Supporting Online Material for

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1 Supporting Online Material for Ages for the Middle Stone Age of Southern Africa: Implications for Human Behavior and Dispersal Zenobia Jacobs,* Richard G. Roberts, Rex F. Galbraith, Hilary J. Deacon, Rainer Grün, Alex Mackay, Peter Mitchell, Ralf Vogelsang, Lyn Wadley This PDF file includes: *To whom correspondence should be addressed. Materials and Methods Figs. S1 to S29 Tables S1 to S29 References Published 31 October 2008, Science 322, 733 (2008) DOI: /science

2 Supporting online material Here we give a brief background to the numerical age estimates obtained previously for the Howieson s Poort (HP) and Still Bay (SB) (Section A), the optical (optically stimulated luminescence, OSL) dating study design, procedures and supporting data (Section B), the statistical treatment of the OSL data set (Section C), and the results particular to each of the 9 sites investigated (Section D). Because this is a systematic study, the same OSL procedures have been used at all sites and these are described in Section B. For ease of use, the information and OSL data (e.g., equivalent dose, dose rate, radial plots) pertaining to each of the sites are assembled in site-specific subsections (D.1 D.9). A. Independent numerical age estimates HP and SB deposits have been found (or are purported to have been found) at many sites across southern Africa. These sites are shown in Fig. 1 in the main text, and the following site acronyms have been used: AA Aar 1; AP Apollo 11; BBC Blombos Cave; BPA Boomplaas; BC Border Cave; B1C Bremen 1C; CH Cave of Hearths; DRS Diepkloof; HAA Haalenberg; HAS Ha Soloja; HR Highlands; HRS Hollow Rock Shelter; HP Howiesons Poort; KP Kathu Pan; KRM Klasies River; KKH Klein Kliphuis; KLP Klipfonteinrand; MLK Melikane; MON Montagu Cave; MOS Moshebi s Shelter; NBC Nelsons Bay Cave; NT Ntloana Tsoana; OAK Oakleigh; PAR Paardeberg; PC Peers Cave; PP Pinnacle Point; POC Pockenbanck; RCC Rose Cottage Cave; SEH Sehonghong; SIB Sibudu; UMH Umhlatuzana; WK Wonderwerk Cave. Some of these sites are the subject of this study, but others have previously been dated using a range of numerical dating techniques. In recent years, methodological developments in Quaternary geochronology have been fundamental in creating a calendar-year timescale for the SB and HP in South Africa. The dating methods most commonly employed have been electron spin resonance (ESR) (S1 7), amino-acid racemisation (AAR) (S8 10), uranium-series (U-series) (S11), thermoluminescence (TL) (S12 18), infrared stimulated luminescence (IRSL) (S12, S17) and optically stimulated luminescence (OSL) (S17, S19, S20). Details regarding each of these studies are discussed in detail in Jacobs and Roberts (S21). All ages that have been published 1

3 with supporting information and are still current (i.e., not superseded by subsequent technological and methodological advances) are presented in Table S1. It is difficult to determine a consensus age for the HP and SB based on the current data set of independent ages because of two main problems: (i) the low precisions (i.e., large relative uncertainties) associated with most of the age estimates, and (ii) the wide spread in ages obtained using the same technique, or several techniques, at any particular site and at different sites. The most precise ages are those determined by U-series dating of speleothem, which have relative uncertainties of 2 4% at the 68% confidence interval (one standard error). All other age estimates have relative uncertainties of 5 17%, with the majority falling towards the upper end of this range. As a consequence, there might appear to be some substantial age inversions down a stratigraphic section, but these ages are mostly statistically consistent with each other. As such, there is scanty evidence for age reversals and much stronger support for scatter in ages explicable solely on the basis of their measurement uncertainties (i.e., the variation expected due to statistical probability). The degree of statistical consistency among the various independent age estimates can be conveniently evaluated by displaying them in the form of radial plots (see Fig. 3 in the main paper). The radial plot (S23) has the advantage that it simultaneously displays the age of a sample, its associated relative uncertainty (precision), and the degree of concordance between ages of differing precision. Each age is denoted by a single point on the radial plot. If a straight line is drawn from the zero-value on the left-hand ( standardised estimate ) axis through one of the plotted points, its corresponding age can be read off as the value where the line intersects the curved (radial) axis on the right-hand side. The relative uncertainty for this age can be found by drawing a vertical line from the same plotted point so that it intersects the Precision axis: the precision is the reciprocal of the relative standard error (i.e., an error of 5% corresponds to a precision of 20), so the most precise age estimates always lie furthest to the right on a radial plot. Also, the statistical consistency between different age estimates can be easily assessed, because ages that are consistent with each other at two standard errors (i.e., at the 95% confidence interval) will fall within the grey band that extends from +2 to 2 on the standardised 2

