Matrilateral biases in the investment of aunts and uncles

In a study of the kin investment of aunts and uncles we show that the laterality effect expected as a result of paternity uncertainty is statistically reliable but somewhat smaller than the sex effect. Matrilateral aunts invest significantly more than patrilateral aunts, and the same is true for uncles. Regardless of laterality, however, aunts invest significantly more than uncles. Multivariate controls show that the matrilateral bias is fully independent of any age or distance confounds that might result from sex differences in age at marriage or dispersal. We discuss our results in relation to recent findings on the kin investment of grandparents (Euler and Weitzel 1996). In addition, we propose a simple method for estimating the level of paternity uncertainty from kin investment data; application of this method to our data on aunts and uncles suggests that between 13% and 20% of children are not the offspring of their putative father. Our parallel analyses of Euler and Weitzel’s (1996) data on grandparental investment suggest a similar estimate, that paternity uncertainty lies between 9% and 17%.     

Multifactorial inheritance with cultural transmission and assortative mating. III. Family structure and the analysis of separation experiments.

Demographic data about family composition or structure in the United States is reviewed. About 25% of white children and a majority of black children are reared in either broken or extended families, and this must be taken into consideration for valid studies of cultural inheritance. Atypical family structures are described including those in which parents include: biological parents, stepparents, grandparents, uncles, aunts, sibs, foster parents, and their spouses. General formulae for a wide variety of kinship correlations are derived using path analysis. The multifactorial model presented allows for cultural inheritance, polygenic inheritance, correlated sibling environments, and phenotypic assortative mating (as previously described for intact families) plus extensions necessary for the analysis of separation experiments. These extensions allow for variable family structure and differences in parental influence due to separation, age or stage of development of the child, birth order, or type of relationship. Family structure is observed to have a marked effect on familial resemblance. Computer simulation studies demonstrate marked heterogeneity among phenotypic correlations for kinships of the same degree of genetic relationship arising in different family structures. Analyses of multiple types of sibs and other relatives in variable family structures offer great promise for the study of cultural inheritance.     

Matrilateral biases in the investment of aunts and uncles

Gaulin, McBurney, and Brakeman-Wartell (1997) found that college students reported both matrilateral and sex biases in the investment of aunts and uncles (aunts invested more than uncles). They interpreted the matrilateral bias as a consequence of paternity uncertainty. We replicated that study with Orthodox Jewish college students, selected because they come from a population we presume to have higher paternity certainty than the general population. The Orthodox sample also showed matrilateral and sex biases. Comparing the two data sets, the Orthodox sample reported more investment, and slightly less matrilateral and sex biases, but the differences were not statistically significant. We did find an interaction between sex of relative and group membership, resulting from greater investment by Orthodox uncles. We interpret the results as reflecting the operation of a facultative investment mechanism whose upper limit is tuned to the maximum levels of paternity certainty found in ancestral environments. Lack of a difference in matrilateral bias between groups may result from levels of paternity certainty near to, or above, that maximum in both groups.     

Grandparental Effects on Fertility Vary by Lineage in the United Kingdom

Grandparental presence is known to correlate with the number of grandchildren born, and this effect may vary according to grandparental sex and lineage. However, existing studies of grandparental effects on fertility mostly concern traditional subsistence societies, while evidence from contemporary developed societies is both scarce and mixed. Here, we explore how grandparents affect the transition to second and subsequent children in the contemporary United Kingdom. The longitudinal Millennium Cohort Study (n = 10,295 families) was used to study the association between grandparental investment and parents’ probability of having a new child within 4.5 years. Results show that contact with paternal grandparents is associated with higher probability of parents having a second child. In contrast, contact with maternal grandparents is associated with lower probability of having a third or subsequent child. Kin may have opposite effects on fertility even in contemporary societies, which may explain the lack of consistent effects of grandparental investment on fertility in previous studies.     

Peanut allergy in relation to heredity,maternal diet,and other atopic diseases: results of a questionnaire survey,skin prick testing,and food challenges.

