Middle Stone Age lithic assemblages from Leba Cave (Southwest Angola)

Highlights

• Leba is a cave excavated 70 years ago with almost any field record.

• Good original labelling and curation allowed to produce a reliable study.

• Detailed lithic analysis shows a coherent stratigraphic MSA sequence.

• Variety of artefacts, sizes and many small artefacts show assemblage reliability.

• Lithic analysis confirms coherent MSA variability.

Abstract

Africa is a key region to understand the emergence and evolution of humans and their distinctive cultural traits. Detailed information exists across the continent, but major areas still lack crucial evidence. One of the most under-represented regions in research about the Middle Stone Age (MSA) is Angola. The geographical position of Angola linking the Central Plateau of Africa to the rainforest, at north, and the Namib Desert, at south, encompasses a mosaic of ecotones that are most relevant to understand the emergence and evolution of human culture in Southwestern Africa.

A detailed analysis of the lithic assemblages from Leba Cave, a site located in the western edge of the Huíla Plateau is presented. These highlands correspond to a strip of the Great Escarpment of Africa, a major landform shaping the relief of the southern half of the continent. In the upper series of the escarpment in southern Angola, the outcrops of dolomites and dolostones present a variety of karstic features with preservation of palaeontological and archaeological remains.

Leba Cave is located at Humpata, Huíla Province, and was discovered during the Portuguese Colonial Missions. A test pit opened in 1950 retrieved a collection of sediments, fauna and lithics. Our study was focused on the lithic assemblages referenced with the three lower horizons in the reported stratigraphy (III, IV, VI). The techno-typological analysis of the lithics showed these assemblages relate to the classic repertoires of the MSA found across Southern and Central Africa. The chrono-cultural significance of these results is discussed, as well as the regional idiosyncrasies that may characterize the lithic assemblages north of the Namib Desert.

Introduction

Current scholarship about African prehistory agrees that the Middle Stone Age (MSA) is a period marked by spatial and temporal variation of archaeological sites and emergence of regional features starting between ~500 and 300 ka (Watts et al., 2016, Wilkins et al., 2012, Wilkins and Chazan, 2012). The beginning of the MSA is usually defined by the transition from a highly persistent mode of stone tool making based on the production of large cutting-tools (LCTs), roughly designated Acheulean or Mode 2 industries, to increasing technological innovation based on pre-determinate blank production roughly designated Mode 3 technologies. The occurrence of prepared core technologies (PCTs) and hafted tools have long been associated with the Homo sapiens and/or “modern cognition” (Shea, 2011, White et al., 2011). Despite their ubiquity, these technologies show variability in time and space, which may reflect different adaptations to contracting environments and habitats due to continental-scale climate change (Basell, 2008, Blome et al., 2012, Trauth et al., 2009). Recent studies about the evolution of the Homo gene emphasize a structured development resulting from a dynamic interplay of ecological drivers, demographics, and inherited traits among African prehistoric populations (Gunz et al., 2009, Skoglund et al., 2017).

Evidence from across the continent supports the paradigm of ‘African multiregionalism’ (Berger et al., 2015, Hublin et al., 2017, Mallick et al., 2016, Mounier and Mirazón Lahr, 2019, Stringer, 2014), rewriting the origins of the Homo sapiens as a deep and complex evolutionary history within Africa. This scenario seems to be consistent with the anachronic emergence of behavioral changes observed in the paleoanthropological record during the Pleistocene (eg. Stewart and Jones, 2016, Wurz, 2013). Yet some regions, where biodiversity is challenged by the extension of shifting environments like the drylands of West and Central Africa, still lack crucial evidence about their specific landscapes, cultural traditions and regional styles. The importance of these shifting environments is a current topic of debate about whether these natural boundaries shaped population genetics and culture within Africa (d’Errico et al., 2017, d’Errico and Stringer, 2011, Scerri et al., 2018).

Angola is located between these two sub-regions encompassing a mosaic of climatic gradients and transitional ecotones between tropical forests, savannah woodlands, desert and coastal regimes. However, vast territories like this have only been superficially explored. During early research on the topic, differences between North and South were highlighted (Breuil and Almeida, 1964, Janmart, 1953), as well as between the Atlantic coast and the inland plains. These were organized in three main ecological zones within Angola (Clark, 1966): the Congo zone, which includes the tropical rainforest between the Congo basin and the Kwanza; the Zambezi zone, including the Zambezi-Okavango basins in the central plateau of Angola; and the Southwest, which comprises the Atlantic coast from the plateau escarpment to the Namib desert. These sub-divisions were adopted by other local researchers (Ervedosa, 1980, Jorge, 1974) as a useful geographical frame for abundant occurrences of lithic industries and regional variants mostly concentrated in the northeast and the coastal southwest.

