How Charles Darwin’s family paid the price of inbreeding
Family man: An undated photograph of Scientist Charles Darwin with one of his daughters
He is the father of evolution, whose discoveries revolutionised our understanding of genetics.
But even Charles Darwin was not exempt from the vagaries of DNA.
Three of Darwin’s 10 children died in childhood, while another three never had any children of their own, despite being married for years.
A study of the scientist’s family tree suggests inbreeding was to blame, with frequent cousin to cousin marriages lowering immunity to disease and raising the odds of infertility.
Darwin’s mother, Susannah, was the daughter of third cousins, one of which was Josiah Wedgwood, the founder of the pottery dynasty of the same name.
Darwin’s wife, Emma Wedgwood, was his first cousin, while the Wedgwood family tree contained several other marriages between cousins.
The couple had ten children – four girls and six boys – between 1839 and 1858. But only seven survived to adulthood.
Annie, Darwin’s adored eldest daughter, succumbed to TB at the age of 10.
Her father kept a vigil at her bedside during the last months of her life and, after she died in his arms in 1851, he wrote of how the household has lost its’ joy’.
Annie’s sister, Mary, lived for just 23 days, while brother Charles Waring died of the bacterial infection scarlet fever as a toddler.
Of Darwin’s remaining seven children, three did not become parents themselves, despite having long-term marriages.
Darwin, who worried about his own health, had done experiments on inbreeding in plants, and was concerned that the fashion for well-to-do families to marry within themselves, was having impacts on human health – including that of his children.
So concerned was he, that he asked neighbour and MP John Lubbock to include a question on the subject in the 1871 census. The request was rejected.
Today, with the potential perils of close marriages well-known, researchers have looked whether Darwin’s fears with regards to his own family were justified.
By looking four generations of Darwin and Wedgwood families, the University of California experts said the high number of close marriages meant his children had less variation in their genes than most.
This, as modern science has shown, can raise susceptibility to diseases, including TB and, likely, scarlet fever.
Close marriages, or consanguineous mating. can also raise the odds of infertility.
Writing in the journal Biology in History, the researchers said: ‘Charles Darwin, who was married to his first cousin, was one of the first experimentalists to demonstrate the adverse effects of inbreeding and to question the consequences of consanguineous mating.
‘He documented the phenomenon of inbreeding depression for numerous plant species and this caused him to worry about the health of his own children, who were often ill.
‘Charles Darwin’s fears of consanguinity appear to have been justified given the context of the Darwin/Wedgwood marriages.’
However, not all his children fared so badly.
Three of his sons, George, Francis and Horace became fellows of the Royal Society, Britain’s most prestigious scientific body. All three also received knighthoods.