by Hipolito Collado, Sara Garcês, José Julio García Arranz, Hugo Gomes and George Nash

Hipolito Collado, Patrimonio & Arte Research Group. Extremadura University, Spain. Quaternary and Prehistory Group of the Geosciences Center (u. ID73-FCT) Portugal. Sara Garcês, Polytechnic Institute of Tomar, Geosciences Centre of University of Coimbra (u. ID73 – FCT). Earth and Memory Institute (ITM) Mação, Portugal. José Julio García Arranz, Patrimonio & Arte Research Group. Extremadura University, Spain. Hugo Gomes, Geosciences Centre of University of Coimbra (u. ID73 – FCT). George Nash, Polytechnic Institute of Tomar, Geosciences Centre of University of Coimbra (u. ID73 – FCT). Earth and Memory Institute (ITM) Mação, Portugal.

The passage grave tradition is one of the main burial monument styles of the European Neolithic. The architectural style is essentially an artificially constructed cave that includes an entrance/façade and a long passage that leads to a sub-rectangular of circular/ovate burial chamber. The passage and chamber are usually covered by massive roofing stones. These elements are covered by a mound made of cairn and sometimes earth (or a combination of the two). The entrance, passage and chamber elements are constructed using large rock boulder, known as uprights (also referred to as orthostats or peristaliths) sometimes deliberately shaped to fit a particular space within the monument. The majority of this monument type is found within western Atlantic Europe, from the Iberian Peninsula in the south to southern Sweden and Denmark in the north and appears to have been in use from the 5th to the 2nd millennium BCE. During this 3000-year period many idiosyncratic changes to the architecture and burial practices occur, one being the incorporation of engraved and painted rock art (Shee-Twohig 1981; Nash 2006a, Nash 2020).

Between 2016 and 2017 and as part of a Junta de Andalucía-funded project, a Portuguese-Spanish-British team was commissioned to record the rock art within the Dolmen de Soto passage grave in Andalucía (Garcês et al. 2020; Nash et al. 2020). Using a variety of modern scientific recording and sampling techniques, the project revealed a unique window onto the monument’s prehistoric ritual and symbolic past.

The origins of Neolithic tomb building in Mediterranean Europe is often difficult to trace. We know that the Neolithic Revolution occurs in what is termed the ‘Fertile Crescent’ (Northern Israel, Syria and Turkey), around 10,000 BCE but in terms of understanding the development and tomb architecture and how it spread across Europe is still unclear (Whittle 1985, 2018). We do know that during the 4th and 5th millennium BCE passage grave building becomes a dominant architectural style and was probably a development from a previous eastern Mediterranean style (Joussaume 1985). The idea of building a ‘house’ for the dead appears to be a classic Neolithic trait (e.g. Tilley 1991, 1993).

The generic passage grave architecture includes a round mound with an entrance or façade that leads to usually a long passage that is roughly orientated east-west, probably acknowledging the rising and setting of the sun at certain times of the [agricultural] year (Tilley 1991). The passage usually merges or connects with a defined chamber; both elements made from stone uprights and stone roofing slabs. In the case of the Dolmen de Soto the passage/chamber appears to form a continuous galley which constricts halfway along the gallery towards the entrance (Figure 1). The constriction appears to be deliberate, restricting the view from the entrance area to the chamber. Other architectural devices such as stone lintels, thresholds and stone pillars would have further restricted the view (Nash 2006b).

At some point either during construction or more likely when in use, various chamber and passage stone uprights were adorned with engraved megalithic art and accompanied by painted Schematic imagery (Garcês et al. 2020; Nash et al. 2020). Coincidentally, several burials within the passage and chamber areas were located next to these decorative stones (Obermaier 1924).

The passage grave tradition appears to have originally developed in the Iberian Peninsula and eventually formed part of a Neolithic package that included a set of unique grave goods (pottery and stone objects) and moved northwards, transmitting the architectural style to most of the core areas of Atlantic Europe, including Portugal, north-western Spain, Brittany, Channel Islands, south-eastern Ireland, southern Scandinavia, and to a limited extent, the North-west coastline of the British Isles (in particular north Wales, northwest England, western Scotland and Orkney) (e.g. Bradley 1998; Cunliffe 2004; Joussaume 1985; Nash 2007, 2009; Patton 1993; Renfrew 1981; Savory 1968) (Figure 2). Although passage graves varied in size and sometimes landscape location, all were constructed using a set of generic architectural elements that included a circular mound that houses a stone passage and chamber that was accessed via an entrance and façade (Nash 2006; Tilley 1994). The entrance was usually set within the eastern part of the mound and the back of the chamber in the west.

