Increasing Age Difference Research Articles

Epigenetic Aging Differs By Race, Subtype and Social Vulnerability Index in Breast Cancer Patients

Purpose: Although breast cancer (BrCa) disparities by age of onset, subtype and mortality are well recognized between Black and White women, the underlying causes remain unknown. We were interested in the impact of methylation on racial disparities, BrCa subtypes and social vulnerability index (SVI). Methods: A whole-genome methylation array was used with DNA extracted from blood samples from women diagnosed with BrCa. After quality control, 158 BrCa patients were included. The biological age and epigenetic age acceleration, defined as the residual from regressing chronological and biological age, were computed using Horvath and GrimAge clocks. The association with aging for the independent factors of self-reported race, BrCa molecular subtypes (ER and HER2), and SVI were evaluated with Mann-Whitney tests and linear regression models. Statistical significance was defined as a P value <0.05. Results: Nearly one-third of our sample were self-reported Black women (28.8%) and the overall mean age at diagnosis was 57.8 years ±11.6. The proportion of women diagnosed with ER− and HER2+ BrCa was 43.6% (N = 68) and 14.7% (N = 23), respectively. Overall, the mean age acceleration is estimated as 2.41 years greater for Black women compared to White women by the GrimAge clock (P = 0.005), and 0.87 years for the Horvath clock (P = 0.52). Among ER- BrCa subtypes, Black women had an average biological age of 1.68 years greater than White women (P = 0.24). Similarly, among HER2+ BrCa, the biological age for Black women was 2.62 years older than White women (P = 0.14). In addition, the SVI median stratified analysis identified a 1.24-year increased age difference for Black women compared to White women in the upper SVI. In the lower SVI stratified analysis, the biological age for Black women was 0.67 years younger than White women. Conclusions: Our analysis identified statistically significant epigenetic age acceleration differences between self-reported Black and White BrCa patients. Both stratified analyses by BrCa subtype and SVI yielded biological age differences by self-reported race, however, directional effects differed based on strata. Although our sample size is limited, our stratified analysis revealed novel research directions to better understand racial disparities in BrCa.

Inferring the age difference in HIV transmission pairs by applying phylogenetic methods on the HIV transmission network of the Swiss HIV Cohort Study.

Age-mixing patterns are of key importance for understanding the dynamics of human immunodeficiency virus (HIV)-epidemics and target public health interventions. We use the densely sampled Swiss HIV Cohort Study (SHCS) resistance database to study the age difference at infection in HIV transmission pairs using phylogenetic methods. In addition, we investigate whether the mean age difference of pairs in the phylogenetic tree is influenced by sampling as well as by additional distance thresholds for including pairs. HIV-1 pol-sequences of 11,922 SHCS patients and approximately 240,000 Los Alamos background sequences were used to build a phylogenetic tree. Using this tree, 100 per cent down to 1 per cent of the tips were sampled repeatedly to generate pruned trees (N = 500 for each sample proportion), of which pairs of SHCS patients were extracted. The mean of the absolute age differences of the pairs, measured as the absolute difference of the birth years, was analyzed with respect to this sample proportion and a distance criterion for inclusion of the pairs. In addition, the transmission groups men having sex with men (MSM), intravenous drug users (IDU), and heterosexuals (HET) were analyzed separately. Considering the tree with all 11,922 SHCS patients, 2,991 pairs could be extracted, with 954 (31.9 per cent) MSM-pairs, 635 (21.2 per cent) HET-pairs, 414 (13.8 per cent) IDU-pairs, and 352 (11.8 per cent) HET/IDU-pairs. For all transmission groups, the age difference at infection was significantly (P < 0.001) smaller for pairs in the tree compared with randomly assigned pairs, meaning that patients of similar age are more likely to be pairs. The mean age difference in the phylogenetic analysis, using a fixed distance of 0.05, was 9.2, 9.0, 7.3 and 5.6 years for MSM-, HET-, HET/IDU-, and IDU-pairs, respectively. Decreasing the cophenetic distance threshold from 0.05 to 0.01 significantly decreased the mean age difference. Similarly, repeated sampling of 100 per cent down to 1 per cent of the tips revealed an increased age difference at lower sample proportions. HIV-transmission is age-assortative, but the age difference of transmission pairs detected by phylogenetic analyses depends on both sampling proportion and distance criterion. The mean age difference decreases when using more conservative distance thresholds, implying an underestimation of age-assortativity when using liberal distance criteria. Similarly, overestimation of the mean age difference occurs for pairs from sparsely sampled trees, as it is often the case in sub-Saharan Africa.

