Auditory exostosis (AE) has been characterised from the medical and anthropological perspectives as an adaptive biological response to repeated immersion in cold water as well as exposure to cold environmental temperatures and wind chill. At the archaeological level, the highest prevalence has been found in societies living in coastal environments in areas located at 30–45° north or south latitude with a subsistence pattern based on fishing and mollusc gathering. The region of the lower Paraná River wetlands in Argentina is an area dissected by multiple rivers, streams, and lakes, especially in the Paraná delta near Buenos Aires where these features create a landscape composed of many islands. A variety of archaeological analyses performed on faunal remains, stone tools, bone, and ceramic artefacts are consistent with the interpretation that towards the end of the late Holocene (2000–700 BP), this region was inhabited by hunter–gatherer populations with a subsistence pattern based mainly on fishing and hunting along with the gathering of molluscs. In this work, we present an analysis of 176 crania of individuals recovered from 21 archaeological sites in the region. Results indicate the presence of AE in 6.25% of the cases, with all of these corresponding to adult male individuals. This moderate prevalence coincides with the expected levels for populations where contact with water is frequent in regions located at 30–45° latitude. The absence of female individuals showing evidence of AE allows us to suggest a possible sex‐based division of labour. We hope that this work can contribute to ongoing discussion of the economic and social aspects that characterised pre‐Hispanic life in the study area, while also expanding the available information on AE at the worldwide level. Copyright © 2015 John Wiley & Sons, Ltd.