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Darwin's family health harmed by inbreeding

10 May 2010
Appeared in BioNews 557

Charles Darwin's concerns that his children's ill health was due to his cousin marriage were justified, according to a new study. The UK-Spanish study, which analysed four generations of Darwin's family, provides statistical evidence of a link between ill health and the degree of inbreeding in his and his wife's families.

Darwin had ten children, but they and his wider family were blighted by high rates of premature death and apparent infertility. Darwin suspected this may have been due to widespread inbreeding.

The study analysed 176 children from the Darwin-Wedgwood dynasty and found a 'significant positive association between child mortality and inbreeding'. In other words, families with the highest levels of inbreeding experienced the highest child mortality. The team calculated that 6.3 per cent of the genes inherited by Darwin's children were identical - approximately four times more than expected from the offspring of second cousin marriages.

Professor Tim Berra, a lead author on the study, said: 'Putting together the mortality of his children and the unexplained fertility [problems], I think Darwin was right to be concerned about these issues'. However, he also said the study also suggested the cause of Darwin's own ill health was not related to inbreeding.

Inbreeding occurs when two genetically related individuals reproduce, increasing the likelihood that identical copies of genes for recessive diseases (where two copies of the faulty gene are required for disease manifestation) are inherited from each parent.

Inbreeding increases the likelihood that children will suffer recessive diseases caused when they inherit both copies of a faulty gene. It has recently re-emerged as a hot topic for debate, with prominent bioethicist Baroness Ruth Deech calling for a 'vigorous' public campaign against first cousin marriage.

The study was published online in BioScience.

Charles Darwin's family tree tangled with inbreeding, early death
Scientific American |  3 May 2010
Darwin dynasty's ill health blamed on inbreeding
New Scientist |  3 May 2010
How Charles Darwin's family paid the price of inbreeding
Daily Mail |  3 May 2010
Inbreeding may have caused Darwin family ills
EurekAlert |  3 May 2010
In Darwin Family, Evidence of Inbreeding's Ill Effects
New York Times |  3 May 2010
Unnatural selection: Darwin's family damaged by inbreeding
TimesOnline |  2 May 2010
8 July 2013 - by Dr Victoria Burchell 
Marriage between first cousins could double the risk of any offspring having a birth defect, researchers say...
4 October 2010 - by Dr Rizwan Alidina and Dr Mohamed Walji 
A Dispatches programme on rare genetic conditions and cousin marriage aired a few weeks ago ignited much debate. Many people commenting on the programme were correct to say consanguinity alone isn't the issue. However, the high rate of autosomal recessive disorders in some communities remains an important issue, regardless of its intricate and complex causes. This needs to be addressed, preferably with input from general practitioners...
31 August 2010 - by Professor Sandy Raeburn 
Why am I criticising a campaign to reduce the incidence of severe autosomal recessive diseases? After all, I spent five years of my 40-year clinical career in medical genetics living in Oman - a Muslim country where over 50 per cent of marriages are consanguineous? Let's dig deeper!...
22 March 2010 - by Professor Marcus Pembrey 
A report and analysis promoting Baroness Ruth Deech's views on cousin marriage, published in the Times newspaper on Saturday, makes some serious errors and does nothing to either clarify the true health impact of cousin marriage or help couples at risk of recessive genetic conditions...
22 March 2010 - by Dr Vivienne Raper 
A leading bioethics professor and crossbench peer is to reignite the debate on the genetic risks of marriage between first cousins...
22 June 2008 - by Dr Alison Shaw 
Marriage between relatives such as first cousins increases the risk in children not of general birth defects and genetic problems of all kinds but of what geneticists call 'recessive' conditions: those caused by inheriting two copies of a gene each of which carries a mutation. It seems we may each...
9 June 2008 - by Ailsa Stevens 
Over a billion people worldwide live in regions where 20-50 per cent of marriages are consanguineous, and first-cousin unions are especially popular. Discussion of this phenomenon is confused by the fact that its causes are social and economic, while its outcomes tend to be measured in terms of child...
31 March 2008 - by Professor Alan Bittles 
First cousin marriage is a topic that frequently evokes distaste and even a sense of moral outrage in the UK and other western countries. Given its sound Biblical tradition (Leviticus 18:7-18) and long-standing legal acceptance this is somewhat surprising, the more so since many famous figures of the...
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