OBJECTIVES: To determine rates of other atopic manifestations in people with peanut allergy and the prevalence of such allergy in their families. DESIGN: A survey of people with self reported peanut allergy and people referred by their general practitioner for suspected peanut allergy; survey and skin testing of 50 children with reported peanut allergy and their available first degree relatives. SUBJECTS: 622 adults and children with reported, suspected, or known peanut allergy. MAIN OUTCOME MEASURES: Prevalence of peanut allergy and other allergies in the families of people with peanut allergy. RESULTS: 622 valid completed questionnaires were returned out of the 833 questionnaires dispatched (74.7%). All forms of atopy were both more common in successive generations (P < 0.0001) and more common in maternal than paternal relatives (P < 0.0001). Peanut allergy was reported by 0.1% (3/2409) of grandparents, 0.6% (7/1213) of aunts and uncles, 1.6% (19/1218) of parents, and 6.9% (42/610) of siblings. Consumption of peanuts while pregnant or breast feeding was more common among mothers of probands aged < or = 5 years than mothers of probands aged > 5 years (P < 0.001). Age of onset correlated inversely with year of birth (r = -0.6, P < 0.001). Skin prick testing of 50 children with reported peanut allergy and their families: 7 probands (14%) had a negative result for peanut. Peanut allergy was refuted by food challenge in all those tested (5/7). No parent and 13% (5/39) of siblings had a positive result on skin prick testing for peanut. Two of these siblings had negative challenge with peanuts. The prevalence of peanut allergy in siblings is therefore 3/39 (7%). CONCLUSIONS: Peanut allergy is more common in siblings of people with peanut allergy than in the parents or the general population. Its apparently increasing prevalence may reflect a general increase of atopy, which is inherited more commonly from the mother. Peanut allergy is presenting earlier in life, possibly reflecting increased consumption of peanut by pregnant and nursing mothers.     

The effects of kin propinquity on infant mortality

This study tests the grandmother hypothesis and analyzes the effect of kin propinquity on infant mortality in a 19th century American frontier communal, polygynous population. The study shows that the presence of maternal grandmothers, aunts, uncles, and paternal aunts were significantly associated with increased infant survivorship while grandfathers, paternal grandmothers, and paternal uncles showed little effect. This study has implications for understanding the evolution of a long postreproductive life span, postmarital residential strategies, and behavioral strategies that enhance inclusive fitness.     

Is there a relationship between sex of cystic fibrosis carriers and sex ratio of their offspring?

Summary Data on the offspring of 198 aunts and 179 uncles of 100 cystic fibrosis index cases were analyzed. Aunts showed higher average number of liveborn sons than uncles. No significant difference was observed in the number of liveborn female offspring. When the sample was subdivided with respect to family size, the proportion of liveborn sons of aunts appeared higher than that of uncles in all classes.The present observations suggest that a female carrier may have a higher probability of male offspring than a male carrier and that she may be mainly responsible for the sex ratio deviations previously reported in sibships of cystic fibrosis patients.     

Excess of malignancies in grandparents of children with malformations? Short communication

In a prospective study, the occurrence of malignancies in children referred to genetic counseling for congenital malformations, in their sibs, parents and grandparents was registered in 120 families by means of personal interviews. One hundred-and-twenty age matched subjects, admitted for acute respiratory infections or trauma, served as controls. No difference in the occurrence of tumors or leukemias between the two groups was found when the values of patients, sibs, and parents were compared. At the same time, the grandparents of probands with malformations had had significantly more malignancies than the grandparents of the controls. This may be explained by the fact that grandparents lived beyond the age of the usual onset of common cancers and leukemias.     

