The story of Franklin's lost expedition to find the Northwest Passage bridges the gap between by sea folklore, forensics, archaeology, and science. Around 170 years ago, Franklin's ships sunk under mysterious circumstances, but now a thumbnail from one of the crew is helping scientists figure out what went on.
The HMS Erebus and HMS Terror headed for the Arctic in a joint expedition under Captain Sir John Franklin in 1845. At some point around King William Island near the Canadian Arctic Archipelago, the ships sunk along with all 129 men. Written logs from the ship go up until April 1848, detailing that much of the crew had fallen ill and the remaining survivors took to the land to find help. Inuits from the area even reported that the men had resorted to cannibalism. Although Erebus was discovered in 2014, and Terror in 2016, the rest of the story remains shrouded in tall tales and doubt.
In 1981, archeologists and scientists found the mummified remains of some of the crew who had managed to reach Beechey Island, but unfortunately died there, and began to carry out analysis on the only physical remains left by the expedition. It’s been the long-held belief that the crew succumbed to lead poisoning, perhaps from their diet of tinned food from soldered cans.
A new study by Candian researchers, and published in the Journal of Archaeological Science: Reports, has taken a further look at the thumbnail of 25-year-old John Hartnell, a crew member of HMS Terror, whose mummified remains were one of the bodies found. The researchers used applied laser ablation technology to test out the lead-poisoning hypothesis, which can be used to determine metals exposure in mammals. Curiously, it showed that Hartnell’s lead levels were within a healthy range.
The researchers then used stable isotope analysis on the nail to assess sources of protein in the sailor's diet. This revealed that Hartnell had a chronic zinc deficiency. This lack of zinc in his diet would have affected his vitamin A metabolism, leaving him with a diminished immune system and subject to the diseases that eventually killed him, namely tuberculosis and pneumonia.
“The process of starvation from tuberculosis in Hartnell resulted in the exponential release of previously stored lead from his bones into the blood. Lead concentrations were only high and increasing at the end of his life when he was already likely near death," said Dr Jennie Christensen, researcher and Founder of TrichAnalytics, in a statement. "This explains why previous researchers discovered high lead concentrations in soft tissue; however, they erroneously concluded it was due to recent exposure.”
Dr Rob Lamb of study partner Canadian Light Source added: “This is a great example of what happens at light source facilities - scientists from different disciplines coming together under one roof, doing great science to solve big problems and, sometimes, great mysteries like this one.”