4 Site name Industry Context Technique Sample material Age (ka) Reference Apollo 11 HP F ( AAR OES 63 ± 6 S10 cm depth) HP F ( AAR OES 69 ± 7 cm depth) SB G AAR OES 83 ± 8 Blombos SB CC OSL quartz grains 73 ± 3 S20 Cave SB BZB TL burnt stone 81 ± 10 S16 SB CAB TL burnt stone 67 ± 7 SB CAC TL burnt stone 77 ± 8 SB CCh1 TL burnt stone 68 ± 6 SB CCh1 TL burnt stone 82 ± 8 SB WAB ESR tooth enamel 64 ± 10 (EU) 81 ± 14 (LU) S5 SB CAA ESR tooth enamel 63 ± 8 (EU) 79 ± 12 (LU) SB BZB ESR tooth enamel 64 ± 6 (EU) 87 ± 11 (LU) SB CA ESR tooth enamel 57 ± 7 (EU) 74 ± 11 (LU) SB CB ESR tooth enamel 68 ± 10 (EU) 82 ± 13 (LU) SB CC ESR tooth enamel 70 ± 7 (EU) 86 ± 11 (LU) SB CD ESR tooth enamel 50 ± 5 (EU) 70 ± 9 (LU) Boomplaas HP OCH2 U-series speleothem 64 ± 2 S11 HP OCH2 U-series speleothem 59 ± 2 HP OCH2 U-series speleothem 66 ± 7 HP OCH2 AAR OES *56 ± 6 or 65 ± 7 S10 Border Cave HP 3BS 1 ESR tooth enamel 55 ± 2 $ S4, S6 HP 3BS 2 ESR tooth enamel 65 ± 3 HP 3BS 3 ESR tooth enamel 71 ± 4 HP 3WA ESR tooth enamel 67 ± 6 HP 3WA ESR tooth enamel 61 ± 3 HP 1RGBS ESR tooth enamel 75 ± 4 Diepkloof HP OB2 TL burnt stone 56 ± 5 S14 HP OB3 TL burnt stone 46 ± 5 HP OB3 LM-OSL burnt stone 44 ± 5 HP OB4 LM-OSL burnt stone 54 ± 5 HP OB4 LM-OSL burnt stone 78 ± 8 3