The passage grave tradition within this part of the Iberian Peninsula appears to emerge around 4th millennium BCE (Aguayo de Hoyos & García Sanjuán 2002; Almargo Basch & Arribas Palau 1963). The design concept of a circular mound probably the result of converging architectural ideas that formed around the concepts of annual celestial or life/death cycles; may be the circularity of the mound represented the life cycle where one is born, lives, dies and reborn again? The monument was also a way to honour the dead and to control communities through restricted visual access to those members of the community who were not part of a ruling elite (Bueno Ramírez & Balbín Behrmann 1996). This architectural concept for monument building, along with idiosyncratic burial practices and regionally differing grave good deposition appears to have been in use for at least two millennia, in which time the passage grave tradition changes considerably, both in style, morphology, size and probably use (Nash et al. 2020).

Archaeological interest into the Dolmen de Soto and other monuments in Andalucía has been ongoing for at least 180 years. From this early interest, many Neolithic burial sites in Andalucía were excavated, including a large number of passage graves that formed the Los Millares group in eastern Andalucía (Almargo Basch & Arribas Palau 1963; Joussaume 1985). Unfortunately, these sites were investigated prior to the advent of systematic archaeological excavation and chronometric dating techniques and therefore, understanding the regional chronological sequence has been difficult to quantify. Based on the early excavation accounts the design in architecture and burial deposition are roughly continuous throughout this region of Spain. Previous fieldwork and research had, by the latter part of the 20th century, established distinct monument groups within Andalucía, forming one of southern Europe's largest and most concentrated core areas of Neolithic burial activity (Joussaume 1985). Since the early part of this century, more specific scientific-led research has been undertaken on a number of monuments, including urgent consolidation and conservation work of the Dolmen de Soto (Linares Catela et al. 2014). As part of this programme of consolidation work, the team recorded the rock art that is present on many of the uprights that form the chamber and passage areas of the monument (Garcês et al. 2020).

The Dolmen de Soto is one of around 1650 Neolithic burial-ritual monuments that occupy the region of Andalucía. Within the province of Huelva where the Dolmen de Soto stands, there are around 210 burial-ritual monuments of varying architectural diversity, each forming a number of distinct clusters (Almargo Basch & Arribas Palau 1963; Joussaume 1985). However, the Dolmen de Soto is essentially an isolated monument that stands north of the Tinto River, within the municipality of Trigueros. Its dimensions and isolation suggest that this monument was indeed special.

Based on its architectural style, the dolmen is dated to between 3000 and 2500 BCE which places it within the most recent dating range of the passage grave tradition, contemporary with, say, the large passage graves of the Boyne Valley in Ireland and the two sites in North Wales (Eogan 1986; O’Kelly 1982). It is more than likely that a similar dating range exists for the majority of the two hundred or so monuments that stand within Huelva, although the passage grave tradition elsewhere was in existence 1,500 years earlier. It is conceivable that the site of the Dolmen de Soto and other passage graves within Andalucía mark earlier sites which may have their origins in the Early Neolithic (if not earlier) (Nash et al. 2020).

The Dolmen de Soto was discovered in 1923 by Armando de Soto Morillas and subsequently excavated over three consecutive seasons by the German archaeologist Hugo Obermaier (Obermaier 1924). Much of the monument stood beneath a farmhouse [Figures 3 & 4]. The excavation occurred at a time when modern scientific techniques such as direct chronometric dating techniques and environmental sampling were not readily available. Despite this Obermaier did manage to thoroughly record eight inhumations within the chamber area, each individual had been placed in a crouched (or foetal) position next to upright stone with rock art. A unique grave good assemblage was also uncovered next to each individual and included such items as stone axes and flint knives, decorated and undecorated ceramics, including bowls, cups and plates, a conical bone bracelet and a small selection of marine fossils; all items essential for the journey to the afterlife or for rebirth!

