Description of the skull and its pathologies
This paper focuses on the finding of a skull from the Dolmen of El Pendón in July 2018. Its chronostratigraphic context corresponds to the second phase of use of this megalith. The skull was lying on its right side with the face pointing south, towards the entrance of the burial chamber (Fig. 3). It retained a complete neurocranium, including frontal, both parietal and temporal bones, and the occipital bone without the basilar section. Of the facial bones, the nasal bone, the zygomatics, and the lower region of the maxillary bone (without teeth nor alveolar cavities except for the first left molar) remained. Furthermore, root impressions were visible in the cortical surface of the frontal and parietal regions (Supplementary Fig. S6 and Video).
Figure 3 Skull under study found at El Pendón site. Superior: Frontal and lateral view of the skull (Photo: ÑFotógrafos Photography Study). Inferior: Skull with mastoidectomy in situ in the context of the megalithic ossuary. Full size image
Analysis indicates that it is a mesocephalic skull that belonged to a woman, who probably died at an advanced age. While the obliteration of the cranial sutures is consistent with a middle-aged individual—35–50 years old, the loss of all the maxillary teeth long before death—given the alveolar reabsorption of the teeth and the loss of bone density—suggests an age range closer to elderly. This statement is based on the general good oral health of the community whose remains are deposited in the dolmen. Therefore, the loss of all teeth in life points to elderly individuals. The presence of elder individuals is confirmed by the documentation of fully ossified thyroid cartilages. This particular ossification is estimated to end at 65 years of age2.
The external auditory canal is enlarged on both sides in a postero-superior and inferior direction, connecting the mastoid cells and the tympanic cavity with the outside (Fig. 4). The edges are smooth and round; on the right side, its diameter is 12 mm, while on the left side it is 9 mm. No fracture zones, fissures, or bone calluses are visible on either side. The inner surface of both cavities shows typical speculated bone formations, which reflect common bone reabsorption changes in inflammatory mastoid processes3,4. However, both cavities reflect no important lack of mastoid pneumatisation, something common in individuals suffering from middle ear inflammatory pathologies in childhood5, suggesting a late onset of an underlying disease. It is important to emphasise that the bony wall separating the ear canal from the mastoid—scutum—has been preserved on both cavities (Fig. 4).
Figure 4 Computed tomography scans and details of both temporal bones of the skull under study and some samples of the comparative analysis. Superior: Details of external auditory region on the right (a) and the left (b) temporal bones of the skull under study. It is to be noted the deterioration of the tympanic cavity in both temporal bones due to taphonomic processes. Middle: Present-day skull with mastoidectomy performed by the students of the Faculty of Medicine of the University of Valladolid (c) and example of an archaeological skull without any pathology used for comparative analysis (d). Red arrows indicate the external auditory canal. White arrows point to bone erosion in the postero-superior part of the external auditory canal due to the mastoidectomy. Yellow arrows indicate the scutum—thin bony spur that is formed by the superior wall of the external auditory canal and the lateral wall of the tympanic cavity. *Mastoid process. Inferior: Computed tomography (CT) scans of para-sagittal sections at right middle ear level—the arrows point to the middle ear—from the skull under study (e) and from a present-day skull without pathology (f). Full size image
Signs of bone regeneration and remodelling are evident. Traces of mastoiditis or mastoid abscesses found in palaeopathological analyses of ancient skulls show major osteolytic defects without repair signs, which, in the absence of medication or adequate surgical drainage, often have a tragic end6. Nevertheless, the surface histological analysis show that signs of bone remodelling are manifest in the performed trepanation of this skull, thus evincing the survival of the individual. Remodelling field are binary features presenting forming or resorbing surfaces7. During adulthood this process is a “secondary remodelling”, in which bone resorption and bone deposition occur at the same site replacing old and damaged bone in highly regulated cycle8. In the dry bones we can detect four distinctive surfaces: resorptive, characterized by osteoclasts and resorption lacunae; depository, characterized by osteoblasts; resting—or neutral, characterized by cells performing no bone activity and remodelling reversals, which are interfaces between fields of resorption and deposition9.
Our results shows that bone resorption and resting are the only activity states present over the area of intervention in the left ear (Supplementary Fig. S10). The resorptive surface is identified for the presence of Howship’s lacunae and could be related to the replacement of damaged bone due to infection. Indeed, we do not find any signal of pathological bone. The most plausible interpretation of these results is that after the intervention this woman survived, since the resorption is ongoing, but the pathological bone has been eliminated. In contrast, in the right ear clearly visible resorption areas as well as a bone deposition area provides evidence that remodelling reversal is ongoing (Supplementary Fig. S11). The resorption phase is approximately two weeks in duration. After this phase, the reversal one lasts approximately 4 to 5 weeks10. Thus, the presence of a well-defined reversal line in this right ear means that this woman survived to the intervention.
