Kangaroo Fathers Modulate Maternal Control of Offspring Sex but Not Postpartum Maternal Expenditure.

AbstractWhen sons and daughters have different fitness costs and benefits, selection may favor deviations from an even offspring sex ratio. Most theories on sex ratio manipulation focus on maternal strategies and sex-biased maternal expenditure. Recent studies report paternal influences on both offspring sex ratio and postpartum sex-biased maternal expenditure. We used long-term data on marked kangaroos to investigate whether and how paternal mass and skeletal size, both determinants of male reproductive success, influenced (a) offspring sex in interaction with maternal mass and (b) postpartum sex-biased maternal expenditure. When mothers were light, the probability of having a son increased with paternal mass. Heavy mothers showed the opposite trend. A similar result emerged when considering paternal size instead of mass. Postpartum maternal sex-specific expenditure was independent of paternal mass or size. Studies of offspring sex manipulation or maternal expenditure would benefit from an explicit consideration of paternal traits, as paternal and maternal effects can modulate each other.

The Effect of China's Two-Child Policy on the Child Sex Ratio: Evidence From Shanghai, China.

OBJECTIVE: The bias towards males at birth has resulted in a major imbalance in the Chinese sex ratio that is often attributed to China's one-child policy. Relaxation of the one-child policy has the potential to reduce the imbalance in the sex ratio away from males. In this study, we assessed whether the bias towards males in the child sex ratio was reduced as a result of the two-child policy in China. Medical records data from one large municipal-level obstetrics hospital in Shanghai, East China. DESIGN: Matching and difference-in-differences (MDID) techniques were used to investigate the effect of the two-child policy on the imbalance in the sex ratio at birth after matching for pregnancy status and socioeconomic factors. RESULTS: Analyzing 133,358 live births suggest that the relaxation of the one-child policy had a small, but statistically significant effect in reducing the imbalance in the male to female sex ratio at birth. CONCLUSION: The results demonstrate that relaxation of the one-child policy reduced the imbalance in the male to female sex ratio at birth from 1.10 to 1.05 over the study period at one of the major obstetrics and gynecology hospitals in China.

Diversity, Equity, and Inclusion: A Current Analysis of General Surgery Residency Programs.

BACKGROUND: Local, regional, and national diversity, equity, and inclusion (DEI) initiatives have been established to combat barriers to entry and promote retention in surgery residency programs. Our study evaluates changes in diversity in general surgery residency programs. We hypothesize that diversity trends have remained stable nationally and regionally. MATERIALS AND METHODS: General surgery residents in all postgraduate years were queried regarding their self-reported sex, race, and ethnicity following the 2020 ABSITE. Residents were then grouped into geographic regions. Data were analyzed utilizing descriptive statistics, Kruskal-Wallis test, and chi-square analyses. RESULTS: A total of 9276 residents responded. Nationally, increases in female residents were noted from 38.0 to 46.0% (P < .001) and in Hispanic or Latinx residents from 7.3 to 8.3% (P = .031). Across geographic regions, a significant increase in female residents was noted in the Northwest (51.9 to 58.3%, P = .039), Midwest (36.9 to 43.3%, P = .006), and Southwest (35.8 to 47.5%, P = .027). A significant increase in black residents was only noted in the Northwest (0 to 15.8%, P = .031). The proportion of white residents decreased nationally by 8.9% and in the Mid-Atlantic, Southeast, and Southwest between 5.5 and 15.9% (P < .05). DISCUSSION: In an increasingly diverse society, expanding the numbers of underrepresented surgeons in training, and ultimately in practice, is a necessity. This study shows that there are region-specific increases in diversity, despite minimal change on a national level. This finding may suggest the need for region-specific DEI strategies and initiatives. Future studies will seek to evaluate individual programs with DEI plans and determine if there is a correlation to changing demographics.

Linked supergenes underlie split sex ratio and social organization in an ant.

