Auditory exostoses as an aquatic activity marker: A comparison of coastal and inland skeletal remains from tropical and subtropical regions of Brazil

Abstract

Auditory exostoses are bone masses located in the external auditory canal. Currently, most researchers agree that the environment (especially water temperature, but also atmospheric temperature and wind action) plays a pivotal role in the development of this trait. This article discusses whether the presence of auditory exostoses can be used as an aquatic activity marker in bioarchaeological studies, especially in groups that inhabited tropical and subtropical regions. We analyzed 676 skeletons (5,000 years BP to historical times) from 27 coastal and inland native Brazilian groups. Very low frequencies of auditory exostoses were found in the inland groups (0.00-0.03), but the expected high frequency of auditory exostoses in the coastal groups was not always observed (0.00-0.56). These differences might be explained by the combination of water and atmospheric temperatures in conjunction with wind effects. In areas with mild atmospheric temperatures and wind chill factors, the coastal populations analyzed do not show high frequencies of auditory exostoses. However, high frequencies of auditory exostoses develop where cold atmospheric temperatures are further lowered by strong wind chill. Therefore, the association between aquatic activities, low atmospheric temperature, and wind chill is strongly correlated with the presence of auditory exostoses, but where these environmental factors are mild, the frequencies of auditory exostoses are not necessarily high. Concluding, auditory exostoses should be cautiously used as a marker of aquatic activity in bioarchaeological studies in tropical and subtropical regions, since these activities do not always result in the presence of this trait.

A Stress or Migration Marker (A Study of the Auditory Canal Exostosis in the Skeleton Material of the Middle Bronze Age Population From the Lower Volga Region Burial Grounds)

“…Актуальна точка зрения, высказаная К. Годде [Godde, 2010] и М. Окамура [Okumura, 2007]. Уче-ными были проанализированы скелетные выборки из тропических и субтропических районов Бра-зилии (5000 до н.э.…”

“…Серьезный вклад в изучение ушного экзостоза был сделан А. Грдличкой [Hrdlicka, 1935], Признаки экостоза в основном характерны для мужской части населения [Бужилова, 1998;Velasco-Vazquez et al, 2000;Milаdinovic-Radmilovic, 2010]. Чаще все-го они встречаются у взрослых индивидов и очень редко у подростков [Hrdlicka, 1935;Okumura et al, 2007]. Основными причинами развития экзостозов в ушном канале являются длительное нахождение в холодной воде или ныряние в холодную воду.…”

Detecting evidence of systemic inflammation from osteological markers in the Indian Knoll population of Ohio county, Kentucky.

“…Populations that lived in the ideal 30-45 degree latitude range were more likely to have exostoses, as would be expected; regions in this latitudinal range include the American Southwest, Near East, and parts of Australia (Kennedy 1986:408). A study by Okumura et al (2007) supports this finding. Okumura et al (2007:564) formulated that air temperature played a more significant role in the formation of exostoses, while water temperature was a contributing factor, supported by the increased occurrence of exostoses in groups where wind chill was increased.…”

“…Exostoses have been attributed to a genetic predisposition with an external stimulant (DiBartolomeo 1979), as well as an exclusively environmental, or incidental, cause (Hong 1965;Kennedy 1986;Kuzminsky et al 2016;Okumura et al 2007;Standen et al 1997). Race was proposed to play a role in the predisposition of certain individuals to develop the condition (DiBartolomeo 1979:15-16).…”

“…Many prehistoric coastal populations exhibit the condition (e.g. Kuzminsky et al 2016;Okumura et al 2007).…”