Racism,disadvantage and multiculturalism: towards effective anti-racist praxis

Measuring ethnicity in any society is a challenge. Given world immigration patterns, many countries face a growing dilemma in determining the cultural antecedents of their populations. A further complication is the reality that such determination occurs within the political and nationalistic settings where ethnic‐cultural groups may be potent forces in their own right. As societies mature and evolve, there is an increasing tendency for populations, especially those with many generations of residence in the country, to see themselves as ‘indigenous’ to the society in which they live. Canada is not alone in having to deal with the fluidity of the concept, ‘Canadian’, ‘American’, ‘Australian’, ‘Yugoslav’, and ‘Soviet’ are parallel concepts in other countries of multiple ethnic composition. Using 1991 National Census Test results, the article explores some of the parameters of the indigenous category ‘Canadian’. In particular, the location in Canada and mother tongue of respondents reporting ‘Canadian’ as the ethnic origin of their parents and grandparents or as their own ethnic identity are important indicators for this emerging ethnic category.     

Parental investment and child health in a Yanomam? village suffering short-term food stress.

The 1998 El Ni?o significantly reduced garden productivity in the Upper Orinoco region in Venezuela. Consequently, parents were forced to allocate food carefully to their children. Nutrition data collected from village children combined with genealogical data allowed the determination of which children suffered most, and whether the patterns of food distribution accorded with predictions from parental investment theory. For boys, three social variables accounted for over 70% of the variance in subcutaneous fat after controlling for age: number of siblings, age of the mother's youngest child, and whether the mother was the senior or junior co-wife, or was married monogamously. These results accord well with parental investment theory. Parents experiencing food stress faced a trade-off between quantity and quality, and between investing in younger versus older offspring. In addition, boys with access to more paternal investment (i.e. no stepmother) were better nourished. These variables did not account for any of the variance in female nutrition. Girls' nutrition was associated with the size of their patrilineage and the number of non-relatives in the village, suggesting that lineage politics may have played a role. An apparent lack of relationship between orphan status and nutrition is also interesting, given that orphans suffered high rates of skin flea infections. The large number of orphans being cared for by only two grandparents suggests that grooming time may have been the resource in short supply.     

Grandparental investment as a function of relational uncertainty and emotional closeness with parents

Several theoretical perspectives have generated research on grandparental investment, notably socialization and evolutionary psychological perspectives. Using data collected from more than 200 older adults (mean age 67 years), we test three hypotheses derived from socialization and evolutionary perspectives about grandparents’ relationships with and investment in grandchildren. Results indicate that (1) emotional closeness with both children and children-in-law is positively related to reports of emotional closeness with grandchildren; (2) maternal grandmothers invest more in grandchildren than do other grandparents; and (3) grandparents invest more in daughters’ children than in sons’ children. Discussion addresses limitations of self-report methodology in this context and situates the current findings within the body of research indicating the existence of psychological mechanisms designed to guide differential nepotism.     

A familial association between twinning and upper-neural tube defects.

An increased twinning rate has been observed in the near relatives (sibs, parents, and aunts and uncles) of probands with neural tube defects (NTDs) occurring at the level of the 11th thoracic vertebra and above (upper NTDs). The twin rate was more than double that of the near relatives of probands with lower NTDs and of those of probands with Mendelian disorders (the controls). The excess twinning was same sex and can therefore consist of either MZ or same-sex DZ twins. Furthermore, upper-NTD families with twins had a higher NTD-sibling occurrence rate than did families without twins. These findings, if corroborated, may imply an etiology common to twinning and NTDs and can perhaps be applied in counseling NTD families.     

