Opinion Community Genet 2008;11:324–330 DOI: 10.1159/000133304
A Community Genetics Perspective on © Free Author Copy – for perConsanguineous Marriagesonal use only ANY DISTRIBUTION OF THIS ARTICLE WITHOUT WRITTEN A.H. Bittles CONSENT FROM S. KARGER AG, BASEL IS A VIOLATION Edith Cowan University and Centre for Comparative Genomics, Murdoch University, Perth, Australia OF THE COPYRIGHT. Written permission to distribute the PDF will be granted against payment of a permission fee, which is based on the number of accesses required. Please contact
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Key Words Consanguinity ⴢ Endogamy ⴢ Sociocultural values
Abstract Consanguineous marriage has long been a controversial topic, with particular attention focused on adverse health outcomes. Unfortunately, the studies that have been conducted on consanguinity to date have usually lacked control for important sociodemographic variables, such as maternal age and birth intervals, and in estimating specific disease gene frequency, they have ignored the influence of population sub-division. Inadequate attention has also been paid to the social benefits associated with intra-familial marriage, resulting in a biased overall cost-benefit assessment. Worldwide, some 1,000 million people live in countries where 20 to more than 50% of marriages are consanguineous, and large migrant communities from these regions are now resident in Western Europe, North America and Oceania. The need for comprehensive and more balanced investigations into all aspects of consanguineous marriage is pressing and merits a substantial international collaborative research effort. Copyright © 2008 S. Karger AG, Basel
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Introduction
Within geographical regions, and in the case of India within the same country, public attitudes towards con© Free Author Copycan – for sonalInuse sanguineous marriage varyper widely. largeonly part, ANY DISTRIBUTION OF THIS ARTICLE WITHOUT WRITTEN CONSENT FROM S. KARGER AG, BASEL IS A VIOLAT these attitudes are driven by religious and cultural beWritten permission to distribute the PDF will be granted against payment of a per mission fee, liefs, as exemplified by the strong preferences for spe- which is based cific types of first cousin unions in different societies, with marriage between a man and his father’s brother’s daughter favoured in Arab Muslim communities, as opposed to mother’s brother’s daughter marriage in Hindu South India [1]. However, in many cases, it is difficult to clearly distinguish one form of influence from the other. Consanguineous marriage was permitted in the early Christian church, initially borrowing from the detailed Judaic rules listed in Book of Leviticus 18, 7–18. Prohibitions on consanguinity introduced within Christianity can be traced back to the 6th and 7th centuries AD, subsequent to changes in the civil marriage code of the Eastern Roman Empire [2]. Although restrictions on marriage between biological relatives persist in the Roman Catholic and Orthodox Churches, as part of the 16th century Reformation, the Protestant denominations opted to revert to the original Levitical guidelines which permit first cousin marriage [3]. Prof. A.H. Bittles Centre for Comparative Genomics, Murdoch University South Street Perth, WA 6150 (Australia) Tel. +61 8 9360 6088, Fax +61 8 9360 7238, E-Mail
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Table 1. Consanguineous marriage relationships
Table 2. Global prevalence of consanguineous marriage
Biological relationship
Genetic relationship
Coefficient of inbreeding
Uncle-niece Double first cousin
second degree
0.125
First cousin
third degree
0.0625
First cousin once removed Double second cousin
fourth degree
0.0313
Second cousin
fifth degree
0.0156
Second cousin once removed Double third cousin
sixth degree
0.0078
Third cousin
seventh degree
0.0039
Consanguinity, %
Numbers in millions
