Geoarchaeological investigation of occupation deposits in Blombos Cave in South Africa indicate changes in site use and settlement dynamics in the southern Cape during MIS 5b-4

Abstract

The archaeological assemblage recovered from the Middle Stone Age (MSA) levels in Blombos Cave, South Africa, is central to our understanding of the development of early modern humans. Here, we demonstrate that the cultural and technological innovations inferred from the Blombos Cave MSA record also correlate with significant shifts in site use and occupational intensity. Through a comprehensive geoarchaeological investigation of three MSA occupation phases, we identified distinct diachronic trends in the frequency of visits and the modes of occupation. During the earliest phases (ca. 88–82 ka), humans inhabited the cave for more extended periods, but cave visits were not frequent. During the later phases (ca. 77–72 ka), the cave was more regularly visited but for shorter periods each time. We argue that these changes in local occupational intensity, which also coincide with shifts in vegetation, sea levels, and subsistence, can best be explained by broader changes in hunter-gatherer mobility strategies and occupation patterns. Fundamental changes in regional settlement dynamics during Marine Oxygen Isotope Stages 5b-4 would have significantly affected the nature and frequency of social interaction within and between prehistoric populations living in the southern Cape, a scenario that ultimately may explain some of the social and technological advances that occurred there during this time frame.

Early, intensive marine resource exploitation by Middle Stone Age humans at Ysterfontein 1 rockshelter, South Africa

“…While it is challenging to deconvolute other depositional processes contributing at other older MSA sites, some midden layers at these sites can be assessed in comparison to YFT1. For example, the main units hosting individual midden layers at Blombos Cave (55,56), such as unit M2 upper (hosting shell-rich layer CFB/CFC) and unit M3 (hosting shell-rich layer CI), correspond with mean accumulation rates of ∼0.12 m/ka and 0.05 m/ka, respectively. unit M3 yields maximum accumulation rates of 0.09 m/ka and 0.27 m/ ka (68% and 95% CI, respectively).…”

The 100,000–77,000-Year Old Middle Stone Age Micromammal Sequence from Blombos Cave, South Africa: Local Climatic Stability or a Tale of Predator Bias?

“…The lack of burnt elements in M3 is probably due to the low intensity of human occupation (Haaland, 2018;Thompson & Henshilwood, 2011). Although the upper layers of M3 have a greater frequency of hearths and human occupation intensity compared to the rest of the analyzed sequence (Haaland et al, 2020), this is not visible with regards to accidental burning of the micromammal assemblage. The general frequency of burnt elements is lower than the high-intensity anthropogenic deposits in the M1 and M2 Upper phases (Nel, 2013;Nel & Henshilwood, 2016).…”

“…Fischer et al (2010) proposed that the shoreline would have been 1.45-2.33 km from the site during the M3 phase, with a potential further regression during M2 Lower to between 2.33 km (minimum) and 9.42 km (maximum). Due to the offshore topography, BBC would thus have been situated inland from the coast during some periods of MIS 5, as lower sea levels would have exposed the Palaeo Agulhas plain (PAP) (Cawthra et al, 2020;Fischer et al, 2010;Haaland et al, 2020;. Climatic fluctuations on glacial-interglacial timescales are likely to have impacted the southern Cape region as changes in polar ice volume, and interhemispheric temperature gradients shift the location of atmospheric circulation systems (Braun et al, 2020).…”

“…The M2 Lower layers are characterized by low frequencies of anthropomorphic material, although some basin hearths and flakes, blades, and cores of quartz, silcrete, and quartzite are present (Thompson & Henshilwood, 2011). The reduced intensity of anthropogenic material defines the transition from M3 to M2 Lower in the M2 Lower phase (Table 2; Haaland et al, 2020). The start of the M3 phase occurs at 97.7 ± 7.6 kya (95.4% probability) based on the Bayesian age estimates (Jacobs et al, 2020).…”

“…The lack of burnt samples in Upper M3 could be a function of sample location. Charred bones may be found in other cave areas where several hearth features have been identified during excavations (van Niekerk, personal communication, December 8, 2020, Bergen) or through micromorphology analyses (Haaland et al, 2020).…”