Offspring production among the extended relatives of Samoan men and fa'afafine

Androphilia refers to sexual attraction to adult males, whereas gynephilia refers to sexual attraction to adult females. Male androphilia is an evolutionary paradox. Its development is at least partially influenced by genetic factors, yet male androphiles exhibit lower reproductive output, thus raising the question of how genetic factors underlying its development persist. The sexual antagonism hypothesis posits that the fitness costs associated with genetic factors underlying male androphilia are offset because these same factors lead to elevated reproduction on the part of the female relatives of androphilic males. Western samples drawn from low fertility populations have yielded inconsistent results when testing this hypothesis. Some studies documented elevated reproduction among the matrilineal female kin of androphilic males, whereas others found such effects in the paternal line. Samoa is a high-fertility population in which individuals reproduce closer to their maximum capacities. This study compared the reproductive output of the paternal and maternal line grandmothers, aunts, and uncles of 86 Samoan androphilic males, known locally as fa'afafine, and 86 Samoan gynephilic males. Reproductive output was elevated in the paternal and maternal line grandmothers, but not aunts or uncles, of fa'afafine. These findings are consistent with the sexual antagonism hypothesis and suggest that male androphilia is associated with elevated reproduction among extended relatives in both the maternal and paternal line. Discussion focuses on how this study, in conjunction with the broader literature, informs various models for the evolution of male androphilia via elevated reproduction on the part of female kin.     

The General Factor of Personality (GFP) and parental support: testing a prediction from Life History Theory

In the present study, we tested whether the General Factor of Personality (GFP) is related to the level of parental support. The GFP is assumed to occupy the apex of the hierarchy of human personality structure and is believed to reflect a socially and sexually selected aggregate of behavioral characteristics that are generally valued as “desirable” in interpersonal relationships. The relationship between the GFP and parental support tested in this study is predicted by Life History Theory, a midlevel evolutionary account of systematic differences in evolved reproductive strategies. A total of 428 families with mother, father, and two children (range 14–16 years) participated. Parents filled out personality questionnaires (Big Five) and their level of parental support. The children also independently rated the amount of support they perceived from their parents. In the present sample, parents' GFPs were found to explain 33% of the variance in the Big Five. Moreover, the parents' GFPs showed significant relationships with the parents' self-rated parental support, but also with the child-rated parental support. The monoinformant (parents ratings) and multi-informant (parent and child ratings) data support the notion of a substantive GFP that is related to the investment of parents into their offspring.     

The three pillars of the new family.

Children are the chief sufferers from the growing fragility of marriages and partnerships. They may also suffer from their mothers going out to paid work unless satisfactory alternative arrangements are made for their care, for instance, by bringing in grandparents to look after their grandchildren when the mothers are not at home. Grandparents may also have an important role when parents separate. There is a dearth of facts about what actually happens. The part played by grandparents has been touched on, but nothing more, in the course of studies in baby care and baby-sitting and the repercussions of the illness of the mother. A Grandparent Commission is proposed to set in motion some of the necessary research and to review official policy as it affects grandparents. If grandparents already do a lot for children, and could do more, a measure of optimism about the future of the family could succeed the prevailing pessimism.     

Studying parents and grandparents to assess genetic contributions to early-onset disease

Suppose DNA is available from affected individuals, their parents, and their grandparents. Particularly for early-onset diseases, maternally mediated genetic effects can play a role, because the mother determines the prenatal environment. The proposed maximum-likelihood approach for the detection of apparent transmission distortion treats the triad consisting of the affected individual and his or her two parents as the outcome, conditioning on grandparental mating types. Under a null model in which the allele under study does not confer susceptibility, either through linkage or directly, and when there are no maternally mediated genetic effects, conditional probabilities for specific triads are easily derived. A log-linear model permits a likelihood-ratio test (LRT) and allows the estimation of relative penetrances. The proposed approach is robust against genetic population stratification. Missing-data methods permit the inclusion of incomplete families, even if the missing person is the affected grandchild, as is the case when an induced abortion has followed the detection of a malformation. When screening multiple markers, one can begin by genotyping only the grandparents and the affected grandchildren. LRTs based on conditioning on grandparental mating types (i.e., ignoring the parents) have asymptotic relative efficiencies that are typically >150% (per family), compared with tests based on parents. A test for asymmetry in the number of copies carried by maternal versus paternal grandparents yields an LRT specific to maternal effects. One can then genotype the parents for only the genes that passed the initial screen. Conditioning on both the grandparents' and the affected grandchild's genotypes, a third log-linear model captures the remaining information, in an independent LRT for maternal effects.     