Sexually reproducing organisms usually invest equally in male and female offspring. Deviations from this pattern have led researchers to new discoveries in the study of parent-offspring conflict, genomic conflict, and cooperative breeding. Some social insect species exhibit the unusual population-level pattern of split sex ratio, wherein some colonies specialize in the production of future queens and others specialize in the production of males. Theoretical work predicted that worker control of sex ratio and variation in relatedness asymmetry among colonies would cause each colony to specialize in the production of one sex. While some empirical tests supported theoretical predictions, others deviated from them, leaving many questions about how split sex ratio emerges. One factor yet to be investigated is whether colony sex ratio may be influenced by the genotypes of queens or workers. Here, we sequence the genomes of 138 Formica glacialis workers from 34 male-producing and 34 gyne-producing colonies to determine whether split sex ratio is under genetic control. We identify a supergene spanning 5.5 Mbp that is closely associated with sex allocation in this system. Strikingly, this supergene is adjacent to another supergene spanning 5 Mbp that is associated with variation in colony queen number. We identify a similar pattern in a second related species, Formica podzolica. The discovery that split sex ratio is determined, at least in part, by a supergene in two species opens future research on the evolutionary drivers of split sex ratio.

Nest temperature assessment in an American crocodile (Crocodylus acutus) population on the central coast of Oaxaca, Mexico.

The temperatures at which eggs of crocodilians are incubated plays an important role in embryo survival, rate of embryonic development and sex definition. The aim of this study was to assess the nest temperatures of an American crocodile (Crocodylus acutus) population on the central coast of Oaxaca state in Mexico. The fieldwork was carried out from February to June 2018 at Palmasola Lagoon, Oaxaca. Ten natural nests of C. acutus were carefully excavated to determine clutch size. When putting the eggs back in the nests, we placed a data logger in the center of the egg mass to determine the temperature parameters in the nest chamber environment, as well as the variation in temperature during the incubation period. All nests were revisited to count the number of hatched eggs (NHE) and to determine the hatching success (HS), along with the duration of the incubation period (IP). Hatching success was 89.04%. The mean clutch size in the American crocodile nests was 30.7 ± 7.83 eggs (ranging from 17 to 46 eggs), and the mean incubation period was 77.6 ± 5.89 days. The mean nest incubation temperature throughout the reproductive season was significantly different among nests. Based on the average temperature during the middle third of the incubation period, the nests should have produced both sexes, but with a higher proportion of males. This study tried to elucidate the impact of nest temperatures during the incubation period on embryo survival, as well as hatchling sex ratio in a local climate on the central coast of Oaxaca.

Levels and potential drivers of under-five mortality sex ratios in low- and middle-income countries.

BACKGROUND: Non-biological childhood mortality sex ratios may reflect community sex preferences and gender discrimination in health care. OBJECTIVE: We assessed the association between contextual factors and gender bias in under-five mortality rates (U5MR) in low- and middle-income countries. METHODS: Full birth histories available from Demographic and Health Surveys and Multiple Indicator Cluster Surveys (2010-2018) in 80 countries were used to estimate U5MR male-to-female sex ratios. Expected sex ratios and their residuals (difference of observed and expected) were derived from a linear regression model, adjusted for overall mortality. Negative residuals indicate more likelihood of discrimination against girls, and we refer to this as a measure of potential gender bias. Associations between residuals and national development and gender inequality indices and with survey-derived child health care indicators were tested using Spearman's correlation. RESULTS: Mortality residuals for under-five mortality were not associated with national development, education, religion, or gender inequality indices. Negative residuals were more common in countries where boys were more likely to be taken to health services than girls (rho -0.24, 95% confidence interval -0.45, -0.01). CONCLUSIONS: Countries where girls were more likely to die than boys, accounting for overall mortality levels, were also countries where boys were more likely to receive health care than girls. Further research is needed to understand which national characteristics explain the presence of gender bias, given that the analyses of development levels and gender equality did not discriminate between countries with or without excess mortality of girls. Reporting on child mortality separately by sex is required to enable such advances.

The secondary sex ratio in Italy over the past eighty years (1940 to 2019) and potential impact of radiological contamination after atmospheric nuclear testing and after Chernobyl: Temporal change-point analysis using Markov Chain Monte Carlo.