Contraceptive non-use and emergency contraceptive use at first sexual intercourse among nearly 12 000 Scandinavian women.

The aim of this study was to describe recent patterns of contraceptive use at first sexual intercourse and to examine whether selected factors are associated with non-use and emergency contraceptive pill use at first sexual intercourse, among 18- to 26-year-old women from Denmark, Norway and Sweden. This was a population-based, questionnaire study of randomly chosen 18- to 26-year-old Scandinavian women. The prevalence of contraception methods used at first sexual intercourse was calculated. Factors associated with contraceptive non-use and emergency contraceptive pill use at first sexual intercourse were determined using log binomial models. The prevalence of contraceptive non-use and emergency contraceptive pill use was lowest in Denmark (9.6 and 2.1%, respectively) compared with Norway (14.1 and 4.4%) and Sweden (16.6 and 4.5%). The risk of contraceptive non-use increased in women who had first sexual intercourse at or before 14 years of age (13-14 years: prevalence ratio 1.40; 95% confidence interval 1.24-1.58). The risk of both non-use and emergency contraceptive pill use increased when the partner at first sexual intercourse was 20 years or older, and with increasing age difference between the partner and the woman at her first sexual intercourse. Smoking initiation prior to first sexual intercourse increased risk of contraceptive non-use (prevalence ratio 1.70; 95% confidence interval 1.50-1.92), and alcohol initiation prior to first sexual intercourse increased risk of emergency contraceptive pill use at first sexual intercourse (prevalence ratio 1.95; 95% confidence interval 1.49-2.54). Contraceptive non-use at first sexual intercourse was strongly associated with early age at first sexual intercourse. Emergency contraceptive pill and contraceptive non-use at first sexual intercourse were both strongly associated with increasing partner age and an increasing difference in age between the woman and her partner. Hence, young women should be educated to negotiate contraceptive use with their partners.

Interaction of older donor age and survival after weight-matched pediatric heart transplantation

Donors are matched for weight in pediatric heart transplantation (PHT), yet age differences are not considered in this decision. In this study we attempt to identify the effect of age differences in weight-matched patients and the effect these differences have on post-transplant survival. The United Network of Organ Sharing (UNOS) database was queried for the period from October 1987 to March 2014 for all pediatric heart transplant patients. Transplants with donor-to-recipient (D-R) weight ratios of 0.8 to 1.5 were identified (weight-matched). D-R age differences were categorized as: donors 5 years younger than recipients (D<R-5); donors within 5 years of recipients (D=R±5); and donors 5 years older than recipients (D>R+5). A total of 4,408 patients were identified as weight-matched transplants. Of these transplants, 681 were D>R+5, 3,596 were D=R±5 and 131 were D<R-5. D>R+5 transplants were found to be associated with decreased post-transplant survival compared with D=R±5 (p = 0.002). Rates of acute rejection were similar among all groups but post-transplant coronary allograft vasculopathy (CAV) was more prevalent in D>R+5 than D=R±5 patients (28% and 18%, respectively; p < 0.001). Increasing age difference by each year was associated with decreasing median post-transplant survival time (p < 0.001; hazard ratio 1.018, range 1.011 to 1.025). The overall negative association with mortality was due to the adolescent cohort (11 to 17 years), specifically D>R+5 transplants, utilizing organs from donors >25 of age. In PHT, increasing D-R age difference decreases survival; however, this effect is driven by recipients 11 to 17 years old and donors >25 years old. Allocation of younger donor organs to adolescent recipients should be a priority.

