Are stepchildren over-represented as victims of lethal parental violence in Sweden?

Evolutionary psychologists have suggested that stepchildren should be over-represented as victims of lethal parental violence compared with children living with their two genetic parents, because of relatively more lapses in parental solicitude among stepparents. In our study, using data over a period of 35 years in Sweden (1965-1999), there was no overall over-representation of stepchildren as victims. For very young stepchildren there was a tendency for over-representation. In families with both stepchildren and children genetically related to the offender, genetic children tended to be more likely to be victims.     

Genes and the intergenerational transmission of BMI and obesity

This paper compares the strength of intergenerational transmission of body mass index (BMI) and obesity in a sample of adoptees relative to a matched sample of biological children with similar observable characteristics. We find that BMI and obesity are strongly correlated among biological parent-child pairs, but there are no significant intergenerational associations in these health traits among adoptive parent-child pairs. The intergenerational elasticity of BMI for children to their parents is 0.2 in the matched biological sample, but indistinguishable from zero for adopted children with a standard error more than three times as large as the coefficient. Under reasonable assumptions, these findings indicate that the intergenerational transmission of BMI and obesity occurs primarily through genetic mechanisms. Additional analyses of transmission rates by parental gender and among step-parents and step-children support this conclusion. The role of determinants of BMI and obesity in the household environment in relation to our findings is discussed. Given the negative consequences of obesity on earnings and other economic measures, our results suggest that the genetic transmission of weight problems contributes substantially to intergenerational persistence in economic outcomes.     

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.     

Genetic and Familial Environmental Effects on Suicide – An Adoption Study of Siblings

Background

While there is clear evidence of familial influences on suicide, the origin of these is less certain. We have investigated genetic and familial environmental factors by studying the occurrence of suicide in biological and adoptive siblings of adoptees who died by suicide compared to siblings of surviving adoptees.

Method

We used the Danish Adoption Register and Danish population registers to compare 221 siblings of adoptees who died by suicide with the siblings of 1,903 adoptees who did not die by suicide. All adoptions in the Danish Adoption Register are non-familial, i.e. the adoptive parents are biologically unrelated to the adoptee. Analyses were conducted on incidence rates of suicide in biological and adoptive siblings given occurrence of suicide in the adoptees while also taking into account psychiatric disorders.

Results

The risk of suicide in full siblings of adoptees who died by suicide before age 60 years was significantly higher than in full siblings of adoptees who had not died by suicide (incidence rate ratios (IRR) = 5.01; 95% confidence interval [CI] = 1.28 - 19.6). This increase persisted after adjustment for history of psychiatric admission of siblings (IRR = 4.19; 95% CI = 1.00 - 17.5).

Conclusions

Genetic factors influence risk of suicide, probably independently of psychiatric disorder. This is relevant in provision of advice to families, including possible prevention of suicide.     

Family Type and Investment in Education: A Comparison of Genetic and Stepparent Families

Data from the U.S. National Education Longitudinal Survey were examined to investigate postsecondary educational investment in two-parent families. Consistent with hypotheses derived from the logic of inclusive fitness theory, contrasting children with two genetic parents with children from stepparent households on a multivariate composite of investment indicators revealed that stepchildren receive significantly less parental support for pursuit of higher education. Univariate tests on the three measures comprising the multivariate composite indicated that relative to children with two genetic parents, stepchildren have parents who (1) delay the start of savings accounts for postsecondary education, (2) put aside less money for subsidizing the costs of higher education, and (3) expect to allocate fewer economic resources to support the first year of postsecondary schooling. Statistical control of child ability, resource availability, and number of family members sharing in parental resources was accomplished in a second multivariate analysis by using child achievement, familial socioeconomic status, and number of financial dependents in each family as covariates. Statistically equating genetic and stepparent families on these measures reduced, but did not eliminate, the investment differences.     

