Data were collected from 368 Rwanda women, 50 non-lactating and 318 lactating, to determine the effect of lactation on conception rate and the return of menstruation. During lactation the majority of conceptions were found to be delayed by some 15 months, but the family spacing effect was maximal during the first 9 months. By 27 months after delivery the contraceptive effect of lactation can be assumed to have largely disappeared.

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.

A survey was made of the new patients at the family planning clinics in Sheffield during 4 months in the first half of 1967. Two hundred and forty-two visited clinics at the outset of marriage and 806 had been married at least 6 months. The FPA had 894 patients and the LA 154. The wives of non-manual workers were over-represented at the FPA clinics but not at the LA clinics. The wives of semi-skilled and unskilled manual workers were generally under-represented. There is some evidence that relative accessibility affects clinic attendance. The most commonly used methods of contraception used before the clinic visit were condom and coitus interrupts—there were variations among different occupational groups. Among those able to give a firm answer there had been more unplanned pregnancies than planned, but not amongst the non-manual groups. 96 of the perimarital and 20 of the other patients were working full-time. The perimarital patients were equally divided in their choice of clinic methods—pill or cap. Among the other patients 49 were prescribed the pill, 27 IUD and 24 the cap.

Data are presented on the ethnological, demographic, reproductive, immunological and medical characteristics of the gypsy isolates in Slovenia. It is concluded that the Slovenian gypsies are a different ethnic group from the surrounding panmictic Slav population and on the basis of anthropological, linguistic, sociological and psychological characteristics their settlements can be characterized as isolates in the population genetics sense.

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.

The birth rates per 1000 married females of specified ages and durations of marriage generally attained their post-war maxima in 1946–47 and then declined. While this declining trend was a brief one for females of younger ages and shorter durations of marriage, it continued for females of older ages and longer durations. Since 1961 the rates for all (younger and older) women have declined markedly. Does this recent decline in annual fertility, especially that for females of younger ages and shorter durations of marriage, herald a decline in the total fertility of cohorts who have not yet completed their childbearing? Many believe it to be so. However, an examination of the cumulative fertility of cohorts marrying since 1936 showed that (a) the total fertility of cohorts who have completed their childbearing varied between a narrow range of 2500–3000 and (b) the cumulative fertility up to 5 or 10 years of marriage duration of later cohorts was considerably higher (13–40% higher) than that of earlier cohorts. These facts, and similar ones for Australia covering a wider period (Basavarajappa, 1964), are thought to suggest that the total fertility of cohorts who have not yet completed their childbearing might not be far outside the limits of 2500 and 3000.

1. It has not been possible to show that the frequency of red/green defectives is different in a school of art from that in the population as a whole, or that the distribution of frequencies of sub-types is different, either for men or women.

2. One colour defective out of seven did not know of the defect until tested in this research, four were tested by a doctor at school before coming to the college of art and two were tested informally by friends after coming to the college. In every case where it was used by non-psychologists the Ishihara Test seems to have given unsatisfactory information, and in this research it was very unsatisfactory except for crude screening.

3. All the subjects showed surprising powers of adaptation, partly as a result of realizing their difficulties consciously and learning to avoid colours which would give rise to difficulty.

4. It is clear that with better testing, which reveals the degree and type of defect accurately, and a more understanding approach on the part of a trained psychologist who realizes how to explain a person's colour difficulties and to give him insight into the nature of his problems, much help could be given. It should not be necessary and is not desirable that all red/green defectives should be excluded from schools of art, because some of them may have quite considerable artistic ability.

Figures published in the Hospital In-Patient Enquiry (1967), and also for a population of known size in Aberdeen, confirm a previous conclusion, derived primarily from mortality statistics, that currently accepted estimates of 100,000 illegal abortions in Great Britain each year before the Abortion Act 1967 came into operation are much exaggerated. A National Opinion Polls estimate of 31,000 is also regarded as too high, and the Aberdeen data suggest that the true figure probably did not exceed 20,000. It is important to arrive at an accurate estimate for the proper assessment of the demographic and other effects of the change in the law. The Registrar General's figures for legal terminations during the first months' operation of the Act are discussed in a postscript.

There are as yet few studies of body hair variation in man. Of all human populations, the Ainu of Japan are most famous for their alleged hirsuteness, and the history of this somewhat controversial subject is reviewed. Data are presented on chest, back and facial hair pattern and quantity in a sample of Ainu and Ainu/Japanese hybrids, resulting initially from field work by the Cambridge Expedition to Northern Japan in 1964. Methodological problems are discussed. Social attitudes to hairiness in Japan over the past few centuries are commented on, in view of their possible relevance in maintaining the biological distinctiveness of the Ainu. It is concluded that although the Ainu have more body hair than other Japanese, compared with some other groups—for instance American ‘Whites’—they can not be considered exceptionally hirsute.