The extensive work of J. Desmond Clark in the region of Lundas, Angolan Congo, under the sponsorship of the Diamang Company, allowed to establish an important stratigraphic baseline for such post-Acheulean industries as the Sangoan and Lupemban, which occurred in late Pleistocene to Holocene redistributed deposits (Cahen and Lepersonne, 1952, Clark, 1968, Clark, 1963). The Sangoan, sometimes called Kalinian or Sangoan-Kalinian in Western Africa (Breuil and Janmart, 1950, Giresse, 2008), is usually defined by the presence of the core-axe, a heavy-duty tool distinctive from the handaxe, shaped bifacially to produce a single crude cutting edge, usually on large pebbles (Davies, 1976, Van Peer et al., 2004). These tools are found widespread in Africa (Andah, 1979, Cole, 1967, Kuman et al., 2005, McBrearty, 1991, McBrearty, 1988, Sampson, 1974, Scerri, 2017, Van Peer et al., 2003) but their geographical distribution, use and function is poorly understood as it rests mostly on relative dating. Presently, the Sangoan lacks evidence of PCT’s and is more often considered part of Mode 2 industries, rather placing focus on the Lupemban as the first specialized woodland adaptation in Central-West Africa (Taylor, 2016). Despite these considerations, the problem of the beginning of the MSA in Southwestern Africa remains largely unresolved due to the absence of correlating features. Few studies have focused specifically on this region (Allchin, 1964, Gibson and Yellen, 1978, Gutierrez et al., 2001, Ramos, 1970), but evidence indicates the Lupemban toolkits typical of the forested belt cultures have not been found south of the Kwanza (Ramos, 1974, Ramos, 1984).

The archaeological collections brought from Africa to Europe in the 19th and 20th Century provide an important primary record of site locations and artefacts, which allow a first outline of potential areas of research in Angola. In 1883, Portugal founded the Commission of Cartography to map its territories overseas. In the 1930′s, the Board of Geographical and Colonial Research (Junta das Missões Geográficas e de Investigações Coloniais), later becoming the Board of Overseas Research (Junta de Investigações do Ultramar), was founded to lead several plans of action for the scientific development of the colonies. Even though Archaeology was not a priority in the colonial agenda of the Portuguese dictatorship, a series of Geological and Anthropological Missions collected and considered archaeological evidence within their own fields of research (eg. de Matos, 2015). In Angola, prehistoric finds were first highlighted by geological and anthropological mapping (Borges and Mouta, 1926, Breuil and Almeida, 1964). In the Southwest, the suspicion of the existence of early hominins raised by the Pliocene primate fauna discovered at the Leba-Tchíua quarries (Arambourg and Mouta, 1952), motivated a series of missions which resulted in several thousands of artefacts being brought to Lisbon. After the dismantling of the colonial offices in 1975, the collections were kept by the Tropical Research Institute (IICT) (Coelho et al., 2014). Since 2015 the Archaeology collections are curated by the University of Lisbon and include 201 sites from Southwest Angola (Fig. 1). These artefacts relate mostly to survey collections with the exclusion of three, one of them being Leba Cave.

The site was first excavated by José Camarate-França during the Anthropobiological Mission of Angola in 1950 (Camarate-França, 1964). In Clark’s (1966) synthesis of the Angolan MSA, he describes a collection from Leba Cave with a total of 28 artefacts interpreted as Wilton industries. In consequence, the only existing Portuguese manual of Angolan Prehistory by Ervedosa (1980), the interpretations of Clark are merged with Camarate-Françás report on the excavations of 1951–53 misleading the readers about the provenance and significance of the latter. In fact, the lithics examined by Clark relate with a previous assemblage probably when the site was first discovered by Fernando Mouta, with whom Clark had good relations and allowed him to access the artefacts at the Geological and Mining Services of Angola in Luanda (Clark, 1966, p. 2). There is also record of another excavation by Portuguese archaeologist V. Oliveira Jorge and the group of students of Lubango, during five days in March 1974, which retrieved a small assemblage from two archaeological horizons close to the entrance of the cave, but very little information is offered about this study (Jorge, 1975, Jorge, 1974) since V. Oliveira Jorge abandoned the country one month later. After the the independence of Angola, the following years of civil conflicts stalled most of the archaeological work in the region, and only a few archaeologists have worked at the southwestern coast (Gutierrez et al., 2018).