSM. Public health interventions should emphasize the importance of blood safety in sexual encounters. Micro-elimination efforts were temporarily aided by reduced opportunities for sexual encounters during the COVID-19 pandemic.

Do men who have sex with men recognise syphilis symptoms? A syphilis awareness campaign in Amsterdam, the Netherlands.

INTRODUCTION: Syphilis incidence is rising among gay, bisexual and other men who have sex with men (GBMSM). To improve early health-seeking behaviour, we developed an online syphilis symptom score tool for GBMSM to self-identify a higher likelihood of infectious syphilis and promoted its use via an online and offline awareness campaign. METHODS: From October 2018 through September 2019, a dedicated website on syphilis including the online symptom score tool was promoted. The reach of the campaign was measured by website metrics and the completion of the self-assessment tool. The impact of the campaign was assessed by comparing the monthly number of syphilis serology tests and the percentages of infectious syphilis diagnoses at the Centre for Sexual Health (CSH) in Amsterdam between three periods: 12 months preceding, 12 months during and 6 months after the campaign. RESULTS: During the campaign, 20 341 visitors viewed the website. A total of 13 499 (66.4%) visitors started the self-assessment algorithm, and 11 626 (86.1%) completed it. Prior to the campaign, the mean number of syphilis tests per month was 1650 compared with 1806 per month during the campaign (p=0.02). In the 6 months after the campaign, the mean number of tests per month was 1798 (compared with the period of the campaign, p=0.94). Prior to the campaign, the percentage of infectious syphilis diagnoses was 2.5% compared with 3.0% during the campaign (p=0.009). The percentage of infectious syphilis diagnoses in the 6 months after the campaign was 2.2% (p<0.0001 compared with the period of the campaign, and p=0.045, compared with the period prior to the campaign). CONCLUSIONS: Although we did not find definite proof of a (sustained) effect, syphilis symptoms awareness campaigns deserve further evaluation and improvements to help those suspected of syphilis to get tested.

Invasive Neisseria meningitidis subtype C in gay, bisexual and other men who have sex with men: a systematic review.

INTRODUCTION: Outbreaks of invasive Neisseria meningitidis subtype C in networks of gay, bisexual and other men who have sex with men (MSM) have been reported. We aimed to explore any factors seen in MSM with invasive N.meningitidis subtype C. METHOD: We searched three bibliographical databases for manuscripts written in English exploring at least one factor seen in MSM with invasive N. meningitidis subtype C published up to May 2024. Following an initial search, removal of duplicates and abstract review, two authors independently reviewed full-text manuscripts and performed a risk of bias assessment using the Joanna Briggs Institute toolkit. Narrative data were synthesised to generate themes. RESULTS: 16 manuscripts were included in this review from the USA (n=10), Germany (n=2), France (n=2), Canada (n=1) and Italy (n=1) and consisted of nine case series, four cross-sectional studies, two case reports and one case-control study published between 2003 and 2024 involving 236 MSM with invasive N. meningitidis subtype C, of which at least 64 died. We have highlighted some demographic (African-American or Hispanic identity in the USA, living with HIV), behavioural (kissing, sharing drinks, visiting sex-on-premises venues, visiting gay-oriented venues, using websites/mobile phone apps to meet sexual partners, recreational drug use, multiple and non-regular sexual partners) and infection (previous Chlamydia trachomatis, Treponema pallidum, Neisseria gonorrhoeae, Mpox) factors in MSM with invasive N. meningitidis subtype C. CONCLUSION: These data serve as an important resource to inform and target future public health strategies and outbreak control measures for the prevention of invasive N. meningitidis subtype C in MSM. PROSPERO REGISTRATION NUMBER: CRD42024543551.

Single case of lymphogranuloma venereum on the tongue.

