This paper could add some interest to a lecture
in an introductory biology class on inbreeding.
Álvarez, G., F. C. Ceballos, and T. M. Berra
(2015). "Darwin was right: inbreeding depression
on male fertility in the Darwin family."
Biological Journal of the Linnean Society 114(2): 474-483.
Charles Darwin, who was married to his
first cousin Emma Wedgwood, was the first
experimentalist to demonstrate the adverse
effects of inbreeding. He documented the
deleterious consequences of self-fertilization on
progeny in numerous plant species, and this
research led him to suspect that the health
problems of his 10 children, who were very often
ill, might have been a consequence of his
marriage to his first cousin. Because Darwin's
concerns regarding the consequences of cousin
marriage on his children even nowadays are
considered controversial, we analyzed the
potential effects of inbreeding on fertility in
30 marriages of the Darwin dynasty, including the
marriages of Darwin's children, which correspond
to the offspring of four cousin marriages and
three marriages between unrelated individuals.
Analysis of the number of children per woman
through zero-inflated regression models showed a
significantly adverse effect of the husband
inbreeding coefficient on family size.
Furthermore, a statistically significant adverse
effect of the husband inbreeding coefficient on
reproductive period duration was also detected.
To our knowledge, this is the first time that
inbreeding depression on male fertility has been
detected in humans. Because Darwin's sons had
fewer children in comparison to non-inbred men of
the dynasty, our findings give empirical support
to Darwin's concerns on the consequences of
consanguineous marriage in his own progeny.
