American Scientist

To the Editors:

I enjoyed Keith Thomson’s Marginalia column “Darwin’s Enigmatic Health” (May–June 2009). I had not known Darwin had a special fondness for sugar. His combination of oral, dermatological, gastrointestinal and, especially, emotional symptoms are consistent with mercurialism. Using amalgam containing 50 percent metallic mercury for dental restorations began in France in 1816. Being upper class and part of a medically knowledgeable family, Darwin might well have had his sugar-induced caries treated with such “state-of-the-art” restorations, even as a child. Darwin also likely consumed calomel (mercurous chloride) and “blue mass” pills, commonly taken to fight intestinal infections in his time. Less than 1 percent of ionic mercury in calomel and the liquid droplets of metallic mercury in “blue mass” are absorbed from the gastrointestinal tract. But their potential for toxicity, especially in children, was noted even in Darwin’s day. In contrast, the 80 percent of inhaled monatomic mercury vapor (released continually by amalgam fillings) that is absorbed across the pulmonary epithelium can produce subtle and often idiosyncratic intoxication that was not widely recognized until the late 20th century. During the approximately 130 years when both modalities were used, the risk for mercury overexposure was considerable. I’d love to know if Darwin’s diaries or the writings of his contemporaries mention that he had any dental problems or therapy.

Anne O. Summers
Athens, GA

Dr. Thomson responds:

Darwin certainly had dental problems; five of his teeth were extracted. He also was dosed repeatedly with calomel in various forms. But I do not know whether he had mercury fillings in his teeth. Mercury exposure was considered briefly by Ralph Colp in his book Darwin’s Illness (2008), but too little is known to judge whether it would account for his illnesses.