Charles Darwin meticulously observed not only the natural world around him but also the strange and troubling events in his own body.
Over much of his life (1809-1882), Darwin recorded a bizarre array of symptoms, from debilitating attacks of nausea to vomiting on special occasions, happy or stressful.
Creationists have tried to use this to paint Darwin as a hypochondriac, sickened with guilt over the godlessness of his natural-selection theory.
The man's suffering could certainly seem biblical. It included palpitations, chest pain, numbness and tingling in the fingers, heat and cold sensitivity, eczema, recurrent boils, hysterical crying, periods of fatigue, and explosive flatulence, which he described as "expulsion of pungent gas both 'upwards and downwards.' "
Others have argued for a more physical cause, but until recently, there hadn't been much agreement on what it was. Over the years, more than 40 conditions have been proposed, said John Hayman, a pathologist in Melbourne, Australia.
Today the emerging consensus points to Cyclic Vomiting Syndrome, a condition that wasn't even known to exist in adults until 2005.
And while they lack a body, or even CT scans of Darwin, today's doctors do have the detailed notes of one of history's keenest observers.
There's still some dispute over the root cause of CVS, and some argue that Darwin also suffered from a parasitic infection known as Chagas disease, a view put forth earlier this month by Thomas Jefferson University gastroenterologist Sidney Cohen.
Cohen gave his opinion at a meeting hosted by the University of Maryland and the Veterans Administration's Maryland Health System as part of an annual series that examines medical conditions afflicting historical figures.
Previous subjects have ranged from Mozart to Alexander the Great.
After examining photos of Darwin and records of his symptoms, Cohen settled on multiple causes, a combination of cyclic vomiting syndrome and Chagas disease.
"It's clear to me that he had multiple diagnoses," said Cohen. And Chagas disease, he said, might have accounted for the heart failure that led to Darwin's death at 73.
Melbourne's Hayman says some attempts to diagnose Darwin have been prejudiced by people's feelings about evolution. "Creationists wanted Darwin to be psychiatrically flawed," he said, citing a passage on the website www.answeringenesis.org:
"Darwin knew that his theory was sheer atheistic materialism - a bombshell which when released on Victorian society would undermine people's faith in God, the Bible, and the Church. In effect, he was shaking his fist at Almighty God . . . It is little wonder that he 'broke out in boils.' "
Hayman said others have pushed the idea that Darwin was stricken with a parasite while exploring South America on his famous Beagle voyage. (Of course, Darwin's scientific ideas have stood the test of time, and the nature of his illness has no bearing on the soundness of evolution.)
The Chagas disease diagnosis is not new, said Darwin biographer Tim Berra. It was first proposed in 1959, he said. It seemed a likely culprit because Darwin recorded being bitten by the bloodsucking insect known to carry it, a triatomid.
The problem with the Chagas-disease explanation, said Hayman, is that Darwin recorded suffering his major symptoms as a student, before his voyage. And a single bite from the triatomid isn't usually enough to bring on the disease, he said.
Another physician citing CVS as the major culprit is University of Missouri gastroenterologist David Fleisher, who first realized this condition could affect adults.
Fleisher said he was reading Darwin's autobiography when he realized that the symptoms Darwin described were remarkably similar to those of his patients. Until recently, Fleisher said, CVS was considered a childhood disease, but he started observing it in adults and published the first paper on adult CVS in 2005.
"It can do horrific things to people," he said. The nausea and vomiting can be as severe as acute food poisoning but can persist for days. "Some people lose their ability to keep a job or go to college."
Many patients with CVS are misdiagnosed and undergo unnecessary surgeries such as gall bladder removal. Fleisher said it's so seldom properly diagnosed that he can't give a good estimate of the incidence.
As Fleisher began to lecture on his discovery of adult CVS, he said, he also spoke on the possible connection to Darwin's mystery symptoms.
Hayman came to a similar conclusion after reading about adult cyclic vomiting. "It was extraordinary how well things matched," he said. CVS, he said, is also associated with motion sickness, eczema, and even flatulence, all of which Darwin reported.
Darwin also noted that when he felt joint pain and got eczema, his gastrointestinal problems and fatigue subsided, which is a common pattern in CVS, Hayman said.
In 2009, Hayman published his ideas on Darwin and CVS in the British Medical Journal. In that paper, he also argued that the root of Darwin's CVS was deep in his cells, a flaw in microscopic structures called mitochondria.
Mitochondria are considered the engines of the cell, critical for converting food into energy. They carry their own DNA and are present only in eggs, not sperm, so they're passed down through maternal lines.
Researchers have identified a number of mitochondrial disorders, which can stem from mutations in the mitochondria's own DNA, or the main "nuclear" DNA in a cell.
Hayman said that Darwin's mother suffered from motion sickness, boils, and other symptoms, which could suggest that faulty mitochondria were being passed down in his family's maternal lineage.
Fleisher says he agrees that CVS alone is enough to account for Darwin's symptoms, but he's skeptical of the role of mitochondrial disease.
He said it's not clear yet whether mitochondrial defects lie at the root of CVS. He also sees a greater interplay of the body and mind than does Hayman. In his patients, he said, there's a link between emotional stress and flare-ups, just as Darwin recorded over his lifetime.
Darwin also recorded that happy anticipation would trigger illness, whether it was seeing two concerts in one day or getting a visit from fellow voyagers on the Beagle.
Fleisher said he's an avid admirer of Darwin's ideas and his gracious manner.
While they disagree over the role of mitochondrial dysfunction, Hayman and Fleisher both wish that CVS attracted more attention so it could be better diagnosed and managed.
The name cyclic vomiting syndrome is not one that attracts sympathy or funding, Hayman said. He'd like to change it to Intermittent Mitochondrial Failure (IMF), though that's unlikely to occur unless science agrees on a mitochondrial cause.
In the meantime, how about Darwin's disease?
Contact staff writer Faye Flam at 215-854-4977 or firstname.lastname@example.org