How Sex Selection Undermines Reproductive Autonomy

Non-medical sex selection is premised on the notion that the sexes are not interchangeable. Studies of individuals who undergo sex selection for non-medical reasons, or who have a preference for a son or daughter, show that they assume their child will conform to the stereotypical roles and norms associated with their sex. However, the evidence currently available has not succeeded in showing that the gender traits and inclinations sought are caused by a “male brain” or a “female brain”. Therefore, as far as we know, there is no biological reason why parents cannot have the kind of parenting experience they seek with a child of any sex. Yet gender essentialism, a set of unfounded assumptions about the sexes which pervade society and underpin sexism, prevents parents from realising this freedom. In other words, unfounded assumptions about gender constrain not only a child’s autonomy, but also the parent’s. To date, reproductive autonomy in relation to sex selection has predominantly been regarded merely as the freedom to choose the sex of one’s child. This paper points to at least two interpretations of reproductive autonomy and argues that sex selection, by being premised on gender essentialism and/or the social pressure on parents to ensure their children conform to gender norms, undermines reproductive autonomy on both accounts.     

Sexual dimorphism,survival, and parental investment in relation to offspring sex in a precocial bird

Differential growth rate between males and females, owing to a sexual size dimorphism, has been proposed as a mechanism driving sex‐biased survival. How parents respond to this selection pressure through sex ratio manipulation and sex‐biased parental investment can have a dramatic influence on fitness. We determined how differential growth rates during early life resulting from sexual size dimorphism affected survival of young and how parents may respond in a precocial bird, the black brant Branta bernicla nigricans. We hypothesized that more rapidly growing male goslings would suffer greater mortality than females during brood rearing and that parents would respond to this by manipulating their primary sex ratio and parental investment. Male brant goslings suffered a 19.5% reduction in survival relative to female goslings and, based on simulation, we determined that a female biased population sex ratio at fledging was never overcome even though previous work demonstrated a slight male‐biased post‐fledging survival rate. Contrary to the Fisherian sex ratio adjustment hypothesis we found that individual adult female brant did not manipulate their primary sex ratio (50.39% male, n = 645), in response to the sex‐biased population level sex ratio. However, female condition at the start of the parental care period was a good predictor of their primary sex ratio. Finally, we examined how females changed their behavior in response to primary sex ratio of their broods. We hypothesized that parents would take male biased broods to areas with increased growth rates. Parents with male biased primary sex ratios took broods to areas with higher growth rates. These factors together suggest that sex‐biased growth rates during early life can dramatically affect population dynamics through sex‐biased survival and recruitment which in turn affects decisions parents make about sex allocation and sex‐biased parental investment in offspring to maximize fitness.     

Parental mortality rates in a western country after the death of a child: assessment of the role of the child's sex

Background: Loss of a child has been associated with elevated mortality rates in parents. Studies that focus on the influence of the child's sex on parental mortality are sparse.Objective: The main objective of the present study was to reevaluate the combined impact of the parents' and child's sex within a larger sample and focus on adverse health effects as an objective measure of possible long-term effects of maladaptive grief reactions.Methods: For the time period between 1980 and 1996, all children in Denmark who died before 18 years of age were identified. Parents who had lost a child were identified as the bereaved (exposed) group. Mortality rates of parents within the same-sex parent-child dyad were compared with mortality rates of parents within the opposite-sex parent-child dyad. Separate analyses were performed for bereaved fathers and for bereaved mothers, and additional analyses were conducted to examine the sole effect of the child's sex, irrespective of parental gender. A Cox proportional hazards regression model was used to estimate the hazard ratios (HRs) with 95% CIs.Results: The study population consisted of 21,062 parents (mean age at entry, 32 years; 11,221 mothers, 9841 fathers). Bereaved parents who had lost a child of the same sex had similar overall mortality as bereaved parents who had lost a child of the opposite sex (HR = 1.02; 95% CI, 0.85–1.22). Similar findings were observed for mortality due to natural death (HR = 0.96; 95% CI, 0.78–1.18) or mortality due to unnatural death (HR = 1.22; 95% CI, 0.84–1.77). Bereaved fathers who had lost a son had similar mortality as those bereaved by the death of a daughter (HR = 1.10; 95% CI, 0.86–1.40). Bereaved mothers who had lost a daughter had similar mortality as those bereaved by the death of a son (HR = 0.93; 95% CI, 0.70–1.22). Bereaved parents who had lost a son had mortality rates similar to those who had lost a daughter (HR = 1.09; 95% CI, 0.91–1.31). The interactions between grouping variable and sex of parents were not significant, indicating that the differential effect of losing a child based on sex of the child was not greater for fathers than for mothers.Conclusions: The results of this study revealed no significant effect of sex of the deceased child on mortality in these bereaved parents. The results might differ if this study was replicated in a population with a different grief culture and, more importantly, different gender schemas.     