Traditionally, lymphogranuloma venereum (LGV) has been associated with disease of the genital area. However, atypical presentations and proctitis are increasingly observed. We report a case of LGV affecting the dorsum of the tongue, which presented as a very painful ulcer. The response to doxycycline (100 mg two times per day for 21 days) was satisfactory. This case may represent a paradigm shift in the differential diagnosis of lingual ulcers.

Association of same-sex criminalisation laws and national HIV policies with HIV testing in African MSM: an ecological single-level and multilevel cross-sectional study of sub-Saharan African countries.

BACKGROUND: HIV incidence among men who have sex with men (MSM) in sub-Saharan Africa (SSA) remains high compared with the general population. Many countries in the region still criminalise consensual homosexual relationships, and some are yet to adopt WHO-recommended interventions for MSM into national HIV policies. This study examines how HIV testing of adult MSM in SSA varies according to the legal climate and presence of targeted HIV policy using data from the cross-sectional 2019 Global LGBTI Internet Survey study. METHODS: Using data from 3191 MSM in 44 SSA countries, we assessed associations of legal climate and HIV policy with ever and recent HIV testing using linear ecological and logistic multilevel analyses. From the single-level analysis, we can compare our findings to previously reported data, then, extending to a two-level multilevel analysis, we account for the hierarchical structure of the population and simultaneously adjust for differences in context and composition in each country. We then test the sensitivity of our analyses to excluding countries from the model. RESULTS: We find evidence that legalised same-sex relationships were associated with increased odds of ever testing (OR=2.00, 95% CI 1.04, 3.82) in multilevel analyses. We also find evidence of an association of targeted HIV policies with increased odds of ever testing (OR=2.49, 95% CI 1.12, 5.52). We did not find evidence of an association of the legal climate (OR=1.01, 95% CI 0.69, 1.46) and targeted HIV policies (OR=1.26, 95% CI 0.78, 2.04) with recent testing. CONCLUSIONS: This study suggests elimination of discriminatory laws and policies might be important for increasing HIV status awareness of MSM, an important first step in epidemic control. Additionally, we highlight heterogeneity between South Africa and other SSA countries, which has implications for studying SSA countries as a homogeneous group.

Synergistic interaction between pay-it-forward incentives and recreational drug use on hepatitis B virus and hepatitis C virus testing among men who have sex with men in China.

OBJECTIVES: Pay-it-forward incentives effectively promote hepatitis B virus (HBV) and hepatitis C virus (HCV) testing among men who have sex with men (MSM) by offering free testing and donation opportunities. This study aims to explore the interaction between pay-it-forward incentives and recreational drug use on HBV and HCV testing uptake among Chinese MSM. METHODS: We pooled data from two pay-it-forward studies that aimed to promote dual HBV and HCV testing among MSM in Jiangsu, China. We explored factors associated with hepatitis testing uptake in the two study groups and examined the interaction between pay-it-forward incentives and recreational drug use on hepatitis testing uptake. RESULTS: Overall, 511 MSM participated in these two studies, with 265 participants in the pay-it-forward incentives group and 246 participants in the standard-of-care group. Among these participants, 59.3% in the pay-it-forward incentive group and 24.8% in the standard-of-care group received dual HBV and HCV testing, respectively. In the pay-it-forward incentives group, participants who used recreational drugs in the past 12 months (adjusted OR (AOR)=1.83, 95% CI 1.09 to 3.06) were more likely to receive dual HBV and HCV testing, compared with those who never used recreational drugs, whereas in the standard-of-care group, those who used recreational drugs were less likely to receive dual HBC and HCV testing (AOR=0.38, 95% CI 0.18 to 0.78). MSM with higher community connectedness (AOR=1.10, 95% CI 1.00 to 1.21) were also more likely to receive hepatitis testing with pay-it-forward incentives. There was a synergistic interaction on both the multiplicative (ratio of ORs=4.83, 95% CI 1.98 to 11.7) and additive scales (the relative excess risk of interaction=2.97, 95% CI 0.56 to 5.38) of pay-it-forward incentives and recreational drug use behaviours on dual HBV and HCV testing uptake among MSM. CONCLUSION: Pay-it-forward incentives may be particularly useful in promoting hepatitis testing among MSM who use recreational drugs.