A postal questionnaire was sent to one randomly selected half of the general practitioners on the Sheffield Executive Council list in April 1967 concerning the advice they give about family planning; 90% responded, and of these 78% suggest contraceptive measures on their own initiative. All the respondents either advise patients directly, refer them elsewhere, or both; 93% will on occasion advise the patient themselves, and 73% refer patients to the FPA. Of those who advise directly 92% prescribe the pill; 32 % of the respondents have had training in contraceptive methods. Doctors trained in Ireland were less likely to suggest contraception measures on their own initiative or to prescribe the pill, and more likely to prescribe the safe period than doctors trained elsewhere in the British Isles.

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.

Using Australian records of human births for the first six decades of the twentieth century, the proportions of male and female births are studied in relation to the mother's age, the father's age, the parents' ages in combination, and certain other factors. The principal data used relate to the years 1931–55, during which over 3 million children were born, yet even so the significant features are not easy to discern.

Masculinity tends to fall as the age of either parent increases. But it is only average or below if one parent is old while the other is young. For high masculinity, both parents must be young.

The Australian data are available in a form which enables the sex ratio to be studied also in relation to (a) the season of the year; (b) urban and rural areas; (c) the different states of the Commonwealth; (d) births inside and outside marriage; and (e) single and multiple births. When the influence of the parents' ages is eliminated, however, it does not appear as though the sex ratio varies significantly with any of these factors.

In 1932 all 11-year-old children in Scottish schools were given a group intelligence test, and a sample of 1000 was individually tested. The future careers of this sample were followed till 1939. In 1968, 709 of the original sample could be traced, and data about education, employment, and family were obtained. In 1947, a parallel survey was conducted in Scotland, and a sample of 1208 children was individually tested, and followed up for 16 years. The same data about education, employment and family are available for the 1947 Sample.A comparison between length of school education indicates a greater proportion completing a full secondary education in the 1947 than in the 1932 Sample. Proportionally, more of the 1947 Sample graduated from university. In marriage, it is possible to cut across the 1932 Sample at the age of 27 years, to make direct comparison with the 1947 Sample at the same age. The greatest incidence of marriage is in the middle range of IQ, but later records for the 1932 Sample show a relative uniformity of marriage over the IQ range. The pattern for occupational class is similar. There is a slight tendency to later marriage in the 1932 Sample. Two measures of differential fertility for IQ are used. For both samples, there is a negative relationship between the mean IQs of the sample members and the number of their sibs, more marked for the 1947 Sample. The number of children born to members of the two samples before the age of 27 years shows a similar relationship, but in the following 20 years the pattern for the 1932 Sample changes to one with a peak of mean IQ at two children. It is suggested that linear differential fertility for IQ may be a function of the age of the parent.

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.

This paper reports the findings of longitudinal studies of married primigravidae resident in Aberdeen city:

(1) All 1026 primigravidae delivered in 1949 were followed up 5 years later.

(2) A 1-in-6 random sample of primigravidae delivered 1950–53 (330 women) were studied intensively and followed up at 5 and 10 years.

The findings are biased in favour of families of manual workers because more upper social class families left Aberdeen.

Many primigravidae had no definite ideas on family size but they made up their minds or changed their preferences (sometimes to accommodate to reality) as they gained experience of marriage and motherhood. Most women wanted 2 or 3 children and none wanted more than 4 children.

There were striking differentials in fertility at both 5 and 10 years. Women who were under 20 years of age when they had their first baby, those who conceived prenuptially, and those married to a semi-skilled or unskilled manual worker had the largest families at both 5 and 10 years. At 5 years, although on average such women were having intercourse more frequently, they were the least likely to have been regular users of contraceptives.

Two-thirds of all pregnancies which occurred in the first 5 years were ‘unintended’. Only 15% of couples had used contraceptives regularly from marriage and a further 20% became regular users in the 5 years following the birth of their first child. At the end of the first 5 years, 10% of women already had more children ‘than they felt able to manage without excessive strain’. The number increased in the following years but was modified partly by delegation of responsibility for a few children to other women but more especially by the liberal policy to sterilization pursued in Aberdeen. The repetition of the disadvantages in the childhood environment of the largest families is illustrated. It is argued that ‘the pill’, which was not available to the women in the studies reported, may reduce the number of ‘unintended‘ pregnancies in future, but that sterilization may remain the most satisfactory measure of family limitation in a small group of women whose way of life is not conducive to forward planning and sustained rational behaviour.

In this Symposium we are to discuss biological and social aspects of race. This is, of course, a tender topic, in dealing with which I feel strongly that we must all take especial care to express our ignorance when we are ignorant. Especially is this so in the most sensitive area of the topic, the question whether or not differences between racial groups in so-called mental abilities have an innate genetic component or not. I hope to convince you that nobody knows the answer to this question, and that in present circumstances it is impossible to know or even to foresee with certainty that it will ever be possible to know. Hence, whoever speaks as if he knows that such a racial difference is genetic, or whoever speaks as if he knows that such a racial difference is not genetic, is showing a bias that cannot be justified by the facts. Both they who say the differences are genetic and they who say they are environmental or cultural are equally prejudiced.