Parental efficacy and child behavior in a community sample of children with and without attention-deficit hyperactivity disorder (ADHD)

Most studies of attention-deficit hyperactivity disorder (ADHD) youth have obtained data from the perspective of either children or parents, but not both simultaneously. The purpose of this study was to examine child and parent perspectives on parenting in a large community-based sample of children with and without ADHD. We identified children in grades 4?C6 and their parents through surveys administered to a random sample of public schools. We used multivariable logistic regression to determine independent associations between child and parent characteristics and the presence of ADHD while controlling for covariates and clustering by school. Sufficient data were achieved for 2,509 child/parent dyads. Ten percent of youths (n?=?240) had been diagnosed with ADHD. Compared with those without ADHD, those with ADHD were more commonly male (67.9 vs. 48.0?%, p?<?.001) and age 12 or over (16.3 vs. 10.3?%). After adjusting for covariates and clustering, compared to children without ADHD, children with ADHD were significantly more likely to report lower self-regulation (OR?=?0.68, 95?% CI?=?0.53, 0.88) and higher levels of rebelliousness (OR?=?2.00, 95?% CI?=?1.52, 2.69). Compared with parents whose children did not have ADHD, parents of children with ADHD rated their overall parental efficacy substantially lower (OR?=?0.23, 95?% CI?=?0.15, 0.33). However, child assessment of parenting style was similar by ADHD. Despite the internal challenges community-based youth with ADHD face, many parents of ADHD youth exhibit valuable parental skills from the perspective of their children. Feedback of this information to parents may improve parental self-efficacy, which is known to be positively associated with improved ADHD outcomes.     

The Trivers–Willard hypothesis of parental investment: No effect in the contemporary United States

The Trivers–Willard hypothesis (TWH) predicts that parents will bias their sex ratio toward sons when in good condition and toward daughters when in poor condition. Many human studies have tested the related hypothesis that parents' bias allocation of resources to existing sons and daughters according to the same principle. The present study used time diary and self-report data from the parents of 3200 children in the US to test the hypothesis that as status increases, parents will allocate more resources to sons vs. daughters. It finds no evidence that higher-status parents invest more in sons or that lower status parents invest more in daughters. This finding illustrates the specificity of situations in which the TWH effects should be expected. Only certain types of parental investment — such as protection and a bias in the sex ratio — may have been selected to vary according to parental condition. Optimal allocation of resources after the child is born, however, is achieved not by the simple bias predicted by the TWH, but by allocating resources among offspring in ways that yield the largest marginal inclusive fitness gains.     

Waiting for Trivers and Willard: Do the rich really favor sons?

Parental investment theory has been put forward as a major evolutionary argument explaining male or female biased birth sex ratio, the Trivers-Willard (T-W) hypothesis, predicting that parents living in good circumstances will bias their investment to sons, whereas parents in poor circumstances will bias their investment toward daughters. Tests of the T-W hypothesis on human beings have shown limited evidence for parents appearing to differentiate their investment to sons or daughters according to the reproductive potential of each sex. The present study tests the T-W hypothesis among a large contemporary Polish sample using first birth interval and extent of breastfeeding as measures of parental investment, and economic status and level of parental education as measures of parental condition. The extents to which parental investment and markers of parental condition vary by sex of the child were examined using log-linear analysis. Weak support for the T-W effect is found among families where fathers were best educated, where a greater proportion of first-born boys are breastfed longer than girls, while the opposite trend is observed among families with fathers with lowest levels of education. Although the present study does not fully support the T-W hypothesis, it gives evidence of greater investment in female offspring at the lower extremes of income, and greater investment in males at higher levels of income.     

