The hypothesis that measures of sub-adult mortality rates in natural fertility populations are associated with subsistence practices in a selected cross-cultural sample (n=39) was tested. After controlling for both distance from the equator and the general likelihood of cultural similarities between genetically closely related cultures using phylogenetic comparative methods, it was found that dependence on extractive modes of subsistence (hunting, gathering and fishing) was a significant positive correlate of total child mortality (15q0). Both increases in dependence on foraging and permanent settlement were associated with increases in child mortality between pairs of historically related cultures. The results indicated little association between infant mortality (1q0) and either dependence on foraging or settlement.

This study examines wife–husband preference for children and subsequent fertility for a period of 5 years in the treatment and comparison areas of Matlab, Bangladesh. The two data sets used were: the In-depth Survey (1984) and the Demographic Surveillance System (1984–89). In the case of wives' preferences for children, subsequent childbearing was 13·8% higher than desired in the treatment area and 44·7% higher than desired in the comparison area. After controlling for all variables in the model, the likelihood of giving birth was 1·78 times higher for wives who wanted no more children, but whose husbands did want more, compared with couples where neither husband nor wife wanted more children. For couples where the wife wanted more, but the husband did not want more children, the likelihood of giving birth was 0·63 times that of couples where both the husband and wife wanted more children. This finding suggests that to enhance the decline in fertility in these two areas of Matlab, it will be necessary to motivate both wives and husbands to cease childbearing.

Fisher (1930) presented both theoretical and empirical results concerning genetic influences on fertility. Since then, only sparse research has been done on the genetics of fertility, although more sophisticated methodogy and data now exist than were available to Fisher. This paper presents a behavioural genetic analysis of age at first intercourse, accounting for genetic, shared environmental, and selected non-shared environmental influences. The data came from the nationally representative National Longitudinal Survey of Youth (NLSY). A newly developed kinship linking procedure was used that identifies links for cousins, half-siblings, full-siblings and twins in the NLSY. The results suggest a genetic influence in the overall dataset, and also among whites and in male–male and opposite-sex pairs. Genetic influences were extremely small or non-existent for blacks and for female–female pairs. Shared environmental influences were small for most subsets of the data, but moderate for female–female pairs. Two specific non-shared environmental influences – self-esteem and locus of control – were ruled out as accounting for any meaningful variance, although other general sources of non-shared environmental influence appear potentially important. Analysis of selected samples from upper and lower tails suggested that genetic influences are important in accounting for both early and late non-virginity. These findings are consistent with work reported by Miller et al. (1999), who used molecular genetic methods. Generally, these findings support the existence of genetic influences and implicate non-shared environmental influences as being important determinants of the timing of loss of virginity among US adolescents and young adults.

The dopaminergic system in the brain seems to play an important role in the regulation of sexual behaviour. The relationship between genes for the D1, D2 and D4 dopamine receptors and age at first sexual intercourse (AFSI) was examined in a sample of 414 non-Hispanic, European–American men and women. A significant association was observed between a DRD2 allele and AFSI and an even stronger association when the DRD2 allele was interacted with a DRD1 allele. A constrained regression model was constructed predicting AFSI using sex and a group of nine psychosocial variables as predictors. Adding the DRD2 and the DRD2-by-DRD1 predictors to this model increased the explained variance by 23 and 55%, respectively. Although these findings suggest a stronger association among males than among females, further research will be necessary to clarify this question, as well as to establish whether the observed association holds in other racial/ethnic groups.

The status of women, which is relative and multidimensional, has an important bearing on any long-term reduction in fertility. In Indian society, where cohabitation and childbearing are socially sanctioned only after marriage, the length of the first-birth interval affects the completed family size by influencing the spacing and childbearing pattern of a family. This study examines the influence of certain aspects of the status of married women – education, employment, role in family decision making, and age at marriage – along with three socioeconomic variables – per capita income of the family, social position of the household, and the caste system – on the duration of the first-birth interval in an urban Hindu society of the north-east Indian state of Assam. The data were analysed by applying life table and hazard regression techniques. The results indicate that a female's age at marriage, education, current age, role in decision making, and the per capita income of the household are the main covariates that strongly influence the length of the first-birth interval of Hindu females of urban Assam. Of all the covariates studied, a female's education appears to be a key mediating factor, through its influence on her probability of employment outside the home and thereby an earned income and on her role in family decision making. Unlike other Indian communities, the effect of the caste system does not have a significant effect on first-birth timing in this urban Hindu society.