Parental generalized EEG alpha activity predisposes to spike wave discharges in offspring

Familial and twin studies have shown that the individual variability of the normal human electroencephalogram (EEG) is largely genetically determined. In epileptology, these genetic parameters of the EEG background activity are almost totally neglected. The aim of the present study has been to investigate whether a special genetic type of background activity might be related to the pathogenesis of epilepsy. EEG recordings of parents of 257 epileptic children were evaluated retrospectively. Some 156 healthy adults served as controls. Special attention was paid to alpha activity extending to the frontal region, both in bipolar and in referential recordings (Alpha I). Alpha I was found significantly more often in parents of children with primary generalized epilepsy (18%) compared with parents of children with focal epilepsy (8%) or controls (9%). In a second step, parental EEGs of children with different EEG patterns associated with epilepsy were studied. Alpha I was found significantly more often in parents of children with focal sharp waves and generalized spikes and waves (26%) than in parents of probands with focal sharp waves without additional generalized spikes and waves (8%) or in controls (9%). Parents of probands with theta rhythms and spikes and waves had alpha I significantly more often (18%) than parents of probands with theta rhythms without additional spikes and waves (8%) or controls (9%). The findings reveal a clear correlation between the type of EEG background activity in parents and the EEG characteristics in their children, thus pointing to common mechanisms.     

Adoption Does Not Increase the Risk of Mortality among Taiwanese Girls in a Longitudinal Analysis

Adopted children often experience health and well-being disadvantages compared to biological children remaining in their natal households. The degree of genetic relatedness is thought to mediate the level of parental investment in children, leading to poorer outcomes of biologically unrelated children. We explore whether mortality is related to adoption in a historical Taiwanese population where adoption rarely occurred among kin. Using Cox proportional hazards models in which adoption is included as a time-dependent covariate, we show that adoption of girls does not increase the risk of mortality, as previously suggested; in fact, it is either protective or neutral with respect to mortality. These results suggest that socio-structural variables may produce positive outcomes for adopted children, even compared to biological children who remain in the care of their parents.     

Email submissions from outside the United Kingdom

ObjectivesTo identify whether psychiatric disturbance in parentally bereaved children and surviving parents is related to service provision.DesignProspective case-control study.SettingTwo adjacent outer London health authorities. Participants45 bereaved families with children aged 2 to 16 years.ResultsParentally bereaved children and surviving parents showed higher than expected levels of psychiatric difficulties. Boys were more affected than girls, and bereaved mothers had more mental health difficulties than bereaved fathers. Levels of psychiatric disturbance in children were higher when parents showed probable psychiatric disorder. Service provision related to the age of the children and the manner of parental death. Children under 5 years of age were less likely to be offered services than older children even though their parents desired it. Children were significantly more likely to be offered services when the parent had committed suicide or when the death was expected. Children least likely to receive service support were those who were not in touch with services before parental death.ConclusionsService provision was not significantly related to parental wishes or to level of psychiatric disturbance in parents or children. There is a role for general practitioners and primary care workers in identifying psychologically distressed surviving parents whose children may be psychiatrically disturbed, and referring them to appropriate services.

Key messages

• Parentally bereaved children show high levels of psychological disturbance, with boys being more vulnerable than girls
• Surviving mothers show more psychiatric morbidity than surviving fathers
• Psychological distress in bereaved parents is associated with psychological difficulties in their children
• Service provision for bereaved children is not determined by mental health difficulties in either parents or children, or by parental wishes; it is influenced only by the manner of parental death and the age of the child
• The mismatch between need and service provision indicates a role for general practitioners and primary care workers in identifying distressed or disturbed families in need of public or voluntary service help

     

Fostering relations: first sex and marital timings for children raised by kin and non-kin carers

