Genetic and environmental contributions to prosocial behaviour in 2- to 9-year-old South Korean twins

Although over 50 twin and adoption studies have been performed on the genetic architecture of antisocial behaviour, far fewer studies have investigated prosocial behaviour, and none have done so on a non-western population. The present study examined mothers' ratings of prosocial behaviour in 514 pairs of 2- to 9-year-old South Korean monozygotic and dizygotic twins. Correlational analyses showed a tendency of increasing genetic effects and decreasing shared environmental effects with age although shared family environment effects and the moderating effects of age did not attain statistical significance in model-fitting analyses. The best-fitting model indicated that 55% (95% CI: 45-64%) of the variance in the 2- to 9-year-olds' prosocial behaviour was due to genetic factors and 45% (95% CI: 36-55%) was due to non-shared environmental factors. It is concluded that genetic and environmental influences on prosocial behaviour in young South Koreans are mostly similar to those in western samples.     

Genetic contributions to the association between height and intelligence: Evidence from Dutch twin data from childhood to middle age

A positive association between intelligence (IQ) and height has been reported previously. It is generally assumed that this association reflects the effect of childhood environment on IQ, but there is still little research supporting directly this hypothesis. We studied the association between height and IQ in 209 Dutch twin pairs at the ages of 5, 7, 10 and 12 years, 208 twin pairs at 16 and 18 years of age and 567 twin pairs and their siblings in adulthood. The heritability of height was high in all cohorts and across all ages (a² = 0.93 − 0.96). In adulthood, heritability was also high for full-scale IQ (FSIQ: a² = 0.83–0.84) and somewhat lower for verbal IQ (VIQ: a² = 0.66–0.84). In early childhood, the heritability was lower, and common environmental factors had a substantial effect on FSIQ and VIQ. A positive association of height and IQ was found in early childhood and adolescence. In adulthood, a correlation was found between height and FSIQ in young adulthood and between height and VIQ in middle age. All correlations could be ascribed to genetic factors influencing both height and IQ. Thus, these results show that the association between height and IQ should not be directly regarded as evidence for childhood living conditions affecting IQ, but the effect of genetic factors affecting independently or interacting with environmental factors should be considered as well.     

Genetic and environmental influences on factors associated with cardiovascular disease and the metabolic syndrome

The relative influence of genetics and the environment on factors associated with cardiovascular disease (CVD) and metabolic syndrome (MetS) remains unclear. We performed model-fitting analyses to quantify genetic, common environmental, and unique environmental variance components of factors associated with CVD and MetS [waist circumference, blood pressure, fasting plasma glucose and insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and fasting plasma lipids] in adult male and female monozygotic twins reared apart or together. We also investigated whether MetS components share common influences. Plasma cholesterol and triglyceride concentrations were highly heritable (56–77%, statistically significant). Waist circumference, plasma glucose and insulin, HOMA-IR, and blood pressure were moderately heritable (43–57%, statistically significant). Unique environmental factors contributed to the variance of all variables (20–38%, perforce statistically significant). Common environmental factors contributed 23, 30, and 42% (statistically significant) of the variance of waist circumference, systolic blood pressure, and plasma glucose, respectively. Two shared factors influenced MetS components; one influenced all components except HDL cholesterol, another influenced only lipid (triglyceride and HDL cholesterol) concentrations. These results suggest that genetic variance has a dominant influence on total variance of factors associated with CVD and MetS and support the proposal of one or more underlying pathologies of MetS.     

Genetic and environmental contributions to the expression of handedness in chimpanzees (Pan troglodytes)

Most humans are right‐handed and, like many behavioral traits, there is good evidence that genetic factors play a role in handedness. Many researchers have argued that non‐human animal limb or hand preferences are not under genetic control but instead are determined by random, non‐genetic factors. We used quantitative genetic analyses to estimate the genetic and environmental contributions to three measures of chimpanzee handedness. Results revealed significant population‐level handedness for two of the three measures—the tube task and manual gestures. Furthermore, significant additive genetic effects for the direction and strength of handedness were found for all three measures, with some modulation due to early social rearing experiences. These findings challenge historical and contemporary views of the mechanisms underlying handedness in non‐human animals.     

Radio‐telemetry shows differences in the behaviour of wild and hatchery‐reared European grayling Thymallus thymallus in response to environmental variables

Juvenile wild and hatchery‐reared European grayling Thymallus thymallus were tagged with radio‐transmitters and tracked in the Blanice River, River Elbe catchment, Czech Republic, to study their behavioural response to stocking and environmental variation. Both wild and hatchery‐reared T. thymallus increased their diel movements and home range with increasing light intensity, flow, temperature and turbidity, but the characteristics of their responses differed. Environmental variables influenced the movement of wild T. thymallus up to a specific threshold, whereas no such threshold was observed in hatchery‐reared T. thymallus. Hatchery‐reared fish displayed greater total migration distance over the study period (total migration) than did wild fish, which was caused mainly by their dispersal in the downstream direction.     