Estimated prevalence and associations of sexually transmissible bacterial enteric pathogens in asymptomatic men who have sex with men: a systematic review and meta-analysis.

OBJECTIVE: The reservoir of sexually transmissible bacterial enteric pathogens in asymptomatic men who have sex with men (MSM) may impact future outbreaks, and the evolution of antimicrobial resistance. We aimed to estimate the pooled prevalence and explore any factors associated with Shigella spp, Campylobacter spp, diarrhoeagenic Escherichia coli and Salmonella spp in asymptomatic MSM using the random effects model. METHODS: We searched Embase, MEDLINE, CINAHL and Web of Science Core Collections for manuscripts published up to February 2024. One author screened citations and abstracts; two authors independently conducted a full-text review. We included manuscripts which measured the prevalence of Shigella spp, Campylobacter spp, diarrhoeagenic E. coli and Salmonella spp in asymptomatic MSM. Quality and risk of bias was assessed independently by two authors using the Joanna Briggs Institute critical appraisal tools. We calculated pooled prevalence and CIs using the random effects model. RESULTS: Six manuscripts were included in the final review. The manuscripts were from Australia (n=2), the UK (n=2), the Netherlands (n=1) and the USA (n=1) and included data from 3766 asymptomatic MSM tested for bacterial enteric pathogens. The prevalence of Shigella spp was 1.1% (95% CI 0.7% to 1.7%), Campylobacter spp 1.9% (95% CI 1.5% to 2.5%), diarrhoeagenic E. coli 3.8% (95% CI 2.1% to 6.7%) and Salmonella spp 0.3% (95% CI 0.1% to 0.6%). Two manuscripts demonstrated that the detection of bacterial enteric pathogen was more frequent in asymptomatic MSM using HIV-pre-exposure prophylaxis (PrEP), living with HIV, reporting <5 new sexual partners in the past 3 months, reporting insertive oral-anal sex and group sex compared with MSM testing negative. CONCLUSION: Despite a small number of manuscripts, this review has estimated the pooled prevalence, and highlighted some possible associations with sexually transmissible bacterial enteric pathogens in asymptomatic MSM, which can inform future clinical guidelines, public health control strategies and research to increase our understanding of transmission and the evolution of antimicrobial resistance. PROSPERO REGISTRATION NUMBER: CRD42024518700.

Sexual network characteristics and partnership types among men who have sex with men diagnosed with syphilis, gonorrhoea and/or chlamydia in Lima, Peru.

OBJECTIVES: Sexual networks are known to structure sexually transmitted infection (STI) transmission among men who have sex with men (MSM). We sought to estimate the risks of STI diagnosis for various partnership types within these networks. METHODS: Our cross-sectional survey analysed data from 1376 MSM screened for a partner management intervention in Lima, Peru. Participants were tested for HIV, syphilis, gonorrhoea (NG) and chlamydia (CT) and completed surveys on their demographics, sexual identity/role, HIV status, partnership types and sexual network from the prior 90 days. χ2 and Wilcoxon rank-sum tests compared participants without an STI to those diagnosed with (1) syphilis, (2) NG and/or CT (NG/CT) and (3) syphilis and NG/CT coinfection (coinfection). RESULTS: 40.8% (n=561/1376) of participants were diagnosed with an STI (syphilis: 14.9%, NG/CT: 16.4%, coinfection: 9.5%). 47.9% of all participants were living with HIV and 8.9% were newly diagnosed. A greater proportion of participants with syphilis and coinfection were living with HIV (73.5%, p<0.001; 71.0%, p<0.001) compared with those with NG/CT (47.8%) or no STI (37.8%). Participants with syphilis more often reported sex-on-premises venues (SOPVs) as the location of their last sexual encounter (51.7%, p=0.038) while those with NG/CT tended to meet their last sexual partner online (72.8%, p=0.031). Respondents with coinfection were the only STI group more likely to report transactional sex than participants without an STI (31.3%, p=0.039). CONCLUSIONS: Sexual networks and partnership types of Peruvian MSM are associated with differential risks for STIs. Participants diagnosed with syphilis tended to meet single-encounter casual partners at SOPV, while MSM with NG/CT were younger and often contacted casual partners online. Coinfection had higher frequency of transactional sex. These findings suggest the potential importance of public health interventions through combined syphilis/HIV screening at SOPV, syphilis screening at routine clinic appointments for MSM living with HIV and directed advertisements and/or access to NG/CT testing through online platforms.

