Exostoses of the ear canal — more commonly called swimmer’s ear — were surprisingly common in Neanderthals, according to new research by scientists from the United States and France.

External auditory exostoses are dense bony growths protruding into the ear canal.

They are frequently observed clinically in modern humans, often in the context of aquatic sports; hence references to their presence as ‘swimmer’s ear’ or ‘surfer’s ear.’

Such exostoses have been noted among the Neanderthals and a few other Pleistocene humans, but little research has examined how the condition might inform our understanding of past human lifestyles.

In the study, Washington University researcher Erik Trinkaus and his colleagues from the University of Bordeaux and CNRS examined well-preserved ear canals in the remains of 77 ancient humans, including Neanderthals, archaic and early modern humans.

While the samples of archaic (20%) and early modern humans (Middle Paleolithic – 25%, Early/Mid Upper Paleolithic – 20.8%, Late Upper Paleolithic – 9.5%) exhibited similar frequencies of exostoses to modern human samples, the condition was exceptionally common (56.5%) in Neanderthals.

Approximately half of the 23 Neanderthal remains examined exhibited mild to severe exostoses.

“The most likely explanation for this pattern is that these Neanderthals spent a significant amount of time collecting resources in aquatic settings,” Dr. Trinkaus and co-authors said.

However, the geographic distribution of exostoses seen in Neanderthals does not exhibit a definitive correlation with proximity to ancient water sources nor to cooler climates as would be expected.

“Multiple factors were probably involved in this high abundance of exostoses, probably including environmental factors as well as genetic predispositions,” they added.

“An exceptionally high frequency of external auditory exostoses among the Neanderthals, and a more modest level among high latitude earlier Upper Paleolithic modern humans, indicate a higher frequency of aquatic resource exploitation among both groups of humans than is suggested by the archeological record,” Dr. Trinkaus said.

“In particular, it reinforces the foraging abilities and resource diversity of the Neanderthals.”

The findings were published in the journal PLoS ONE.

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E. Trinkaus et al. 2019. External auditory exostoses among western Eurasian late Middle and Late Pleistocene humans. PLoS ONE 14 (8): e0220464; doi: 10.1371/journal.pone.0220464