Intralocus sexual conflict,adaptive sex allocation,and the heritability of fitness

Intralocus sexual conflict arises when selection favours alternative fitness optima in males and females. Unresolved conflict can create negative between‐sex genetic correlations for fitness, such that high‐fitness parents produce high‐fitness progeny of their same sex, but low‐fitness progeny of the opposite sex. This cost of sexual conflict could be mitigated if high‐fitness parents bias sex allocation to produce more offspring of their same sex. Previous studies of the brown anole lizard (Anolis sagrei) show that viability selection on body size is sexually antagonistic, favouring large males and smaller females. However, sexual conflict over body size may be partially mitigated by adaptive sex allocation: large males sire more sons than daughters, whereas small males sire more daughters than sons. We explored the evolutionary implications of these phenomena by assessing the additive genetic (co)variance of fitness within and between sexes in a wild population. We measured two components of fitness: viability of adults over the breeding season, and the number of their progeny that survived to sexual maturity, which includes components of parental reproductive success and offspring viability (RS^V). Viability of parents was not correlated with adult viability of their sons or daughters. RS^V was positively correlated between sires and their offspring, but not between dams and their offspring. Neither component of fitness was significantly heritable, and neither exhibited negative between‐sex genetic correlations that would indicate unresolved sexual conflict. Rather, our results are more consistent with predictions regarding adaptive sex allocation in that, as the number of sons produced by a sire increased, the adult viability of his male progeny increased.     

Patterns of child fosterage in rural northern Thailand

Evolutionary theory guides an investigation of foster parent selection in two northern Thai villages with different biosocial environments: one village has high levels of labour migration and divorce, and growing numbers of parental death due to HIV/AIDS, while the other village has lower migration, divorce and parental mortality levels. Focus groups examine mothers' and fathers' motivations and ideals regarding foster caretaker selection, and quantitative family surveys examine real fostering outcomes: specifically, the laterality (matrilateral versus patrilateral) and genetic distance of the foster caretakers of all ever-fostered children in these two villages. As predicted, in environments of high marital stability and paternity certainty, parents seem to prefer close genetic kin from either side as foster parents for their children. In low marital stability and paternity certainty environments, parents trust their own lateral kin, regardless of genetic distance, over close genetic kin from the other side. The striking exception to this pattern, however, occurs in the case of parental death, in which case children are fostered to the deceased parent's kin, regardless of the child's sex or other factors. In general, the foster parents for girls are selected with more care, reflecting the daughter/female preference expected in traditionally matrilineal, matrilocal societies. An ordered decision-making pathway for foster parent selection is proposed, taking into consideration the key factors of (a) the circumstances driving the fostering decision, (b) the gender of the child, (c) the gender of the key decision-making parent, and (d) the degree of marital and population fluidity (and subsequent, paternity certainty) in the village.     

Better‐surviving barn swallow mothers produce more and better‐surviving sons

Sex allocation theory predicts that parents are selected to bias their progeny sex ratio (SR) toward the sex that will benefit the most from parental quality. Because parental quality may differentially affect survival of sons and daughters, a pivotal test of the adaptive value of SR adjustment is whether parents overproduce offspring of the sex that accrues larger fitness advantages from high parental quality. However, this crucial test of the long‐term fitness consequences of sex allocation decisions has seldom been performed. In this study of the barn swallow (Hirundo rustica), we showed a positive correlation between the proportion of sons and maternal annual survival. We then experimentally demonstrated that this association did not depend on the differential costs of rearing offspring of either sex. Finally, we showed that maternal lifespan positively predicted lifespan of sons but not of daughters. Because in barn swallows lifespan is a strong determinant of lifetime reproductive success, the results suggest that mothers overproduce offspring of the sex that benefits the most from maternal quality. Hence, irrespective of mechanisms causing the SR bias and mother–son covariation in lifespan, we provide strong evidence that sex allocation decisions of mothers can highly impact on their lifetime fitness.     