5 Klasies River HP Layer 14 U-series carbonate crust 66 ± 3 S11 HP AAR OES 80 S8 HP near base US-ESR tooth enamel 52 ± 4 S7 HP YS4 TL burnt stone 57 ± 8 S14, S15 HP CP7 TL burnt stone 58 ± 7 HP CP7 TL burnt stone 59 ± 7 HP CP8 TL burnt stone 55 ± 7 HP CP18 TL burnt stone 51 ± 6 HP CP18 TL burnt stone 58 ± 8 HP CP3 TL burnt stone 58 ± 5 HP CP4 C TL burnt stone 57 ± 5 HP CP4 C TL burnt stone 62 ± 7 HP CP6 TL burnt stone 55 ± 5 HP CP7AF2 TL burnt stone 54 ± 9 HP CP7AF2 TL burnt stone 50 ± 4 HP CP10 TL burnt stone 59 ± 7 HP Layer 15 TL/OSL/IRSL sediments 42 ± 5 to 63 ± 10 S17 HP Layer 1/2 TL/OSL/IRSL sediments 51 ± 5 to 64 ± 6 Rose Cottage HP SUZ TL burnt stone 59 ± 7 S13 Cave HP ETH TL burnt stone 42 ± 4 HP BER TL burnt stone 56 ± 5 HP BER TL burnt stone 60 ± 5 HP ETH OSL quartz grains 54 ± 5 S22 HP BER OSL quartz grains 63 ± 4 HP EMC OSL quartz grains 69 ± 3 Table S1: List of ages obtained using numerical dating techniques applied to samples collected from SB and HP contexts. The ages shown are the most current estimates. Many ages reported previously in the literature have been superseded (as discussed in S21) and, therefore, are not shown. For each method and at each site, the ages are presented in stratigraphic order. The asterisk (*) denotes that (S10) proposed two alternative temperature calibrations for the HP samples from Boomplaas. The AAR age can be one of the estimates listed, but not both, although the two estimates delimit the likely age range. The hash symbol (#) marks the sample collected from Cave 2 at Klasies River. All other samples listed were collected from Cave 1a. The dollar sign ($) indicates that the Border Cave ESR ages differ from those presented in S4, owing to the inclusion here of the cosmic-ray dose rate, as recommended by S6. The latter authors discussed the revised ESR ages, but did not present them in a table. Also, the ESR ages listed here represent the weighted mean ages of the 2 4 different enamel fragments measured for each tooth. 4

6 estimate axis. For convenience, the grey bands have been centred on the weighted mean ages for the HP and SB, as calculated from all of the plotted ages. The ages presented for the HP industry range from ~40 to 80 ka (Table S1), but the majority of these estimates are consistent with a weighted mean of 59.1 ± 1.2 ka, which takes account of the differing precisions of the age estimates. Almost identical values are obtained, however, when the arithmetic mean is calculated from the point estimates of age (i.e., taking no account of their differing precisions) and the uncertainty is determined as the standard error associated with these point estimates. The radial plot (Fig. 3) shows that the vast majority of the HP ages are of low precision (relative errors of >5%), and that the most precise ages (i.e., those obtained by U-series dating, shown as filled circles) are slightly older than the weighted mean of ~59 ka. The ages of the SB industry extend from ~50 to 90 ka, with a weighted mean of 71.4 ± 2.1 ka (and an arithmetic mean of 72.7 ± 2.2 ka). Much of the spread in apparent age is associated with the alternative ESR model ages of S5. The radial plot (Fig. 3) indicates that the SB ages are more self-consistent, but generally of lower precision (relative errors of >10%), than the HP ages. The comparatively high-precision estimate (shown as an open square) is the OSL age from the SB levels at Blombos Cave (S20). The data listed in Table S1 provide a statistically meaningful number of independent estimates of HP and SB age from a variety of sites, which makes it feasible to calculate mean ages of ~59 and 72 ka for samples collected from various HP and SB levels, respectively. But the low precision on most of the individual age estimates prohibits the detection of any stratigraphic trends (e.g., increasing age with depth) and prevents the determination of the duration of these industries and whether the HP immediately followed the SB or was separated from it by a hiatus. This lack of temporal resolution has been noted previously by Millard (S24), who applied Bayesian statistics to the ESR data set from Border Cave, which contains among the most precise set of ages encountered in our survey (Fig. 3). Millard attempted to discern if the HP industry persisted for 10 or 20 ka, but he was unable to differentiate between these two options because the ESR ages were not sufficiently precise for either the HP levels or the stratigraphically constraining layers. At the present time, therefore, the numerical ages available for the HP and SB are inadequate to answer questions about the start and end dates of these industries, their durations, or the existence of a time gap between them. Such shortcomings have major implications for our capacity to interpret the archaeological record. 5