In Europe, the male to female ratio at birth (secondary sex ratio: SSR; sex odds: SO) is 1.04-1.06, is influenced by many factors and is declining in industrialized countries. This study was carried out to identify possible impacts of fallout by atomic bomb tests or by the Chernobyl event on SSR in Italy. Italy is a country without commercial nuclear power generation for the last four decades and thus nearly free of radiological confounders. Counts of annual male and female live births in Italy are provided by the World Health Organization (WHO) and by the Italian Istituto Nazionale di Statistica (ISTAT). This study included 57.7 million live births (1940-2019) with overall SSR 1.05829. The Italian SSR trend was modelled with linear and non-linear logistic regression. Trend changes, i.e., periods with level shifts were estimated with Markov Chain Monte Carlo (MCMC). Two distinct idealized level shifts were identified superimposed on a uniform secular downward trend. The first one is seen towards the end of the 1960s with a jump sex odds ratio (SOR) 1.00681, p < 0.0001. The second one occurred in 1987 with SOR 1.00474, p < 0.0001. In each of the 3 periods separated by the two jumps, SSR uniformly decreased with trend SOR per 100 years of 0.98549, p < 0.0001. In conclusion, the secular trend in the Italian SSR showed two marked level shifts, at the end of the 1960s and from 1987 onward. These follow the release of radioactivity by atmospheric atomic bomb tests during the 1960s and by Chernobyl in 1986 and corroborate the hypothesis that ionizing radiation increases SSR.

Effects of Socio-demographic Factors on the Decreasing Trend in the Sex Ratio at Birth in Korea, 1997-2017.

OBJECTIVES: This study investigated the effects of socio-demographic factors on the decreasing trend in the sex ratio at birth from 1997 to 2017 in Korea. METHODS: Data from 10 349 602 live births registered with Statistics Korea from 1997 to 2017 were analyzed. The secondary sex ratio (SSR), defined as the ratio of male to female live births, during the study period (1997-1999 [phase I], 2000-2002 [phase II], 2003-2005 [phase III], 2006-2008 [phase IV], 2009-2011 [phase V], 2012-2014 [phase VI], and 2015-2017 [phase VII]) was calculated according to selected socio-demographic factors, such as parental age, education, occupation, and birth order. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals for a male birth after adjusting for potential confounders. RESULTS: The SSR gradually decreased from 1.10 (in 1998-2000 and 2002) to 1.05 (in 2013-2016). While a decreasing trend in the SSR was not noted among first births, male-biased sex ratios were prominent among third and higher-order births, for which the highest SSR was 1.46 in 1998. Higher birth order was significantly associated with an excess of male births in phases I-VI (≥third vs. first, OR range, 1.03 to 1.35). Advanced maternal age was significantly associated with an excess of female births in phases II, III, and V (≥40 vs. 20-24 years, OR range, 0.92 to 0.95). CONCLUSIONS: This study demonstrated that advanced maternal age and reduction of the artificially-biased SSR among third and higher-order births may partially explain the decreasing trend in the SSR from 1997 to 2017 in Korea.

Gender Discrimination and Excess Female Under-5 Mortality in India: A New Perspective Using Mixed-Sex Twins.

Son preference has been linked to excess female under-5 mortality in India, and considerable literature has explored whether parents invest more resources in sons relative to daughters-which we refer to as explicit discrimination-leading to girls' poorer health status and, consequently, higher mortality. However, this literature has not adequately controlled for the implicit discrimination processes that sort girls into different types of families (e.g., larger) and at earlier parities. To better address the endogeneity associated with implicit discrimination processes, we explore the association between child sex and postneonatal under-5 mortality using a sample of mixed-sex twins from four waves of the Indian National Family Health Survey. Mixed-sex twins provide a natural experiment that exogenously assigns a boy and a girl to families at the same time, thus controlling for selectivity into having an unwanted female child. We document a sizable impact of explicit discrimination on girls' excess mortality in India, particularly compared with a placebo analysis in sub-Saharan Africa, where girls have a survival advantage. We also show that explicit discrimination weakened for birth cohorts after the mid-1990s, especially in northern India, but further weakening has stalled since the mid-2000s, thus contributing to understandings of how the micro-processes underlying the female mortality disadvantage have changed over time.

