Steve GannIrony: Darwin's Family Suffered From Inbreeding
May 6th 2010 01:40
Unfortunately this revelation came too late to save the scientist from the perils of inbreeding.
Darwin's family tree was literally rooted in first cousin marriages, which were commonly known as blood marriages in his time.
Darwin married his first cousin Emma Wedgwood. The couple had 10 children, three of whom died as children. Three of the others married but remained childless, suggesting infertility problems.
Darwin himself, who suffered ill health following his epic trip on The Beagle, was the product of an "inter-Wedgwood" union, his maternal grandparents being third cousins to each another.
New analysis supports Darwin's fears that inbreeding was damaging his health and that of his children "This caused him to reflect on his own condition," says Tim Berra of Ohio State University in Mansfield.
Working with geneticists Gonzalo Alvarez and Francisco Ceballos of the University of Santiago de Compostela in Spain, Berra revealed correlations between the likelihood of death and the amount of inbreeding in families.
From the family tree they worked out an "inbreeding coefficient" for each marriage – a figure reflecting the proportion of inherited genes in the children that would be identical from both parents. For Darwin's own children, the coefficient was 0.063, meaning that 6.3 per cent of his children's genes inherited from both father and mother were identical.
The researchers say that the higher the coefficient, the likelier that children would inherit pairs of faulty genes, with no prospect of a "good" gene from either parent to compensate.
Darwin himself became so concerned about inbreeding that he lobbied unsuccessfully in 1870 for questions about first-cousin marriages to be added to the following year's national census form.
At the time, "blood marriages" were common, unions with first or second cousins accounting for 10 per cent of all marriages, often to keep money or influence in the family. Today, around a fifth of all marriages in the world are consanguineous, although there is some dispute about how damaging it is to descendants, some arguing that the effects are inconsequential and no different to those affecting older parents.
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