Heritage Cases

This application is to export flotation samples containing charred plant macrofossils from the archaeological site Boomplaas to Australia for the purpose of understanding the role of plant foods in ancient human diets. The goal of the analysis is to provide the first systematic study of plants foods in Boomplaas Cave’s Pleistocene archaeological deposits. Charred plant macrofossils include endocarp and mesocarp (‘nutshell’ or ‘fruitstone’) from a variety of fruit and nut producing species; vegetative parenchyma from USOs (‘roots and tubers’); stem tissue from the Arecaceae (palm) family and (iv) various other fragments of plant material. For many plants the energy reserve to feed new plant growth comes from starch stored in underground storage organs, such as underground stems (tubers), rhizomes and roots. The parenchyma found in underground storage organs has several distinct morphological and identifying characteristics: the cells have a distinct organisation structure; the cells are different from the elongated fibres, tracheids and vessels in wood fragments; rhizomes and tubers can have secretory cavities (that can contain essential oils such as the flavour in ginger or secondary metabolites as a defence mechanism) and lateral or terminal buds and detachment scars on the endermis; and distinct organisation of the vascular structure. These features allow the identification of cooked starchy plants. These remains provide important and unique information that can aid in the identification of ancient plant foods. Furthermore, these microscopic plant remains may be used to reconstruct changes in environmental conditions. Recovering these plant remains can be difficult, but the newly implement complete flotation strategies employed at Boomplaas ensure maximum recovery of charred plant remains from excavated deposits. These then provide the basis for the reconstruction of ancient plant dietary processes and human occupation patterns at high resolutions. Archaeologists have demonstrated the importance of these charred plant remains elsewhere in the world (Florin et al. 2020, 2021) and in South Africa (Larbey et al. 2019) but the potential to use these methods more widely remains under-explored. Therefore, for this project, we propose to use charred plant macrofossils to better understand Boomplaas’ ancient dietary patterns more accurately and to better understand the site’s paleoenvironmental context. The charred plant macrofossils derive from sediment passed through a water flotation system designed to maximize the recovery of these lighter plant remains. Additionally, we will use these samples to provide contextual data that will guide other aspects of the research at Boomplaas including the site’s excavation strategy and future sampling. Samples necessary for this project consist of bulk sample bags of floated and sieved sediment-NO soils. All samples were piece-plotted and recorded. Samples will be analyzed by Dr. Anna Florin at the Australian National University in Brisbane. Boomplaas Cave We are applying for an export permit to undertake the first systematic analysis of charred plant macrofossils recovered from flotation samples at Boomplaas (BPA) Cave. This project is taking place at ERF 30/33, Boomplaas, Cango Valley, Eden District, Western Cape (HWC permit case number 18021501AS0223E). BPA is an important site to study because it is located along the northern margin of the Little Karoo Basin within a year-round rainfall regime and can provide insight into how environmental change in this rainfall regime may have influenced past populations, specifically during the Middle Stone Age-Later Stone Age transition. The deposits date back to 80 ka; however, exact nature of the site’s occupation history and the site’s depositional history remain under-studied (Pargeter et al. 2018). Hilary Deacon’s excavations pioneered several field techniques at Boomplaas, including early efforts at sediment flotation for plant macrofossil recovery, however, that study did not employ the complete flotation strategies now in use at the site nor did it sample the resulting charred macro plant remains in the manner we now propose. Currently, the site’s macro plant remains are only coarsely defined and described leaving several questions about the role of plant foods in ancient human diets at the site and the role these remains could play in paleoenvironmental reconstructions. Field Methods Between August and October 2022, we excavated 173 contexts (lots) including hearths, activity areas, and general archaeological layers from Boomplaas covering deposits dating to 80-19 ka. The sediment from each of these contexts was then passed through a custom-built flotation machine that allowed for the separation of lighter charred macro plant remains from other archaeological finds in each sample. Flotation is the common method for collecting charred botanical samples, such as wood charcoal and parenchyma. The flotation process involves depositing sediment from archaeological contexts into water and collecting charred plant fragments as they float to the top. The resulting charred macro plant remains, referred to as ‘flot’, were dried, bagged, and weighed separately from the rest of the resulting floated materials (which include stone tools, bone, ochre etc.) High-resolution photography is taken to document the location of each excavated lot so that sample locations can be modeled in 3-dimensions in ArcGIS. All the samples are currently stored at the Palaeoecology Laboratory at Nelson Mandela University in Port Elizabeth. We propose to export for analysis 173 flot samples of about 40 grams each. These flot samples are essential for building a high-resolution understanding of plant food use at Boomplaas and building a richer paleoenvironmental record for the site. Figure 1 shows an example of the flot samples while Figures 2 and 3 provide examples of the kinds of charred macro plant remains recoverable from these flot materials. Laboratory Methods In the laboratory the flot samples are micro-sorted under a stereo-microscope (Nikon SMZ800 x10, x20, x40). Featherweight spring forceps are used to sort, sample, and select charred macro plant fragments. Fragments are mounted onto Agar Scientific 25mm diameter, 8mm pin SEM stubs, covered with 25 mm carbon adhesive discs, with fragment numbers marked in white ink. Each stub is then analysed in a Hitachi TM 3000 environmental scanning electron microscope. X30 and x40 magnifications are used for whole fragment images and x300-x500 used for parenchyma and morphological feature images. Charred fragments remained stored on SEM stubs and curated in labelled Agar Scientific SEM stub boxes (14 pin type).