Probabilistic projection of the sex ratio at birth and missing female births by State and Union Territory in India.

The sex ratio at birth (SRB) in India has been reported to be imbalanced since the 1970s. Previous studies have shown there is a great variation in the SRB between geographic locations across India till 2016. Considering the enormous population and regional heterogeneity of India, producing probabilistic SRB projections at the state level is crucial for policy planning and population projection. In this paper, we implement a Bayesian hierarchical time series model to project the SRB across India by state. We generate SRB probabilistic projections from 2017 to 2030 for 29 States and Union Territories (UTs) in India, and present results for 21 States/UTs with data available from the Sample Registration System. Our analysis takes into account two state-specific factors that contribute to sex-selective abortion in India, resulting in sex imbalances at birth: the intensity of son preference and fertility squeeze. We project that the highest deficits in female births will occur in Uttar Pradesh, with a cumulative number of missing female births of 2.0 (95% credible interval [1.9; 2.2]) million from 2017 to 2030. The total female birth deficits during 2017-2030 for the whole of India is projected to be 6.8 [6.6; 7.0] million.

Gender difference in suicide in Taiwan over a century: a time trend analysis in 1905-1940 and 1959-2012.

BACKGROUND: Suicide rates are higher in men than in women in most countries, although the gender ratios vary markedly worldwide. We investigated long-term trends in suicide rates and the male-to-female ratios in relation to age, method and economic factors in Taiwan during the Japanese colonial (1905-1940) and postwar (1959-2012) periods. METHODS: Suicide data were from the Statistical Reports of Taiwan Governor's Office (1905-1940), Vital Statistics (1959-1970) and cause-of-death mortality data files (1971-2012). Annual age-standardised and age-specific/method-specific suicide rates by gender and the gender ratios were calculated and examined graphically. The associations between trends in economic indicators, suicide and suicide gender ratio were investigated using Prais-Winsten regression. RESULTS: The male-to-female suicide rate ratio increased from below 1 in the 1900s to around 2 by 2000; the reversal was mainly due to a marked reduction in suicide rates in young women coupled with a rise in male suicide between 1905 and 1940. The gender ratio increased again from the 1980s onwards. Poisoning was the most common method in the 1970s-1980s, but its use decreased afterwards, more in women than in men proportionally. The use of gassing for suicide increased markedly in the 2000s and contributed to the rises in overall suicide and the gender ratio. Unemployment rates were more strongly associated with male suicide than female suicide in 1959-2012. Unemployment rates and gross domestic product per capita were positively associated with suicide gender ratios. CONCLUSIONS: Gender differences in suicide changed remarkably in Taiwan over the past century; such change may be related to cultural, socioeconomic and method-specific factors.

Finding gaps in TB notifications: spatial analysis of geographical patterns of TB notifications, associations with TB program efforts and social determinants of TB risk in Bangladesh, Nepal and Pakistan.

