17 September 2012
ByAppeared in BioNews 673
Consanguinity in Context
Published by Cambridge University Press
ISBN-10: 0521781868, ISBN-13: 978-0521781862
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The title told me that this was the monograph for which I had been waiting. A further delight was that the author was a good friend and colleague. By the way, there are no conflicts of interest (!); Alan Bittles advised my colleagues and me as we planned studies in consanguineous families in the Trent region in the UK during the 1990s and, more recently, in Oman. So, there was extra confidence due to this book's reputable provenance.
This monograph is desperately needed. Western societies, who often chose consanguineous marriage in the past, have grown to fear it and to denigrate communities where it is commonly practiced. Criticisms of consanguineous marriage come from sources expected to be objective, but often failing in this respect. Healthcare workers and laboratory scientists who have investigated disabilities in selected high-risk families have been known to make comparisons without appropriate control subjects. Sometimes, selective arguments, for or against, come from within the communities who often choose cousin marriages (reported in BioNews 573).
The usual culprits then join the chorus. For example, immoderate and ill-informed politicians or other seekers of publicity, who have never attended real patients with disabilities nor looked at healthy control families for comparisons of the burden of disease, may nevertheless add their own honest concerns whilst using crooked thinking. Bittles' book is not just for those in wealthy Western countries, geneticists, other scientists or healthcare workers. It is also for professionals and families with genetic disorders throughout the world.
Despite the unassuming title, this book is packed with carefully collated information, covering all aspects of consanguineous marriage. This includes genetics, culture, religion, legislation, demography, socioeconomics and the relationship to many conditions that occur more often in some marriages between close relatives. The compilation is exhaustive, fascinating and rigorously discussed. Like all good scientists, Bittles does not select data to augment his particular view; he gives all the facts, covering the historical, social, geographical and scientific framework of consanguinity. He also includes many gems, such as Francis Galton's wicked, non-politically correct, comment to Darwin's son, George, who had published one of the first studies of the limited adverse effects of consanguinity. You will now need to read the book to find out what Francis said to his first cousin, once removed!
OK there's the hyperbole. Does this monograph fulfil expectations? My answer is like that of the character Meg Ryan played in the restaurant scene of 'When Harry met Sally': 'Yes, yes, yes, yes...Yes!'.
Every chapter starts with a clear introduction and ends with a commentary that summarises the information available and all key issues. The first chapter covers 'Consanguineous marriage, past and present' and the last 'Consanguinity in context'. The wealth of information in between discusses a range of topics, with the first third dealing with subjects such as religious attitudes and rulings, historic scientific/medical debates and population genetics. Bittles then delves into the influence of consanguinity on reproductive behaviour, early life morbidity and disease in adults. In the final third of this comprehensive book incest, genetic screening, education and counselling are tackled.
Bittles' discussion of genetic screening and counselling made me appreciate how little data there is showing what happens if high-risk affected families with an autosomal recessive disease are provided with non-directive genetic counselling based on an accurate family tree. Gathering this data will surely be better than a general, ill-informed clarion call that cousin marriage be outlawed!
There is so much information here, but it is all relevant, well-validated, significant and stimulating. The book is littered with fascinating facts, such as that in China, Taiwan, Korea and the Philippines, legislation bans first cousin marriage, although China distinguishes between marriages involving the daughter of a father's brother (banned) and marriages involving the daughter of a mother's brother (acceptable)!
In the penultimate chapter there is a thoughtful discussion of when consanguinity can be beneficial to human health, the role of epigenetics and the influence of consanguinity on donor matching for organ transplantation. As I read this chapter, I realised that only if we learn the lessons implicit in Bittles' amazingly comprehensive, and yet readable tome, will the opportunities for good 'blue skies' research into customary cousin marriage be fully realised. Put simply, this book is exactly what is needed to clarify discussions and debates about consanguinity. It deserves to be influential in scientific, political and religious thinking. We should applaud the single author of a major opus by giving his data the attention it deserves.
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