Evolution of human serial pairbonding

Data on divorce taken for all available years between 1947 and 1981 from the Demographic Yearbooks of the United Nations on 58 peoples illustrate that divorce has a consistent pattern. Divorces exhibit a skewed distribution, characterized by the occurrence of the mode early in marriage (with a divorce peak on or around the fourth year) and a gradual, long-tailed decline following this peak. Divorce risk peaks in age category 25-29 for males and age categories 20-24 and 25-29 for females, the height of reproductive and parenting years, and divorce counts peak among couples with two or fewer children. These properties of divorce are unrelated to divorce rate; they occur in societies with both high and low divorce rates. Data on available horticultural and gathering/hunting societies illustrate that divorce also peaks among young couples early in marriage. Remarriage by divorced and widowed individuals of reproductive age is also common cross-culturally. It is proposed that the above four-year modal marriage duration among couples of reproductive age who divorce reflects a hominid reproductive strategy that probably evolved some time after the appearance of Homo in response to increased female "reproductive burden" and functioned to ensure the survival of the hominid infant through weaning. Serial pairbonding during the female's reproductive years had ancestral adaptive advantages, producing the modern cross-cultural pattern of serial pairbonding.     

Marriage as a reproductive contract: Patterns of marriage,divorce, and remarriage

Patterns of marriage, divorce, remarriage, and redivorce were examined in several representative Western cultures through survey questions and archival data to test the hypothesis that marriage and divorce can be understood as expressions of underlying gender-specific, fitness maximization strategies. Differences between males and females were found for the relationship between age and patterns of both marriage and divorce, with females being far more likely at almost all ages to initiate divorce proceedings than males. Once divorced, however, formerly married females were less likely to remarry than formerly married males. The presence of children from a prior marriage had the effect of further decreasing the likelihood of remarriage for females, but not for males. Formerly married males without children tended to remarry females who had never been married, whereas just the opposite was true for divorced males with children. Consistent with our view of marriage as a reproductive contract, the absence of children was not only conducive to divorce and remarriage, but appeared to increase the likelihood of redivorce as well.     

Gift-giving in romantic couples serves as a commitment signal: Relational mobility is associated with more frequent gift-giving

The present study explored why married couples periodically exchange gifts. Based on the commitment signal hypothesis, we tested whether relational mobility, which was operationalized as divorce rate in Study 1 and relational opportunities in Study 2, is positively correlated with the frequency of gift exchanges among married couples. In Study 1, we found that married couples in the U.S., which is associated with a relatively high divorce rate, were more likely to give and receive gifts to and from their partners than those in Japan, which is associated with a relatively low divorce rate. This societal difference, in contrast, was not observed among unmarried couples, who were still developing their relationship (and thus, partner changes could frequently happen regardless of the country-level divorce rate). Study 2, a secondary analysis of extant survey data, revealed that Japanese married couples who have more relational opportunities more frequently engage in gift exchanges than those who do not. Together, these results support our hypothesis that periodical gift exchanges work as commitment signals among married couples.     

Divorce in Ethiopia: the impact of early marriage and childlessness

Forty-five per cent of first marriages in Ethiopia end in divorce within 30 years, and two-thirds of women who divorce do so within the first 5 years of marriage. This paper looks at two factors that may have an impact on the risk of divorce in Ethiopia: early age of first marriage, and childlessness within the first marriage. Data used were from the 1990 National Family and Fertility Survey conducted by the Government of Ethiopia. A total of 8757 women of reproductive age (15-49) were analysed. Life table analysis was used to determine the median age at first marriage, first birth and the median duration of marriage. Cox models were analysed to determine the differentials of divorce. The results of this analysis showed that both early age at marriage and childlessness have a significant impact on the risk of divorce. An inverse relationship was found between age at marriage and risk of divorce. Having a child within the first marriage also significantly reduced the risk of divorce. In addition, several cultural and socioeconomic variables were significant predictors of divorce.     

Early marriage and maternal health care utilisation: Evidence from sub-Saharan Africa

We use the recursive bivariate probit (RBVP) model to estimate the effects of early marriage on the utilisation of maternal health services in five sub-Saharan countries: Burkina Faso, Guinea, Mali, Niger and Chad. Based on recent Demographic and Health Surveys (DHS), we find that a woman who married before age 15 was 17 percentage points less likely to use prenatal services; and marrying before age 16 reduced that likelihood by 9.6 percentage points. We have not found any statistically significant reduction in maternal health care utilisation for women who married at age 17 or older.     