7 B. Single-grain optical dating Optical dating provides a means of determining burial ages for sediments (S25 28). The method is based on the increase in number of trapped electrons in mineral grains (such as quartz and feldspar) with increasing time after burial, in response to the energy supplied by background levels of ionising radiation from environmental sources. The time elapsed since sediments were last exposed to sufficient heat or sunlight to empty the relevant electron traps can be estimated from measurements of the optically stimulated luminescence (OSL) signal, together with determinations of the radioactivity of the sample and the material surrounding it to a distance of ~50 cm. The equivalent dose (D e ), which represents the radiation dose to which sedimentary grains have been exposed in their burial environment, can be determined by measuring the OSL signal from a sample of sediment, which can be as small as a single sand-sized grain. The dose rate (D r ) represents the rate of exposure of these grains to ionising radiation over the entire period of burial; this dose is mostly derived from the radioactive decay of 238 U, 235 U, 232 Th (and their daughter products) and 40 K, with lesser contributions from cosmic rays and from radioactive inclusions internal to the dated mineral grains. The burial age of grains that were well bleached by sunlight at the time of deposition can then be calculated from the D e divided by the D r. Optical ages are obtained in calendar years, and thus can be compared directly with calibrated radiocarbon ages and with uranium-series and electronspin resonance age estimates. All laboratory measurements of OSL and sample radioactivity were made at the University of Wollongong, Australia, while field determinations of the dose rate due to gamma rays were made using a portable gammaray spectrometer. B.1. Sampling strategy Our sampling strategy was twofold: 1) to collect samples from archaeological sites spread across a geographically widespread area of southern Africa, incorporating coastal, near-coastal, inland and mountainous environments; and 2) at each of these sites, to collect samples to bracket the earliest and latest evidence for the HP industry and the SB, where present, as well as the intermediate levels containing these cultural industries. We also collected samples from the layers immediately preceding and following the HP and SB to further constrain their start and end dates, as 6

8 any individual site is unlikely to preserve a continuous cultural sequence spanning both industries. This dual strategy allows an assessment of: 1) any spatial variations in the timing or pattern of HP and SB appearance and disappearance due to differences in environmental factors (e.g., climate and ecology); and 2) the start and end dates, and durations, of the HP and SB industries, as well as the continuity (or lack thereof) between them and those that occur before and after. Where the relevant units were thick, multiple samples were collected for OSL dating; where they were thin, however, we collected samples only from near the middle of the unit, to avoid inadvertently sampling sediments associated with different industries. A total of 63 samples are relevant to the aims of this study, and represent a random sample from the entire duration of the HP and SB industries. At sites preserving longer sequences, samples were also collected from other units, but they are not germane to the present study and are, therefore, not discussed further. B.2. Sample collection We collected samples during the course of controlled archaeological excavations or from previously excavated sections revealed after removing backfill. Samples from Apollo-11, Border Cave, Diepkloof, Klasies River, Klein Kliphuis, Melikane, Ntloana Tsoana and Sehonghong were collected in dim red light beneath an opaque (black) tarpaulin. Sediments were collected either by hammering PVC tubes into the cleaned faces of the excavated sections or by using a trowel to carefully scrape material from the unit of interest into opaque (black) plastic bags. In many cases, the latter procedure was the only option, because of the presence of large pieces of stone or because of the small depth interval of the unit/layer of interest. The tubes and bags were then sealed for transport to Australia. At Rose Cottage Cave, Sibudu and Umhlatuzana, PVC tubes were hammered into the cleaned face of the excavated sections in daylight, but shaded from direct sunlight. The tubes were removed from the sections and sealed for transport to Australia. In such cases, the sediment at both ends of the tubes will have been exposed to some scattered sunlight at the time of collection. These outermost portions were removed in the laboratory to ensure that only light-safe grains were subsequently processed for dating. At each sample location, separate plastic zip-lock bags of sediment were collected to determine the moisture content and to enable laboratory measurements of dose rate. A general photograph and a stratigraphic drawing indicating the stratigraphic association of each of the majority of OSL samples are shown for each site in Sections D.1-D.9. 7