Genetic analysis of febrile convulsions: twin and family studies

Summary Thirty-two twin pairs and 673 sibship-cases with febrile convulsions (FC) were studied. Twin study: (1) The pairwise concordance rate for FC was 56% (10/18 pairs) in monozygotic and 14% (2/14 pairs) in dizygotic twins (P<0.05). (2) Intra-pair similarity of clinical symptoms in concordant twin pairs was greater than that in sibship-cases. Sibship-pair study (population): (3) In sibship-pair study a large positive correlation of some clinical symptoms — in particular, age at onset of FC, exogenous factors, and degree of fever (P<0.001 for each) — was indicated. (4) Compared with FC children with no family history, those with such family history had a higher frequency of age at onset between 8 and 19 months, exogenous factors, low degree of fever before onset of convulsions, many recurrences, and recurrence after age 3 (P<0.01–0.001 for each). (5) Morbidity risk among near relatives was highest in first-degree relatives (16%) than in second (4.0%) or third-degree relatives (4.1%). The following differences were found: siblings (24%)>parents (12%), uncles (4.5%)>aunts (3.5%), male cousins (4.4%)>female cousins (3.8%). Segregation ratio, influence by affection of father or mother, and maternal preponderance were analysed. (6) Similar findings were also observed in the clinic study. (7) A multifactorial mode of inheritance for FC receives some support from this study, and the heritability was estimated to be 75% in the population study. The results may be useful for genetic counselling for FC.     

Perceived mate fidelity and paternal resemblance predict men's investment in children

Here, we investigate whether variation in male parental investment can be explained in terms of (1) men's perception of the degree of resemblance between themselves and their offspring and (2) men's perception of their mates' fidelity. In a sample of men from London's Heathrow airport, both variables were found to predict reported investment. We also examined whether the predictors of investment varied when men were no longer in a relationship with the mother of their children and are therefore no longer investing in mating effort with them. Among men no longer in a relationship with the mother of their children, resemblance became a stronger predictor of investment, while fidelity was no longer a significant predictor. Overall, men provided less investment to their children if they were no longer in a relationship with the mother of their children.     

Predictors of Grandparental Investment Decisions in Contemporary Europe: Biological Relatedness and Beyond

Across human cultures, grandparents make a valued contribution to the health of their families and communities. Moreover, evidence is gathering that grandparents have a positive impact on the development of grandchildren in contemporary industrialized societies. A broad range of factors that influence the likelihood grandparents will invest in their grandchildren has been explored by disciplines as diverse as sociology, economics, psychology and evolutionary biology. To progress toward an encompassing framework, this study will include biological relatedness between grandparents and grandchildren, a factor central to some discipline''s theoretical frameworks (e.g., evolutionary biology), next to a wide range of other factors in an analysis of grandparental investment in contemporary Europe. This study draws on data collected in the Survey of Health, Ageing and Retirement in Europe from 11 European countries that included 22,967 grandparent–child dyads. Grandparents reported biological relatedness, and grandparental investment was measured as the frequency of informal childcare. Biological and non-biological grandparents differed significantly in a variety of individual, familial and area-level characteristics. Furthermore, many other economic, sociological, and psychological factors also influenced grandparental investment. When they were controlled, biological grandparents, relative to non-biological grandparents, were more likely to invest heavily, looking after their grandchildren almost daily or weekly. Paradoxically, however, they were also more likely to invest nothing at all. We discuss the methodological and theoretical implications of these findings across disciplines.     

Cystic fibrosis—a single locus disease?

Summary In a population genetics study of cystic fibrosis (CF), we investigated the state of health of 1276 first cousins of CF index patients. Six hundred seventy-five married aunts and uncles (siblings of CF index patients' mothers and fathers) who had at least one child were interviewed. In only 1 of these 675 families, three children of a total of eight had died of CF. If CF occurs more frequently than in 1 in 3000 newborn babies in our population, our investigation supports the hypothesis that CF is caused by mutations at more than one locus. We also determined that the evidence furnished by such a study of other, more uncommon autosomal recessive disorders is limited.