External auditory exostosis in adult individuals from late holocene (1500 AP - 19th century) in Southern Patagonia

Abstract

External auditory exostosis (EAE) is a new bone formation of the external auditory canal. It is particularly associated with cold water exposition, but also with low environmental temperatures, wind, trauma, and repetitive infections. Its prevalence has been scarcely studied in past human populations from Southern Patagonia. The aim of this work was to study the prevalence of EAE and its possible relationship to region, sex, age-at-death, and economic strategies in a sample of 24 skulls of Late Holocene adult individuals (18 males, 5 females, and 1 undetermined) from Southern Patagonia. Presence, size, location, form, and laterality of the EAE were determined. In the studied sample, 79.2% (n=19) of individuals were affected by EAE, bilateral in 56.3 % (9/16), of small and middle size (73.7% and 21.1%, respectively). EAE was more frequent in males and middle adults, without presenting significant differences. Similar prevalence of EAE was observed in individuals from coastal and inland regions. However, this was more pronounced in individuals with a terrestrial diet (58.3%), in particular, those from Santa Cruz/Magellan region (33.3%) and from the north of Tierra del Fuego (25%); no significant differences were found with respect to those from southern Tierra del Fuego. These first results suggest the combination of environmental factors (cold water, wind, and low environmental temperature) as possible causes for the high frequency of EAE in these individuals from Southern Patagonia. However, further research including larger samples is necessary.