Psychosis risk for lesbian, gay, and bisexual individuals: systematic review and meta-analysis.

The social defeat hypothesis posits that low status and repeated humiliation increase the risk for psychotic disorders (PDs) and psychotic experiences (PEs). The purpose of this paper was to provide a systematic review of studies on risk of PDs and PEs among lesbian, gay, or bisexual (LGB) people and a quantitative synthesis of any difference in risk. PubMed, PsycINFO, Embase, and Web of Science were searched from database inception until January 30, 2024. Two independent reviewers assessed the eligibility and quality of studies, extracted effect sizes, and noted the results of mediation analyses. Using a random effects model we computed pooled odds ratios (ORs). Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. The search identified seven studies of PDs and six of PEs. As for PDs, the unadjusted (2.13; 95% confidence interval 0.72-6.34) and covariate-adjusted pooled OR (2.24; 1.72-3.53) were not significantly increased for LGB individuals. After exclusion of a study of limited quality, both the unadjusted pooled OR (2.77; 1.21-6.32) and the covariate-adjusted pooled OR (2.67; 1.53-4.66) were significantly increased. The pooled ORs were increased for PEs: unadjusted, pooled OR = 1.97 (1.47-2.63), covariate-adjusted, pooled OR = 1.85 (1.50-2.28). Studies of PE that examined the mediating role of several variables reported that the contribution of drug abuse was small compared to that of psychosocial stressors. The results of a study in adolescents suggested a protective effect of parental support. These findings suggest an increased psychosis risk for LGB people and support the social defeat hypothesis.

Interventions, Barriers, and Facilitators to Address the Sexual Problems of Gay, Bisexual and Other Men Who Have Sex with Men Living with HIV: A Rapid Scoping Review.

