Progestin-only birth control (e.g., hormonal IUD) does not contain ethinylestradiol (EE), the synthetic estrogen found in combined hormonal contraceptives (ChCs) (e.g., oral pill). Ethinylestradiol has been linked to relationship jealousy; however, it suppresses testosterone, a hormone implicated in intrasexual competitiveness. This study examined the relationship between contraceptive type and self-reported intrasexual competitiveness and jealousy, with the goal of identifying practical differences among existing groups of contraceptive users. A between-subjects design compared combined hormonal contraceptive users, progestin-only contraceptive users, and non-users on self-reported intrasexual competition and jealousy. Participants (N = 398) reported contraceptive information and then completed Buunk and Fisher’s (Journal of Evolutionary Psychology, 7(1), 37-48, 2009) intrasexual competitiveness scale and Buunk’s (Personality and Individual Differences, 23(6), 997-1006, 1997) jealousy scale. Hormonal contraceptive users reported slightly higher levels of jealousy than non-users (p = .012, η2 = 0.01), but the difference between contraceptive types was not significant (p = .098, η2 = 0.01). Among levonorgestrel users, combined hormonal contraceptive users reported significantly higher jealousy than progestin-only contraceptive users (p = .012, η2 = 0.08), although practical differences were small. No dosage effects of ethinylestradiol on jealousy were found. No relationship between contraceptive type and intrasexual competition was found. Combined-hormonal contraceptive users may experience greater relationship jealousy than non-users and potentially progestin-only users. Differences may only be practically meaningful for specific populations. Further research is necessary to standardize the route of administration and explain the null findings regarding intrasexual competition. Our findings provide a basis for future research that can inform contraceptive choice.
The aim of the study was to determine whether there were any differences in women’s evaluations of facial masculinity, beardedness, body shape and muscularity according to their age and menopausal status. The women assessed warp-modified photographs of a man in which the prominence of his secondary sexual characteristics was altered in three areas of evaluation: physical attractiveness, degree of aggression and social dominance. The material consisted of 122 Polish women, aged 19–70 years (mean age: 45.6 y., SD = 15.1 y.), representing three menopausal stages: premenopause, perimenopause and postmenopause. Significant differences in women’s assessments were found. Both age and menopausal status had a significant impact on the rating of physical attractiveness. Older women rated men with medium and full facial hair as more attractive, while menopausal status had no effect. Postmenopausal women rate V shaped bodies as less attractive. Women’s age had no effect on their ratings of male body shape attractiveness. Older women rated men with light muscularity as more attractive than younger women. No effect on menopausal status was found. There was no significant effect of age nor menopausal status on ratings of aggression and social dominance. The degree of development of the secondary sexual characteristics is an important biological signal to others in the population, as it indicates the biological fitness of the individual. A man with outstanding sexual characteristics is perceived by women as a carrier of ‘good genes’, which indicates his readiness to undertake the parental investment.
Climate variation during the Late Pleistocene and Holocene may have shaped human behavioral evolution through selection on personality-related genetic variants. However, direct evidence for climatically driven selection on behavioral polygenic scores (PGS) remains limited. We tested for climate-linked selection on behavioral PGS using modern global genomes and ancient DNA from Western and Eastern Eurasia. PGS were computed for Extraversion, Agreeableness, and Neuroticism, and temporal trends were modeled with hinge regressions at 12,000 and 19,000 years before present (BP), adjusting for latitude and genomic coverage. In Eastern Eurasia, ancestry components were used to predict trait scores within the Holocene period. In modern populations, all three traits exhibited latitude-associated differentiation, consistent with cold-climate adaptation. In Western Eurasian ancient genomes, Extraversion and Neuroticism declined with sample age before the Last Glacial Maximum (pre-knot slopes ≈ −0.018 and −0.045 to −0.051 SD/kyr), then reversed direction after 12–19k BP (Δβ ≈ +0.036 to +0.104, all p < 0.001), suggesting post-LGM relaxation of selection. Agreeableness showed the complementary trend, increasing before and attenuating after the knots. A latent factor summarizing higher Agreeableness and lower Extraversion/Neuroticism captured these coordinated population-level shifts (Δβ ≈ −0.17, p < 0.001). In Eastern Eurasia, Holocene ancestry components (e.g., Jōmon, Tibetan, Northeast Chinese) predicted trait scores consistent with Arctic adaptation, while latitude effects weakened after accounting for admixture. Both trait-specific and factor-level analyses indicate that Late Pleistocene cold climates intensified selection against Extraversion and Neuroticism while favoring Agreeableness, with Holocene warming leading to a reversal or relaxation of these pressures. These results support a model of climate-driven directional selection on behavioral tendencies across the Late Quaternary.
Some researchers have suggested that longer eyelashes may serve as a sexually selected cue to underlying immunocompetence, based on findings that individuals with longer eyelashes are rated as more attractive and healthier. Yet no prior research has directly tested whether eyelash morphology is associated with health symptoms or biological markers of immune function. In the present study, participants (N= 163, ages 18–38) provided eyelash samples(measured for total length and lash length-to-eye-width ratio), self-reported health data, saliva samples (assayed for immunoglobulin A and cortisol), and blood samples (assayed for serum lysozyme and lactoferrin). Results indicate no significant associations between eyelash morphology and any of the measures of underlying health and immunocompetence. Together, these findings do not support the hypothesis that eyelash morphology has been sexually selected as a reliable cue of underlying immunocompetence, but that it may provide a cue to age.
T helper (Th) 1 and Th2 cells are crucial in mediating immune responses, with their balance influenced by factors such as age, body mass index (BMI), and estradiol (E2) levels. This study investigates the IFN-γ/IL-10 ratio across different demographic and physiological variables to understand how these factors may interact and impact immune function. Serum levels of E2, IFN-γ, and IL-10 were measured in a community-based cross-sectional study involving 238 women and 143 men in Texas, USA. Participants completed a comprehensive survey on demographics, health status, and reproductive history. Multiple linear regression models assessed the relationships between the IFN-γ/IL-10 cytokine ratio and variables such as age, BMI, and reproductive status, with particular attention to sex differences and menopausal status. The study found that females had a higher IFN-γ/IL-10 cytokine ratio compared to males. The IFN-γ/IL-10 ratio increased with age in both sexes and was positively associated with BMI in females. Estradiol levels were negatively correlated with the IFN-γ/IL-10 ratio, suggesting that higher estrogen levels may shift the balance toward IL-10 dominance. These patterns were consistent across pre- and post-menopausal women, indicating that age, BMI, and E2 levels play similar roles regardless of reproductive status. These findings provide new insights into the dynamic regulation of the IFN-γ/IL-10 balance, particularly highlighting the complex interactions between sex hormones and immune function across the lifespan.