BACKGROUND: In order to effectively combat Tuberculosis, resources to diagnose and treat TB should be allocated effectively to the areas and population that need them. Although a wealth of subnational data on TB is routinely collected to support local planning, it is often underutilized. Therefore, this study uses spatial analytical techniques and profiling to understand and identify factors underlying spatial variation in TB case notification rates (CNR) in Bangladesh, Nepal and Pakistan for better TB program planning. METHODS: Spatial analytical techniques and profiling was used to identify subnational patterns of TB CNRs at the district level in Bangladesh (N = 64, 2015), Nepal (N = 75, 2014) and Pakistan (N = 142, 2015). A multivariable linear regression analysis was performed to assess the association between subnational CNR and demographic and health indicators associated with TB burden and indicators of TB programme efforts. To correct for spatial dependencies of the observations, the residuals of the multivariable models were tested for unexplained spatial autocorrelation. Spatial autocorrelation among the residuals was adjusted for by fitting a simultaneous autoregressive model (SAR). RESULTS: Spatial clustering of TB CNRs was observed in all three countries. In Bangladesh, TB CNR were found significantly associated with testing rate (0.06%, p < 0.001), test positivity rate (14.44%, p < 0.001), proportion of bacteriologically confirmed cases (- 1.33%, p < 0.001) and population density (4.5*10-3%, p < 0.01). In Nepal, TB CNR were associated with population sex ratio (1.54%, p < 0.01), facility density (- 0.19%, p < 0.05) and treatment success rate (- 3.68%, p < 0.001). Finally, TB CNR in Pakistan were found significantly associated with testing rate (0.08%, p < 0.001), positivity rate (4.29, p < 0.001), proportion of bacteriologically confirmed cases (- 1.45, p < 0.001), vaccination coverage (1.17%, p < 0.001) and facility density (20.41%, p < 0.001). CONCLUSION: Subnational TB CNRs are more likely reflective of TB programme efforts and access to healthcare than TB burden. TB CNRs are better used for monitoring and evaluation of TB control efforts than the TB epidemic. Using spatial analytical techniques and profiling can help identify areas where TB is underreported. Applying these techniques routinely in the surveillance facilitates the use of TB CNRs in program planning.

Son preference, security concerns and crime against women: Expanding the public health discourse in India.

The phenomenon of son preference in India and the declining number of girls due to such a mindset has been an area of concern. While the Preconception and Prenatal Diagnostic Techniques Act and the Beti Bachao and Beti Padhao scheme have been the mainstay of the government's initiative to counter this reproductive injustice, recognizing son preference and crime against women as public health concern opens up a new vista to counter this injustice. This study has identified that the public health system needs to engage with the following aspects to counter the problem: counseling services to women and men around fertility choices; access/availability to contraceptive choices; engaging men and boys in developing a response against violence; gender-sensitive training and capacity building; access to sexual and reproductive rights awareness amongst girls, women, boys, and men; and health insurance for senior citizens.

Disability among children of immigrants from India and China: Is there excess disability among girls?

We investigate whether there is excess morbidity among daughters of Indian or Chinese immigrants in the US by studying the prevalence of disability among children. We use data from the 2012-14 American Community Surveys on approximately 20,000 US-born children of Indian and Chinese immigrants. Children of US natives are used as a comparison group to account for innate differences in disability between the sexes. Results indicate that there is excess disability among daughters compared with sons among children of Chinese immigrants and children of immigrants from northern or western Indian states; this excess disability declines with younger age at arrival or longer exposure to the host country. Analysis using children of Filipino immigrants as an alternative comparison group yields similar excess disability rates for females. Supplementary material is available for this article at: https://doi.org/10.1080/00324728.2020.1762911.

Transition of Son Preference: Evidence From South Korea.

Sex ratio at birth remains highly skewed in many Asian countries because of son preference. The ratio in South Korea, however, declined beginning in 1990 and reached the natural range in 2007. We study changes in child gender effects on fertility and parental investment during this period of decreasing sex ratio at birth. We find that gender discrimination on the extensive margin (fertility), such as sex-selective abortions and son-biased stopping rules, have nearly disappeared among recent cohorts. On the intensive margin (parental inputs), boys receive higher expenditures on private academic education, have mothers with fewer hours of labor supply, and spend less time on household chores relative to girls. These gender gaps have also narrowed substantially, however, over the past two decades. We consider alternative explanations, but altogether, evidence suggests the weakening of son preference in South Korea.

Molecular sexing and preliminary assessment of population sex ratio of the endangered Malayan tapir (Tapirus indicus) in Peninsular Malaysia.