Sexual problems are common among gay, bisexual, and other men who have sex with men (GBM) after diagnosis with HIV. However, these are often overlooked in care and research, where sexual risk reduction and biomedical aspects of sexual health tend to dominate. We conducted a rapid scoping review to investigate which sexual problems of GBM living with HIV are addressed by interventions, and the barriers and facilitators to their implementation. Literature from high-income countries published in English since 2010 was reviewed. Medline, Embase, PsycInfo, and Scopus databases were searched on July 4, 2022. Targeted sexual problems were categorized according to the ten dimensions of Robinson's Sexual Health Model, and barriers and facilitators, according to the five domains of the Consolidated Framework for Implementation Research (CFIR). Interventions focused solely on the dimension of Sexual Health Care/Safer Sex were excluded. Relevant information was extracted from the qualifying documents with NVivo 12 software for content analysis. Fifty-two documents were included, referring to 37 interventions which mainly took place in the United States (n = 29/37; 78%), were group-based (n = 16; 41%), and used counselling techniques (n = 23; 62%; e.g., motivational interviewing, cognitive-behavioral therapy). Their settings were mostly primary care (n = 15; 40%) or community-based (n = 16; 43%). On average, interventions addressed three sexual health dimensions (SD = 2; range: 1-10). The most targeted dimension was Sexual Health Care/Safer Sex (n = 26; 70%), which concerned sexual risk reduction. Next, Challenges (n = 23; 62%), included substance use (n = 7; 19%), sexual compulsivity (n = 6; 16%), sexual abuse (n = 6; 16%), and intimate partner violence (n = 4; 11%). Third was Talking About Sex (n = 22; 59%) which mostly concerned HIV disclosure. About a third of interventions addressed Culture/Sexual identity (n = 14; 38%), Intimacy/Relationships (n = 12; 33%), and Positive sexuality (n = 11; 30%). Finally, few targeted Body Image (n = 4; 11%), Spirituality (n = 3; 8%), Sexual Anatomy Functioning (n = 2; 5%) or Masturbation/Fantasy (n = 1; 3%). Forty-one documents (79%) mentioned implementation barriers or facilitators, particularly about the characteristics of the interventions (41% and 78%, respectively; e.g., cost, excessive duration, acceptability, feasibility) and of the individuals involved (37% and 46%; e.g., perceived stigmatization, provider expertise). The other three CFIR dimensions were less common (5%-17%). The search strategy of this review may not have captured all eligible documents, due to its limit to English-language publications. Overall, most interventions incorporated a focus on Sexual Health Care/Safer Sex, at the expenses of other prevalent sexual problems among GBM living with HIV, such as intimate partner violence (Challenges), erectile dysfunction (Sexual Anatomy Functioning), and Body Image dissatisfaction. These findings suggest they could receive more attention within clinical care and at the community level. They also highlight the importance of cost-effective and acceptable interventions conducted in non-stigmatizing environments, where patients' needs can be met by providers who are adequately trained on sexuality-related topics.

Exploring group differences in the response to a sexual risk reduction intervention to prevent hepatitis C virus reinfection in HIV-infected MSM: a mixed-methods study.

To prevent hepatitis C virus (HCV) reinfection, within the Swiss HCVree Trial, a preventive risk reduction intervention was implemented alongside curative treatment. Formative qualitative research identified three response patterns to the intervention. This mixed-methods study's aim was to cross-validate group differences in (a) the content of sexual risk reduction goals set during intervention and (b) the extent of their behavioural change in condomless anal intercourse with non-steady partners (nsCAI), sexualised and intravenous drug use at start and six-month post-intervention. Qualitative thematic analysis was used to summarise goal setting domains. Quantitative descriptive analysis was used to evaluate group differences based on assumptions of the group descriptions. Results largely confirmed assumptions on inter-group response differences in goal setting and behaviour: as expected group 1 Avoid risks showed the lowest HCV risk profile with changes in nsCAI. Group 2 Minimize-risks and Group 3 Accept-risks showed unchanged nsCAI. Group 3 had the highest HCV risk profile. Differences in their goal preferences (1: condom use; 2 reduction blood exposure; 3 safer dating) highlight diversity in attitudes to behavioural change. Our results improve understanding of variability in intervention responses such as changes in attitudes and behaviour. This provides evidence for intervention tailoring and outcome measurement.

Australian consensus statement on doxycycline post-exposure prophylaxis (doxy-PEP) for the prevention of syphilis, chlamydia and gonorrhoea among gay, bisexual and other men who have sex with men.

