In an analysis of more than 100 ancient adult skulls from the Gulf of Panama, researchers have observed a number of examples of “surfer’s ear”, a condition where a small, bony bump in the ear canal begins to grow after exposure to cold water.

“Bone is a dynamic tissue that responds to external stimuli, so changes in bone structure provide great clues about where and how a person lived and died,” said study author Nicole Smith-Guzmán in a statement. “When I looked at an additional 125 skulls from nine burial sites across Panama, I found seven cases of surfer's ear in males and one in a female skull, all from sites near the Gulf of Panama.” 

Smith-Guzmán believes that the skulls belonged to ancient male divers who lived along the Pacific coast of Panama long ago and probably spent their time looking for pearls and oyster shells that were used for jewelry making. Though Panama is considered a tropical country, the water temperature in its Gulf drops between January and April when northern trade winds force warm water out into the open ocean. Colder water from the depths rises to the surface to replace the warmer water in a process called upwelling, providing nutrient-rich water to sea organisms at the bottom of the food chain.

“We think it more likely that diving in the cold waters of the Gulf caused these cases of surfer’s ear,” said Smith-Guzmán. “Silvery mother-of-pearl ornaments, and orange and purple ones from two large ‘thorny’ oysters in the Spondylus genus were common in burials and comprised an important trade item in the region. Some of these shells wash up on beaches, but by the time Vasco Nuñez de Balboa and other Spanish explorers arrived, their chronicles tell us that expert divers were trained from childhood to dive down to four fathoms to retrieve pearl oysters of desirable large size.”

But why and how these bone growths occur still remains a mystery. The general theory holds that the skin in the ear canal is thin, and cold water or temperatures caused by water and wind force the bone to grow extra layers in the same way that bone spurs can form in the feet after repeated stress. Sea surface temperatures, particularly those below 19°C (66°F), are a strong predictor of ear exostosis, according to the study published in the American Journal of Physical Anthropology. Aquatic activities like deep-water diving in the cold, upwelled waters of the Gulf of Panama probably resulted in bone growths on the ear bones, especially in men.

“I spoke to one ear, nose, and throat specialist in Panama and she has never seen a case of surfer’s ear here, but we want to do a follow-up study in which we look at skulls from a much wider area and also do a survey of doctors in Panama to find out if surfers or divers ever show up with surfer’s ear these days,” said Smith-Guzmán.