Research Article: 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)

Date Published: June 4, 2018

Publisher: Public Library of Science

Author(s): Irene Esteban, Curtis W. Marean, Erich C. Fisher, Panagiotis Karkanas, Dan Cabanes, Rosa M. Albert, Michael D. Petraglia.

http://doi.org/10.1371/journal.pone.0198558

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.

Partial Text

The southern African sub-region provides some of the richest archaeological records for a key phase in the evolution of modern humans, dating between ~160–40 ka, when modern humans evolved, began displaying advanced behaviours, and then dispersed from Africa [1]. These advanced behaviours include the systematic exploitation of marine resources [2,3], heat-treatment of lithic raw materials [4–6], shell bead production [3,7], bone tool technology [8–10], the engraving of objects such as ochre nodules, faunal remains and ostrich eggshell [3,8,11–18], the use of pigments [2,15,19], and early microlithic technology and perhaps advanced projectile weapons [20,21].

Table 1 lists the sixty-three samples with a minimum number of recognizable phytolith morphotypes (>50), together with their stratigraphic location and description, and the main phytolith and mineralogical results. The description of samples with insufficient number of identifiable phytoliths is given in Supplementary Material (S1 Table). The phytolith morphotypes identified, taxonomic association and its frequencies in samples from the different StratAggs are listed in S2 Table. Sixty-two phytolith morphotypes were identified [see phytolith morphotype descriptions in Esteban [118], which were later grouped by plant types and plant parts into twelve general categories: grasses (Poaceae), restios (Restionaceae), sedges (Cyperaceae), palms (Arecaceae), leaves, wood/bark and fruits of dicots, spheroids (non-decorated margins), stomata, elongates with and without decorated margins, and irregular and indeterminate morphologies. Note that the term dicot was used for all non-monocotyledonous (hereafter—monocots) angiosperms because based on phytoliths it is difficult to distinguish between early-diverging angiosperms and eudicots. Despite non–decorated spheroid morphologies have been typically associated to the wood/bark of dicot and other non-flowering plants (i.e. Gymnosperms) (e.g., [95,109,119,120]), they were grouped separately as they constitute an important component also in restios [96,97].

This study explored the strategies of exploitation of vegetal resources by past hunter-gatherers inhabiting Pinnacle Point during the time span of the origins of modern humans. The main results of this study shed light on the fire fuel used, the mode of occupation of PP5-6N and changes in the strategies of plant exploitation by modern humans inhabiting the south coast of South Africa from ~160–49 ka.

 

Source:

http://doi.org/10.1371/journal.pone.0198558

 

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