Marrying women 15 years younger maximized men's evolutionary fitness in historical Sami

Most men marry younger women. This has been attributed to men selecting young women due to their high reproductive value and women preferring older men due to their wealth and high social status. Such mate preferences have been suggested to be adaptive, but despite a flourishing number of studies on the mate selection patterns themselves, little is still known of their actual fitness consequences. We examined how the age difference between spouses who married only once affected their lifetime reproductive success in historical monogamous Sami populations. We found that men maximized their fitness by marrying women approximately 15 years younger and vice versa. However, most couples failed to marry optimally. Only 10% of marriages fell within the optimal parental age difference, suggesting that cultural and ecological constraints for maximizing fitness were considerable. Those who succeeded in marrying optimally were the most preferred partners: young women and old men. Our findings indicate that, in Sami, parental age difference was under natural and sexual selection, as suggested by evolutionary theory.     

Social-demographic influence on first birth interval in China, 1980-1992

This study examines the delay between first marriage and first live birth in China among a sample of women who married between 1980 and 1992. Most couples in China only use contraception after the first child is born. Most sample women had their first child within 2 years of marriage. However, there are significant rural-urban differences in the first birth interval, indicating that there was most probably deliberate fertility regulation after marriage among many urban couples. Survival analysis shows that place of residence, level of education, age at first marriage and marriage cohort affect the first birth interval.     

Cessation of childbearing in the absence of contraception in Sri Lanka

In data from the Sri Lanka Fertility Survey, 1975, the cessation of childbearing is examined among women who have never used contraception. The sample consisted of 6810 currently or previously married women, 57% of whom reported that they had never used contraception. Cessation of childbearing is studied according to age and marriage duration. The variables analyzed are age at last birth, proportions infertile during the last 5 or 7 years, and the infertile open interval. The duration of breastfeeding is taken into account where necessary, and the contraceptive users and nonusers are compared where appropriate. Non-users tend to cease childbearing early, and therefore are infertile for longer periods during their marriages. It is probably age of the 1st child that influences decisions on future fertility. Among women aged 45-49 who married before age 20 and continued in their 1st marriage, mean age at last live birth in non-users, was 34.5 years, about 2 years earlier than in those who had used contraception. Non-users who married at any age below 30 years cease childbearing well below age 40. The proportion not currently pregnant and infertile over the past 5 years increases with marriage duration among the fertile non-users in each age group. When age at last birth and the duration of breastfeeding in the open interval are taken into account and the reference period is increased to 7 years, the period of infertility increases with marriage duration among nonpregnant non-users below age 45. The proportion of women who were currently not pregnant and had remained infertile over the past 7 years is higher among the older non-users whose 1st child was born more than 10 years ago.     

Legalization of consensual unions in Mexico

Abstract

There is ample evidence that there are important behavioral differences in Latin America between couples living in consensual unions and those who are legally married. In this paper, we examine the frequency of and variations in legalization of consensual unions in Mexico, using data from the 1976–77 Encuesta Mexicana de Fecundidad. Our results indicate that the frequency of legalization of consensual unions appears to have risen among recent cohorts. Women in first unions, those who start a union at older ages, and those who are more highly educated are also more likely to marry their partners. Our results also indicate that pregnancy does not appear to be a major factor precipitating legalization, and that whether a couple lived together before marriage has no effect on the stability of the marriage.     

Measuring the childbearing motivation of couples referred to the Shiraz Health Center for premarital examinations

Millions of children who were born during the first decade after the Islamic revolution in Iran are now reaching the age of marriage and childbearing. Short spacing between marriage and the birth of the first child has the potential to cause an excessive and costly increase in the growth of population in Iran. Research into the motivations for the birth of first child among newly married couples can create a knowledge base that will enable health centres to help these couples make better decisions about the timing of their first pregnancy. Using a consecutive sampling technique and administering Miller's Childbearing Questionnaire, data were gathered regarding the childbearing motivations and desires of 300 couples who had been referred to the Shiraz Health Center for premarital counselling. The Childbearing Questionnaire, with some minor modifications, was found to be a valid and reliable instrument for measuring the childbearing motivations of newly married couples of Shiraz County, Fars Province, Iran. The utility of these findings for counselling in health centres is discussed. Based on the results, a longitudinal study is being designed that will allow the development of models for predicting the time of first pregnancy after marriage.     

