Phytoliths as an indicator of early modern humans plant gathering strategies, fire fuel and site occupation intensity during the Middle Stone Age at Pinnacle Point 5-6 (south coast, South Africa)

Abstract

The study of plant remains in archaeological sites, along with a better understanding of the use of plants by prehistoric populations, can help us shed light on changes in survival strategies of hunter-gatherers and consequent impacts on modern human cognition, social organization, and technology. The archaeological locality of Pinnacle Point (Mossel Bay, South Africa) includes a series of coastal caves, rock-shelters, and open-air sites with human occupations spanning the Acheulian through Middle Stone Age (MSA) and Later Stone Age (LSA). These sites have provided some of the earliest evidence for complex human behaviour and technology during the MSA. We used phytoliths—amorphous silica particles that are deposited in cells of plants—as a proxy for the reconstruction of past human plant foraging strategies on the south coast of South Africa during the Middle and Late Pleistocene, emphasizing the use and control of fire as well as other possible plant uses. We analysed sediment samples from the different occupation periods at the rock shelter Pinnacle Point 5–6 North (PP5-6N). We also present an overview of the taphonomic processes affecting phytolith preservation in this site that will be critical to conduct a more reliable interpretation of the original plant use in the rock shelter. Our study reports the first evidence of the intentional gathering and introduction into living areas of plants from the Restionaceae family by MSA hunter-gatherers inhabiting the south coast of South Africa. We suggest that humans inhabiting Pinnacle Point during short-term occupation events during Marine Isotope Stage (MIS) 5 built fast fires using mainly grasses with some wood from trees and/or shrubs for specific purposes, perhaps for shellfish cooking. With the onset of MIS 4 we observed a change in the plant gathering strategies towards the intentional and intensive exploitation of dry wood to improve, we hypothesise, combustion for heating silcrete. This human behaviour is associated with changes in stone tool technology, site occupation intensity and climate change.

FTIR-Based Crystallinity Assessment of Aragonite–Calcite Mixtures in Archaeological Lime Binders Altered by Diagenesis

“…However, the simultaneous presence of biogenic aragonite from shells, which is a common component of the archaeological record at many sites across the globe, requires a spectroscopic approach able to distinguish between the two. This becomes especially apparent in the case of combustion features where aragonite may be present as a byproduct of high-temperature burning of fuel and as shell fragments embedded in the sedimentary matrix [51,52]. The same applies to aragonitic shells embedded in lime mortars [53].…”

New Excavations at Umhlatuzana Rockshelter, KwaZulu-Natal, South Africa: a Stratigraphic and Taphonomic Evaluation

“…(2) the percentage of fragile morphologies (Esteban et al 2018, and references therein); (3) the diversity of the phytolith assemblage (number of morphotypes identified; Madella and Lancelotti 2012); and (4) the percentage of broken grass silica short cell phytoliths (GSSCPs) bilobate for each unit. This method measures the strength and direction of the association between two ranked variables (phytolith concentration and the taphonomic indicators).…”

The significance of aragonite in the interpretation of the microscopic archaeological record

“…Weiner, Goldberg, and Bar‐Yosef (2002) tracked with FTIR the three‐dimensional distribution of aragonite within prehistoric sediments at Hayonim Cave, Israel, to exclude bone dissolution in places where aragonite was preserved but bones were not found. A similar approach was used at other prehistoric sites such as Kebara Cave, also located in Israel (Weiner et al, 2007), Grotte XVI in France (Karkanas, Rigaud, Simek, Albert, & Weiner, 2002), Pinnacle Point 5‐6 in South Africa (Esteban et al, 2018), and at Iron Age Tell es‐Safi/Gath, Israel (Namdar et al, 2011). Aldeias, Goldberg, Dibble, and El‐Hajraoui (2014) characterized the degree of preservation of biogenic aragonite at Contrebandiers Cave (Morocco) using micromorphology thin sections.…”

“…They showed that biogenic aragonite from G. insubrica , one of the most common bivalves found at archaeological sites in Israel (e.g., Sivan et al, 2006), has a grinding curve markedly different from the curve of pyrogenic aragonite (Figure 3). Therefore, it is possible to assess whether aragonite found within combustion features is of biogenic or pyrogenic origin (e.g., Albert et al, 2008, table 2; Esteban et al, 2018). This method should be calibrated based on the type of biogenic aragonite available at the site, since different organisms mineralize aragonite crystals with various degrees of atomic order (Suzuki et al, 2011).…”