Middle Stone Age (MSA) in the Atlantic rainforests of Central Africa. The case of Río Campo region in Equatorial Guinea

Understanding the evolutionary history of humans within the rainforest ecosystems of Central West Africa poses a significant challenge. These environments are crucial for exploring both the biological and cultural development of Homo sapiens . However, the lack of comprehensive archaeological and chronological sequences in African rainforests hampers efforts to situate them within a broader evolutionary framework. In this study, we present findings from our surveys conducted in northern Equatorial Guinea. Specifically, in the Río Campo (also referred to as Río Ntem) region, we investigated 30 Quaternary stratigraphic outcrops, 16 of which contained stone tools. Among these, the Campo 11 site stands out due to the complexity of its lithic assemblage, representing one of the most significant indicators of human occupation in the Pleistocene of Central West Africa. Geomorphological reconstruction of the area suggests the development of a meandering fluvial system during the Upper Pleistocene. This system was characterized by sandbars and shallow channel beds overlaying a Cretaceous basement. Optically Stimulated Luminescence (OSL) and radiocarbon (14C) dating place the occupation phases within these sedimentary units between over 44,000 and 20,000 years ago, with a lower sand unit dating back 76,000 years, marking the beginning of the Quaternary sequence. The lithic assemblages from Río Campo, particularly those from Campo 11 and Campo 4, provide compelling evidence of human presence approximately 24,000 years ago. These assemblages are characterized by tools associated with the Lupemban technocomplex, including large cutting tools, bifacial points, heavy-duty implements, Levallois cores, and occasional blade production. Their techno-typological attributes align with Middle Stone Age traditions and point to a cultural continuity rooted in the Acheulean–Sangoan–Lupemban succession, which dates back some 250,000 to 300,000 years. Nevertheless, the absence of earlier stratigraphic records limits our findings to a minimum age for human occupation in this region. The timing and extent of the earliest settlements along the Atlantic fringe remain elusive. While Lupemban industries hint at profound cultural continuity in Central African rainforests, the paucity of high-quality archaeological data prevents definitive conclusions. Further research is essential to address these gaps and fully integrate the Central West African rainforests into the broader narrative of human evolutionary history. • Systematic surveys document human presence during the Upper Pleistocene in the Río Campo region, Equatorial Guinea. • MSA human occupations in the Río Campo region occurred between at least 44 ka and 20.6 ka ago. • The lack of earlier archaeological data is attributed to the absence of stratigraphic records predating MIS5. • The persistence of MSA human occupations in west-central Africa is evidenced by a late chronology around 20 ka.