Kinship fostering is generally preferred to non-kin fostering by policy makers in the U.S. and elsewhere. Researchers and policy makers alike tend to provide several proximate reasons for why this may be, generally neglecting an ultimate evolutionary framework. However, kin selection theory predicts that in the absence of genetically related parents, care from kin will result in the most similar life history outcomes. In low-fertility settings, parents typically favour increased investment in embodied capital and thus delayed reproductive life history strategy. Using archival data from the original Kinsey survey, collected in the U.S. from 1938 to 1963, we used survival analyses to compare the effects of living with kin and non-kin fosterers in childhood on timings of first sex and marriage. Our results support a kin selection hypothesis showing that while fostered children have accelerated life histories compared to children from “intact families”, kin fosterers buffer children from early sexual and reproductive behaviors, compared to children cared for by non-kin.     

A Preliminary Investigation of Parent–Progeny Olfactory Recognition and Parental Investment

The role of olfaction in kin recognition and parental investment is documented in many mammalian/vertebrate species. Research on humans, however, has only focused on whether parents are able to recognize their children by smell, not whether humans use these cues for investment decisions. Here we show that fathers exhibit more affection and attachment and fewer ignoring behaviors toward children whose smell they can identify than toward those whose smell they cannot recognize. Thus, olfaction might serve as a means for males to determine their genetic relatedness to purported offspring. We also demonstrate that mothers’ olfactory recognition and hedonistic ratings are linked with the use of physical punishment. Mothers report using more punishment with children whose odor they cannot recognize and less with children whose odor they rated as more pleasant. These results provide the first preliminary evidence in humans that olfactory cues may guide parents in the allocation of care.     

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.     

Some differential attributes of lethal assaults on small children by stepfathers versus genetic fathers

Killings of children less than five years of age by stepfathers versus (putative) genetic fathers are compared on the basis of Canadian and British national archives of homicides. In addition to previously reported differences in gross rates, the two categories of killings differed in their attributes. Beatings constituted a relatively large proportion of steppaternal homicides, whereas genetic fathers were relatively likely to shoot or asphyxiate their victims. A substantial proportion of killings by genetic fathers, but almost none of those by stepfathers, were accompanied by suicide and/or uxoricide. These contrasts lend support to the hypothesis that the differential risks incurred by children in different household types reflect the differential parental solicitude that is predictable from an evolutionary model of parental motivation.     

Genetic and early environmental components in sociodemographic influences on adult body fatness.

OBJECTIVE--To explore genetic and environmental contributions to the influence of parental social class and region of upbringing on adult human fatness. DESIGN--Survey of sample of adults who had been adopted in childhood to relate their body mass index to sociodemographic variables in a series of multiple linear regression analyses. SUBJECTS--4643 Subjects traced from a register of 5455 non-familial adoptees registered in 1924-47, of whom 3651 gave details of current height, weight, and occupation. The final sample totalled 2015 adoptees for whom there was also information on their region of upbringing and on the social class of their adoptive and biological fathers. MAIN OUTCOME MEASURES--Age, sex, body mass index, social class (of adoptee and adoptive and biological father), and geographical region. RESULTS--There was a significant inverse relation of adoptees'' body mass index with their own social class and that of both their biological and adoptive fathers. Adoptees raised in provincial areas had a significantly greater body mass index than did those raised in Copenhagen. A multivariate regression model, including age, sex, and social class of the adoptee, confirmed the significant independent influence of the social class of both adoptive and biological fathers and of region of rearing on adoptees'' body mass index. CONCLUSION--Both familial environmental and genetic factors contribute to the relation of parental social class to adult fatness, and they are partly independent of the effect of an individual''s own social class. The influence of region of upbringing on adult fatness is of environmental origin and is independent of social class characteristics.     

Good genes and old age: Do old mates provide superior genes?