Alloparental behaviour in Sinai spiny mice Acomys dimidiatus: a case of misdirected parental care?

Communal breeding, where reproducing females share a nest and the care of their pups, occurs in many animal species. According to kin selection theory, alloparental behaviour should occur predominantly among closely related conspecifics. However, familiarity between females, a prerequisite for reciprocal altruism, may also play a role. The aim of our study was to analyse the effect of kinship and familiarity on the occurrence of two types of alloparental care—nursing and the retrieval of pups wandering from the nest—in a communally breeding rodent, the Sinai spiny mice Acomys dimidiatus. In addition, the effects of other factors that may also have an impact on alloparental care were tested; these included age difference between litters, pup age, maternal experience, pup sex ratio, litter size, group age, and mother’s weight. We found that kinship and familiarity had no effect on alloparental care. The nursing of alien pups depended on the maternal reproductive experience measured as the number of weaned litters and also on the age difference between the litters of both females. Less experienced females nursed alien pups more often than experienced ones. With increasing age difference between litters, females preferentially nursed their own pups. Similarly, the retrieval of alien pups was affected by the age disparity between the litters; with increased age difference, the females more readily retrieved their own pups. These results indicate that the occurrence of alloparental care in the Sinai spiny mouse may be more related to misdirected parental care than to kin selection.

High prevalence of sexually transmitted infections in pregnant adolescent girls in Tanzania: a multi-community cross-sectional study

BackgroundLimited data document sexually transmitted infections (STIs) among pregnant adolescents in sub-Saharan Africa, where prenatal screening typically includes only HIV and syphilis. Given that HIV incidence in this population is...

The Flynn effect in sibships: Investigating the role of age differences between siblings

Abstract The aim of the study was to investigate the relationship between the Flynn effect and the effects of age differences between siblings on the intelligence difference between them. In Norway, the secular trends in intelligence-test score means vary both in magnitude and direction. We identified three periods: one period where the mean intelligence increased across birth cohorts (1950–1956), one period where the means decreased (1976–1983), and one period with no appreciable Flynn effect (1960–1965). In a data base comprising birth year and intelligence data on more than 900,000 males meeting at mandatory conscription between their 18th and 21st birthday, we identified more than 69,000 brother pairs where both brothers had been born in exactly one of the periods mentioned above. In this study group the relationship between age differences between brothers and the intelligence difference could be studied. The results showed that in the period with increasing intelligence means across cohorts, the intelligence difference between brothers decreased with increasing age differences. In the period with decreasing means, the difference between the later-born and the earlier-born brother increased across age differences. No systematic effects of age difference on mean intelligence differences were found in the period without a Flynn effect. Regression analyses showed that the Flynn effect can be quite well predicted from the effects of the age differences between brothers on their intelligence-test scores. We conclude that the factors causing the Flynn effect also work within sibships. Hypotheses positing that the Flynn effect is solely caused by between-families factors (e.g. the heterosis hypothesis) are weakened. The present results also entail that the birth order effect observed in Norway is in part conditional on the Flynn effect.

Inheritance of fertility in broiler chickens

BackgroundThe fertility of a chicken's egg is a trait which depends on both the hen that lays the egg and on her mate. It is also known that fertility of an individual changes over the laying period.MethodsLongitudinal models including both random genetic and permanent environmental effects of both the female and her male mate were used to model the proportion of fertile eggs in a pedigree broiler population over the ages 29-54 weeks.ResultsBoth the male and the female contribute to variation in fertility. Estimates of heritability of weekly records were typically 7% for female and 10% for male contributions to fertility. Repeatability estimates ranged from 24 to 33%, respectively. The estimated genetic variance remained almost constant for both sexes over the laying period and the genetic correlations between different ages were close to 1.0. The permanent environment components increased substantially towards the end of the analyzed period, and correlations between permanent environment effects at different ages declined with increasing age difference The heritability of mean fertility over the whole laying period was estimated at 13% for females and 17% for males. A small positive correlation between genetic effects for male and female fertility was found.ConclusionOpportunities to improve fertility in broiler stocks by selection on both sexes exist and should have an impact throughout the laying period.

