Charles Darwin may have been right in worrying that the ill health that plagued his family were a result of inbreeding. Darwin didn’t only marry his first cousin, Emma Wedgwood–in fact, the Darwins and the Wedgwoods made a habit of intermarrying (Darwin’s maternal grandparents were also third cousins). Now a new study, which crunched the numbers on first-cousin marriages over four generations of the two dynasties, suggests that his children had an elevated risk of health problems.
The degree of inbreeding among Darwin’s children, while not excessive, was enough to increase the risk of recessive diseases — ones that occur if a harmful version of a gene is inherited from both parents. Three of his 10 children died before age 10 — 2 of bacterial diseases. Childhood mortality from bacterial infections is associated with inbreeding. So, too, is infertility, and three of Darwin’s children who had long marriages left no children [The New York Times].
The study (pdf), published in the journal BioScience, serves as an ironic footnote to the work of the great evolutionary biologist.
Charles Darwin’s studies of heredity, adaptation and evolution included many experiments into the effects of crossbreeding and inbreeding in both plants and animals. Such consanguineous pairing often resulted in weaker, more sickly descendants [Scientific American].
And Darwin wasn’t blind to the possible implications of his studies; in his letters he wrote of “the evil effects of close interbreeding” and worried that this problem might be playing out in his own family.
Other genetic researchers have argued in recent years that cousin marriages, which are banned in many parts of the world, don’t actually pose enough of a health threat to justify the bans; but that argument dealt only with infrequent cousin marriages, not consistent patterns of inbreeding.
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