Retrospective Reports of Child Feeding Practices,Current Eating Behaviors,and BMI in College Students

Research concerning child feeding practices has focused on children and adolescents, and little is known about how feeding practices used in childhood relate to eating behaviors and weight status in early adulthood. We assessed college students' and their parents' retrospective reports of child feeding practices used when the students were in middle childhood. We also assessed the college students' current reports of their eating behaviors using the Dutch Eating Behavior Questionnaire (DEBQ) and the Intuitive Eating Scale (IES), and measured their current BMI. Results showed that college students' and their parents' reports about previous parental use of child feeding practices were not correlated. Parent reports of their own use of child feeding practices were more related to students' eating behaviors and BMI than were students' recollections about feeding practices used by their parents. An analysis of gender effects showed that there were positive correlations between parental child feeding practices, BMI, and emotional eating for female students. These relationships did not exist for male students. The results suggest that child feeding practices recollected by parents are linked to the development of emotional eating and weight status of women in early adulthood.     

The Links Between Parent Behaviors and Boys' and Girls' Science Achievement Beliefs

This study examined whether parental involvement in children's science schoolwork (i.e., discussions about science, homework helping and encouragement of science interest) varies for boys and girls, and how these behaviors relate to children's science achievement beliefs (i.e., ability perceptions and task-value) at the end of a school year. We analyzed these links both for fathers and mothers and examined whether child gender moderates how parental behaviors relate to children's beliefs over time. Data were gathered over a span of a school year from 114 middle-school students (50% girls, 81% European American) and their parents (mothers: n = 103, fathers: n = 90). We found support for the moderating effect of gender. Specifically, the findings indicated that only parents' encouragement of science interest varied by child gender; mothers' encouragement positively predicted girls' self-assessments of science ability at the end of the year, but was a negative estimator of boys' self-assessments. Additionally, mothers' discussions about science showed similar findings with respect to girls' and boys' utility beliefs about science.     

Does surgical genitoplasty affect gender identity in the intersex infant?

There is no clear-cut answer to the question of whether surgical genitoplasty affects gender identity in the intersex infant. The debate centres around which is more important for the development of gender identity: the biological sex of a child or the sex in which a child is reared. We believe that the surgical achievement of a phenotype concordant with the sex of rearing is a tremendous help to the parents of an intersex infant. We do not consider that the 'neutral' upbringing of a child with ambiguous genitalia is a feasible option, first because of the parents' distress which prevents them from raising their child normally and second because in most cultures around the world gender variants are not treated as equals. A neutral upbringing may induce psychosocial consequences that are more pernicious than carefully considered neonatal sex attribution and concordant surgical genitoplasty.     

Are offspring begging levels exaggerated beyond the parental optimum? Evidence from a bidirectional selection experiment

Parental care involves elaborate behavioural interactions between parents and their offspring, with offspring stimulating their parents via begging to provision resources. Thus, begging has direct fitness benefits as it enhances offspring growth and survival. It is nevertheless subject to a complex evolutionary trajectory, because begging may serve as a means for the offspring to manipulate parents in the context of evolutionary conflicts of interest. Furthermore, it has been hypothesized that begging is coadapted and potentially genetically correlated with parental care traits as a result of social selection. Further experiments on the causal processes that shape the evolution of begging are therefore essential. We applied bidirectional artificial selection on begging behaviour, using canaries (Serinus canaria) as a model species. We measured the response to selection, the consequences for offspring development, changes in parental care traits, here the rate of parental provisioning, as well as the effects on reproductive success. After three generations of selection, offspring differed in begging behaviour according to our artificial selection regime: nestlings of the high begging line begged significantly more than nestlings of the low begging line. Intriguingly, begging less benefitted the nestlings, as reflected by on average significantly higher growth rates, and increased reproductive success in terms of a higher number of fledglings in the low selected line. Begging could thus represent an exaggerated trait, possibly because parent–offspring conflict enhanced the selection on begging. We did not find evidence that we co‐selected on parental provisioning, which may be due to the lack of power, but may also suggest that the evolution of begging is probably not constrained by a genetic correlation between parental provisioning and offspring begging.     

Social status and the secondary sex ratio: new evidence on a lingering controversy

Because women are more likely than men to use social status as a criterion in mate selection, evolutionary theory has led to the hypothesis that higher proportions of males will be born to parents of high social status than to parents of low status. To date, the research that has tested this deduction has not provided consistent support. This could be partly due to the small sample size in several of the studies. The present study tested the hypothesis using 6 different social status measures provided by more than 11,000 United States and Canadian college students. The offspring sex ratio was measured by asking the students their own sex plus that of each of their siblings. No evidence was found to support the hypothesis that parental social status has any significant effect on the sex ratio of offspring.     