9 B.3. Sample preparation All samples were opened in the laboratory under the appropriate lighting conditions (dim red/orange illumination). Sediments collected in clear plastic bags were weighed and dried to obtain estimates of current field moisture contents, and these same sediments were then ground to a fine powder for laboratory determinations of dose rate (see Section B.4.e, below). For the OSL samples collected in daylight using PVC tubes, the lightexposed end portions were first removed. The remaining material was processed in an identical manner to the sediments collected beneath the black tarpaulin, which were subjected to a series of chemical treatments to isolate quartz grains of a specific sizerange for measurement of the OSL signal. Carbonates were dissolved in 10% HCl acid and organic matter was oxidized in 30 vols H 2 O 2. The μm diameter grain-size fraction was then separated by mechanical dry sieving and the quartz grains isolated by density separation, using sodium polytungstate solutions of specific gravity 2.62 (to reduce the potassium-rich feldspar content) and 2.70 (to remove heavy minerals). The quartz grains were etched in 48% HF acid for 40 mins to destroy any remaining feldspars, and then washed with concentrated HCl acid for 40 mins to remove any precipitated fluorides. The etched quartz grains were then sieved again, using the smaller mesh diameter (180 μm), and only the grains retained on this sieve were used for dating. This same procedure was systematically applied to each sample to ensure consistency between samples. Sufficient material for dating was obtained from all samples except those from Border Cave, which yielded no quartz grains. The latter samples were dominated by pumice and feldspar, and were accordingly abandoned from our study. B.4. Luminescence measurements B.4.a. Dating strategy In this study, we systematically applied single-grain optical dating procedures to all of our samples to maximise the benefits inherent in the measurement of individual sandsized grains of quartz. These include the identification of contaminant grains in a sample and their exclusion before final age determination, and the ability to directly check the stratigraphic integrity of archaeological sequences and address concerns about postdepositional sediment mixing. These dual advantages over the more conventional analysis of aliquots composed of multiple grains result in an improvement in the accuracy and precision of optical ages. Further details of single-grain dating methodology and 8

10 archaeological applications can be found in S28. This approach offered a practical means of reliably dating the HP and SB industries, both of which lie beyond the age-range of radiocarbon dating, and to answer specific questions about the duration and continuity of these industries. An additional feature of our study design is that all samples were measured using the same OSL stimulation and detection instrument, irradiated using the same laboratory beta source, and the data were analysed by a single operator (Z.J.) using identical procedures. The majority of experimental parameters were also kept constant for all samples, the only exceptions being some of the thermal treatments administered before optical stimulation, which differed slightly between samples for fundamental physical reasons (see below). By holding these variables near-constant for all samples, we remove any unwanted noise in the data arising solely from variations in these factors, which could widen the spread in apparent age and, hence, blur the timing of the HP and SB industries, their durations, and any hiatus between them. Furthermore, this systematic approach enables us to compare optical ages and age intervals with enhanced precision because any possible bias ( systematic uncertainty ) associated with laboratory beta-source calibration applies equally to all samples and can, therefore, be eliminated for purposes of comparing and combining the optical ages. But we have added, in quadrature, the possible bias (± 2% of the age) to all other uncertainties when comparing the optical ages to other forms of age determination, in line with the recommendations of (S29). B.4.b. Equipment A Risø TL/OSL-DA-15 optical stimulation and detection system, equipped with a focussed laser attachment for optical stimulation of single, sand-sized grains, was used to measure all individual grains in this study. OSL measurements were made using the beam from a 10 mw Nd:YVO 4 diode-pumped green laser (532 nm) focussed down to a 10 μm diameter spot with a power density of ~50 W/cm 2 (S30). The ultraviolet OSL emissions were detected using an Electron Tubes Ltd 9635Q photomultiplier tube fitted with 7.5 mm of Hoya U-340 filter, and laboratory doses were given using a calibrated 90 Sr/ 90 Y beta source mounted on the Risø instrument. Further design and performance specifications for this apparatus are given in (S30, S31). 9