The dolmen de Soto remained in private ownership until 1987 when it was placed in the jurisdiction of Spain’s Ministry of Culture. In 2008 the area of protection was greatly extended following investigations which also provided potential dating evidence that placed its construction towards the latter part of the third millennium BCE [Figure 5]. Excavations on passage graves elsewhere within this part of south-western Europe clearly indicates that the immediate landscape around the monument would have played a significant role in how the monument would have functioned (e.g. Arteaga Matute & Cruz-Auñón 1999, 2001; Carriazo 1962; Collantes de Terán 1969; García Sánchez & Spahni 1959; Linares Catela et al. 2014; Santos Estévez, et al. 1997).

The east-west orientated passage and chamber collectively measure c. 21m in length and is constructed of a series of uprights, 31 of these forms the northern wall, whilst a further 33 stones construct the southern side; both walls in part support twenty large capstones [Figure 6]. The chamber area though, prior to excavation had part of its capstone roof removed. The passage and chamber are set within a low 4m high mound that measures 75 m in diameter making it one of Europe’s largest passage graves monuments [Figure 7]. The vast majority of the uprights were made of greywacke (a type of harden sandstone) with several also made of calcarenite (a type of limestone) and quartzite (Garcês et al. 2020; Linares Catela et al. 2014; Obermaier 1924).

Based on the plan of the monument, the passage gains width and height as one moves from the entrance through to the chamber. The height at the entrance is c. 1.55m and c. 3.9m at the eastern end of the chamber. Both the width and the height are graduated, allowing ancient and modern 'visitors' to move from the entrance into the passage (or corridor) and onto the chamber with relative ease; however, visual access from outside the entrance area to the chamber would have been restricted in order to maintain religious and political power of the people who would controlled and used the internal spaces of the monument (see Tilley 1991).

Rock art was first recognised within the monument during its excavation in 1923 (Obermaier 1924).¹ The rock art comprised a series of representative and abstract figures, usually one to three engravings per passage or chamber upright, 43 stones (60% of the uprights) in total. Engravings include circles, daggers, human figures, cupmarks, geometrics, and circular motifs. Based on the motif style present, the engravings are considered to represent the Schematic rock art tradition of the Late Neolithic/Early Bronze Age that is inclusive to the Iberian Peninsula. Discovered during our survey and associated with the engravings is evidence of haematite and gypsum pigments that have been painted over the engravings, present on 13 uprights. The act of painting over an engraving appears to be an intentional act, probably used to enhance those engravings that were difficult to view when processing through the monument with an oblique lighting source (Nash et al. 2020). However, over the millennia much of the rock art, in particular, the paintings have been absorbed into the stones and therefore cannot be seen with the naked eye. To make sense of these faint images, the team employed a variety of photogrammetric techniques that are now standard practice in rock art research (Garcês et al. 2020). The key recording techniques included 2D / 3D photographic surveys and Decorrelation-Stretch (commonly known as D-Stretch) [Figure 8]. Also employed was Raman spectroscopy which identified the geochemistry of the pigment recipe used to paint some of the uprights [Figure 9].

The photographic survey included all 63 upright stones that delineated the interior walling and the roofing slabs they supported. Although many of the engraved stones had in the past been recorded, our survey identified new rock art. The photogrammetry survey also provided an accurate account of all engravings, however faint they were (Garcês 2020).

One of the important pieces of equipment was lighting. The passage and chambered areas are naturally dark places. In order to understand the wealth and number of engravings present, oblique lighting assisted in illuminating even the faintest engravings. Lighting also assisted in the 3D photogrammetry and animation project, again the angle of the light source was essential. It is probable that our ancient ancestors would have applied a similar technique in order to fully read and comprehend the various symbols and motifs that were encountered along the passage and chamber areas.

¹ See detail account of the rock art from the Dolmen de Soto in Garcês et al. (2020) and conservation issues in Linares Catela et al. (2014).

