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Science 31 October 2008:
Vol. 322. no. 5902, pp. 733 - 735
DOI: 10.1126/science.1162219
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Reports

Ages for the Middle Stone Age of Southern Africa: Implications for Human Behavior and Dispersal

Zenobia Jacobs1*, Richard G. Roberts1, Rex F. Galbraith2, Hilary J. Deacon3, Rainer Grün4, Alex Mackay5, Peter Mitchell6, Ralf Vogelsang7 and Lyn Wadley8

1 GeoQuEST Research Centre, School of Earth and Environmental Sciences, University of Wollongong, Wollongong, New South Wales 2522, Australia.
2 Department of Statistical Science, University College London, London WC1E 6BT, UK.
3 Iziko Museums of Cape Town, Cape Town 8000, South Africa.
4 Research School of Earth Sciences, Australian National University, Canberra, Australian Capital Territory (ACT) 0200, Australia.
5 School of Archaeology and Anthropology, Australian National University, Canberra, ACT 0200, Australia.
6 School of Archaeology, University of Oxford, Oxford OX1 2PG, UK.
7 Institute of Prehistoric Archaeology, African Archaeology Unit, University of Cologne, Köln 50823, Germany.
8 School of Geography, Archaeology and Environmental Sciences, and Institute for Human Evolution, University of the Witwatersrand, WITS 2050, South Africa.


Figure 1 Fig. 1. Locations of sites at which SB and HP artifacts have been found. Solid circles indicate those sites where HP deposits, have been dated in this study, whereas open circles with a central dot denote study sites that contain both dated SB and HB industries. The symbols x and + indicate other known (or claimed) occurrences of SB and HP, respectively; these sites may have associated independent age estimates. Also shown are the modern rainfall zones: winter (dark gray), all year (medium gray), and summer (light gray). Site acronyms are defined in (20). [View Larger Version of this Image (42K GIF file)]
 

Figure 2 Fig. 2. Optical age estimates (ka) classified by region, archaeological association, and site. Samples are listed in stratigraphic order within each site. Samples with the association "pre-HP" have been identified as being before the start of the HP but not necessarily after the end of the SB. Standard errors {sigma}1 and {sigma}2 exclude and include, respectively, possible systematic error (any systematic error is the same for each estimate and does not affect comparisons between estimates). Shaded boxes and error bars denote 50 and 95% CIs, respectively, calculated using {sigma}1. Intervals for samples from the HP and SB are highlighted in black. Dotted lines indicate the start and end ages of the HP and SB, estimated separately for each region. ZKR denotes samples from Klasies River; other site acronyms are defined in (20). [View Larger Version of this Image (29K GIF file)]
 

Figure 3 Fig. 3. Radial plots comparing age estimates of samples from the HP and SB obtained in different studies. Solid squares denote estimates from this study presented in Fig. 2, with precisions obtained using {sigma}2 (that is, including possible systematic error). Other symbols denote estimates obtained independently by various researchers using different dating methods (table S1). Dashed lines show the estimated start and end ages of the HP period and the midpoint of the SB. Shaded bands indicate ±2 SE (for any age estimate) about each of these lines. Estimates consistent with a common age should scatter mostly within such a band. [View Larger Version of this Image (22K GIF file)]
 

Figure 4 Fig. 4. Age estimates (with 95% CIs) from Fig. 2 plotted alongside oxygen isotope data ({per thousand}, per mil) from the Byrd and European Project for Ice Coring in Antarctica (EPICA) Dronning Maud Land (EDML) ice cores from Antarctica (23, 24). Both records are plotted on a common time scale, achieved by synchronization with Greenland ice core data (24), and the EDML data are lowess-smoothed to 100-year resolution. Ages labeled "pre-HP" in Fig. 2 are omitted here, as they cannot be identified with a specific period. Vertical gray bands show our estimates of the HP and SB periods as well as the pulse immediately post-HP. The gray horizontal bars show mean age estimates and 95% CIs for the late and final MSA periods obtained in (26). [View Larger Version of this Image (20K GIF file)]
 

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Science. ISSN 0036-8075 (print), 1095-9203 (online)