Cross-cousin marriage among the Yanomamö shows evidence of parent-offspring conflict and mate competition between brothers

Marriage in many traditional societies often concerns the institutionalized exchange of reproductive partners among groups of kin. Such exchanges most often involve cross-cousins-marriage with the child of a parent's opposite-sex sibling-but it is unclear who benefits from these exchanges. Here we analyze the fitness consequences of marrying relatives among the Yanomamö from the Amazon. When individuals marry close kin, we find that (i) both husbands and wives have slightly lower fertility; (ii) offspring suffer from inbreeding depression; (iii) parents have more grandchildren; and (iv) siblings, especially brothers, benefit when their opposite-sex siblings marry relatives but not when their same-sex siblings do. Therefore, individuals seem to benefit when their children or opposite-sex siblings marry relatives but suffer costs when they, their parents, or same-sex siblings do. These asymmetric fitness outcomes suggest conflicts between parents and offspring and among siblings over optimal mating strategies. Parental control of marriages is reinforced by cultural norms prescribing cross-cousin marriage. We posit that local mate competition combined with parental control over marriages may escalate conflict between same-sex siblings who compete over mates, while simultaneously forging alliances between opposite-sex siblings. If these relationships are carried forward to subsequent generations, they may drive bilateral cross-cousin marriage rules. This study provides insights into the evolutionary importance of how kinship and reciprocity underlie conflicts over who controls mate choice and the origins of cross-cousin marriage prescriptions.

THE CAUSAL RELATIONSHIP BETWEEN CONSANGUINEOUS MARRIAGES AND INFANT MORTALITY IN TURKEY

Turkey has high levels of infant mortality and consanguineous marriages. It has had a high level of infant mortality for its economic level for many years. Over recent decades, although adult mortality rates have not been very different from those of other countries with similar socioeconomic structures, its life expectancy at birth has remained low due to its high infant mortality rate. This has been called the Turkish Puzzle. According to the Turkey Family Structure and Population Issues Survey, 27% of women had a consanguineous marriage in 1968. Subsequent Turkish Demographic and Health Surveys (TDHSs) found the rate of consanguineous marriages to be stagnated at 22-24%, with a resistance to reduction. According to the TDHS-2008, 24% of women had a consanguineous marriage. Numerous studies in various countries of the world have indicated that consanguineous marriages, particularly of first-degree, have the effect of increasing infant mortality. The main aim of this study was to assess the causal impact of consanguineous, particularly first-degree consanguineous, marriages on infant mortality, controlling for individual, cultural, bio-demographic and environmental factors. Data were merged from four Turkish DHS data sets (1993, 1998, 2003 and 2008). Multivariate analysis revealed that first-degree consanguineous marriages have increased infant mortality by 45% in Turkey: 57% in urban areas and 39% in rural areas. The results indicate that there is a causal relationship between consanguineous marriages and infant mortality. This finding should be taken into account when planning policies to reduce infant mortality in Turkey, and in other countries with high rates of consanguineous marriage and infant mortality.

They aren't all first cousins: Bedouin marriage and health policies in Lebanon

OBJECTIVE

Fertility and consanguineous marriages among the Bedouin tribes of the Middle East have long generated interest particularly around health outcomes and social relations. In particular, Bedouin in Lebanon have increasingly embraced the Lebanese national bio-medical health system in the past two decades, while Lebanese policy-makers' responses continue to be minimal and ill-informed. This paper investigates the mismatch between policy-makers' formulations of Bedouin consanguineous marriages and the Bedouins's actual reproductive practices and discusses the implications of these formulations on the Bedouins's access to health services.

DESIGN

The findings are drawn from the data collected as part of the Bedouin Health Project, an EU-funded five-year study (2005-2010), aiming at assessing access to reproductive and child health care among the Bedouin in Lebanon. The data was collected from 6 clusters representing the main Bedouin informal and unrecognized settlements in the Bekaa Valley of Lebanon. The data consists of 111 socioeconomic questionnaires with Bedouin women users of local public, private, and nongovernmental reproductive and child health-focused clinics, in addition to 40 in-depth interviews with Bedouin women across the clusters and 17 semi-structured interviews with policy-makers.

