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Internal architecture and micro-biomechanical behaviour of the Neanderthal Kebara 2 hyoid bone compared with modern human hyoids: implication for speech capacity

The origin of human language and in particular the question of whether Neanderthals were capable of speech or complex language remains a highly controversial topic, of great interest to anthropologists. In 1989, Arensburg and his group discovered a well-preserved human hyoid bone from Middle Palaeolithic layers of Kebara Cave (Israel), dating from about 60,000 years BP (Arensburg et al., A Middle Palaeolithic human hyoid bone, Nature 338, 758 (1989)). More recent discoveries of other fossil hominin hyoids have generated a renewed interest in the potential of this bone to give information on the evolution of speech and complex language.

The hyoid is, in fact, the only bone of the vocal tract and therefore its only part that can fossilize (see Figure 1). The hyoid provides support to the larynx and serves as anchor for the tongue and other muscles needed, at least in Homo sapiens, in phonation. It was already known, from the study of its external morphology that the hyoid bones of Neanderthal and modern humans do not differ significantly, while their shape is definitely different  from that of other primates such as chimpanzees. However, to be able to obtain more informatio on the function of the hyoid bone, it was crucial to analyze its internal microstructure, which remodels in response to the mechanical stress to which the bone is subjected.

In the present study, several research groups, with different expertise, have adopted an approach based on the comparison between the microstructural and micro-biomechanical properties of the Kebara 2 hyoid and those of the same bone in Homo sapiens. The study was conducted by an international research team with members from the University of Chieti, ICTP (UNESCO) and Elettra in Italy, the University of New England and of New South Wales in Australia, and the University of Toronto in Canada.


The data for the study were obtained using laboratory-based computed X-ray microtomography (micro-CT), combined with Finite Element Analyses (FEA). In particular, X-ray micro-CT technique can provide, in a non-invasive way, a virtual 3D reconstruction of the bone samples, showing its histological characteristics (trabecular thickness and pattern distribution of the vascular channels) (see Figure 2). FEA modelling allowed us to evaluate the biomechanical response of the bone as a result of the external forces applied to the hyoid by the muscles (Figure 3).
X-ray micro-CT analyses were conducted at the Elettra Tomolab station while FEA modelling was performed by the Australian and Canadian teams under the supervision of Prof. Stephen Wroe. These advanced analytical techniques provided crucial information on morphology and micro-biomechanical behavior of the investigated hyoid bones. They have confirmed that the internal microstructure of the hyoid bone from Kebara is similar to that of modern humans and that, in all the samples, the histological structure is typical of a bone subjected to intense and constant metabolic activity (such as language). Comparisons based on FEA show significant similarities in the micro-biomechanical behavior.

 

Figure 1. (top) Picture showing a mold of Kebara 2 hyoid. (bottom) Volume rendering obtained by X-ray micro-CT showing a virtual sectioning of the Kebara 2 bone. 

 

Figure 2:  3D distribution of stress through cross-section of Kebara 2 hyoid bone. Areas of high stress are displayed in red/white and areas of low stress are shown in blue/green.

This work represents a decisive step forward supporting the hypothesis that the Neanderthals engaged in speech. We infer this from the fact that the hyoid bone of the two species had the same type of biomechanical usage. With the data and analytical tools currently available is not possible to give a conclusive answer to the question if Neanderthals were capable of the critical and syntactical ability needed for complex language. Anyway, these results added to other evidence coming from paleontology, archaeology and paleogenetics. The use of pigments, the subdivision of residential areas into zones, the burial of the dead, the use of feathers as personal ornament, the development of advanced bone tools for leather-working and other behaviors that can be interpreted as forms of symbolism implying complex communication, were part of a cultural package common to both  H. sapiens, and H. neanderthalensis.
 

This research was conducted by the following research team:

  • Ruggero D’Anastasio, Deneb T. Cesana, Luigi Capasso, University Museum – State University “G. d’Annunzio”, Chieti, Italy.

  • Stephen Wroe, Marie Attard, William C. H. Parr, Computational Biomechanics Research Group, Zoology, School of Environmental and Rural Sciences, University of New England, New South Wales, Australia.

  • ClaudioTuniz,“Abdus Salam” International Centre for Theoretical Physics, Trieste, Italy and University of Wollongong, New South Wales, Australia.

  • Lucia Mancini, Diego Dreossi, Elettra - Sincrotrone Trieste S.C.p.A., Basovizza, Italy.

  • Mayoorendra Ravichandiran, Anne Agur, Division of Anatomy, University of Toronto, Department of Surgery, Toronto, Ontario, Canada.

Contact persons:
Lucia Mancini: lucia.mancini@elettra.eu

 

Reference

Ruggero D’Anastasio, Stephen Wroe, Claudio Tuniz, Lucia Mancini, Deneb T. Cesana, Diego Dreossi, Mayoorendra Ravichandiran, Marie Attard, William C. H. Parr, Anne Agur, Luigi Capasso, ”Micro-Biomechanics of the Kebara 2 Hyoid and Its Implications for Speech in Neanderthals”, PLoS ONE 8, e82261 (2013); DOI: 10.1371/journal.pone.0082261

 

Last Updated on Monday, 27 January 2014 16:39