Many criticisms can be made of the practice of dividing the population into social classes solely on the basis of occupation. This paper reports the results of an attempt to improve one aspect of such classifications (The Registrar General's Classification). The lowest social class (social class V) is the most heterogeneous of all the classes; it is suggested that it can usefully be subdivided into a ‘stable’ and an ‘unstable’ social class. Into the stable class (V) go the steadily employed, though unskilled, men and their families. Into the unstable class (V) would go those families most lacking in skill and property, signified by long-term or frequent unemployment, or the complete absence of a male head of the household. An attempt is made to justify this subdivision both theoretically and empirically by the demonstration that there are significant differences between social classes V stable and V unstable with regard to selected social class attributes.

Data for 6910 families each containing one set of twins have been obtained from genealogical records in the Archives of the Mormon Church in Salt Lake City and analysed according to intervals between births. The findings indicate that intervals following singleton females are shorter than those following singleton males, particularly in sibships in which the sex ratio (excluding twins) is high. This relationship holds, with few exceptions, when sibship size is held constant and whatever the sex of the following child. There is no evidence in these data that the interval between births is shorter when the children are of the same sex. Our most striking finding is that twins tend to be preceded by an unusually long interval.

Some of the literature on the interrelationships between suicidal acts, accidents, surgical operations and other forms of violent experience is reviewed.

It was postulated that persons making suicidal attempts would, more commonly than non-suicidal controls, have encountered violent experiences during their life-time. To test this hypothesis, 50 persons attempting suicide were compared with 50 non-suicidal psychiatric patients and with 50 healthy persons attending a chest clinic. The groups were matched for age, sex and social class.

Using a questionnaire, all relevant data were recorded. Classes of violent experience were graded numerically on a basis of severity and on the degree of responsibility of the person involved. It was found that the suicidal patients had significantly higher violence scores than either control group, a finding which remained significant when previous suicidal attempts were excluded from the score. The possible implications of this finding are discussed.

In 1966, a National Survey on Fecundity and Fertility was organized in Belgium. Approximately 3000 married women under 41 years of age and living with their husbands were interviewed and asked about their reproductive histories. The present paper records the sociobiological aims and methods and some preliminary results of this survey. The aims were to:

(1) study the influences of contraception on human needs and qualities, in this case mainly potential fecundity;

(2) study the influence of attempts to increase the potential fecundity level in modern society on fecundity gene frequencies;

(3) study the influences of the overall socio-cultural environment on fecundity and fertility variables with particular reference to differences in social status in Western society;

(4) analyse the role of social assortment of fecundity and fertility variables on the biological structure, and possibly the composition, of modern populations.

A relatively large, but far from complete body of data has been collected on a number of individual fecundity and fertility variables, on the medical processes employed to increase fecundity, on contraception, and on a number of conventional sociological and demographic variables.

The principles underlying the present approach to the study of fecundity are explained, and a few preliminary results for one of the general fecundity classifications are shown.

The information collected on contraception has been qualitatively analysed and a correction and evaluation method is described. Data on the use of the different contraceptive methods show that substantial sections of the Belgian population are limiting their family size in a way which is inefficient, from both sexual and familial standpoints.

From statistics on Australian confinements during the period 1944–63 it seems that the following conclusions can legitimately be drawn:

(1) The proportion of multiple births increases with increasing age of mother up to about age 37, turns, and decreases thereafter.

(2) The proportion of multiple births increases with increasing age of father up to about age 34–38 and is fairly constant thereafter.

(3) The variation with age of father, however, only arises because of the high correlation with age of mother which is the determining factor.

(4) The proportion of multiple confinements increases with birth order. This effect holds for all ages of mother except those over 40 where there is no significant variation.

(5) The proportion of multiple confinements decreases from the first year of marriage to the second, then increases steadily to a maximum after about 15 years of marriage and then decreases slightly.

(6) The proportion of binovular twins increases steadily with increasing age of mother up to about age 37, turns, and thereafter decreases steadily.

(7) The proportion of monovular twins increases slightly with increasing age of mother up to about age 37 and is fairly constant thereafter.

(8) From the small amount of data it appears that the proportion of triplets also increases with increasing age of mother.

The first Hammond Memorial Lecture was given in London in March 1969 by Dr C. P. McMeekan, CBE, formerly Director of the Ruakura Research Centre in New Zealand, afterwards on the staff of, and currently consultant to, the World Bank. Apart from its special interest to those engaged in animal science, the lecture contained much of general interest to natural and social scientists and we are grateful to Dr McMeekan, the Hammond Memorial Trustees and the British Society for Animal Production, under whose auspices the lecture was delivered, for permission to print a substantial portion of it in the Journal of Biosocial Science.

Some of the selected material is provocative. For instance, it would be interesting to know the basis of the assumption that world population having risen to 6000 million by the end of this century, will then stabilize. Again, many will disagree with the estimates of unused usable land. But all of the material stimulates thought and we are glad to have the opportunity of publishing it.

After discussing the outstanding achievements of Sir John Hammond and the progress of animal science generally, Dr McMeekan continued: