External auditory exostoses among western Eurasian late Middle and Late Pleistocene humans.

Erik Trinkaus,Mathilde Samsel,Sébastien Villotte,Michael D Petraglia

doi:10.1371/journal.pone.0220464

Abstract

External auditory exostoses (EAE) have been noted among the Neandertals and a few other Pleistocene humans, but until recently they have been discussed primary as minor pathological lesions with possible auditory consequences. An assessment of available western Eurasian late Middle and Late Pleistocene human temporal bones with sufficiently preserved auditory canals (n = 77) provides modest levels of EAE among late Middle Pleistocene archaic humans (≈20%) and early modern humans (Middle Paleolithic: ≈25%; Early/Mid Upper Paleolithic: 20.8%; Late Upper Paleolithic: 9.5%). The Neandertals, however, exhibit an exceptionally high level of EAE (56.5%; 47.8% if two anomalous cases are considered normal). The levels of EAE for the early modern humans are well within recent human ranges of variation, frequencies which are low for equatorial inland and high latitude samples but occasionally higher elsewhere. The Early/Mid Upper Paleolithic frequency is nonetheless high for a high latitude sample under interpleniglacial conditions. Given the strong etiological and environmental associations of EAE development with exposure to cold water and/or damp wind chill, the high frequency of EAE among the Neandertals implies frequent aquatic resource exploitation, more frequent than the archeological and stable isotopic evidence for Middle Paleolithic/Neandertal littoral and freshwater resource foraging implies. As such, the Neandertal data parallel a similar pattern evident in eastern Eurasian archaic humans. Yet, factors in addition to cold water/wind exposure may well have contributed to their high EAE frequencies.

Highlights

In his classic monograph on the Neandertal skeleton from the Bouffia Bonneval in La Chapelle-aux-Saints, Corrèze, France, Marcellin Boule [1] noted the presence of bony growths in the auditory canals
External auditory exostoses among western Eurasian later Pleistocene humans auditory exostoses has been noted in ten Middle Pleistocene humans [2,3,4,5], three additional Neandertals [6,7], three eastern Eurasian later archaic human [5], a few eastern early modern humans [5,8], and in one western Upper Paleolithic modern human [9]
The frequency of External auditory exostoses (EAE) for the Early/Mid Upper Paleolithic (E/MUP) sample is moderately high for a sample that should have been paleoclimatically similar to recent human high latitude (>45 ̊) populations

Summary

Introduction

In his classic monograph on the Neandertal skeleton from the Bouffia Bonneval in La Chapelle-aux-Saints, Corrèze, France, Marcellin Boule [1] noted the presence of bony growths (exostoses) in the auditory canals External auditory exostoses (EAE; torus acusticus) are dense bony growths protruding into the external auditory canal. They are frequently observed clinically in modern humans, often in the context of aquatic sports ( references to their presence as “swimmer’s ear” or “surfer’s ear”). First documented more than a century ago clinically [11,12], their distributions across human populations have been considered anthropologically since the 1930s [13,14,15,16,17], being employed as one of suite of discrete cranial traits for population affinity studies Their distribution among later Holocene humans has been shown to vary latitudinally and to correlate with habitual exposure to cold water [5,18,19,20,21]. Clinical reports show that ears exposed to a combination of water and cold air, as represented by wind chill, are more likely to develop EAE and at a faster rate [25,28,35]

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