Intelligence Correlations Between Brothers Decrease With Increasing Age Difference

Research on twins and unrelated persons living together indicates that, although differences in intelligence between persons are caused by both genetic and environmental factors, similarities--and especially those between adults--are mostly or exclusively due to shared genes. However, twin and adoption designs have been criticized for incorrectly estimating the effects of the environment on the similarity between relatives, and studies of environmental effects in other family constellations may be enlightening. In a sample comprising more than 334,000 pairs of brothers (ages 18-21 years) who were tested at the mandatory conscription for military service in Norway, correlations between brothers' intelligence-test scores decreased with increasing age difference between the brothers. This result indicates that family environmental factors have an impact on the intelligence of young adults. Analyses of subgroups defined by family size and parental education demonstrated that the effects of age difference are essentially independent of these factors.

Competition between larvae in a butterfly Pieris napi and maintenance of different life‐history strategies

1. In scramble competition all individuals suffer equally from competition, whereas in contest competition some individuals outperform the others. Generally, larger individuals gain asymmetric advantage in competition over smaller ones. Given the positive correlation between age and size, asynchronous birth may result in asymmetric competition among juveniles. 2. In Pieris napi (Lepidoptera: Pieridae), reproductive rate is determined by the females' intrinsic mating tactic. The early reproductive rate is high in females with a low mating frequency and low in females with a high mating frequency, whereas lifetime fecundity shows the opposite pattern. Thus, offspring of monandrous females start to develop in relatively low densities and they are relatively large when the offspring of highly polyandrous females start to hatch. 3. The purpose of this study was to explore if asymmetry in larval competition could outweigh the late-life benefits of polyandry. In a laboratory experiment, P. napi larvae of different ages were reared together in different densities. 4. Increasing density decreased both larval survival and reachable pupal mass, but had no effect on duration of larval period. Younger larvae suffered from high mortality and reduced size compared with the older larvae. Mortality decreased in the older cohort with increasing age difference between the cohorts, and the reverse occurred in the younger cohort. Increasing age difference between the cohorts was associated with increase in pupal mass in both cohorts. All the variables showed a lot of variation between broods of different females. 5. The results suggest that polyandrous females, or more generally females with a low early reproductive rate, may lose a great proportion of their late-life benefits, which may partly explain the maintenance of polymorphism in reproductive strategies within species.

Genetic Regulation of Growth in Height and Weight from 3 to 12 Years of Age: A Longitudinal Study of Dutch Twin Children

Human growth is a complex and poorly understood process. We studied the effect of genetic and environmental factors on height and body mass index (BMI, kg/m(2)) based on maternal reports at 3, 4, 5, 7, 10 and 12 years of age in a large longitudinal cohort of Dutch twins (7755 complete twin pairs at age 3). Several multivariate variance component models for twins were fitted to the data using the Mx statistical package. The first-born twin was taller until age 10 and heavier until age 12 than the second-born co-twin. Heritability estimates were high for height (a(2) = .58-.91) and BMI (a(2) = .31-.82), but common and unshared environmental factors were also important. The phenotypic correlations across the ages for height and BMI were mainly explained by correlated additive genetic factors (r(a) = .77-.96 for height and .43-.92 for BMI), but common (r(c) = .40-.84 and .09-.78, respectively) and specific environmental correlations (r(e) = .50-.81 and .42-.80, respectively) were also significant. Additive genetic factors decreased with increasing age difference for both height and BMI. However, the full Cholesky model, which does not make any assumptions regarding the underlying genetic structure, had the best fit. High genetic correlations across the ages, especially for height, may help further molecular genetic studies of human growth. Environmental factors affecting height and BMI during growth period are also important, and further studies are needed to identify these factors and test whether they interact with genetic factors.

Intensification of the oxygen minimum zone in the northeast Pacific off Vancouver Island during the last deglaciation: Ventilation and/or export production?

