The Cochlear Labyrinth of Krapina Neandertals

Abstract

This study presents measurements of the cochlear labyrinth of Krapina Neandertals based on ultra high-resolution computed tomography. The cochlea, a membranous, fluid-filled structure, houses the sensory end organ of the auditory system. Located within the inner ear, the cochlea occupies a spiral shaped cavity within the bony labyrinth of the petrous bone. The close anatomical relationship between the membranous cochlea and the bony cochlear labyrinth allows for the determination of cochlear size from fossil specimens. Recent studies with extant primate taxa suggest that cochlear labyrinth volume is functionally related to the range of audible frequencies. Specifically, cochlear volume is negatively correlated with both the high and low frequency limits of hearing so that the smaller the cochlea, the higher the range of audible frequencies. This study shows that the Krapina Neandertals' cochlear volumes are similar to modern Homo sapiens and larger than chimpanzee and gorilla cochlear volumes. Although the nature of the relationship between cochlear volume and hearing abilities remains speculative, the measured cochlear volume in Krapina Neandertals suggests they had a range of audible frequencies that is similar to the modern human range.