Consistent findings about the inverse association of social network level with coronary heart disease mortality and morbidity suggest the importance of investigating biological pathways of association. Differences in plasma fibrinogen level were investigated among middle-aged men with weak and strong structural and functional social network ties. Men with low scores in the adequacy of social participation variable (structural) had higher mean values of plasma fibrinogen than those with high scores. The difference remained after adjustment for age, smoking and cardiovascular health status and after possible modifying factors were taken into account, but did not remain significant after allowing for physical fitness. Men with high scores in overall support (functional) had higher plasma fibrinogen levels compared to the men with low scores. This difference persisted after age and cardiovascular health status were taken into account but was explained by smoking. The data suggest that smoking and cardiorespiratory fitness are important mediating or modifying factors between structural and functional aspects of social network ties and plasma fibrinogen.

The relationships between selected demographic and socioeconomic variables and current use status of contraception were examined using logistic regression technique. Information on current contraceptive use was provided by 3156 out of 4488 currently married women aged 15–49 interviewed in the 1988 Ghana Demographic and Health Survey. Respondents' approval of family planning emerged as the most important predictor of current contraceptive use, followed by discussion of family planning with partner and level of education. As a policy measure, information, education and communication programmes on family planning should be intensified, particularly in rural areas. Female education, at least up to secondary level, should be given top priority.

Illegitimacy in a historic, single community at Penrith, Cumbria (1557–1812), has been studied using aggregative analysis, family reconstitution and time series analysis. This population was living under extreme conditions of hardship. Long, medium and short wavelength cycles in the rate of illegitimacy have been identified by time series analysis; each represents a different response to social and economic pressures. In a complex interaction of events, the peaks of the cycles in wheat prices were associated with rises in adult mortality which promoted an influx of migrants and a concomitant rise in illegitimacy. The association between immigration and illegitimacy was particularly noticeable after the mortality crises of the late sixteenth and early seventeenth centuries. Children of immigrant families also tended to produce illegitimate offspring. Native and immigrant families responded differently to extrinsic fluctuations, and variations in their reproductive behaviour were probably related to access to resources.

Data on patterns of marriage, differential fertility and mortality were collected from 211 Kotia women residing in Visakhapatnam district of Andhra Pradesh, India. Consanguineous marriages made up just over a quarter of the total, and of these, father's sister's daughter (FSD) were more common than mother's brother's daughter (MBD). The mean inbreeding coefficient for the sample (F) was 0·0172. Women in consanguineous marriages had a lower mean number of total conceptions, live births and living offspring (net fertility) than women in non-consanguineous marriages. Significant heterogeneity was found in the means of living offspring for FSD, MBD and non-consanguineous couples, but not for conceptions and live births.

Classification of the boys in 48 families of three or more brothers according to their Moray House Test (VIQ) scores awarded at age 11±1½ years in 1947–75 confirms the postulated existence of a total of nine male phenotypes for this X-linked trait in the score range <70 to 140 points. The phenotypic means lie close to the sequence 69(8)133. Recombination is shown to occur. An additive effect of three alleles at each of two X-chromosome loci is the most likely simple scheme. An iterative approach matching the observed mixtures of proposed genotypes in the families with probabilities for variable levels of homozygosity, non-crossover/crossover heterozygosity, and maternal meiotic recombination yields a best goodness of fit where this last is 20%.

Botswana is one of the sub-Saharan countries where actual fertility has declined. This study examines the fertility preferences of both men and women and shows that fertility intentions have a significant influence on future fertility behaviour. Fertility preferences are relatively low and there is no significant difference between those of men and women. Men's preference for sons influences desired family size and eventual fertility. For women as well as men, child survival is an important factor. Women's income is also influential.

Marriage patterns of California's eighteenth and nineteenth century Spanish-Mexican families are analysed using data from genealogies and mission records. A shortage of women among the military based colonists led to an unusual marriage pattern with a large age differential between husbands and wives. The average age at marriage was 18·4 years for women and 28·4 years for men. Spatial mobility was high for both sexes, particularly for men. More husbands than wives were born in Mexico. The Monterey presidial district of central California was the birthplace of a disproportionate number of husbands and the southern California districts were a source of wives. The transition between a founding population predominantly composed of Mexican immigrants and a population of native-born Californians occurred at the beginning of the nineteenth century.

The cost effectiveness of several modes of family planning service delivery based on the cost per couple-year of protection (CYP), including commodity costs, is assessed for 1991–92 using programme and project data from fourteen developing countries (five in Africa, four in Asia, three in Latin America and two in the Middle East). More than 100 million CYP were provided through these family planning services during the 12 months studied. Sterilisation services provided both the highest volume (over 60% of total) and the lowest cost per CYP ($1.85). Social marketing programmes (CSM), delivering almost 9 million CYPs, had the next lowest cost per CYP on average ($2.14). Clinic-based services excluding sterilisation had an average cost of $6.10. The highest costs were for community-based distribution projects (0·7 million CYPs), which averaged $9.93, and clinic-based services with a community-based distribution component (almost 6 million CYPs), at a cost of $14.00 per CYP. Based on a weighted average, costs were lowest in the Middle East ($3.37 per CYP for all modes of delivery combined) and highest in Africa ($11.20).

Trends in multiple birth rates are thought to have been substantially affected by subfertility treatments in the last 25 years, but there are few quantitative assessments of this. This paper examines trends in twin and higher multiple birth rates separately in Scotland, England and Wales and compares their course with corresponding multiple birth rates in the Oxford Record Linkage Study area, where the proportions following subfertility treatment are documented. National data on prescriptions for subfertility treatments reinforce the view that they have had a major effect on the trends, and currently perhaps 60% of triplet and higher order births and 15% of twins follow their use in Britain.

The tenth Annual Workshop of the Biosocial Society will be held on Friday 2 May 1997 at University College Stockton, University Boulevard, Thonaby-on-Tees.