Sex differences in the association of childhood socioeconomic position and later-life depressive symptoms in Europe: the mediating effect of education.

PURPOSE: We aimed to study sex differences in the association of childhood socioeconomic position (SEP) with later-life depressive symptoms, the mediating effect of education and explore regional differences across Europe. METHODS: The study included 58,851 participants (55% women, mean age 65 years) from the multicentre, population-based Survey on Health, Ageing and Retirement in Europe. Interviews were conducted in six waves and included measurements of childhood SEP (household characteristics at the age of 10) and depressive symptoms (EURO-D scale). Linear regression was used to study the association of childhood SEP with depressive symptoms, adjusting for covariates, and structural equation modelling assessed the mediating effect of education. RESULTS: In the fully adjusted model, higher childhood SEP was associated with lower depressive symptoms with a greater magnitude in women (B = - 0.07; 95% CI - 0.08, - 0.05) than in men (B = - 0.02; 95% CI - 0.03, - 0.00). Relative to men, childhood SEP had 3 times greater direct effect on depressive symptoms in women, and education had 3.7 times stronger mediating effect against childhood SEP. These associations and the sex differences were particularly pronounced in Southern, Central and Eastern Europe. CONCLUSION: Growing up in poor socioeconomic conditions is a stronger risk factor for the development of depressive symptoms for women than for men. Education may have a stronger preventive potential for women in reducing the adverse effects of childhood socioeconomic hardship. Central and Eastern European populations experience disproportionately higher risk of later-life depression due to lower SEP and greater sex differences.

Birth size and morphological femininity in adult women.

BACKGROUND: Women's morphological femininity is perceived to develop under the influence of sex hormones and to serve as a cue of estradiol level, fertility and health in mating context. However, as the studies on direct relationship between femininity and sex steroid levels have reported mixed results, it is still not well understood what factors contribute to inter-women variation in morphological femininity. Epidemiological studies show that indicators of adverse conditions during intrauterine growth and development in utero, such as low birthweight or relative thinness at birth, influence women's physiology ovarian functioning and may be associated with life-time exposure to estradiol in women. Thus, here we tested if birth parameters are also related with the level of morphological femininity in adult women. RESULTS: One hundred sixty-five healthy women of mean age 28.47 years (SD = 2.39) participated in the study. Facial femininity was estimated based on facial width-to-height ratio (fWHR) and facial shape sexual dimorphism measured in the photos. Body femininity was estimated based on waist-to-hip ratio (WHR) and breast size. Birth weight and birth length were obtained from medical records and ponderal index at birth was calculated. No relationship between birth parameters and facial or body femininity in women of reproductive age was found, also when controlled for adult sex steroid levels and BMI. CONCLUSIONS: The results suggest that, although previous research showed that birth parameters predict reproductive development and adult oestradiol level, they do not explain the variance in morphological femininity in women of reproductive age, trait that is thought to be a cue of a woman's estradiol level and fertility in mating context.

Do adipokines levels influence facial attractiveness of young women?

OBJECTIVES: Facial attractiveness is thought to reflect an individual's biological condition. This seems to be largely explained by the relationship between facial appearance and body adiposity, a trait that affects various aspects of body homeostasis, including fertility and immunity. The aim of this study was to test if, a part of adipose tissue amount, also levels of hormones secreted by adipose tissue are reflected in women's appearance, focusing on the two most abundant adipokines. Due to the opposing effects of adiponectin and leptin on health, we hypothesized that leptin negatively and adiponectin positively correlate with women's attractiveness. METHODS: The study sample included 174 young, healthy women (Mage = 28.50, SDage = 2.38). Serum leptin and adiponectin levels were measured. Estradiol (E2), testosterone (T), and BMI levels were controlled in the analyses. Face photographs were taken and facial attractiveness ratings, assessed by men, were gathered in online questionnaires. RESULTS: Perceived facial attractiveness correlated negatively with leptin level and leptin/adiponectin ratio, but did not correlate with adiponectin level. The results were similar, when controlled for E2, T, and BMI. Adipokines levels did not mediate or moderate the relationship between facial attractiveness and BMI. CONCLUSIONS: The results showed that perceived facial attractiveness is predicted by adipose-derived hormones detrimental for health, like leptin, but is not related with beneficial hormones, such as adiponectin. However, the levels of these two adipokines do not impact the relationship between perceived facial attractiveness and adiposity, and thus do not explain the relationship between facial attractiveness, body adiposity, and biological condition.