The oxygen minimum zone (OMZ) off Vancouver Island was more oxygen depleted relative to modern conditions during the Allerød (∼13.5 to 12.6 calendar kyr) and again from ∼11 to 10 kyr. The timing of OMZ intensification is similar to that seen throughout the North Pacific, although the onset appears to have been delayed by ∼1500 years off Vancouver Island. Radiocarbon dating of coeval benthic and planktonic foraminifera shows that between 16.0 and 12.6 kyr the age contrast between surface and intermediate waters (920 m depth) off Vancouver Island was similar to, or slightly less than, that today. There is no evidence of an increased age difference (i.e., decreased ventilation) during the deglaciation, particularly during the Allerød. However, sedimentary marine organic carbon concentration and mass accumulation rate increased substantially in the Allerød, suggesting that increased organic matter export was the principal cause of late Pleistocene OMZ intensification off Vancouver Island.

Qualification status and estimation of breeding value in French trotters

The objective of this study was to review the current selection model for French trotters. Data were obtained from the French central registration system for horses—and contained records of performance at the age of 2 through 6 of 183,955 trotters born between 1975 and 1994, and 46,629 of their mothers born after 1966. Genetic parameters were obtained for six traits that could be included in a revised model. Because of the absence of selection of mares in this breed, maternal–offspring regression analysis was used to estimate heritabilities and genetic correlations. Parameters were estimated per age, per trait and over the whole career. Heritabilities were generally moderate except for number of starts, which were low (0.07–0.13) and earnings at the age of 6 (0.13). Regarding estimates per age, genetic correlations between binary traits and performance traits were generally high (0.52–0.99 for earnings and [−1.00]–[−0.53] for best time). Binary traits were all genetically similar in relation to performance traits. Regarding estimates per trait, genetic as well as phenotypic correlations decreased with increasing age difference. Heritabilities for career traits were generally higher than those for age traits. It was concluded that a model based on career traits could very well be used for the selection of French trotters, for both scientific and practical reasons. This model would then contain three traits: qualification status and career earnings as index traits and number of starts as covariable.

A Structural and Dynamical Study of Late-Type, Edge-on Galaxies. II. Vertical Color Gradients and the Detection of Ubiquitous Thick Disks

We present an analysis of optical (B-R) and optical-infrared (R-Ks) color maps for 47 extremely late-type edge-on unwarped, bulgeless disk galaxies spanning a wide range of mass. The color maps show that the thin disks of these galaxies are embedded in a low surface brightness red envelope. This component is substantially thicker than the thin disk (a : b ∼ 4 : 1 vs. >8 : 1), extends to at least 5 vertical disk scale heights above the galaxy midplane, and has a radial scale length that appears to be uncorrelated with that of the embedded thin disk. The color of the red envelope is similar from galaxy to galaxy, even when the thin disk is extremely blue, and is consistent with a relatively old (>6 Gyr) stellar population that is not particularly metal-poor. The color difference between the embedded thin disk and the red stellar envelope varies systematically with rotation speed, reflecting an increasing age difference between the thin and thick components in lower mass galaxies, driven primarily by changes in the age of the thin disk. The red stellar envelopes are similar to the thick disk of the Milky Way, having common surface brightnesses, spatial distributions, mean ages, and metallicities. We argue that the ubiquity of the red stellar envelopes implies that the formation of the thick disk is a nearly universal feature of disk formation and is not necessarily connected to the formation of a bulge. Our data suggest that the thick disk forms early (>6 Gyr ago), even within galaxies where the bulk of the stars formed very recently (<2 Gyr). We argue that several aspects of our data and the observed properties of the Milky Way thick disk argue in favor of a merger origin for the thick disk population. If so, then the age of the thick disk marks the end of the epoch of major merging, and the age difference between the younger thin disk and the older thick disk can become a strong constraint on cosmological constants and models of galaxy and/or structure formation.