Getting ready for the marriage market? The association between divorce risks and investments in attractive body mass among married Europeans

This article explores to what extent married middle-aged individuals in Europe are governed by the risk of experiencing divorce, when shaping their physical appearance. The main result is that divorce risks, proxied by national divorce rates, are negatively connected to body mass index (BMI) among married individuals but unrelated to BMI among singles. Hence, it seems that married people in societies where divorce risks are high are more inclined to invest in their outer appearance. One interpretation is that high divorce rates make married people prepare for a potential divorce and future return to the marriage market.     

Mate selection and its impact on female marriage age, pregnancy wastages, and first child survival in Tamil Nadu, India

Marriage in Indian society is a religious duty. Consanguineous marriage is common, where individuals prefer to marry within their clan (a unilateral kin group based on either matrilineal or patrilineal descent). Keeping in mind that this form of marriage has certain disadvantages for social and biological as well as demographic aspects of individuals and families, the present study examines the influence of mate selection (i.e., close relatives, distant relatives, not related) on female age at marriage, pregnancy wastages, and survival status of the first child. The study was designed based on the information collected on a sample size of 3,948 married women aged 13-49 in Tamil Nadu, India, by the National Family Health Survey (NFHS), 1992. Results suggest that 48 per cent of women in Tamil Nadu marry their relatives. This practice of marrying relatives is high in rural areas, among Hindus, Scheduled Castes/tribes, and illiterate women as compared to urban areas, among non-Hindus, non-SC/ST, and educated women, respectively. The bivariate analysis reveals that women marrying their close relatives had low age at marriage and experienced a higher per cent of pregnancy wastage and child loss (first child) as compared to those women marrying their distant relatives or nonrelatives. The result is found to be consistent even after controlling for selected background variables through multivariate techniques (applied separately for age at marriage, pregnancy wastages, and the survival status of first child). Hence, this study suggests that steps should be taken to inform people about the problems of marrying close relatives through appropriate IEC programs in Tamil Nadu.     

High income men have high value as long-term mates in the U.S.: personal income and the probability of marriage,divorce, and childbearing in the U.S.

Using data from the first Census data set that includes complete measures of male biological fertility for a large-scale probability sample of the U.S. population (the 2014 wave of the Study of Income and Program Participation-N = 55,281), this study shows that high income men are more likely to marry, are less likely to divorce, if divorced are more likely to remarry, and are less likely to be childless than low income men. Men who remarry marry relatively younger women than other men, on average, although this does not vary by personal income. For men who divorce who have children, high income is not associated with an increased probability of having children with new partners. Income is not associated with the probability of marriage for women and is positively associated with the probability of divorce. High income women are less likely to remarry after divorce and more likely to be childless than low income women. For women who divorce who have children, high income is associated with a lower chance of having children with new partners, although the relationship is curvilinear. These results are behavioral evidence that women are more likely than men to prioritize earning capabilities in a long-term mate and suggest that high income men have high value as long-term mates in the U.S.     

An Analysis of the Matching Hypothesis in Networks

The matching hypothesis in social psychology claims that people are more likely to form a committed relationship with someone equally attractive. Previous works on stochastic models of human mate choice process indicate that patterns supporting the matching hypothesis could occur even when similarity is not the primary consideration in seeking partners. Yet, most if not all of these works concentrate on fully-connected systems. Here we extend the analysis to networks. Our results indicate that the correlation of the couple’s attractiveness grows monotonically with the increased average degree and decreased degree diversity of the network. This correlation is lower in sparse networks than in fully-connected systems, because in the former less attractive individuals who find partners are likely to be coupled with ones who are more attractive than them. The chance of failing to be matched decreases exponentially with both the attractiveness and the degree. The matching hypothesis may not hold when the degree-attractiveness correlation is present, which can give rise to negative attractiveness correlation. Finally, we find that the ratio between the number of matched couples and the size of the maximum matching varies non-monotonically with the average degree of the network. Our results reveal the role of network topology in the process of human mate choice and bring insights into future investigations of different matching processes in networks.     

How partnerships end in guillemots Uria aalge: chance events, adaptive change, or forced divorce?

Divorce in socially monogamous species can result from differentmechanisms, for example, chance events, active desertion ofthe partner, or the intrusion of a third individual oustingthe partner. We compared the predictions associated with suchmechanisms with data from common guillemots (Uria aalge) breedingon the Isle of May, Scotland. The data cover the years 1982–2005and show a yearly divorce rate of 10.2%. In most divorces (86%),one of the original partners moved to another breeding site,whereas the other bird stayed and bred with a new partner. Onaverage, movers had a significantly lower breeding success afterdivorce, stayers were largely unaffected, whereas the incomingbirds benefited significantly from the change. This patternfits best the predictions of the "forced-divorce" hypothesis,suggesting that many divorces were caused by incoming birdsrather than the original partners or chance events. Althoughwe are unable to document the precise behavioral sequence thatled to divorces, our interpretation is supported by observationsof frequent fights over breeding-site ownership. Our data alsoindicate within-population diversity of divorce mechanisms:some divorces were apparently accidental, others desertion ofpartners and sites if the latter were of low quality. Our studyfinally illustrates that a negative correlation between breedingsuccess and probability of divorce (which our data show) neednot indicate the adaptiveness of divorce for the original partners.Because such a connection has often been made, adaptive divorcemay in general be less common than usually assumed.     