Prenatal exposure to oestrogens estimated by digit ratio (2d/4d) and breast size in young nulliparous women.

Digit ratio (2d/4d) in humans is commonly used as a proxy for the exposure to oestrogens and androgens in prenatal life. Masculinisation/feminisation in adults may be also related to digit ratio and therefore to the oestrogen/androgen ratio in prenatal life. It has been shown, for instance, that Waist-to-Hip ratio (WHR) and the amount and distribution of body fat are related to digit ratio in women. A species-specific, sexually dimorphic morphological trait in humans is also a pair of permanent breasts that develop during puberty, under the influence of oestrogens. Here we test if prenatal exposure to oestrogens (in relation to androgens), measured by digit ratio, may also be related to breast size in young, nulliparous women. 133 Turkish students (mean age 22.2) were measured. Breast size was calculated as the difference between breast and under-breast circumferences. We found that when controlling for body mass index (BMI), both right and left digit ratios correlate positively with breast size. This relationship is stronger for the digit ratio of the right hand, which confirms that this side is a better measure of sex differences. Thus, higher exposure to oestrogens in prenatal life is related with stronger expression of a sexually dimorphic trait, such as breast size, in adult women.

Maternal breast volume in pregnancy and lactation capacity.

OBJECTIVES: Successful breastfeeding, crucial for a child's development, depends on a woman's ability to initiate lactation, milk yield, and composition. Those traits differ among women, but the cause and physiological mechanisms responsible for this variation are not fully understood yet. Growing evidence shows that lactation and milk composition vary among women and depend on maternal traits. The aim of this study was to test whether breast volume and its changes during pregnancy are related to the nutritional quality of breastmilk and to breastfeeding dynamics. MATERIAL AND METHODS: Almost 93 pregnant women (mean age: 29.67 ± 3.65), participated in the longitudinal study. Breast measurement was performed at each pregnancy trimester using 3D scanning. Milk samples were collected in the beginning of the second month of lactation from 69 women. Milk macronutrient and calorie content were measured. Women were also interviewed on breastfeeding time and frequency. RESULTS: Breast volume changes during pregnancy were not related to the probability of establishing successful lactation, milk calorie, fat and protein content. We found a negative correlation between milk lactose content and breast volume in the second and third trimester but not with breast volume change. Maternal breast volume in pregnancy was also positively related to the total breastfeeding time (per 24 hr). CONCLUSIONS: The results are in line with the notion that milk macronutrient content tends to be weakly associated with various maternal factors and adverse conditions. However, maternal breast volume and its changes during pregnancy are related with time spent breastfeeding per day, what suggests a positive correlation between breast volume in pregnancy and milk yield.

Parasite stress and pathogen avoidance relate to distinct dimensions of political ideology across 30 nations.

People who are more avoidant of pathogens are more politically conservative, as are nations with greater parasite stress. In the current research, we test two prominent hypotheses that have been proposed as explanations for these relationships. The first, which is an intragroup account, holds that these relationships between pathogens and politics are based on motivations to adhere to local norms, which are sometimes shaped by cultural evolution to have pathogen-neutralizing properties. The second, which is an intergroup account, holds that these same relationships are based on motivations to avoid contact with outgroups, who might pose greater infectious disease threats than ingroup members. Results from a study surveying 11,501 participants across 30 nations are more consistent with the intragroup account than with the intergroup account. National parasite stress relates to traditionalism (an aspect of conservatism especially related to adherence to group norms) but not to social dominance orientation (SDO; an aspect of conservatism especially related to endorsements of intergroup barriers and negativity toward ethnic and racial outgroups). Further, individual differences in pathogen-avoidance motives (i.e., disgust sensitivity) relate more strongly to traditionalism than to SDO within the 30 nations.

Body symmetry and reproductive hormone levels in women.

