Still Bay and serrated points from Umhlatuzana Rock Shelter, Kwazulu-Natal, South Africa

What is Still Bay? Human biogeography and bifacial point variability

“…Atypical Still Bay bifacial points from Apollo 11 in Namibia, and serrated bifacial points within the~71 ka Still Bay point-bearing layers at Umhlatuzana may be examples of this (Lombard et al, 2010;Vogelsang et al, 2010). Still Bay sites of the southern and western Cape coasts are well over 1000 km from the cluster of sites further to the north-east (NE).…”

“…There is also growing support for the notion that behavioural complexity in the MSA arose as a function of oscillating population interactions, with the caveat that inferences regarding specific causes and effects are difficult to draw (Jacobs et al, 2008;Jacobs and Roberts, 2009;Powell et al, 2009). Moreover it is argued that similarity between technological elements in contemporaneous but spatially distant sites provides evidence for such interaction, which occurred across substantial distances in the Still Bay and Howiesons Poort (Wadley, 2007;Lombard et al, 2010;Henshilwood and Dubreuil, 2011;Henshilwood, 2012;Mackay et al, 2014;Soriano et al, 2015). In short, these phases of the MSA play a central role in our understanding of both human behavioural evolution and of early modern human demography.…”

“…Still Bay sites of the southern and western Cape coasts are well over 1000 km from the cluster of sites further to the north-east (NE). However, bifacial point industries in~70e77 ka levels found across the southern African sub-continent tend to be associated with the Still Bay techno-tradition, although this attribution has been carefully qualified in some cases (Lombard et al, 2010;Conard et al, 2013). In the context of continental scale variability, it is of critical importance where the lines are drawn for particular assemblage types and requires rigorous testing before inferences can be drawn about cultural transmission and biogeography.…”

Single-grain OSL dating at La Grotte des Contrebandiers (‘Smugglers’ Cave’), Morocco: improved age constraints for the Middle Paleolithic levels

“…Overdispersion is a quantitative estimate of the amount of spread in the D e data set after allowance has been made for measurement uncertainties Roberts et al, 2000). At archaeological sites, D e overdispersion may reflect the post-depositional intrusion of younger or older grains by natural processes or anthropogenic activities (e.g., Bateman et al, 2003Bateman et al, , 2007aFeathers et al, 2006a,b;Jacobs et al, 2006bJacobs et al, , 2008aDavid et al, 2007;Marean et al, 2007;Porat et al, 2006;Lombard et al, 2010;Tribolo et al, 2010), the in situ breakdown of unbleached roof spall in otherwise well-bleached sediments (e.g., Roberts et al, 1998Roberts et al, , 1999, inhomogeneous or partial resetting of the OSL signal prior to burial (e.g., Olley et al, 1999Olley et al, , 2004Olley et al, , 2006Murray and Olley, 2002), and/or the effects of variations in the beta dose received by individual grains of sand (e.g., Murray and Roberts, 1997;Olley et al, 1997;Roberts et al, 1999;Jacobs et al, 2008a,c;Haslam et al, 2011). To discriminate between these possibilities, the extent of overdispersion is routinely quantified and the D e distributions are examined visually to discern any patterns in the data.…”

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“…By measuring grains individually, those with aberrant OSL properties can be identified and discarded from the data set, and grains with bright signals, which are in agreement with the underlying physical and mathematical models, can be selected for determination of the equivalent dose (D e ), which is divided by the environmental dose rate to calculate the OSL age (Jacobs and Roberts 2007). With single-grain analysis, it is also possible to directly check the stratigraphic integrity of archaeological deposits for possible effects of post-depositional disturbance (e.g., mixing by anthropogenic or other processes) and to assess the adequacy of pre-depositional light exposure (David et al 2007; Jacobs 2010; Jacobs and Roberts 2007; Jacobs et al 2006Jacobs et al , 2008Lombard et al 2010; Roberts data sets and avoid shortcomings in any single technique or sample type. All three techniques rely on the same physical principles-ages are calculated by measuring the total accumulated ionizing radiation stored in the crystal structure within the mineral compared to the total radiation dose rate arising from within and without the sample (Aitken 1985).…”