A professor of dentistry and his colleagues have published a theory that seeks to explain why Inuit who encountered members of the doomed Franklin Expedition in the 19th century noticed the men had hard, dry and black mouths.
Russell Taichman at the University of Michigan says several explorers who interviewed Inuit who encountered the British sailors after they had abandoned their icebound ships noticed strange dental symptoms.
Taichman, who is from Toronto and has long been fascinated with Sir John Franklin's failed mission to locate the Northwest Passage, said the symptoms didn't seem to fit other theories about what befell the crew, such as scurvy, lead poisoning or spoilage in the tinned food they carried.
So, he and a librarian at the university, Mark MacEachern, began combing through medical literature to figure it out.
"What kept coming up several times was tuberculosis," said Taichman in an interview from Ann Arbor, Mich.
"It was pretty common in British sailors at the time, living in close quarters."
Taichman, who typically examines how tumours spread to bone marrow, said he discussed the finding with an oncologist and hematologist Frank Cackowski, who explained that tuberculosis can cause adrenal deficiency, or Addison's disease.
Addison's can produce the symptoms that were observed by the Inuit, Taichman said, although he noted it rarely progresses to that point in modern times.
He said that long term, it can be fatal.
The theory was published earlier this year in the journal Arctic.
Franklin left England in 1845 with 129 men to search for a northern sea route between the Atlantic and Pacific oceans. No one from the two ships ever returned, and search missions determined that both ships became icebound and were abandoned.
Remains of some of the sailors have been found. The ships weren't located until 2014 and 2016.
Taichman said the descriptions of the Inuit are particularly valuable because he believes they would have noticed and remembered small details.
"They'd never seen white guys before. So any weird looking things besides their skin would have been picked up. They were keen observers of nature," Taichman said.
"It would be like seeing Martians. They weren't functioning like the people you normally knew. So it would have stuck in their minds really clearly."
Taichman said Addison's is often a side-effect of steroid use today, but it was mostly caused by tuberculosis in the 19th century.
Evidence of tuberculosis was noted in three Franklin crewmember's bodies that were exhumed near where the ships were abandoned.
Taichman said people with adrenal deficiency can't regulate sodium well and have dry mouths from dehydration. They also have trouble keeping weight on.
"The Inuit couldn't understand why (the men) were so thin because they were carrying with them cans of food," he said. "And the Inuit opened it up and tasted it and said, 'Hey, it tasted pretty good.'"
The Addison's theory isn't perfect. Even though tuberculosis may have been common in the close quarters of ships at the time, Taichman said Addison's disease wasn't widespread.
However, he said medical literature indicates tuberculosis combined with scurvy or lead poisoning, can bring on Addison's.
High lead concentrations were observed in the recovered bones, which could have come from lead that was used for the tinned food, as well as from lead pipes on the ships that distilled drinking water.
Taichman said the men were also likely suffering from scurvy and that Addison's could have been brought on by a combination of factors.
"It adds another dimension about what could have possibly happened," Taichman said.