Affiliation and aggression among adult female rhesus macaques: a genetic analysis of paternal cohorts

Kin selection promotes the evolution of social behaviour that increases the survival and reproductive success of close relatives. One prerequisite for kin selection is that individuals have the ability to discriminate between kin and nonkin. Studies incorporating data on paternal kinship are still rare, but in species with a high male reproductive skew, many adult females will be paternal half siblings. Using both microsatellites and DNA-fingerprinting, we here analyse data on paternal relatedness in order to compare the influence of maternal and paternal kinship on rates of affiliative and aggressive interactions among semi free-ranging adult female rhesus macaques (Macaca mulatta). Because paternal half siblings tend to be peers whereas maternal half siblings are almost always nonpeers, we also examine the interactions between age proximity and genetic relatedness on social behaviour. Genetic analyses show that male reproductive success is strongly skewed with 75% of infants within the troop having a paternal half sibling in the same age cohort. The highest rates of both affiliation and aggression occur among maternal half sisters. Adult females are significantly more affiliative, but not more aggressive, with paternal half sisters than with nonkin. Affiliative relationships declined in conjunction with increasing age difference among paternal half sisters, but the reverse effect was found for affiliative relationships among maternal half siblings. No association emerged among nonkin. Among both maternal and paternal kin, rates of affiliative and aggressive interactions increase as the degree of relatedness increased, thereby questioning the concept of a relatedness threshold as a mediator of social interactions in rhesus macaques. The asymmetry in affiliation and aggression between maternal and paternal half siblings, and the effect of age proximity on partitioning social interactions suggests that context-dependent kin discrimination characterises rhesus macaques. Paternal kin discrimination probably results from an interaction between phenotype matching and familiarity, rather than from one process or the other.

Effects of family characteristics on the labor force status of older married women in Finland

Using individual-level characteristics derived from the census of 1985 or earlier, the article examines labor force status (employment, unemployment, household work, retirement) of married Finnish women aged 45-64 on the basis of multinomial logit analysis. Controlling for background characteristics, i.e., age, education, health, industry and unemployment in the local labor market area, the effects of family characteristics were analyzed. Both higher family net income (excluding the income of the women concerned) and higher family liabilities were related to lower likelihoods of unemployment and retirement instead of employment. Household work was more likely with higher family income, but less likely with higher liabilities. A larger number of children living at home was related to the lower likelihood of women occupying non-employment statuses instead of employment. The spouses’ increasing age difference was related to the lower likelihood of unemployment and retirement instead of employment. The husband's labor force status was consistent with the wife’s labor force status.

Low genetic effect and age-specific family effect for symptoms of anxiety and depression in nuclear families, halfsibs and twins

Questionnaire information on symptoms of anxiety/depression was obtained from 61, 286 persons, most of whom could be grouped in families as spouses, parents, offspring, siblings, halfsibs and twins. The correlations between mental health in relatives, varying somewhat by sex, were: 0.27 for 18,768 pairs of spouses, 0.12 to 0.17 for 30,888 pairs of parents and offspring, 0.11 to 0.18 for 13,134 pairs of siblings, 0.27 to 0.35 for 57 pairs of MS twins, -0.06 to 0.10 for 60 pairs of DZ twins, 0.30 for 88 pairs of halfsibs reared together, and 0.16 for 40 pairs of halfsibs reared apart. The heritability was estimated to be between 0 and 0.20. There was a significant effect of environmental transmission from mother, but not from father, to offspring. The effect of environmental factors shared by sisters was substantial, the corresponding effect was lower in brothers, and zero in siblings of opposite sex. The correlations decreased with increasing age differences between relatives, implying effects of age-specific genes or environmental factors in the family.