INTRODUCTION: Doxycycline post-exposure prophylaxis (doxy-PEP) involves consuming 200 mg of doxycycline up to 72 hours after a condomless sex act to reduce the risk of bacterial sexually transmitted infections (STIs). Recent clinical trials of doxy-PEP have demonstrated significant reductions in syphilis, chlamydia and, to a lesser degree, gonorrhoea among gay, bisexual and other men who have sex with men (GBMSM). There is a high level of interest in doxy-PEP in the GBMSM community and, in response, the Australasian Society for HIV, Viral Hepatitis and Sexual Health Medicine (ASHM) held a national consensus conference with the aim of creating preliminary guidance for clinicians, community, researchers and policy makers. MAIN RECOMMENDATIONS: There was broad agreement that doxy-PEP should be considered primarily for the prevention of syphilis in GBMSM who are at risk of this STI, with a secondary benefit of reductions in other bacterial STIs. At the end of the consensus process, there remained some disagreement, as some stakeholders felt strongly that doxy-PEP should be considered only for the prevention of syphilis in GBMSM, and that the risk of increasing antimicrobial resistance outweighed any potential benefit from reductions in other bacterial STIs in the target population. The national roundtable made several other recommendations for clinicians, community, researchers and policy makers, as detailed in this article. ASHM will support the development of detailed clinical guidelines and education materials on doxy-PEP (www.ashm.org.au/doxy-pep). CHANGES IN MANAGEMENT AS A RESULT OF THIS CONSENSUS STATEMENT: For GBMSM at high risk of syphilis, and perhaps other bacterial STIs, clinicians may consider prescribing doxy-PEP for a limited period of time, followed by a review of ongoing need. Unlike human immunodeficiency virus (HIV) pre-exposure prophylaxis (PrEP), doxy-PEP may not be suitable as a population-level intervention and should instead be used more selectively.

Examining the Fraternal Birth Order Effect and Sexual Orientation: Insights from an East European Population.

The development of human sexual orientation remains a complex and multifaceted subject. It is often studied but its origins continue to elude us. In this preregistered study, our primary objective was to demonstrate the fraternal birth order effect (FBOE), which assumes a higher prevalence of older brothers in gay men than in their straight counterparts and which has also been recently recorded in lesbian women. Our second aim was to explore any potential impact of the FBOE on anal-erotic role orientation (AERO), both in gay and straight men. Our study sample included 693 gay men, 843 straight men, 265 lesbian women, and 331 straight women from Czechia and Slovakia. Employing a conventionally parameterized logistic regression model, we substantiated the FBOE among both gay men (OR = 1.35 for maternal older brothers) and lesbian women (OR = 1.71). These outcomes were confirmed by a more nuanced parameterization recently proposed by Blanchard (2022). Nonmaternal older brothers did not exhibit a significant influence on their younger brothers' sexual orientation. Contrary to some earlier reports, however, our data did not establish the FBOE as exclusive to gay men with the receptive AERO. Furthermore, our observations indicated a lower offspring count for mothers of gay men compared to mothers of straight men. Emphasizing the positive FBOE outcomes, we acknowledge the need for caution regarding the various options that can be used to estimate the familial influences on sexual orientation.

Divergence in Chinese Sexual Attitudes: An Age-Period-Cohort Analysis.

A crucial component of comprehending societal change is understanding how sexual attitudes have evolved over time. The substantial and typical changes in China have created an ideal quasi-experimental design and a wealth of empirical data for tracking the evolution of sexual attitudes. However, existing research has failed to adequately analyze the temporal trends in Chinese sexual attitudes. This study employed an age-period-cohort framework to investigate changes in public sexual attitudes, including premarital sex, extramarital sex, and homosexuality. And it further delved into these attitudes in light of two unique aspects of Chinese society: urban-rural divide and political status. It explored the contributing elements and potential processes of changing public sexual attitudes in China using data from seven waves of national social survey conducted from 2010 to 2021. The findings indicated that public sexual attitudes became more conservative with age; the period effect exhibited a fluctuating upward trend, indicating a general increase in acceptance of the three sexual attitudes; notable differences in sexual attitudes among cohorts were identified. The divergence in sexual attitudes was significantly influenced by urban-rural divide and political status.

The Desirable Dad Hypothesis: Male Same-Sex Attraction as the Product of Selection for Paternal Care via Antagonistic Pleiotropy.