It has been suggested that female preference for older mates in species without parental care has evolved in response to an alleged higher genetic quality of older individuals. This is based on the widespread assumption that viability selection produces older individuals that are genetically superior to younger individuals. In contrast, we propose that the oldest individuals rarely are genetically superior. Quantitative genetic models of life history evolution indicate that young to intermediately aged individuals are likely to possess the highest breeding values of fitness. This conclusion is based on four arguments: 1) Viability selection on older individuals may decrease or at least not substantially increase breeding values of fitness, because there may exist negative genetic correlations between late-age and early-age life history parameters, 2) Fertility selection is likely to raise the fitness of gametes produced by young individuals more than those produced by old individuals, because the covariance between fertility and fitness often decreases with age, 3) The history of selection on their parents makes younger individuals more fit than older individuals, 4) Germ-line mutations, which are generally deleterious, significantly decrease the breeding value of fitness of an individual throughout its lifespan, especially in males. Therefore, females that mate with the oldest males in a population are doing so for reasons other than to obtain offspring of high genetic quality.     

Evolution of egg dumping in a subsocial insect

Egg dumping, or abandonment of eggs and young to the care of other conspecifics, frees individuals from costs of maternal care while potentially imposing energetic and ecological costs on egg recipients. It is not clear, however, that egg dumping necessarily represents selfish manipulation of egg recipients, and in some ecological contexts, recipients may benefit from enlarged broods. Thus, egg dumping may either be mutually beneficial for dumpers and recipients or entail costs for dumpers that are compensated by other means, such as improving reproduction of genetically related egg recipients. Here I use field experiments to test the relative importance of manipulation (i.e., "parasitism"), mutualism, and kin selection in the evolution of egg dumping in the tingid lace bug Gargaphia solani. In support of mutualism and kin selection, I found that reproduction of egg recipient G. solani benefits from brood enlargement, most likely because eggs and gregarious nymphs find safety in greater numbers. But contrary to both parasitism and mutualism, egg dumper reproduction was not improved by offspring abandonment. Indeed, dumpers laid smaller clutches than recipients, and dumpers did not convert a survival advantage into greater future reproduction. Genetic analyses of a natural G. solani population revealed, however, that dumpers are related to their egg recipients. Moreover, Hamilton's rule showed that egg-dumping G. solani earn sufficient indirect genetic benefits for kin selection to favor the behavior. Thus, egg dumping in some species may be kin-selected cooperation rather than parasitism or mutualism.     

Hamilton's rule and kin competition: the Kipsigis case

Evolutionary studies of human behavior have emphasized the importance of kin selection in explaining social institutions and fitness outcomes. Our relatives can nevertheless be competitors as well as sources of altruism. This is particularly likely when there is local competition over resources, where conflict can lead to strife among nondispersing relatives, reducing or even negating the effects of relatedness on promoting altruism. Here, I present demographic data on a land-limited human population, utilizing large within-population variation in land ownership to determine the interactions between local resource competition and the benefits of kin in enhancing child survival, a key component of fitness in this population. As predicted, wealth affects the extent of kin altruism, in that paternal relatives (specifically father's brothers) appear to buffer young children from mortality much more effectively in rich than in poor households. This interaction effect is interpreted as evidence that the extent of nepotism among humans depends critically on resource availability. Further unanticipated evidence that maternal kin play a role in buffering children from mortality in situations where paternal kin control few resources speaks to the important role that specific local circumstance plays in shaping kin contributions to child welfare.     

Accepting Adoption’s Uncertainty: The Limited Ethics of Pre-Adoption Genetic Testing

An increasing number of children are adopted in the United States from countries where both medical care and environmental conditions are extremely poor. In response to worries about the accuracy of medical histories, prospective adoptive parents increasingly request genetic testing of children prior to adoption. Though a general consensus on the ethics of pre-adoption genetic testing (PAGT) argues against permitting genetic testing on children available for adoption that is not also permitted for children in general, a view gaining traction argues for expanding the tests permitted. The reasoning behind this view is that the State has a duty to provide a child with parents who are the best “match,” and thus all information that advances this end should be obtained. While the matching argument aims to promote the best interests of children, I show how it rests on the claim that what is in the best interests of children available for adoption is for prospective adoptive parents to have their genetic preferences satisfied such that the “genetics” of the children they end up adopting accurately reflects those preferences. Instead of protecting a vulnerable population, I conclude, PAGT contributes to the risks of harm such children face as it encourages people with strong genetic preferences to adopt children whose genetic backgrounds will always be uncertain.     

