Alverez, Walter C. "The Nature of Charles Darwin's Lifelong Ill-Health," New England Journal
of Medicine 261 (October 1959), pp. 1109-1112.
When this was written the author was well along in years. He explained illnesses as the
profession did in the 19th century. His hypothesis is that Darwin suffered from a family disease,
a "tendency" to melancholia and hypochondriasis. Darwin's tendency to fatigue might have been
called neurasthenia just a few years before.
With his assumption that diseases run in families, Alverez is quick to find evidence: in Darwin's
grandfather's generation, in his parents' and in Darwin's children. It is easy to find evidence of
psychological problems once one starts looking.
Alverez finds that Darwin's children had problems, but his judgment is biased. One of the
children was apparently mentally retarded but Alverez does not, therefore, conclude that Darwin
was an idiot. His choice of evidence is selective.