Darwin worried about marrying cousin

COLUMBUS, Ohio, May 5 (UPI) -- Charles Darwin was right to worry that his children may suffer because of intermarriage between his family and his wife's, U.S. and Spanish researchers said.

Darwin wrote three botanical books showing cross-fertilization was much more beneficial than self-fertilization of plants.

Darwin married his first cousin, Emma Wedgwood, with whom he had 10 children. Three died before age 10 -- two from infectious diseases -- and three of the six surviving children could not have children.

"He fretted that the ill health of his children might be due to the nature of the marriage, and he came to that because of his work on plants," lead author Tim Berra of Ohio State University says in a statement.

Berra, author of the book "Charles Darwin: The Concise Story of an Extraordinary Man," says intermarriage between the Darwins and the Wedgwoods occurred often because it was a common practice among prominent families in Victorian England.

Berra and Gonzalo Alvarez and Francisco Ceballos of the Universidad de Santiago de Compostela traced 25 families among four generations of the Darwin-Wedgwood dynasty.

The study, published in the journal BioScience, found there is about a 2 percent chance that the children of first cousins will develop a congenital defect making them more at risk of dying from infectious diseases such as tuberculosis and scarlet fever -- diseases that killed two of Darwin's children.