Demographic factor affecting the fitness of polyandry for human males: A mathematical model and computer simulation

Polyandry has occurred rarely among humans; and has almost always consisted of brothers sharing a wife. The reduced opportunity for fertilization of females that occurs in polyandry would appear to make it a maladaptive mating system for human males. Previous evolutionary studies of human polyandry have suggested that kin selection may play a role in maintaining polyandry in some populations. A mathematical model for determining the fitness of polyandry for males is presented, and a simple deterministic analytic solution is derived. The model indicates that for polyandry to be an adaptive alternative to monogamy, the number of surviving offspring must be greater than the number of surviving offspring under monogamy times the number of males sharing a wife. This model exists in the literature. The unrealistic assumptions made in deriving this simple equation are revealed. An alternative stochastic computer simulation model is presented. The reproductive life history of a set of brothers is simulated under different demographic conditions, using data from polyandrous societies to estimate probabilities of fitness-related events. Under the assumption of equality of values of demographic variables for polyandry and monogamy, polyandry achieved or exceeded fitness parity with monogamy one third of the time. This contrasts with the prediction of the deterministic model stating that polyandry will never be an adaptive alternative to monogamy when fitness-related parameters are equal. The conditions improving fitness expectations for polyandry are conditions where genetic replication is decreased, i.e., with fewer brothers, high female sterility, decreased offspring survival, and decreased female fertility. Also, increased age difference between brothers enhances the fitness of polyandry. Genetic relatedness between brothers did not significantly affect the fitness of polyandry; therefore the kin selection hypothesis does not receive support. To a certain degree, these conditions exist for polyandrous populations in the Himalayas. Multivariate statistical analyses of simulation results revealed that most of the effects of these demographic factors could be accounted for by their association with increased probability of household extinction under monogamy and increased number of years of reproductive monogamy within polyandry. Although conditions favoring polyandry could be specified, analysis of the correlation between adaptiveness of polyandry and amount of genetic replication revealed that the demographic conditions favoring polyandry also lead to family extinction. Deficiencies in the model are discussed. It is suggested that future studies identify the advantages polyandry may have over monogamy in the values of demographic variables (e.g., increased offspring survival, increased extramarital reproduction), and take a multigenerational approach.

Analysis of Grooming Relationships in a Free-ranging Group of Japanese Macaques (Macaca fuscata)

This study was conducted on a free-ranging group of Japanese macaques (Macaca fuscata) at Katsuyama, Okayama Prefecture for 52 days during the period from June 1977 through June 1978. A total of 119 animals over the age of three years were observed and a total of 2, 467 bouts of groomings were collected.Of all the grooming bouts observed, 1, 561 (63. 3%) were between relatives. Of all the grooming between relatives, slightly less than 80% of groomings were performed between mothers and daughters. In both mating and non-mating seasons, groomings occurred predominantly between females. But in the mating season, the occurrences of cross-genealogical groomings between females decreased from 35. 8% to 12. 8% of all the grooming (Table 1).In cross-genealogical grooming between females, animals tended to groom dominant ones (73. 1%) more often than they did subordinate ones (26. 9%) (Fig. 1). Analysis of grooming relationships between non-genealogical females according to age differences indicated that occurrences of grooming declined with increasing age differences (Fig. 3).With respect to the characteristic of each genealogy in grooming relationships, animals in lower-ranking genealogies had grooming relationships predominantly with animals in their own genealogy. Proportion of groomings done by animals in lower-ranking genealogies declined with decreasing dominance ranking of genealogy. Grooming relationships between central males and females were maily determined by the leader-follower relationships rather than by the dominance relationships (Tables 2 and 3).These results illustrate that groomings performed between relatives differ from those performed between non-genealogical animals with respect to primary function of grooming, and that cross-genealogical groomings play an important role in integrating animals separated by kinship into a group.

Transient environmental effects detected in sibling correlations.

Detection of environmental effects in sibling correlation is difficult. Mueller (1978) has proposed that transient environmental effects should be associated with a decrease in the sibling correlation with increasing age difference between members of a pair of adult sibs. The present report suggests that an environmental effect can also be detected by partialing out environmental indicators from correlations between sibs measured at the same chronological age. Correlations for 12 variables were computed between 208 pairs of 10-year-old French-Canadian sibs from Montreal. Partialing out seven socio-economic indicators from these correlations resulted in significant changes for three skeletal measurements as well as for body weight and triceps skinfold. These results differ from those reported earlier. The proposed method may be sufficiently sensitive to detect environmental effects, provided simple assumptions are met.