Neanderthal Surfer’s Ear

I’ve blogged about Neanderthal ear’s recently as a paper had suggested they might have been at increased risk of ear infections, but it turns out that might not be the only ear problem Neanderthal’s faced.

Earlier this year (2019) a paper was published discussing an unusual feature of Neanderthal skulls. It’s been known for a long time that lots of Neanderthal, and archaic human skulls, have small, bony protuberances within their ear canals. Known properly as external auditory exostoses (EAE) these are also seen in modern humans and are caused by repeated exposure to cold, wet conditions. This exposure irritates the ear canal and causes lumps of bone to grow. For this reason it’s often colloquially referred to as surfer’s ear although it equally affects divers and cold-water swimmers.

Studies of ancient human skulls show a prevalence of EAE of around 20%, which is well within modern variation, however Neanderthal skulls show a much higher rate, closer to 50%.  Previous studies had given very little significance to these findings but the new paper focused on the well established connection between EAE and cold water exposure. Since it had long been accepted in humans that EAEs are caused by persistent exposure to cold water and windchill what did this potentially tell us about Neanderthals?

journal.pone.0220464.g004
Examples of external auditory exostoses (EAE) in Neanderthal skulls. Source is scientific paper.

Whether Neanderthals exploited aquatic environments for food to the same extent that ancient humans did is still unclear. There is some scattered evidence of coastal living Neanderthals eating fish and marine molluscs, even seals and dolphins, but it’s hardly overwhelming. If these EAEs really are caused by cold water exposure this would be a crucial piece of evidence that Neanderthals were spending a lot of time either in the water, or in the cold, wet environments along the shore. This would greatly alter what we think we know about our close cousins because until now their diets and behaviours had been thought to be much more limited than those of archaic Homo sapiens. 

There is a problem with what is an extremely alluring idea though. Yes it is true that in modern humans most, if not all of EAE, are associated with cold water exposure but the problem is that a lot of the Neanderthal skulls studied came from populations that were living inland, far away from the chilly coastlines. In the case of two skulls found from a population living near a river, which they could arguably have used for fishing instead, isotope tests on the bones showed they were eating very little fresh fish. More interestingly still the rates of EAE in the skulls were extremely high, far higher even than those in modern populations that we know spend a lot of time in the water. That suggests that although some of this variation probably is caused by exposure to cold water there were also other factors at play here.

There may be a genetic component to the rates of EAE. In modern humans it’s thought that perhaps genetics might predispose some people to developing EAE. Interestingly this article from 1979 actually lists chronic ear infections as a potential cause of EAE which would link nicely to the recent findings about Neanderthal Eustachian tubes.

Most likely it was a combination of factors that led to these very high rates. Neanderthals may have have a genetic predisposition, they may have suffered chronic infections or irritations in the ear canal, and they may also have exploited aquatic habitats for food in some areas. Still it does offer a fascinating insight into the lives of Neanderthals and suggests they were much more complex than we’d first realised.

 

References:

Trinkaus, E. et al. 2019. External auditory exostoses among western Eurasian late Middle and Late Pleistocene humans. PLosOne 14(8).

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