Development of Overweight in Children in Relation to Parental Weight and Socioeconomic Status

The purpose of the study was to test the hypothesis that socioeconomic status (SES) moderates the association between parental weight and changes in BMI from childhood to early adolescence. Participants included 428 twin children from 100 families with obese parents (“obese families”) and 114 sociodemographically matched families with normal‐weight parents (“lean families”) who were assessed in their homes (age = 4.4). Follow‐up study was conducted 7 years later (age = 11.2) on 346 children (81%). Complete data were available for 333 children. Family SES was indexed with maternal education. Children's weights and heights were measured to calculate BMI s.d. scores based on 1990 British norms. Overweight was defined as >91st BMI centile. In children with obese parents, BMI s.d. scores increased from 0.51 at age 4 to 1.06 at age 11. In children with lean parents, BMI s.d. scores decreased from 0.11 to 0.05. Prevalence of overweight remained stable from age 4 to 11 in children with lean parents (8% to 9%), but it more than doubled in children with obese parents (17% to 45%). There was a significant interaction between parental weight and family SES (P < 0.01), so that in children with lean parents there was no SES difference in the BMI status from age 4 to 11; however, in children with obese parents, the increase in adiposity was significantly greater in lower SES families. These results suggest that parental leanness confers significant protection against development of overweight in children regardless of family SES, while parental obesity is an adverse prognostic sign, especially in lower SES families.     

Water mold infection but not paternity induces selective filial cannibalism in a goby

Many animals heavily invest in parental care but still reject at least some of their offspring. Although seemingly paradoxical, selection can favor parents to neglect offspring of particularly low reproductive value, for example, because of small survival chances. We here assess whether filial cannibalism (FC), where parents routinely eat some of their own young, is selective in response to individual offspring reproductive value. We performed two independent laboratory experiments in the common goby (Pomatoschistus microps) to test whether caring fathers preferentially cannibalize eggs of a given infection history and paternity. While males did not discriminate kin from nonkin eggs, they consumed significantly more eggs previously exposed to water mold compared to uninfected eggs. Our findings clearly show that parents differentiate between eggs based on differences in egg condition, and thus complement the prevailing view that FC arises for energetic reasons. By preventing the spread of microbial infections, the removal of molded eggs can constitute an important component of parental care and may represent a key driver of selective FC in a wide array of parental fish.     

CLONING, PARENTHOOD, AND GENETIC RELATEDNESS

In this paper I examine what I take to be the best case for reproductive human cloning, as a medical procedure designed to overcome infertility, and argue that it founders on an irresolvable tension in the attitude towards the importance of being ‘genetically related’ to our children implied in the desire to clone. Except in the case where couples are cloning a child they have previously conceived naturally, cloning is unable to establish the right sort of genetic relation to make couples the parents of their cloned child. If anybody is the genetic parent of a cloned child it is the natural parent(s) of the DNA donor. Paradoxically, in order to resist the claims of the parents of the donor to the cloned child, the argument for human reproductive cloning must place more weight on the intention to parent a child, than we do in cases of ordinary reproduction. It must insist that the parental relation is established by the intentions of the couple who bring a clone into the world and not by their genetic relation to the child. The emphasis placed on intention as establishing the parental relationship works to undermine the justification for cloning in the first place. For cloning to play a useful role as a reproductive technology, it must allow couples to become parents who could do so no other way. However, to the extent that intention is sufficient to establish parenthood, adoption or surrogacy, which are existing alternatives to cloning, will serve equally well to allow couples to become parents.