Hostility-related variables have been categorized as to kinds of emotions, attitudes, and behaviors. Relatively few studies have explored whether genetic factors contribute to individual differences in these variables. Moreover, the majority of this research has involved male subjects. The present study utilized the twin method to evaluate the influence of genetic factors on hostility-related emotions, namely, trait anger and irritability, hostility-related attitudes, namely cynical hostility and suspiciousness, and hostility-related behaviors, namely, physical, verbal, and indirect aggression in adult women. Responses on the measure of trait anger showed evidence of significant heritability. However, evidence for a genetic component to responses on the irritability scale was less clear. There was no support for the notion of a genetic component to the measure of suspiciousness, and the evidence of a genetic contribution for cynical hostility was not significant. It was expected that due to environmental influences for women, only certain forms of aggression would show genetic variance, namely, verbal and indirect as opposed to physical forms. The results were generally congruent with these expectations.

Surnames can be used to investigate the genetic structure of human populations. The repeated-pairs approach (RP) uses information on the repetition of the same pairs of names from marital data sets to indicate the influence of clanlike behavior on mate choice. RP estimates the subdivision of the population into subgroups that breed among themselves and the kind of inbreeding ascribed to the Wahlund effect. The application of this method to the Fog0 Island, Newfoundland, data set indicates a large percentage excess of observed over random repetitions. Presumably at least a part of this excess in the island population is due to denominational subdivision and endogamy. The expected relationship between RP and heterozygosity is observed in this case. Given these results, it would seem worthwhile to explore the relationship between the frequency of repetitions of pairs of surnames in marriages and genetic variation in other populations as well and, at the same time, to begin to inquire into the validity of such assumptions concerning the use of surnames as the monophyletic origin of common names.

Numerous studies have shown that longevity is moderately heritable in human populations. Longevity, however, contains limited information on functional status, since individuals may exhibit differential survival patterns. In this study, we employed a stepwise multiple regression approach to estimate biological aging in a Mennonite population, using chronological age as a dependent variable and various predictors of chronological age including subphenotypes related to diabetes, coronary heart disease, hypertension, renal function, and markers of functional ability. The residual (the difference between chronological and predicted ages) is considered a marker of biological age. In fact, two different data sets were used to obtain residuals due to the availability of data. In each analysis, chronological age was regressed on predictor variables in a stepwise manner, retaining the variables significant at the 5% level. The first analysis (N=729) included 6 significant predictors (R(2)=44.3%): glucose, blood urea nitrogen (BUN), cholesterol, albumin, systolic blood pressure (SBP), and ln potassium, and the second analysis (N=232) included 9 significant predictors (R(2)=71.5%): BUN, albumin, SBP, low-density lipoprotein cholesterol, forced expiratory volume in 1 sec (FEV1), grip strength, trunk flexibility, reaction time, and FEV1xsex. Using a variance components approach, we found that the data set-specific residuals were significantly heritable (h(2)+/-SE): first analysis=0.265+/-0.106, and second analysis=0.469+/-0.180. The residuals from the second data set appear to be more informative for biological aging, perhaps due to the inclusion of functional ability-related phenotypes in addition to the blood chemistry variables. In summary, we have shown that markers of biological aging in Mennonites are under substantial additive genetic influences.