In the Inner Depths of the Ear: The Shape of the Cochlea is an Indicator of Sex

Archaeology
Biology

The auditory section of the inner ear, or the “cochlea,” does not have the same shape from birth depending on whether one is a man or a woman. This is due to the torsion of the cochlear spiral, which differs based on gender, especially at its tip. Demonstrated by a French-South African collaboration, an interdisciplinary effort evolving scientists primarily from the CNRS, UT3 Paul Sabatier, and l’Université Clermont Auvergne,1 these results have helped develop the first reliable method for sex determination, including among children and cases where DNA is missing or too altered. Until now, it was impossible to determine the sex of a child from its skeleton, while for adults this could be done reliably only from studying the pelvis, which is not always preserved. Since the cochlea is among the hardest bones in the skull—a bone that is found very frequently at archaeological sites—this technique can determine the sex of very old fossils, even when fragmentary or immature. This research was featured in an article published by Scientific Reports.

This research received support from the CNRS as part of the 80|Prime programme, designed to support and strengthen interdisciplinarity among CNRS institutes.

spirales montrant l'enroulement de la cochlée
Average female (left) and male (right) shapes for the cochlear spiral curve, whose torsion has been coded on a coloured scale. While the two forms are oriented in the same way, the geometric differences are visible. Credit: C. Samir, A. Fradi, and J. Braga

 

  • 1. From the laboratoire “Anthropologie moléculaire et imagerie de synthèse” (CNRS/UT3 Paul Sabatier), the Laboratoire d'informatique, de modélisation et d'optimisation des systèmes (CNRS/UCA/Mines St-Etienne), and the Institut de mathématiques de Toulouse (CNRS/ UT3 Paul Sabatier/Insa Toulouse/UT1 Capitole/Univ. Toulouse - Jean Jaurès). An otologist from the Clinique Pasteur in Toulouse also co-wrote the article.
Bibliography

Cochlear shape reveals that the human organ of hearing is sex-typed from birth. J. Braga, C. Samir, L. Risser, J. Dumoncel, D. Descouens, J. F. Thackeray, P. Balaresque, A. Oettlé, J.-M. Loubes & A. Fradi, Scientific Reports, 26 July 2019. https://doi.org/10.1038/s41598-019-47433-9

Contact

José Braga
Researcher, Université Toulouse 3 Paul Sabatier
Priscilla Dacher
Deputy head of CNRS press office