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. 2017 Mar 28;114(13):3397-3402.
doi: 10.1073/pnas.1619040114. Epub 2017 Mar 13.

New Middle Pleistocene Hominin Cranium From Gruta Da Aroeira (Portugal)

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Free PMC article

New Middle Pleistocene Hominin Cranium From Gruta Da Aroeira (Portugal)

Joan Daura et al. Proc Natl Acad Sci U S A. .
Free PMC article

Abstract

The Middle Pleistocene is a crucial time period for studying human evolution in Europe, because it marks the appearance of both fossil hominins ancestral to the later Neandertals and the Acheulean technology. Nevertheless, European sites containing well-dated human remains associated with an Acheulean toolkit remain scarce. The earliest European hominin crania associated with Acheulean handaxes are at the sites of Arago, Atapuerca Sima de los Huesos (SH), and Swanscombe, dating to 400-500 ka (Marine Isotope Stage 11-12). The Atapuerca (SH) fossils and the Swanscombe cranium belong to the Neandertal clade, whereas the Arago hominins have been attributed to an incipient stage of Neandertal evolution, to Homo heidelbergensis, or to a subspecies of Homo erectus A recently discovered cranium (Aroeira 3) from the Gruta da Aroeira (Almonda karst system, Portugal) dating to 390-436 ka provides important evidence on the earliest European Acheulean-bearing hominins. This cranium is represented by most of the right half of a calvarium (with the exception of the missing occipital bone) and a fragmentary right maxilla preserving part of the nasal floor and two fragmentary molars. The combination of traits in the Aroeira 3 cranium augments the previously documented diversity in the European Middle Pleistocene fossil record.

Keywords: Acheulean; Europe; Neandertal roots; evolutionary patterns; human evolution.

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Fig. 1.
Fig. 1.
(A) Geographical location of Gruta da Aroeira and main sites mentioned in the text. (B) Detail of the excavation area and provenance of the ARO2 U-series sample. (C) Stratigraphic profile and cranium provenance (denoted by its field inventory no. 606).
Fig. S1.
Fig. S1.
(A and E) Almonda escarpment with the position of Gruta da Aroeira and the Almonda River in the foreground. (B) General view of Gruta da Aroeira and the location of the main dated speleothems. (C) Estremadura Limestone Massif with the position of the Almonda spring, the Tagus River, and the Serra d’Aire. (D) Schematic cross-section of the Almonda karst system. (F) Acheulean biface (flint) from level Xb/c. (G) Gruta da Aroeira site plan.
Fig. S2.
Fig. S2.
Acheulean handaxes (bifaces) from level Xb/c. (A) Flint. (BE) Quartzite.
Fig. S3.
Fig. S3.
(A and B) The Aroeira 1 left mandibular canine (A) and the Aroeira 2 left maxillary third molar (B) in mesial (Mes), distal (Dist), buccal (Bucc), and lingual view (Ling). (C) Aroeira 3 maxilla in medial view. Arrows indicate the lateral nasal crest (1), turbinal crest (2); nasal floor (3), and root of the inferior nasal concha (4). (Scale bar, 2 cm.)
Fig. 2.
Fig. 2.
Stratigraphic longitudinal profile of the Gruta da Aroeira, with the location of dating samples (nos.1–8) and human remains indicated. Dating samples are referred to in Table S1.
Fig. 3.
Fig. 3.
The original completely restored Aroeira 3 cranium in lateral view (A) and the virtual reconstruction and original fossil in inferior view (B) (also Figs. S4 and S5). (Scale bars, 5 cm.)
Fig. S4.
Fig. S4.
Various stages during the in situ extraction and restoration process of the fossil, and reconstruction of the Aroeira 3 cranium after cleaning. (A) Outline of the cranium embedded in the breccia. (B) Location of the cranium after its protection with gauze coating and polyurethane resin. (C) Cutting of the breccia with a circular saw to remove the cranium. (D) Protection of the fossil with wooden boards during the fracturing of the speleothem adhering to the wall with a pneumatic hammer. (E) Final stage of the extraction of the cranium. Wooden boards were placed along both sides of the wall while the breccia block containing the cranium was cut along the bottom. (F) Main portion of the cranium embedded within the breccia block. (G) Isolated cranial fragments before restoration. (H) Main portion of the cranium during the removal of the hardened sediments from the endocranial surface. (I) Main portion of the cranium during the cleaning process (Left) and reconstruction of some of the isolated cranial fragments (Right). (J) Detail of the cranial base and temporal bone during the cleaning process. The arrow indicates a thin layer of speleothem coating which remains on the superior portion of the petrous pyramid. (K) Fragments comprising the cranium before reconstruction. (L) Manually joining the fragments together with adhesive. (M) Endocranial view of the reconstructed cranium. (N) Lateral view of the reconstructed cranium. (Scale bars, 5 cm.) Images in KN are from J. Trueba (photographer).
Fig. S5.
Fig. S5.
Virtual reconstruction of the Aroeira 3 cranium in frontal (A), posterior (B), superior (C), and endocranial (D) views. The frontal sinus in D is exposed in a parasagittal section located 4 mm to the right of the sagittal plane. (E) Virtual reconstruction of the Aroeira 3 cranium in a three-quarters view compared with Bilzingsleben B1 (cast).
Fig. S6.
Fig. S6.
The Aroeira 3 cranium compared with Atapuerca SH Cranium 4 and Cranium 5. Atapuerca SH Cranium 5 is oriented in the Frankfurt horizontal orientation; this orientation is estimated for the Aroeira 3 cranium and Atapuerca SH Cranium 4. Aroeira 3 shows a slightly depressed nasion (n) with respect to the glabella (g), whereas in the Atapuerca SH Cranium 5 the nasion and glabella are located in the same vertical plane. The mastoid projection measured from the parietal incisure is shorter in the Aroeira 3 cranium than in the Atapuerca (SH) crania, but the projection is similar in all three crania when measured from the level of the porion. It is possible that the relatively high position of the transverse sulcus in the Aroeira 3 cranium (see Text) is related to the low position of the parietomastoid suture and asterion (a). A clear torus angularis (t.a.) is present is both the Aroeira 3 cranium and Atapuerca SH Cranium 4 but can only be insinuated in Atapuerca SH Cranium 5.
Fig. S7.
Fig. S7.
The Aroeira 3 cranium compared with Atapuerca SH Cranium 5 and the Steinheim specimen. The Frankfurt horizontal orientation is estimated in both the Aroeira 3 cranuim and the Steinheim specimen. The nasion seems depressed relative to the glabella in the Steinheim cranium, but the strong deformation of this specimen precludes a conclusive assessment. The Aroeira 3 cranium is reminiscent of the Steinheim specimen in both the low position of the parietomastoid suture (compared with Atapuerca SH Cranium 4 and 5) and the corresponding short mastoid process when measured from the parietal incisure.

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