Fluctuating asymmetry (FA), a morphological marker of developmental stability, may be related to an individual's biological condition, e.g., health or fertility. The aim of this study was to test if the level of a woman's FA was related to her fertility and reproductive potential as measured by reproductive hormone levels. Fifty-three healthy, non-pregnant, naturally cycling women (mean age = 23.42, SD = 1.85 years), participated in the study, conducted in Wroclaw (Poland) in May 2015. Early-follicular phase serum levels of anti-Müllerian hormone (AMH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and estradiol (E2) were measured. FA was calculated based on anthropometric measures of six bilateral body traits, and the composite FA index was used in statistical analyses. No relationship was observed between FA and the levels of FSH, LH, and AMH (p > .05), controlled for potential confounders. However, the level of E2 was positively correlated with FA (p < .05). Thus, in young women, FA was not related to hormones levels related to ovarian reserve, but more symmetrical women had lower E2 levels. As FA is an index of developmental stability, environmental, and genetic stress, the results of the study confirm previous research suggesting that developmental conditions may be related to women's endogenous estrogen levels.

Maternal breast and body symmetry in pregnancy and offspring condition.

OBJECTIVES: Fluctuating asymmetry (FA) is hypothesized to reflect the level of an individual's developmental instability, and therefore genetic quality. As a potential signal of biological condition, female body (including breast) symmetry was shown to be perceived as more attractive in mate choice context. If symmetry reflects a woman's genetic quality, it is possible that FA, similarly to other maternal anthropometric cues of biological condition (e.g., body height or waist-to-hip ratio), may be also related to her offspring condition. MATERIALS AND METHODS: To test this, breast and body asymmetry was measured in 93 pregnant women in the 1st, 2nd, and 3rd pregnancy trimester. Child's birth weight, length, chest and head circumference, information on the Apgar score, congenital malformations, and birth complications was taken from hospital records. The relationships between offspring birth characteristics and maternal breast FA and body FA were analyzed separately, controlled for a child's sex and maternal weight in pregnancy. RESULTS: Breast asymmetry was not a predictor of a child's neonatal condition assessed from morphological parameters at birth. Asymmetry of maternal non-ornamental body characteristcs, commonly used to assess body FA, correlated negatively with a child's weight, head and chest circumference at birth. DISCUSSION: A composite asymmetry index of eight body traits, non-sexually selected characteristics, seems to be a better predictor of a woman's ability to invest in fetus during pregnancy than breast asymmetry, sexual ornamentation that is perceived as a signal of a woman's attractiveness and biological condition.

Human body symmetry and immune efficacy in healthy adults.

OBJECTIVES: More symmetric organisms are perceived as more attractive. Fluctuating asymmetry (FA) i.e. small, random deviations from perfect bilateral symmetry, is supposed to inform about developmental instability. According to the good genes hypothesis, a low level of FA is a putative cue to an organism's biological quality. An important aspect of this quality is the immune system functioning. The aim of this study was to evaluate the relationship between immune system functioning and body symmetry in healthy people. MATERIALS AND METHODS: The composite body FA (cFA) was assessed on the basis of six bilateral traits (on hands and feet). The ISF was determined by many innate (total complement and lysozyme activity, neutrophils function) and adaptive immune parameters (T CD3 and B CD19 lymphocytes, total IgA and IgG and response to flu vaccine). A total of 98 men and 92 women were subjected to flu (among them 37 men and 30 women also to tetanus) vaccination. The blood samples were collected before and 4 weeks after the antigens exposure. Immunomodulatory factors: participant's age, body fat, and free testosterone level, were controlled. RESULTS: Apart from the weak positive association between CD3 or CD19 and cFA in men, we found no association between the level of body symmetry and the rest of the analyzed immune parameters for both sexes. DISCUSSION: Our results are the opposite of the good genes hypothesis prediction and suggest that in western, healthy populations, human mate preferences for more symmetric bodies are not related to immune competence.

Body height and immune efficacy: testing body stature as a signal of biological quality.

According to the good genes hypothesis and energy allocation theory, human adult body height may reflect biological quality. An important aspect of this quality is immune system functioning (ISF). The aim of this study was to evaluate the relationship between ISF and body height in healthy people. The ISF was determined by several important innate (total complement and lysozyme activity, neutrophil function) and adaptive immune parameters (lymphocytes, IgA and IgG, and response to the flu vaccine). Overall, 96 males and 97 females were subjected to flu vaccination, and of these, 35 males and 34 females were subjected to tetanus. Blood samples were collected before and four weeks after vaccination. Immunomodulatory factors, participant's age, body fat, and free testosterone levels, were controlled. There was no association between body height and all analysed immune parameters for both sexes. That might suggest that in Western society, a women's preference for taller men is not related to 'good genes for immune competence'. We propose the novel Immunity Priority Hypothesis that explains the lack of relationship between adult body stature and ISF. This hypothesis, however, does not contradict the signalling role of a man's body height as a morphological marker of biological quality.

