Cátedra de Otoacústica Evolutiva y Paleoantropología (Hospitales Madrid-Universidad de Alcalá), Departamento de Ciencias de la Vida, Universidad de Alcalá, Campus Universitario, Ctra. Madrid-Barcelona km 33,600, 28871 Alcalá de Henares, Madrid, Spain.
Cátedra de Otoacústica Evolutiva y Paleoantropología (Hospitales Madrid-Universidad de Alcalá), Departamento de Ciencias de la Vida, Universidad de Alcalá, Campus Universitario, Ctra. Madrid-Barcelona km 33,600, 28871 Alcalá de Henares, Madrid, Spain; Departamento de Teoría de la Señal y Comunicaciones, Escuela Politécnica Superior, Universidad de Alcalá, Campus Universitario, 28805 Alcalá de Henares, Spain.
J Hum Evol. 2019 Oct;135:102663. doi: 10.1016/j.jhevol.2019.102663. Epub 2019 Sep 11.
Pathological conditions have been previously documented in the Middle Pleistocene Sima de los Huesos hominins from northern Spain, and several of these have clear behavioral implications. Within this fossil assemblage, Cranium 4 shows bilateral external auditory exostoses which have been preliminarily interpreted as causing a significant hearing loss in this individual. If confirmed, this would be the oldest recorded case of deafness in human history and could have important implications for the antiquity of this condition, as well as social interactions. To further investigate this case, the current study presents 3D reconstructions of the entire outer and middle ear, based on computed tomography scans of both temporal bones in Cranium 4. We established the degree of stenosis in both external auditory canals, showing that in both cases the degree of stenosis is less than 52% of the original cross-sectional area of each canal. Based on clinical studies in living humans, the buildup of wax due to the degree of stenosis in Cranium 4 is unlikely to have caused frequent external ear infections. In addition, we estimated the pattern of sound power transmission up to 5 kHz in both ears relying on a comprehensive model developed in the bioengineering literature and which has been applied previously to the Sima de los Huesos hominins. The model was modified to account for the peculiar shape of the pathological external ear canals in Cranium 4. The results show that this pathology had little to no influence on the sound power transmission in this individual. Thus, we conclude that the exostoses present in both ears of Cranium 4 did not significantly affect their hearing.
先前已经在西班牙北部中更新世西玛德洛斯 huesos 古人类中记录了病理状况，其中一些状况具有明显的行为意义。在这个化石组合中，4 号头骨显示双侧外耳外生骨赘，初步解释为该个体听力严重损失。如果得到证实，这将是人类历史上有记录的最早的耳聋病例，可能对该状况的古老程度以及社会互动产生重要影响。为了进一步研究这个案例，目前的研究根据 4 号头骨中颞骨的计算机断层扫描，呈现了整个外耳和中耳的 3D 重建。我们确定了两个外耳通道的狭窄程度，结果表明在两种情况下，狭窄程度都小于每个通道原始横截面积的 52%。基于对活体人类的临床研究，由于 4 号头骨的狭窄程度而导致的耳垢堆积不太可能导致频繁的外耳感染。此外，我们还根据生物工程文献中开发的综合模型，估计了双耳在 5 kHz 及以下的声功率传输模式，该模型之前已经应用于西玛德洛斯 huesos 古人类。模型经过修改，以适应 4 号头骨病理性外耳通道的特殊形状。结果表明，这种病理学对该个体的声功率传输几乎没有影响。因此，我们得出结论，4 号头骨双耳的外生骨赘并没有显著影响其听力。