Hybridity effect on mortality

Abstract

Several techniques for preselecting the sex of offspring are available now or will be in the near future. Although hundreds of studies indicate that sons are desired by the overwhelming proportion of persons asked, few studies ask whether preselecting of sex of offspring ought to be made available generally, as the technologies become perfected. In northern California, 2,138 respondents indicated widespread acceptance of ongoing biomedical research to perfect preselection methods and of making these procedures available to potential parents. Almost half agreed that they might want to use such techniques. Variation in levels of agreement were assessed by sex, race, marital status, child‐parity, religious affiliation and attendance, level of education, class, and general attitudes toward medical and scientific leaders. The implications of the general acceptability of sex selection go far beyond the freedom of parental choice—to such matters as socialization patterns of first son, second daughter ordering, sex role inflexibilities, sex ratio imbalances, and also include possibilities for curtailing rapid population growth.     

Sex roles in nest keeping – how information asymmetry contributes to parent‐offspring co‐adaptation

Parental food provisioning and offspring begging influence each other reciprocally. This makes both traits agents and targets of selection, which may ultimately lead to co‐adaptation. The latter may reflect co‐adapted parent and offspring genotypes or could be due to maternal effects. Maternal effects are in turn likely to facilitate in particular mother‐offspring co‐adaptation, further emphasized by the possibility that mothers are sometimes found to be more responsive to offspring need. However, parents may not only differ in their sensitivity, but often play different roles in postnatal care. This potentially impinges on the access to information about offspring need. We here manipulated the information on offspring need as perceived by parents by playing back begging calls at a constant frequency in the nest‐box of blue tits (Cyanistes caeruleus). We measured the parental response in provisioning to our treatment, paying particular attention to sex differences in parental roles and whether such differences alter the perception of the intensity of our manipulation. This enabled us to investigate whether an information asymmetry about offspring need exists between parents and how such an asymmetry relates to co‐adaptation between parental provisioning and offspring begging. Our results show that parents indeed differed in the frequency how often they perceived the playback due to the fact that females spent more time with their offspring in the nest box. Correcting for the effective exposure of an adult to the playback, the parental response in provisioning covaried more strongly (positive) with offspring begging intensity, independent of the parental sex, indicating coadaptation on the phenotypic level. Females were not more sensitive to experimentally increased offspring need than males, but they were exposed to more broadcasted begging calls. Therefore, sex differences in access to information about offspring need, due to different parental roles, have the potential to impinge on family conflicts and their resolution.     

Parental investment, sexual selection and sex ratios

Conventional sex roles imply caring females and competitive males. The evolution of sex role divergence is widely attributed to anisogamy initiating a self‐reinforcing process. The initial asymmetry in pre‐mating parental investment (eggs vs. sperm) is assumed to promote even greater divergence in post‐mating parental investment (parental care). But do we really understand the process? Trivers [Sexual Selection and the Descent of Man 1871–1971 (1972), Aldine Press, Chicago] introduced two arguments with a female and male perspective on whether to care for offspring that try to link pre‐mating and post‐mating investment. Here we review their merits and subsequent theoretical developments. The first argument is that females are more committed than males to providing care because they stand to lose a greater initial investment. This, however, commits the ‘Concorde Fallacy’ as optimal decisions should depend on future pay‐offs not past costs. Although the argument can be rephrased in terms of residual reproductive value when past investment affects future pay‐offs, it remains weak. The factors likely to change future pay‐offs seem to work against females providing more care than males. The second argument takes the reasonable premise that anisogamy produces a male‐biased operational sex ratio (OSR) leading to males competing for mates. Male care is then predicted to be less likely to evolve as it consumes resources that could otherwise be used to increase competitiveness. However, given each offspring has precisely two genetic parents (the Fisher condition), a biased OSR generates frequency‐dependent selection, analogous to Fisherian sex ratio selection, that favours increased parental investment by whichever sex faces more intense competition. Sex role divergence is therefore still an evolutionary conundrum. Here we review some possible solutions. Factors that promote conventional sex roles are sexual selection on males (but non‐random variance in male mating success must be high to override the Fisher condition), loss of paternity because of female multiple mating or group spawning and patterns of mortality that generate female‐biased adult sex ratios (ASR). We present an integrative model that shows how these factors interact to generate sex roles. We emphasize the need to distinguish between the ASR and the operational sex ratio (OSR). If mortality is higher when caring than competing this diminishes the likelihood of sex role divergence because this strongly limits the mating success of the earlier deserting sex. We illustrate this in a model where a change in relative mortality rates while caring and competing generates a shift from a mammalian type breeding system (female‐only care, male‐biased OSR and female‐biased ASR) to an avian type system (biparental care and a male‐biased OSR and ASR).     