In Tokyo Megalopolis, long-distance commuting between residences in the suburbs and work places in the centre of the city was examined. Using a questionnaire, heads of household in two suburbs were asked about the influences of long commuting hours on their daily time budgets. The results showed that on workdays, the workers who spent longer commuting rose and left home for work earlier, and came back home and retired later; accordingly, both time spent on in-home activities on workdays and hours slept on the day before a workday were shorter. Comparison of time budgets between the subjects who work 5 and 6 days per week revealed more vulnerable influences of long commuting hours in the former than the latter. The expected health consequences of these findings are discussed from a biosocial/human ecological viewpoint.

Qualitative research and cross-sectional survey methods were used in a study conducted in rural and urban areas of the Greater Accra Region, Ghana, to explore people's understanding of the cause of malaria and patterns of mosquito avoidance, in particular bed net ownership and use. The study indicated far higher bed net ownership and use in rural than urban areas, which was related partly to perceived affordability and partly to the different contexts of and reasons for avoiding mosquitoes. Knowledge of an association between mosquitoes and malaria, the most common cause of illness in both areas, was related to residence but not to literacy or formal education, and this knowledge did not predict bed net use. The paper points to the complexity of social and personal factors implicated in behavioural interventions for malaria control, and questions behavioural models that assume a linear relationship between knowledge and practice.

Analysis of the 1992 Niger Demographic and Health Survey showed that although roughly two-thirds of both polygamous and monogamous women approve of birth control, polygamous wives are less likely than monogamous wives to discuss family size or birth control with their husband or to plan on using birth control. The study suggests that characteristics of polygamous couples have caused polygamous women to be more resistant to birth control use than monogamous women. The polygamous women tended to be married to older men who had not gone to primary school and who desired more children than monogamous husbands. The influence of marital structure is not significantly associated with intention to use birth control when the husband's age and the wife's ideal number of children were controlled for in the multivariate logistic regression model suggesting that background social factors may be more influential. In fact, educational level and age at first marriage were significantly associated with attitudes towards birth control and also with marital structure.

Using a sub-sample of ever-married women from the 1993 Ghana Demographic and Health Survey (GDHS), this study examines differentials in contraceptive use in six cultural groups: Ga-Adangbe, Twi, Fante/other Akans, Ewe, Guan/others and Mole-Dagbani. Multivariate analysis is used to explore whether reported ethnic differentials in contraceptive use can be attributed to ethnicity or to other characteristics that distinguish the ethnic groups. Overall, the findings are generally more consistent with the 'characteristics' hypothesis, because contraceptive use differentials by ethnic group is accounted for by differences in socioeconomic and demographic characteristics of these women. However, for the Fante/other Akans, even after the necessary controls, ethnicity continued to emerge as a significant determinant of contraceptive use. Programmatic implications of these results are discussed.

Fertility rates in Pakistan have remained consistently high over the past three decades. While numerous studies have examined sociodemographic determinants, the role of biological factors, and particularly consanguinity, has received little attention, even though marriage between close biological relatives continues to be the norm in Pakistan. Reproductive behaviour among women in consanguineous (first cousin) and non-consanguineous unions was compared, using data from a 1995 study of multi-ethnic communities in Karachi and the 1990–91 Pakistan Demographic & Health Survey (PDHS). The results show that, although female age at first marriage has been gradually rising in both study samples, women in consanguineous unions married at younger ages and were less likely to use modern contraceptive methods. In the Karachi sample, women in first cousin unions experienced a higher mean number of pregnancies and also reported a higher mean number of children ever born (CEB). However, their mean number of surviving children did not differ from those born to women in non-consanguineous unions, implying higher prenatal and/or postnatal losses in couples related as first cousins. On the other hand, the PDHS showed both lower CEB values for women in consanguineous marriages and a lower number of surviving children. Given the continuing popularity of consanguineous marriage, these findings have important implications for future fertility reduction in Pakistan.