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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.

SOURCES & REFERENCES
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
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