External auditory exostosis in prehistoric Chilean populations: a test of the cold water hypothesis

Over one thousand prehistoric crania (n = 1,149) from northern Chile were analyzed to determine if the presence of external auditory exostosis (EAE) was a type of subsistence-induced pathology, a consequence of habitual fishing in the cold water of the Pacific Ocean, rather than genetically determined. To test this occupational hypothesis, the sample was divided according to chronology, type of economy, site elevation, and sex. The crania came from 43 sites, including the coast, lowland valleys (100-2,000 m), and highlands (2,000 to 4,000 m) with a time frame of 7,000 B.C. to the Inca era (1500 A.D.). There was a significant association between EAE, environment, and sex. The coastal inhabitants had the highest prevalence of EAE with 30.7% (103/336), followed by 2.3% (6/24) for the valley people and 0% (0/549) for highlanders. Coastal and valley men were significantly more affected than their female counterparts. Contrary to expectations, there was no significant association between EAE and economy and/or chronology. In the Arica area, the early Chinchorro fishers, without agriculture, had 27.7% (26/94) EAE, the subsequent agro-pastoralists, 42.7% (32/75), and the late Arican agro-pastoral fishers had 35.6% (36/101) EAE. Apparently, with the advent of agriculture, the coastal Arican populations increased their ocean harvests, rather than decreased them, to gain a surplus in order to trade with nonmaritime groups.