A molecular sexing method by polymerase chain reaction (PCR) amplification of a portion of the sex-determining region Y (SRY) and the zinc finger (ZF) gene, as well as six equine Y-chromosome-specific microsatellite markers, were tested in the Malayan tapir (Tapirus indicus). While the microsatellite markers did not yield any male-specific amplicons for sex-typing, the SRY/ZF marker system produced reliable molecular sexing results by accurately sex-typing 31 reference Malayan tapirs, using whole blood, dried blood spot (DBS), or tissue samples as materials for DNA extraction. The marker system was also tested on 16 faecal samples, and the results were in general consistent with the pre-determined sexes of the animals, despite some amplification failures. A preliminary estimation of wild Malayan tapir population sex ratio was estimated from the Wildlife Genomic Resource Bank (WGRB) database of the Malaysian Department of Wildlife and National Parks (PERHILITAN), zoos, and the Sungai Dusun Wildlife Conservation Centre (WCC), as well as from the results of molecular sexing 12 samples of unknown sex. The overall sex ratio favoured females, but the deviation from parity was statistically not significant when tested using the binomial test (p > 0.05), which may be due to reduced statistical power caused by small sample sizes.

Survival and sex composition of offspring: Individual-level responses in the quantum and tempo of childbearing during the demographic transition.

Previous studies have documented varying fertility responses to childhood mortality and to the sex composition of the surviving offspring during the demographic transition. We contribute to this literature by applying a mixture cure model to reproductive histories of Estonian women born 1850-99. This model, unlike standard event history models, is capable of separating the effect of the covariates on the propensity of having another birth from their effect on its timing. Child fatalities, not having sons, and to a smaller extent, not having daughters, increased the propensity to have another child and decreased the interval to it. The response was stronger among later cohorts, but only with respect to parity progression. By contrast, the accelerated childbearing response diminished over time. Our findings suggest that behavioural responses in the quantum and tempo of childbearing can occur relatively independently.

Older mothers produce more successful daughters.

Annual reproductive success and senescence patterns vary substantially among individuals in the wild. However, it is still seldom considered that senescence may not only affect an individual but also affect age-specific reproductive success in its offspring, generating transgenerational reproductive senescence. We used long-term data from wild yellow-bellied marmots (Marmota flaviventer) living in two different elevational environments to quantify age-specific reproductive success of daughters born to mothers differing in age. Contrary to prediction, daughters born to older mothers had greater annual reproductive success on average than daughters born to younger mothers, and this translated into greater lifetime reproductive success. However, in the favorable lower elevation environment, daughters born to older mothers also had greater age-specific decreases in annual reproductive success. In the harsher higher elevation environment on the other hand, daughters born to older mothers tended to die before reaching ages at which such senescent decreases could be observed. Our study highlights the importance of incorporating environment-specific transgenerational parent age effects on adult offspring age-specific life-history traits to fully understand the substantial variation observed in senescence patterns in wild populations.

No genetic contribution to variation in human offspring sex ratio: a total population study of 4.7 million births.

The ratio of males to females among an individual's offspring at birth (offspring sex ratio) has long been of great interest to evolutionary biologists. The human offspring sex ratio is around 1 : 1 and is understood primarily in terms of Fisher's principle (R. A. Fisher, The genetical theory of natural selection, 1930), which is based on the insight that in a population with an unequal sex ratio, each individual of the rarer sex will on average have greater reproductive value than each individual of the more common sex. Accordingly, individuals genetically predisposed to produce the rarer sex will tend to have greater fitness and thus genes predisposing to bearing that sex will increase in frequency until the population sex ratio approaches 1 : 1. An assumption of this perspective is that individuals' offspring sex ratio is heritable. However, the heritability in humans remains remarkably uncertain, with inconsistent findings and important power limitations of existing studies. To address this persistent uncertainty, we used data from the entire Swedish-born population born 1932 or later, including 3 543 243 individuals and their 4 753 269 children. To investigate whether offspring sex ratio is influenced by genetic variation, we tested the association between individuals' offspring's sex and their siblings' offspring's sex (n pairs = 14 015 421). We estimated that the heritability for offspring sex ratio was zero, with an upper 95% confidence interval of 0.002, rendering Fisher's principle and several other existing hypotheses untenable as frameworks for understanding human offspring sex ratio.