During the excavation programme at the Dolmen de Soto, Obermaier identified a large number of engravings present on uprights within the passage and chamber areas (Obermaier 1924, 10-15). Of the 43 decorated stones identified within our 2017 survey, four were of significant interest as that revealed something of the warrior society who carved and venerated them. The period when these and other motifs were carved, European society appears to be undergoing significant change. The archaeological evidence shows the introduction and marked rise in the production and use of copper and bronze weaponry. This is also portrayed on the rock art, especially on the walls of burial-ritual monuments. Are we witnessing a period of social and political stress (cf. Bradley 1998)?

Stone 5 which is located on the right-hand side of the passage stands around 1.60m from the ground surface to the roof and is made of greywacke. Apart from engravings this stone also has traces of red pigment on its upper section [Figure 10], along with three engraved circular motifs of similar size below the painted area [Figure 11]. One of the circular motifs retains traces of pigment, probably applied in order to visually enhance it. According to the original excavator Obermaier, a burial was found in front of this monolith.

Stone 20, also made from greywacke is located on the left side of the passage and stands 1.70m above the ground surface. Engraved on this stone are several dagger engravings that, based on archaeological evidence elsewhere are of Bronze Age date. This weaponry is represented by two triangular engravings on the upper section of the stone and one in the lower section. These motifs, along with a diagonal engraved figure, and the way they are positioned may represent a styled human figure [Figure 12]. Interestingly, Obermaier uncovered another burial in front of this stone during his excavation.

Next to Stone 20 is Stone 21. This monolith stands 1.68m in height and is made from greywacke. The stone has several motifs that are clearly engraved in the Schematic style. Several images are made in bas-relief, a technique that is considered a rare occurrence in Europe. Based on the images present, the team considered this stone to have been previously used as a statue-menhir, an engraved standing stone shaped into an anthropomorph that had probably been decommissioned and later re-erected as a passage grave upright, albeit inverted! [Figure 13] It appears that whilst in its current position, several, additional motifs were added including a central band, possibly representing a belt.

Finally, we come to Stone 25, located on the right-hand side of the chamber, and again made of greywacke and standing 1.97m in height [Figure 14]. This stone possesses a unique set of motifs including weaponry. Within the lower section of the upright is a sword or long-bladed knife. Two further weapons are engraved above this and occupy the central section of the upright. Immediately above these motifs and occupying the upper section of the stone is a complex arrangement of lines that appear to represent several stick-like anthropomorphic figures, one of which is holding a weapon above its head.

The project involved both on-site and off-site analysis which included digital photographic enhancement, along with laboratory analysis on the minute pigment samples taken from carefully chosen upright stones, using an archaeometric approach (Gomes 2020) [Figure 15].

The results of the Raman spectroscopy chemical-mineralogical characterisation analysis on the red pigmentation revealed the predominance of hematite (Fe2O3); its presence was consistent throughout the sampling element of the project. Hematite constitutes one of the main components of natural ochre that are used as pigments throughout prehistory and the paintings present in the Dolmen de Soto are no exception to this rule. What is conclusive though is the need by prehistoric artists to enhance engraved motifs with paint. Could this act merely be for visual enhancement or did the paint add to the potency to the engravings?

Within rock art research, this archaeometric-based scientific method is considered relatively innovative and provides some of the answers to many of the fundamental questions about why rock art was executed. The chemical-mineralogical analyses carried out on samples of prehistoric pigments taken from the uprights within the Dolmen De Soto has yielded significant results. The components identified through this method revealed the homogeneity of the raw materials used in pigment production, such as iron oxides. Raman spectroscopy has been used to characterise the main components of prehistoric paintings from many sites world-wide previously; however, it is not easy to uncover these pigment recipes, including possible binders used.

The results show that the raw materials used from creating the reddish pigments were essentially iron oxides and hydroxides (hematite and goethite, in particular). In order to dig deeper into this element of the project, in the future other archaeometric techniques, such as FTIR or Chromatography could be applied with the aim of identify other substances, in particular those chemical constituents associated with binding agents (although these organic substances were not identified in the samples analysed by Raman spectroscopy.

² Permission to sample the pigments for archaeometric analysis, was authorized by Junta de Andalucía.

The techniques employed by the team have been used to record rock art in other Neolithic monuments elsewhere. The Dolmen de Soto is not the only monument possessing both painted and engraved rock art; however, the way the art is constructed, and the stones used to construct the chamber and passage shows that this dolmen is altogether unique. The architecture of the monument is made more significant by Hugo Obermaier’s remarkable discovery of human burials below selected upright stones that contain rock art. Surely, there must have been an association between art and death; the art, providing a poignant memorial to the dolmen’s occupants?

