The deduction of the level of the human larynx from bony landmarks: Its relevance to the evolutionos speech

Abstract

It has been claimed that the capacity for speech in hominids is related to the level of the larynx relative to its surrounding structures. Lower positioned larynges, such as those found in modern humans, have been said to be a prerequisite for articulate speech. In certain fossil hominids, the level of the larynx has been deduced from the angulation of the styloid process and the distance from the posterior nasal spine to the basion (the distance PB). The hypothesis that correlations exist between these bony features and the level of the larynx was tested in this study. The inclination of the styloid process and the level of the larynx were measured on human cadavers and on lateral x-ray cephalograms of the same cadavers. In addition, the distance PB and the level of the larynx were measured on lateral cephalograms of living adult humans. The inclination of the styloid process and the distance PB were also measured on a series of adult dry skulls. Pearson's correlation coefficients for the three sets of measurements were calculated. Only slight correlations between the inclination of the styloid process, the distance PB, and the level the larynx were found. The results of this study indicate that accurate prediction of the level of the larynx from the inclination of the styloid process and the distance PB is not possible. © 1991 Editrice Il Sedicesimo.