Lack of support for relation between woman's masculinity preference, estradiol level and mating context.

It has been proposed that women's preferences for male facial sexual dimorphism are positively correlated with conception probability and differ between short- and long-term mating contexts. In this study, we tested this assumption by analyzing relationships between estradiol levels to the women's preferences of male faces that were manipulated to vary in masculinity. Estradiol was measured in daily saliva samples throughout the entire menstrual cycle collected by Polish women with regular menstrual cycles. In our analyses, we included the three most commonly used definitions of the fertile window in the literature. After computing the overall masculinity preference of each participant and measuring hormone levels, we found that i) the timing of ovulation varied greatly among women (between -11 and -17days from the onset of the next menses, counting backwards), ii) there was no relationship between daily, measured during the day of the test (N=83) or average for the cycle (N=115) estradiol levels and masculinity preferences, iii) there were no differences in masculinity preferences between women in low- and high-conception probability phases of the cycle, and iv) there were no differences in masculinity preferences between short- and long-term mating contexts. Our results do not support the idea that women's preferences for a potential sexual partner's facial masculinity fluctuate throughout the cycle.

Leukocyte changes across menstruation, ovulation, and mid-luteal phase and association with sex hormone variation.

OBJECTIVES: Total leukocyte count (white blood cells-WBC) and the count of each subpopulation vary across the menstrual cycle, but results of studies examining the time and direction of these changes are inconsistent and methodologically flawed. Besides, no previous study focused on leukocyte count on the day of ovulation. METHODS: Blood samples were obtained from 37 healthy and regularly cycling women aged 19.8-36.1 years. Samples were taken three times: during menstruation (M), ovulation (O), and in the mid-luteal phase (ML). WBC, neutrophils, lymphocytes, mixed cells, progesterone (P,) and estradiol (E) were measured in each of the three target phases of the cycle. RESULTS: Compared to menstruation, WBC (P = 0.002) and neutrophils (P < 0.001) increased around ovulation and remained stable in the mid-luteal phase, whereas lymphocyte and mixed cell counts did not change throughout the menstrual cycle. There were some correlations of sex hormone variation with leukocyte changes between M and O (positive for E and WBC, negative for P and WBC and for P and neutrophil count; P < 0.05), but not between O and ML. CONCLUSIONS: Peripheral leukocyte changes taking place in the second half of the cycle are already observable on the day of ovulation and they are associated with sex hormone variation. We speculate that these changes may lead to increased immune protection against pathogens at a time when fertilization and implantation typically occur. Am. J. Hum. Biol. 28:721-728, 2016. © 2016 Wiley Periodicals, Inc.

Breast size and asymmetry during pregnancy in dependence of a fetus's sex.

OBJECTIVES: Breast size and fluctuating asymmetry (FA) are related to women's biological condition, as size correlates positively with fecundity, whereas FA correlates negatively with biological quality. We tested if breast volume, FA, and their changes during pregnancy are related to a fetus's sex. Women with bigger, symmetrical breasts, with a greater increase in size during pregnancy, should be more likely to carry a more ecologically sensitive and energetically demanding male fetus. METHODS: Ninety-three women participated in a 3-stage longitudinal study. 3D breast scans were performed in the first, second, and third trimester of pregnancy. As there was a small variation in pregnancy week at each research stage between the participants, the expected breast volume and FA values for the 12th, 22nd, and 32nd pregnancy week were calculated, basing on the obtained measurements. Those values were compared between mothers who carried a boy and mothers who carried a girl. RESULTS: Although women who carried a boy had somewhat larger breasts at each trimester than women who carried a girl, the difference was not significant. ANOVA for repeated measurements revealed a greater breast size increase in women carrying a boy (P = 0.039). FA decreased during pregnancy, but was not related to a fetus's sex. CONCLUSION: Pregnancy-induced breast volume increase is a better cue of a fetus's sex than breast asymmetry or breast size per se, i.e., the traits that are supposed to indicate a woman's biological condition. Women with a larger increase in breast size during pregnancy are more likely to carry to term a more ecologically vulnerable male fetus.