AGUAYO DE HOYOS, P. & GARCÍA SANJUÁN, L., 2002. The megalithic phenomenon in Andalusia (Spain): an overview. In: Proceedings of the Colloquium Origin and Development of the Megalithic Phenomenon in Western Europe (Bougon, Paris) pp. 451-476.

ALMARGO BASCH, M. & ARRIBAS PALAU, A., 1963. El Poblado y la Necrópolis Megalíticos de Los Millares (Santa Fe de Mondújar, Almería). Bibliotheca Praehistorica Hispana ². Madrid. CSIC.

ARTEAGA MATUTE, O. & CRUZ-AUÑÓN, R., 1999. El sector funerario de Los Cabezuelos (Valen-cina de la Concepción, Sevilla). Resultados preliminares de una excavación de urgencia.  Anuario Ar-queológico de Andalucía/1995. Tomo III, 589 - 600. Sevilla. Junta de Andalucía.

ARTEAGA MATUTE, O. & CRUZ-AUÑÓN, R., 2001. Las nuevas sepulturas prehistóricas (tholoi) y los enterramientos bajo túmulo (tartessios) de Castilleja de Guzmán (Sevilla). Excavación de Urgencia de1996). Anuario Arqueológico de Andalucía/1996, 640-651. Sevilla. Junta de Andalucía.

BRADLEY, R., 1998. The Significance of Monuments: On the Shaping of Human Experience in Neolithic and Bronze Age Europe. London: Routledge.

BUENO RAMÍREZ, P. & BALBÍN BEHRMANN, R., 1996. La decoración del Dolmen de Alberite. En J. Ramos Muñoz y F. Giles Pacheco (Eds.): El Dolmen de Alberite (Villamartín). Aportaciones a lasFormas Económicas y Sociales de las Comunidades Neolíticas en el Noroeste de Cádiz, 285-312. Cádiz.Universidad de Cádiz.

CARRIAZO, J., 1962. El dolmen de Ontiveros (Valencina de la Concepción, Sevilla). Homenaje al Profesor Cayetano de Mergelina (Murcia, 1961), 209-229. Murcia. Universidad de Murcia.

COLLANTES DE TERÁN, F., 1969. El dolmen de Matarrubilla. Actas del V Simposium Internacio-nal de Prehistoria Peninsular. Tartessos y sus Problemas, 47-61. Barcelona.

CUNLIFFE, B., 2004. Facing the Ocean: The Atlantic and its Peoples, 8,000 BC to AD 1500, Oxford: Oxford University Press.

EOGAN, G., 1986. Knowth and the passage graves of Ireland. London: Thames and Hudson.

GARCÊS, S., COLLADO GIRALDO, H., GARCÍA ARRANZ, J.J. & OOSTERBEEK, L., 2020. Catálogo de manifestaciones gráficas pintadas y grabadas en el dolmen de Soto. In . In S. Garcês, H. Collado, P. Rosina, P., J.J. García Arranz & L. Oosterbeek (eds.) Pinturas y grabados del Dolmen de Soto, Trigueros, Huelva. (In press).

GARCÊS, S., COLLADO, H., ROSINA, P., GARCÍA ARRANZ, J.J., & OOSTERBEEK, L.., (eds.) 2020. Pinturas y grabados del Dolmen de Soto, Trigueros, Huelva. (In press).

GARCÍA SÁNCHEZ, M. & SPAHNI, J.C., 1959. Sepulcros megalíticos de la región de Gorafe (Granada). Archivo de Prehistoria Levantina, VIII, 43-113. Valencia.

GOMES, H., ROSINA, P., GARCÊS, S., NICOLI, M., VACCARO, C., & PEPI, P., 2020. Análisis de los pigmentos del dolmen de Soto. In S. Garcês, H. Collado, P. Rosina, P., J.J. García Arranz & L. Oosterbeek (eds.) Pinturas y grabados del Dolmen de Soto, Trigueros, Huelva. (In press).