Book notes

Abstract

Marriage in Indian society is a religious duty. Consanguineous marriage is common, where individuals prefer to marry within their clan (a unilateral kin group based on either matrilineal or patrilineal descent). Keeping in mind that this form of marriage has certain disadvantages for social and biological as well as demographic aspects of individuals and families, the present study examines the influence of mate selection (i.e., close relatives, distant relatives, not related) on female age at marriage, pregnancy wastages, and survival status of the first child. The study was designed based on the information collected on a sample size of 3,948 married women aged 13–49 in Tamil Nadu, India, by the National Family Health Survey (NFHS), 1992. Results suggest that 48 per cent of women in Tamil Nadu marry their relatives. This practice of marrying relatives is high in rural areas, among Hindus, Scheduled Castes/tribes, and illiterate women as compared to urban areas, among non‐Hindus, non‐SC/ST, and educated women, respectively. The bivariate analysis reveals that women marrying their close relatives had low age at marriage and experienced a higher per cent of pregnancy wastage and child loss (first child) as compared to those women marrying their distant relatives or nonrelatives. The result is found to be consistent even after controlling for selected background variables through multivariate techniques (applied separately for age at marriage, pregnancy wastages, and the survival status of first child). Hence, this study suggests that steps should be taken to inform people about the problems of marrying close relatives through appropriate IEC programs in Tamil Nadu.     

Heredity of progressive muscular dystrophy: Reflections on a case study

Abstract

Data on the prevalence of divorce and separation among parents of children with cystic fibrosis and other chronic diseases indicate that marital breakdown is no more prevalent among these couples than it is in a general population. For couples who attended genetic counseling clinics or had children with spina bifida or leukemia, the divorce rate is lower than the United States national average. For parents of children with cystic fibrosis, the divorce rate is the same as the national average. The high recurrence risk for cystic fibrosis may deter many parents from further reproduction. We speculate that the inability to plan more children may be the factor responsible for the higher prevalence of divorce among these parents compared to those of children with other chronic diseases.     

Who asks for vasectomy reversal and why?

Of the 76 men requesting reversal of vasectomy who were interviewed at Charing Cross Hospital between June 1978 and September 1981, 31 were still married. These men had decided to have a vasectomy during a crisis-a recent pregnancy or financial stress being the commonest reason. Most wanted another child but others wished to be "put back to normal," and a few hoped reversal would help their marriage. Forty-five (59%) were divorced or separated and felt disadvantaged in courtship or remarriage by being infertile, many wives or partners being "desperate" for a pregnancy. A greater number of requests for reversal came from men who had been under 35 at the time of vasectomy and who were more likely to have been divorced, especially if there had been a teenage pregnancy. The risks of regret after sterilisation appear to relate to immaturity at the time of the vasectomy and to be as great for young men as for young women.     

Reproduction: the Canadian family in transition

3 trends suggest that the reproductive function of the Canadian family is in transition. 1st, fertility has fallen and remains below the replacement level. In 1985, the total fertility rate was 1.67, the lowest in 60 years. Since 1971, it has not risen above 2.1 births/woman, the replacement level. 2nd, an increasing proportion of women are spending a larger part of their lives without having any children. In the 1981 census, 22% of ever-married women between 15 and 44 years had not yet borne children, compared with only 14% recorded in the 1961 census. While the proportion of women who are childless at the end of their reproductive years has risen only slightly, a larger number of women are postponing having children even as the risk of becoming sterile in the interim becomes greater. The combined effect of postponing both marriage and childbearing will most probably be to increase the proportion of women remaining without children. The 3rd trend is the increasing proportion of women who are having children without getting married. Among the consequences of premarital pregnancy are the stress on single mothers, the need for social assistance, the cost of maintenance programs, and the need for more child care. These changes in attitude toward marriage and family formation could have major implications for individuals and society. A fertility rate below replacement level could be stressful for society, resulting in population decline, and changes in age structure that could negatively affect the economy.