Differential diagnosis
The hypothesis proposed in this research is that the individual to whom the skull belonged was probably surgically intervened on both ears, with an undetermined period between both interventions. Based on the differences in bone remodelling between the two temporals, it appears that the procedure was first conducted on the right ear, due to an ear pathology sufficiently alarming to require an intervention, which this prehistoric woman survived. Subsequently, the left ear would have been intervened; however, it is not possible to determine whether both interventions were performed back-to-back or several months, or even years had passed. It is thus the earliest documented evidence of a surgery on both temporal bones, and, therefore, most likely, the first known radical mastoidectomy in the history of humankind.
A well documented disease in palaeopathological studies of ancient skulls are cholesteatomas11. A cholesteatoma is a destructive injury of the temporal bone, which tends to expand and progressively erode the adjacent structures, causing hearing loss, vertigo and intracranial complications; it is treated surgically12. A rare type of cholesteatoma is the congenital cholesteatoma, characterised by the presence of epithelial embryological remains in the middle ear, generally associated with well-pneumatised mastoids in young patients, where the destruction of the tympanic cavity predominates5. Acquired cholesteatomas are more frequent; they are associated with sclerotic or diploic mastoids, in which epithelial remains are introduced in the middle ear through tympanic perforation or invagination. This tends to occur in postero-superior quadrants, starting with the initial erosion of the scutum or the bony wall of the atticus13. It is also known as the external auditory canal cholesteatoma, which is usually unilateral and characterised by an epithelial accumulation that may evolve into extensive temporal bone erosion in patients with a history of injuries or surgery. Its spontaneous appearance is quite rare14. Lastly, malignant external otitis, histiocytosis, or tumours can produce extensive bone destruction. However, they are rarely bilateral and often cause the premature death of the individual.
Here, acquired cholesteatoma of the middle ear must be ruled out, since the scutum is present on both temporal bones. Other diseases, such as malignant external otitis or temporal bone tumours are also discarded a priori, since they are rarely bilateral and generally result in an untimely death, for which the documented bone remodelling previously described on both temporals would be impossible. Finally, a bilateral congenital cholesteatoma or one from the external auditory canal—both rare—can hardly be the cause of the mastoid condition found in the tympanic cavity that led to the performance of this pioneering surgery.
Surgical instruments
Together with the above-mentioned macroscopically visible evidences in the temporal bones, seven cut marks at the anterior edge of the surgical trepanation made in the left ear have been identified. They are parallel, short (2–4 mm) and linear with a clear triangular or "V" section. However, these marks are not visible on the right side, probably due to the bone remodelling process that was ongoing (Fig. 5).
Figure 5 Set of cut marks identified on the left temporal bone of the skull under study. Lateral view of the left side of the skull (a), detail of the left temporal bone with the otological surgery (b), and enlarged image of the cut marks located at the anterior edge of the surgical trepanation made in the left ear, next to the mastoid process (c). Full size image
This finding is further strong evidence that this is the earliest mastoidectomy documented to date. Given the pre-metallurgical chronology of the site, this surgical intervention had to be performed with a lithic instrument. Several pieces were deposited as grave goods or ritual offerings next to the dead. The most important were tools made of flint of different provenance, of which several typologies have been identified: simple and retouched blades of different sizes, geometric microliths and arrowheads of different shapes (Fig. 6).
Figure 6 Selection of a set of flint lithic tools—blades, geometric microliths, and arrowheads—from the El Pendón ossuary. In the line below, four lithic tools that were submitted to a 'blind' analysis by a specialist in traceology and use-wear analysis (Supplementary Text S3). Full size image
A blind traceological analysis was conducted on a set of lithic tools from the dolmen with the purpose of identifying the possible technique or tool that allowed performing this particular surgery. One piece showed signs of having been used for butchering and probably came into contact with bone material: a flint blade, 31 mm in length and 7 mm wide at its distal end, with simple direct retouches that formed slight indentations (Fig. 6). The traceological analysis has revealed that after being extracted from the core the blade was subjected to heating that did not exceed 300/350 °C, given the lack of fire-cracks and other type of heat treatment marks (Supplementary Fig. S9 and Text S3).