Woman's body symmetry and oxidative stress in the first trimester of pregnancy.

OBJECTIVES: High level of oxidative stress (OS) during the first weeks of pregnancy is related to many serious pregnancy complications. Previous studies showed that body fluctuating asymmetry (FA) is related to OS level in men, suggesting that FA is a marker of oxidative balance in an individual. The aim of this study was to analyze if body FA was related to the level of biomarkers of OS in the first trimester of pregnancy. METHODS: The sample included 34 women in the first trimester of pregnancy, not smoking, and not exposed to toxins in their work environment. The composite FA and levels of two biomarkers of OS, 8-iso-ProstaglandinF2α (an indicator of oxidative damage to lipids) and 8-OH-dG (an indicator of oxidative damage to DNA) were measured. Factors that may affect the level of OS (vitamin supplementation, age, smoking, alcohol drinking, physical activity, and health condition) were controlled. RESULTS: The levels of OS markers in the first trimester of pregnancy correlated positively with women's FA (r = 0.52, P = 0.002 for 8-OH-dG; r = 0.50; P = 0.003 for 8-iso-PGF2α level) and positively with body height (r = 0.37, P = 0.03 for 8-OH-dG level). CONCLUSION: The level of OS is likely to be a substantial and important fitness trait, and FA may convey information on the level of OS in women. The result confirms that FA is an indicator of biological condition, as suggested by an evolutionary approach to morphological human traits perceived as attractive.

Human body morphology, prevalence of nasopharyngeal potential bacterial pathogens, and immunocompetence handicap principal.

OBJECTIVE: Body height, body mass index (BMI) and waist-to-hip ratio (WHR) are the main traits characterizing human body morphology. Studies show that these traits are related to attractiveness and, therefore, according to an evolutionary point of view, are supposed to be honest signals of biological quality. If the immunocompetence handicap principal (IHP) is true, people with more attractive values of these traits should be more immunologically competent. To test this, we analyzed whether nasal and throat colonization with potentially pathogenic bacteria is related to body height and BMI in both sexes and to WHR in females. METHODS: 103 healthy females and 90 healthy males (with the mean age of 21.4 and 22.8, respectively) participated in the study. The heights and weights were self-reported and waist and hip circumferences measured. Six potentially pathogenic species (with the most common Staphylococcus aureus) isolated from nasal and throat swabs were identified by colony morphology, standard biochemical assays, and latex tests. To compare carrier and noncarrier individuals, Kruskal-Wallis test was used. RESULTS: Colonized males had higher BMI than non-colonized males (no difference for females) and colonized females had lower WHR's. Body height was not related to colonization in either sex. CONCLUSIONS: We confirmed our hypothesis only for BMI in males. This result and a higher WHR in non-colonized females indicate higher immunocompetence of those who bear the costs of higher levels of testosterone, which according to previous studies is correlated negatively to BMI in males and positively to WHR in females.

Autoimmune Hashimoto's Disease and Feminization Level-Testing the Immunocompetence Hypothesis.

Morphological femininity depends mainly on estrogen levels at puberty and is perceived as a cue of a woman's biological condition. Due to the immunostimulant properties of estradiol, estradiol-dependent feminine traits are expected to be positively related to immunity. However, heightened immunity in women may increase the risk of autoimmune disease, thus the relationship between femininity and immune quality may be complex. This study aimed to assess the relationship between morphological femininity and both the occurrence and severity of Hashimoto thyroiditis (HT) in women of reproductive age. Moreover, 95 women with HT and 84 without HT (all between 20 and 37 years) participated in the study. Morphological femininity was assessed based on somatic measurements of sexually dimorphic traits (2D:4D ratio, WHR, breast size, facial sexual dimorphism). The occurrence and severity of HT were assessed by serum TPOAb levels. The results showed that only the 2D:4D ratio of the right hand was higher in the HT group, indicating higher femininity in these women. However, there was also a positive relationship between facial femininity and TPOAb level in women with HT, indicating a higher severity of the disease. The results suggest that prenatal and pubertal exposure to estrogens may increase the probability or severity of autoimmune diseases in adulthood, but the relationship is tentative.

Kin term mimicry hypothesis.

