Ignacio MARTÍNEZ^1,2, Rolf QUAM^2,3,4, Manuel ROSA⁵, Pilar JARABO⁵, Carlos LORENZO^2,6, Ana GRACIA^1,2 , José Luis ARSUAGA^2,7

1. Universidad de Alcalá. Dpto. de Geología (Área de Paleontología), Alcalá de Henares 28871 Spain; 2. Centro de Investigación (UCM-ISCIII) sobre la Evolución y Comportamiento Humanos, Madrid 28029 Spain; 3. Department of Anthropology, Binghamton University (SUNY), Binghamton, NY 13902-6000 USA; 4. Division of Anthropology, American Museum of Natural History, New York, NY 10024 USA; 5 Universidad de Alcalá de Henares, Alcalá de Henares 28871 Spain; 6. Institut de Paleoecologia Humana i Evolució Social, Área de Prehistoria, Universitat Rovira i Virgili, Tarragona 43005 Spain; 7. Universidad Complutense de Madrid. Departamento de Paleontología, Facultad de Ciencias Geológicas, Madrid 28040 Spain.

ABSTRACT: The origin and evolution of speech can be approached from the analysis of the paleontological record. Historically, this has mainly dealt with the reconstruction of the upper respiratory tract of human fossils [1-2]. However, after decades of controversy no clear results have arisen from these studies. We propose a new approach to this issue based on the possibility to reconstruct the sound power transmission, through the external and middle ear, in fossil specimens. Of all the human special senses, audition is the most readily accessible in skeletal remains since it is based on physical properties that can be approached through their skeletal structures [3-4]. Studying auditory capacities in fossil species is a major challenge, but has become feasible since the advent of CT-based analyses. The results obtained in the more than 500 kyr old fossils from the site of the Sima de los Huesos (SH) in the Sierra de Atapuerca (Spain) show that these hominins had the same auditory capacities as modern humans [5]. Specifically, they show a widened bandwidth of heightened sensitivity in the midrange frequencies compared with chimpanzees. The Mathematical Theory of Information developed by Claude Shannon [6-7] offers an appropriate theoretical framework within which to interpret these results. The widened bandwidth suggests a greater channel capacity characterized the Atapuerca (SH) hominins, a feature that is directly correlated with the amount of acoustic information that can be received by the human ear.