JOUSSAUME, R., 1985. Dolmens for the Dead: Megalithic Building throughout the World, London: Batsford.

LINARES CATELA, J.A., MORA MOLINA, C., LÓPEZ MADROÑERO, M.J., BACEIREDO RODRÍGUEZ, M.I., FONDEVILLA APARICIO, J.J., USÍN GAYO, R., GARCÍA RINCÓN, J.M., OTERO BÉJAR, R., MUÑOZ MATEOS, E., RODRÍGUEZ SOTO, I., AYERBE GARCÍA, J. & TEJADA PUNTA, R., 2014. Dolmen de Soto - Restauración y Puesta en Valor: Un proceso de diagnosis y conocimiento del bien cultural. Sevilla: Consejería de Educación, Cultura y Deporte.

NASH, G.H., 2006a. Light at the end of the tunnel: the way megalithic art was viewed and experienced. Documenta Praehistorica Vol. XXXIII, 209-28.

NASH, G.H., 2006b. The Architecture of Death: The Neolithic Chambered Tombs of Wales. Hereford: Logaston Press.

NASH, G.H., 2009. Gesture, Image, Architecture: how fire and rock art may have behaved in the passage graves of Anglesey, North Wales In. G. Dimitriadis (ed.) Landscape in Mind: Dialogue on Space between Anthropology and Archaeology. BAR International Series 2003, 93-104.

NASH, G.H., 2020. El dolmen de Soto en el contexto de la consolidación de las sociedades agropastorales en el suroeste de la península ibérica y el arte esquemático de la fachada atlántica europea. In S. Garcês, H. Collado, P. Rosina, P., J.J. García Arranz & L. Oosterbeek (eds.) Pinturas y grabados del Dolmen de Soto, Trigueros, Huelva. (In press).

NASH, G.H. & GARCÊS, S., 2017. Secrets of the Dolmens: Discovering lost masterpieces by
ancient artists of the Iberian Peninsula. Current World Archaeology 82, 34-36.

NASH, G.H, GARCÊS, S., GARCÍA ARRANZ, J.J. & COLLADO, H., 2020. A 5,000-year-old mystery: Recording rock art within the Dolmen de Soto. Current World Archaeology, 101, 24-31.

OBERMAIER, H., 1924. El Dolmen de Soto, Trigueros (Huelva). Boletín de la Sociedad Española de Excursiones, Tomo XXXII, 1-31. Madrid. 

O'KELLY, M., 1982. Newgrange: Archaeology, Art and Legend. London: Thames and Hudson.

PATTON, M., 1993. Statements in Stone: Monuments and Society in Neolithic Brittany. London: Routledge.

RENFREW, C., 1981. The Megalithic Monuments of Western Europe. London: Thames and Hudson.

SANTOS ESTÉVEZ, M., PARCERO OUBIÑA, C. & CRIADO BOADO, F., 1997. De la arqueología simbólica del paisaje a la arqueología de los paisajes sagrados. Trabajos de Prehistoria, 54 (2): 61-80. Spanish National Research Council.

SAVORY, H. N., 1968. Spain and Portugal: The Prehistory of the Iberian Peninsula. London: Thames and Hudson.

SHEE-TWOHIG, E., 1981. The Megalithic Art of North-Western Europe. Oxford: Oxford University Press.

TILLEY, C., 1991. Constructing a ritual landscape. In Regions and Reflections (in honour of Marta Stromberg). K. Jennbert, L. Larsson, R. Petre and B. Wyszomirska-Werbart (eds.) Acta Archaeologica Lundensia Series 8, No. 20: 67—79.

TILLEY, C., 1993. Art, architecture and the landscape in Neolithic Sweden, in B. Bender (ed.) Landscape, Politics and Perspectives. London: Berg.

TILLEY, C., 1994. A Phenomenology of Landscape: Places, Paths and Monuments, Oxford: Berg.

WHITTLE, A., 1985. Neolithic Europe: A Survey, Cambridge: Cambridge University Press.

WHITTLE, A., 2018. The Times of their Lives: Hunting History in the Archaeology of Neolithic Europe. Oxford: Oxbow Books.

³ See Nash & Garcês (2017).

→ Discover more about the Rock Art Network
→ Members and affiliated institutions of the Rock Art Network