Genetic and environmental influences on Anxious/Depression during childhood: a study from the Netherlands Twin Register

For a large sample of twin pairs from the Netherlands Twins Register who were recruited at birth and followed through childhood, we obtained parental ratings of Anxious/Depression (A/D). Maternal ratings were obtained at ages 3 years (for 9025 twin pairs), 5 years (9222 pairs), 7 years (7331 pairs), 10 years (4430 pairs) and 12 years (2363 pairs). For 60-90% of the pairs, father ratings were also available. Multivariate genetic models were used to test for rater-independent and rater-specific assessments of A/D and to determine the genetic and environmental influences on individual differences in A/D at different ages. At all ages, monozygotic twins resembled each other more closely for A/D than dizygotic twins, implying genetic influences on variation in A/D. Opposite sex twin pairs resembled each other to same extent as same-sex dizygotic twins, suggesting that the same genes are expressed in boys and girls. Heritability estimates for rater-independent A/D were high in 3-year olds (76%) and decreased in size as children grew up [60% at age 5, 67% at age 7, 53% at age 10 (60% in boys) and 48% at age 12 years]. The decrease in genetic influences was accompanied by an increase in the influence of the shared family environment [absent at ages 3 and 7, 16% at age 5, 20% at age 10 (5% in boys) and 18% at age 12 years]. The agreement between parental A/D ratings was between 0.5 and 0.7, with somewhat higher correlations for the youngest group. Disagreement in ratings between the parents was not merely the result of unreliability or rater bias. Both the parents provided unique information from their own perspective on the behavior of their children. Significant influences of genetic and shared environmental factors were found for the unique parental views. At all ages, the contribution of shared environmental factors to variation in rater-specific views was higher for father ratings. Also, at all ages except age 12, the heritability estimates for the rater-specific phenotype were higher for mother ratings (59% at age 3 and decreasing to 27% at age 12 years) than for father ratings (between 14 and 29%). Differences between children, even as young as 3 years, in A/D are to a large extent due to genetic differences. As children grow up, the variation in A/D is due in equal parts to genetic and environmental influences. Anxious/Depression, unlike many other common childhood psychopathologies, is influenced by the shared family environment. These findings may provide support for why certain family therapeutic approaches are effective in the A/D spectrum of illnesses.     

Blood group antigens and the population genetics of Macaca mulatta on Cayo Santiago. I. Genetic differentiation of social groups

The red blood cell phenotypes for eight polymorphic loci were determined for 293 free-ranging Macaca mulatta living on Cayo Santiago; this number represents the total population of the island, disposed in four social groups plus peripheral males. The rhesus population shows significant genetic heterogeneity over blood group systems (loci) and social groups. No particular genetic locus or social group is solely responsible for the genetic heterogeneity observed. The distributions of genotypes for two loci (G and H) do not deviate significantly from Hardy-Weinberg expectations within social groups or in the population as a whole. Correction of the equilibrium expectations for the effect of population subdivision yields no statistically significant results. Overall, the results suggest that the interaction of a variety of processes (random genetic drift, founder effect, migration and selection) may be responsible for the diversity observed. These data, combined with those from further studies, may allow an application of behavioral and genetic knowledge to the study of microevolutionary processes among nonhuman primates.     

Genetic and Environmental Influences on the Tracking of Body Size from Birth to Early Adulthood

Objective: This study identified genetic and environmental influences on the tracking of body size from birth to 16 to 18.5 years of age. Research Methods and Procedures: Longitudinal information was collected from a nationally representative sample of Finnish twin adolescents (birth cohorts 1975 to 1979) and their parents through questionnaires mailed when the twins were ages 16 and 18.5 years old. The sample included 702 monozygotic, 724 same‐sex dizygotic, and 762 opposite‐sex dizygotic sets of twins. The measures used were length, weight, ponderal index (kilograms per cubic meters), and gestational age at birth, and height, weight, and body mass index (kilograms per square meters) at 16 to 18.5 years of age. The changes in genetic and environmental influences on body size from birth to early adulthood were analyzed by quantitative genetic modeling. Results: The twins who had a higher weight or ponderal index at birth were taller and heavier in early adulthood, whereas those who were longer at birth were taller, but not heavier, later in life. Adult height was affected more by the birth size than body mass index. In the genetic modeling analyses, the genetic factors accounting for the variation of body size became more apparent with age, and both genetic and environmental influences on stature had a sizable carry‐over effect from birth to late adolescence, whereas for relative weight, the influences were more age‐specific. Discussion: The genetic and environmental architecture of body size changes from birth to adulthood. Even in monozygotic twins who share their genetic background, the initially larger twin tended to remain larger, demonstrating the long‐lasting effects of fetal environment on final body size.