Same-sex attraction, a heritable trait with a reproductive cost, lacks a comprehensive evolutionary explanation. Here we build on a hypothesis invoking antagonistic pleiotropy, which suggests that genes linked to male same-sex attraction remain in the gene pool because they have conferred some fitness advantage to heterosexual men possessing them. We posit the "desirable dad hypothesis," which proposes that alleles linked to male non-heterosexual orientations increase traits conducive to childcare; heterosexual men possessing same-sex attracted alleles are more desirable mating partners as a function of possessing superior paternal qualities. We conducted three studies to test predictions from this hypothesis. Results were consistent with all three predictions. Study 1 (N = 1632) showed that heterosexual men with same-sex attracted relatives were more feminine than men without, as indicated by self-report measures of femininity (η2 = .007), warmth (η2 = .002), and nurturance (η2 = .004 - .006). In Study 2 (N = 152), women rated feminine male profiles as more romantically appealing than masculine ones (d = 0.83)-but less so than profiles possessing a combination of feminine and masculine traits. In Study 3 (N = 153), women perceived feminine male profiles as depicting the best fathers and masculine profiles the worst (d = 1.56): consistent with the idea that femininity is attractive for childcare reasons. Together, these findings are consistent with the idea that sexual selection for male parental care may be involved in the evolution of male same-sex attraction.

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.

Digit Ratio (2D:4D; Right-Left 2D:4D) and Multiple Phenotypes for Same-Sex Attraction: The BBC Internet Study Revisited.

Same-sex attraction may be linked to low prenatal androgen (in men) and high prenatal androgen (in women). Digit ratio (2D:4D) is thought to be a negative correlate of prenatal androgen and right-left 2D:4D (Dr-l) to reflect lateralized differences in sensitivity to prenatal androgen. Lower 2D:4D has been reported for lesbians compared to heterosexuals, but links to high 2D:4D in gay men are less clear. The largest study thus far (the BBC Internet study) found no significant difference between the 2D:4D of lesbians and heterosexual women but a higher 2D:4D in gay men compared to heterosexual men. Here we consider the possibility that low and high prenatal androgen is associated with same-sex attraction in men (n = 108,779) and women (n = 87,742), resulting in more than two phenotypes. We examined the associations between 2D:4D, Dr-l, and same-sex attraction scores in the BBC Internet study. In contrast to the earlier report, which considered sexual orientation in categories, there were positive linear associations in men (right and left 2D:4D, but not Dr-l) and negative linear associations in women (right 2D:4D and Dr-l, but not left 2D:4D). There were no curvilinear relationships for right and left 2D:4D. However, Dr-l showed a U-shaped association with same-sex attraction in men. Thus, (1) high prenatal androgen may be implicated in female homosexuality, while both low and high prenatal androgen may be implicated in male homosexuality, and (2) large side differences in sensitivity to androgen may be associated with elevated same-sex attraction in men.

Birth Order and Family Size of UK Biobank Subjects Identified as Asexual, Bisexual, Heterosexual, or Homosexual According to Self-Reported Sexual Histories.

This study used a recently developed statistical technique to investigate the relations between various elements of a subject's family background and the odds of that subject reporting a sexual history indicative of a minority sexual orientation. The subjects were 78,983 men and 92,150 women who completed relevant questionnaire items in the UK Biobank, a large-scale biomedical database of volunteers aged 40-69 years. The men were divided into three sexual minority groups-homosexual, bisexual, and asexual-and a comparison group of heterosexual men. The same was done for the women. The analytic procedure consisted of logistic regressions specifically designed to disentangle the effects of birth order and family size. The results showed that older brothers increased the odds of homosexuality in both men and women, and that older sisters increased the odds in men. In contrast, neither older brothers or older sisters affected the odds of bisexuality or asexuality in men or in women. These results suggest that birth order effects may be specific to homosexuality and not common to all minority orientations. The only family size finding was the negative association between family size and the odds of asexuality in both men and women. The outcomes of this study indicate that the maternal immune hypothesis, which was advanced to explain the relation between older brothers and homosexuality in later-born males, might have to be abandoned or else expanded to explain the findings concerning females. A few such modifications are considered.