RESULTS

The findings suggest a gap between the perceptions of policy-makers and the incidence of consanguineous marriages and reproductive practices among the Bedouin. While there was no national data available for the Bedouin populations, policy-makers relied on a constructed 'Bedouin reproductive profile' that portrayed them as 'a problematic health group'. The national policy formulation of the Bedouin reproductive profile has an exclusionary impact on the Bedouin population as they are ignored from any targeted health policies or provided with politically motivated palliative care provision.

CONCLUSION

These findings highlight the importance of addressing stereotyping and discrimination among health practitioners and policy-makers, as a crucial part of improving the overall marriage and reproductive health practices of the Bedouin.

Bedouin in Lebanon: Social discrimination, political exclusion, and compromised health care

Global inequalities in health have long been associated with disparities between rich and poor nations. The middle-income countries of the Levant (Lebanon, Syria and Jordan) have developed models of health care delivery that mirror the often complex make-up of their states. In Lebanon, which is characterized by political clientelism and sectarian structures, access to health care is more contingent on ethnicity and religious affiliation than on poverty. This case study of the Bedouin of the Middle Bekaa Valley of Lebanon is based on interviews with policymakers, health care providers and the Bedouin as part of a study funded by the European Commission between 2006 and 2010. The study explores the importance of considering social discrimination and political exclusion in understanding compromised health care. Three decades after the Declaration of Alma Ata (1978), which declared that an acceptable level of health care for all should be attained by the year 2000, the Bedouin community of Lebanon remains largely invisible to the government and, thus, invisible to national health care policy and practice. They experience significant social discrimination from health practitioners and policymakers alike. Their unfair treatment under the health system is generally disassociated from issues of wealth or poverty; it is manifested in issues of access and use, discrimination, and resistance and agency. Overcoming their political exclusion and recognizing the social discrimination they face are steps that can be taken to protect and promote equal access to basic reproductive and child health care. This case study of the Bedouin in Lebanon is also relevant to the health needs of other marginalized populations in remote and rural areas.

PREVALENCE OF CONSANGUINEOUS MARRIAGES AMONG SHI'A POPULATIONS OF LEBANON

In genetics, a consanguineous marriage means union between couples who are related as second cousins or closer. The present cross-sectional study was carried out in order to illustrate the prevalence and types of consanguineous marriages in the Shi'a population living in widespread territories in Lebanon including the Bekaa Valley, the south of Lebanon and the southern suburb of Beirut. Data on types of marriages were collected using a simple questionnaire. The total number of couples in the study was 1203. Consanguineous marriage was classified by the degree of relationship between couples. The overall frequency of consanguinity was found to be 28.4%, with first cousin marriages (21.3%) being the most common type followed by first cousins once removed (5.5%), then double first cousins (0.8%). The frequencies of second cousin and beyond second cousin marriages were the same at 0.4% of all the marriages. The mean inbreeding coefficient (α) was estimated at about 0.0161 for the population. There were no significant differences between the three studied territories for frequencies of different types of marriages (p>0.1), nor were there significant differences between the rural and urban areas (p>0.1).

On the Adaptive Origins and Maladaptive Consequences of Human Inbreeding: Parasite Prevalence, Immune Functioning, and Consanguineous Marriage

We propose that consanguineous marriages arise adaptively in response to high parasite prevalence and function to maintain coadapted gene complexes and associated local adaptation that defend against local pathogens. Therefore, a greater prevalence of inbreeding by consanguineous marriage is expected in geographical regions that historically have had high levels of disease-causing parasites. Eventually such marriages may, under the contemporary high movement of people with modern transportation, jeopardize the immunity of those who practice inbreeding as this leads to an increased susceptibility to novel pathogens. Therefore, a greater frequency of inbreeding is expected to predict higher levels of contemporary mortality and morbidity from infectious diseases. This parasite model of human inbreeding was supported by an analysis involving 72 countries worldwide. We found that historically high levels of pathogen prevalence were related positively to the proportion of consanguineous marriages, and that a higher prevalence of such marriages was associated with higher contemporary mortality and morbidity due to pathogens. Our study addresses plausible alternative explanations. The results suggest that consanguineous marriage is an adaptive consequence of historical pathogen ecologies, but is maladaptive in contemporary disease ecologies.