Adaptive mimicry in animals is a well-known phenomenon. Here, we propose that a similarly adaptive strategy in humans is using kin terms for people who are not closely genetically related. Irrespective of the initiator attributing a kin term to a non-kin, we call this kin term mimicry (KTM). The emergence of human sociality and language allowed not only easy kin recognition, but also led to strong positive emotions related to such kin names as "mother," "father," "brother," "sister," "aunt" or "uncle." Although the phenomenon of using kin terms of genetically unrelated people is well known in the social sciences, here we discuss it in the light of evolution. We notice this is an evolutionary adaptive cooperation strategy, which allows us to predict in which ecological or social circumstances it will be more prevalent. We postulate specific testable factors that affect the prevalence of kin mimicry. We also discuss who is more likely to be an initiator of calling non-kin a fictive kin, and who benefits from such behavior. The KTM hypothesis postulates that an individual or social group initiating or bestowing kin terms usually receives more benefits (economic and/or psychological support) from such mimicry.

Birth size and the serum level of biological age markers in men.

Previous studies showed that intrauterine growth restrictions, resulting in smaller body size at birth, are associated with altered development and the risk of age-related diseases in adult life. Thus, prenatal development may predict aging trajectories in humans. The study aimed to verify if body size at birth is related to biological age in adult men. The study sample consisted of 159 healthy, non-smoking men with a mean age of 35.24 (SD 3.44) years. Birth weight and length were taken from medical records. The ponderal index at birth was calculated. Biological age was evaluated based on serum levels of s-Klotho, hsCRP, DHEA/S, and oxidative stress markers. Pregnancy age at birth, lifestyle, weight, cortisol, and testosterone levels were controlled. The results showed no relationship between birth size and s-Klotho, DHEA/S level, inflammation, or oxidative stress. Also, men born as small-for-gestational-age (N = 49) and men born as appropriate-for-gestational-age (N = 110) did not differ in terms of biological age markers levels. The results were similar when controlled for pregnancy week at birth, chronological age, BMI, testosterone, or cortisol level. The results suggest that there is no relationship between intrauterine growth and biomarkers of aging in men aged 30-45 years from the affluent population.

Temperament and ovarian reproductive hormones in women: evidence from a study during the entire menstrual cycle.

Personality and temperament were hypothesized to function as important factors affecting life history strategies. Recent research has demonstrated the association between temperamental traits and reproduction in humans, however, the underlying mechanisms are still poorly understood. This study presents evidence for an association between temperamental traits and woman's fecundity, as indicated by levels of ovarian steroid hormones during the menstrual cycle. On a large sample of urban, reproductive age women (n = 108) we demonstrated that activity, endurance and emotional reactivity are associated with levels of estrogen and with a pattern of change of progesterone levels. Women high in activity, high in endurance and low in emotional reactivity had up to twice as high estradiol levels and more favorable progesterone profiles as women low in activity, low in endurance and high in emotional reactivity. The temperamental traits we measured highly overlap with extraversion, neuroticism and negative emotionality that were reported to correlate with reproductive success. Our findings thus suggest a possible explanation for these relationships, linking personality and women's reproductive success through a hormonal pathway.

Newborn's condition at birth does not depend on maternal sexual strategy--evidence against the "hunting for good genes" hypothesis.

OBJECTIVES: Neonatal weight and health depend on many epigenetic and environmental factors and also on a child's genes as inherited from the mother and the father. The "Hunting for Good Genes" (HfGG) hypothesis claims that women pursue short-term mating strategies in order to obtain good genes for their progeny. If this is true, one should expect that in comparison to children born in long-term relationships (LR), children born in short-term relationships (SR) should have a larger neonatal size and be healthier. METHODS: To test the HfGG hypothesis, and whether sexual strategy influences neonatal parameters, we used an on-line questionnaire aimed at mothers. Totally, 1,558 women took part in this study, and among them 130 conceived their first-born child in a short-term relationship (SR mothers) and 1,428 in a long-term relationship (LR mothers). RESULTS: There was no difference between those two groups of children in terms of birth weight and Apgar score. Although we found no difference in the occurrence of genetic diseases and birth defects between SR and LR boys, the girls born by LR mothers were healthier than those born by SR mothers. We also did not find any difference in the sex ratio of the children born to SR and LR mothers. CONCLUSIONS: The results of our study do not support the "Hunting for Good Genes" hypothesis for the first born child. In the contemporary western society of the study, women do not seem to derive genetic benefits expressed as child condition at birth from short-term relationships.