Charles Darwin

New Delhi, May 4: Charles Darwin’s marital choice may have hurt his own children’s chances of success in the evolutionary game of survival of the fittest, a new study has shown.

The study has confirmed fears expressed by the 19th century icon who had fathered the theory of evolution that his marriage to his cousin may have harmed his children’s health.

Three of Darwin’s 10 children died at age 10 or younger, while three of his six children with long-term marital relationships did not have children of their own. The new research published this week in the journal BioScience suggests that the mortality and the infertility may have been the result of inbreeding.

Tim Berra at the Ohio State University in the US, and two colleagues in Spain have used previously published paternal and maternal family trees of Darwin dating back to the 16th century to calculate for the first time the measure of inbreeding in the families.

Darwin was 30 when he married his 31-year old first cousin Emma Wedgwood, and his mother Susannah Wedgwood was herself the daughter of third cousins.

The researchers have calculated Darwin’s children had an inbreeding coefficient of 0.0630 — a 6 per cent chance a child will receive an identical copy of a gene from each parent because of common descent.

“If there is a deleterious gene in both parents on the same spot on the chromosome, it increases the chance that these two genes will come together in the offspring and cause problems,” said Berra, professor emeritus at the department of evolution at the Ohio university and lead author of the study.

Darwin, who had shown through controlled experiments that the offspring of cross-fertilised plants were healthier and more numerous than the offspring of self-fertilised plants, himself suspected that his marriage to his first cousin may have caused some of his children’s health problems.

“I wanted to find out if Darwin’s fears were reasonable. Apparently, they were,” Berra told The Telegraph. “Darwin had no knowledge of modern genetics. He was far ahead of his time. His research with plants led him to correct conclusions regarding humans.”

A paper by biologist Michael Golubovsky at the University of California, Berkeley, published in the journal Human Reproduction two years ago, had suggested that infertility in Darwin’s three children could have resulted from cousin marriage and the segregation of a recessive mutation leading to infertility.

However, all the three infertile children William, Henrietta, and Leonard “expressed normal vitality, living 75, 86, and 93 years,” Golubovsky wrote in his paper. But researchers also point out that three other sons of Darwin had outstanding careers, each elected as Fellow of the Royal Society. Berra said Darwin was among the first experimental scientists to raise concerns about the effects of consanguineous marriages, using data from plants and animals.