500 k.a. of human settlement of the Atlantic façade of Iberia

 

This is one of the many non dated handaxes made from quartzite, found in the Tagus valley in Portugal.  Although the Lower Paleolithic occupation of the Iberia peninsula is now well documented in several contexts, particularly by the archeological findings of the Sierra de Atapuerca region, the early Paleolithic, located in Portugal  is characterized mainly by surface assemblages. This holds true for “Chopper / Chopping tool” sites on the Portuguese littoral (Acafora, Magoito, Praia da Aguda, Laredo das Corchas, and Leifio) that are said to be Lower Pleistocene and numerous, putatively Middle Pleistocene, handaxe ensembles.

The Almonda karstic system opens the window for reviewing 500 k.a. of human settlement of the Atlantic façade of Iberia. The Almonda karstic system is located in the Central Limestone Massif of Estremadura, formed by an ensemble of interconected cavities associated with the spring of the Almonda River. Here, collapsed cave entrances connected to a  network of underground passages document the successive stages of the spring’s downward migration. These ancient outlets were identifed through geophysics-aided speleo- archeological exploration of the system, and some of them have been meretricious excavated. Speleothems formed in the interior passages through the Pleistocene and can be dated by U-series (Diffusion/Adsorption). 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 Almonda karstic system is one of these sites.

So far, the excavated and dated loci relate to: three moments of the Lower Paleolithic (Entrada Superior, Entrada do Vale da Serra, Gruta da Aroeira), the  Middle Paleolithic (Gruta da Oliveira), the Solutrean and the Magdalenian (Galeria da Cisterna and Lapa dos Coelhos), later Prehistory (Galeria da Cisterna), and a Pleistocene hyena den (Gruta do Pinheiro).

The Galeria Pesada Cave (Gruta da Aroeira) in the Almonda karstic system is located in a south-facing cliff. The excavation of this site started in the early 1990ies and the currently published data indicate the existence of a series of geological units within the brecciated deposits. These units present five stratigraphic layers that yielded a dense quantity of lithic and bone remains. The abundant faunal assemblage records species that suggest a late Middle Pleistocene age for the upper part of the Galeria Pesada deposits, indicated by the presence of Corvus cf. antecorax, which became extinct at the end of the Middle Pleistocene.

The numerical dates of a Equus aff. and Mosbachensis tooth which provided an ESR date of ca 241  k.a. corroborate these assumptions. The bone record of this site contains  human remains (Aroeira 1 and 2) . Two archaic human teeth, a mandibular canine and a maxillary third molar, have been recovered and considered has being similar to those of other Middle Pleistocene European humans, though no more precise identification on a species level has been accomplished. The lithic assemblage of Galeria Pesada, essentially made on local raw materials (quartzite, quartz, flint and limestone) contains some Handaxes considered as typical Acheulian. The Levallois method is present, but not as extensively as the discoid one and the excavators underline the important component of small asymmetric bifacial tools, partly bifacial tools and bifacial retouched knives, that are, from a morphological point of view, typical of the Micoquian (Keilmessergruppe; KMG) of central Europe. Despite the striking morphological resemblance, the excavators stated that ‘‘while it may be tempting to proclaim possible connection, such seem highly unlikely”. Within Iberia, there are simply no comparable assemblages of any age. At the moment, the Galeria Pesada assemblages stand alone. According to the extensive cut marks and other modifications found on faunal bones, extensive butchering and defleshing took place in the site; the assemblages may represent the material remains of, if not base camps, than of camp sites where a range of activities took place.

Deeper in the stratigraphy, during MIS11, a human cranium (Aroeira 3)  dating to 390–436 ka provides important evidence on Acheulean-bearing hominins. The human remains were found together with a classical Acheulian. This cranium ( Aroeira 3) 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 with affinities to H. Heidelbergensis,  Homo steinheimensis  and the hominin from Bilzingsleben points to a high diversity in the European Middle Pleistocene hominin record.

Plains animals, namely horse, aurochs, rhino and red deer, form the bulk of hunted game through the entire Paleolithic. Rabbit, birds and tortoise are present through both the Aroeira and the Oliveira sequences, but so far only the tortoise remains from Oliveira show evidence of having been collected and processed by humans. Burnt bone is found in association with anthropogenic faunal assemblages in the basal deposit of Aroeira, ca. 400 ka, and is ubiquitous through the 70,000 years covered by the Middle Paleolithic sequence of Oliveira.

Gruta da Oliveira was discovered in 1989, the site was excavated until 2012 by J. Zilhão. Its 9 m-thick archaeo-stratigraphic sequence is sealed by a thick colmatation breccia and the stone tool assemblages found therein are of Middle Palaeolithic technology from top to bottom. Made on flint, quartz and quartzite, these assemblages are associated with abundant faunal and microfaunal remains. Fragmentary Neandertal fossils were also found in a number of stratigraphic units.Combined with the results of radiocarbon, TL and U-series dating, stratigraphic constraints suggest that the upper part of the sequence (layers 7-12) is of MIS3 age, its middle part (layers 13-14) of MIS4 age, and its lower part (layers 15-27) of MIS5 age.

Hearths were found at the base of layer 14, dated to MIS4, and in layer 21, stratigraphically constrained to MIS5. The layer 21 feature has a diameter of ca.1.5 m, was excavated into the underlying sediment along half of its periphery, and contained large amounts of burnt bone.

The percentage of formal tools, mostly notches and denticulates, is very low. The Levallois method is common. A nearly complete Levallois reduction sequence could be refitted from the lithics scattered around the layer 21 hearth, corroborating the integrity of the context.

Cleavers made on flakes, and hand-axes — are selectively found in low numbers in layers 19-17 (MIS5). This pattern suggests that their production is a temporally discrete phenomenon and, hence, a distinctive feature of the late MIS 5 stone tool assemblages of the region, with possible relationship with the cleaver-yielding assemblages from Northern Spain. Here  numerous sites with flake cleavers ( the “Vasconian”) have been assigned to MIS 5 based on geological or sedimentological evidence and MIS3 by AMS C-14 , TL or OSL.

The Galeria da Cisterna yielded an ensemble of human remains in Pleistocene remnant deposits radiocarbon–dated to the later part of the Magdalenian, in good agreement with their scarce stone tool and faunal content. The archeological context also includes a set of perforated shell beads, suggesting that the human remains entered the site as a result of burial practices.

Chopper from Praia da Agudan

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