Paternal effects on functional gender account for cryptic dioecy in a perennial plant

Natural selection operates on the mating strategies of hermaphrodites through their functional gender, i.e. their relative success as male versus female parents. Because functional gender will tend to be strongly influenced by sex allocation, it is often estimated in plants by counting seeds and pollen grains. However, a plant's functional gender must also depend on the fate of the seeds and pollen grains it produces. We provide clear evidence of a paternal effect on the functional gender of a plant that is independent of the resources invested in pollen. In the Mediterranean tree Fraxinus ornus, males coexist with hermaphrodites that disperse viable pollen and that sire seeds; the population would thus appear to be functionally androdioecious. However, we found that seedlings sired by hermaphrodites grew significantly less well than those sired by males, suggesting that hermaphrodites may be functionally less male than they seem. The observed 1 : 1 sex ratios in F. ornus, which have hitherto been difficult to explain in the light of the seed-siring ability of hermaphrodites, support our interpretation that this species is cryptically dioecious. Our results underscore the importance of considering progeny quality when estimating gender, and caution against inferring androdioecy on the basis of a siring ability of hermaphrodites alone.     

Do Characteristics of Parental Child Homicide in Sweden Fit Evolutionary Predictions?

Evolutionary models have been used to explain parental child homicide. One idea is that children with low fitness value to their parents will be less loved and cared for and therefore more at risk in conflict situations. It is then important to investigate if conflicts with the children are the major pattern in cases of parental child homicide. The aim of this study is to survey the background circumstances of parental child homicide in Sweden and relate them to the evolutionary model suggested. We more specifically investigate if the homicides occur in conflict situations with the child, the frequency of several victims (including the partner or former partner) and if there are differences in characteristics of homicides between stepparents and genetic parents. Our results show that parental child homicide is a heterogeneous phenomenon, where relatively few cases were the result of a conflict with the child‐victims. Instead severe conflicts between parents were the most common circumstance in which children were killed. Many children were victims of an extended suicide, which often included several members of the family. Step‐parents were more likely to kill children aggressively in conflicts with them than genetic parents. The complexity of the phenomenon suggests that an evolutionary model based upon a mechanism related to conflicts with the child‐victim has limited explanatory value on parental child homicide in general.     

Expression of anatomical leaf traits in homoploid hybrids between deciduous and evergreen species of Vaccinium

We investigated the anatomical expression of leaf traits in hybrids between evergreen Vaccinium vitis‐idaea and deciduous V. myrtillus. We compared parents from four populations with their respective F1 hybrids and tested whether (i) transgression can be the source of novel anatomical traits in hybrids; (ii) expression of transgressive traits is more probable for traits with similar values in parents and intermediate for more distinct values, as predicted by theory; and (iii) independent origin of hybrids leads to identical trait expression profiles among populations. We found that anatomical leaf traits can be divided into four categories based on their similarity to parents: intermediate, parental‐like, transgressive and non‐significant. Contrary to the common view, parental‐like trait values were equally important in shaping the hybrid profile, as were intermediate traits. Transgression was revealed in 17/144 cases and concerned mainly cell and tissue sizes. As predicted by theory, we observed transgressive segregation more often when there was little phenotypic divergence, but intermediate values when parental traits were differentiated. It is likely that cell and tissue sizes are phylogenetically more conserved due to stabilising selection, whereas traits such as leaf thickness and volume fraction of the intercellular spaces, showing a consistent intermediate pattern across populations, are more susceptible to directional selection. Hybrid populations showed little similarity in expression profile, with only three traits identically expressed across all populations. Thus local adaptation of parental species and specific genetic background may be of importance.