11 B.4.c. Equivalent dose (D e ) determination To obtain useful information about the depositional age of quartz grains, it is necessary to convert the natural OSL signal (photon counts) to a reliable estimate of D e, the equivalent radiation dose in grays (Gy). We have applied a single-aliquot regenerative-dose (SAR) procedure, similar to that of S32, to all our samples. The SAR procedure involves the measurement of the natural OSL signal (denoted L N ) and successive regenerated OSL signals (L x ) for each grain. The latter are used to construct a dose-response curve, on to which L N is projected to determine the D e. This procedure has been shown to yield reliable results (see review by S27) provided that any changes in OSL sensitivity between successive regenerative-dose cycles are monitored and corrected for. The latter is achieved using the OSL response (T x ) to a fixed test dose (T D ) given after optical stimulation of each regenerative dose (R x ). In practice, therefore, L N and L x are divided by their respective test-dose signals (T N and T x ), and the D e is estimated by comparing the L N /T N ratio with the sensitivity-corrected L x /T x ratios used to construct the dose-response curve. Dose-response curves for individual grains consist of a range of regenerative doses (n 5) that bracket the expected D e estimate, including an OSL measurement after zero applied dose to monitor for any transfer of charge into the OSL traps due to the laboratory thermal treatment ( recuperation, see below). In addition, a repeated regenerative dose was stimulated at the end of the SAR cycle to check the efficacy of the sensitivity-correction procedure; we considered the latter to be confirmed if the ratio between the duplicate L x estimates (the recycling ratio ) was statistically consistent with unity. The range of regenerative doses differed for each sample, because the size of the D e (and, therefore, the regenerative doses) depends on the magnitude of the radiation flux to which the grains have been exposed. The size of T D was kept constant for all samples at 9 Gy. The temperature at which the optical stimulations were recorded to obtain L N, T N, L x and T x were kept constant at 125 C and for a fixed duration of 1 s, using the green laser at constant intensity (90% of full power). For all grains, the D e was determined from the first 0.1 s of OSL decay, with the mean count recorded over the last 0.17 s being subtracted as background. The experimental error associated with each OSL measurement (L N, L x, T N and T x ) was determined from photon counting statistics, using equation (3) of (S33). An uncertainty of 2% was added (in quadrature) to each OSL measurement error as an estimate of instrument reproducibility (S34) and, for each grain, a dose-response curve was fitted to the L x /T x ratios using a saturating-exponential-plus-linear function. The D e was obtained 10

12 by interpolating the L N /T N ratio on to the dose axis, and the corresponding standard error associated with the uncertainty in this ratio and in the curve fits was estimated by Monte Carlo simulation (S35, S36). Two different thermal treatments before OSL measurement are also required in optical dating and form an integral part of the SAR procedure: namely, the preheat applied to the natural and regenerative doses (commonly held for a duration of 10 s), and the cutheat given to the test doses (but not held at this temperature). The preheat removes charge from thermally unstable but optically-sensitive traps that have been filled during laboratory irradiation, (e.g., the 110 C and 160 C traps in quartz; S37, S38), and also transfers charge into the OSL trap from optically-insensitive traps (e.g., the 280 C trap) that occur at lower temperatures than the 325 C trap responsible for the OSL signal (S38). The temperature of the cutheat must be sufficient to remove any signals that may interfere with the OSL measurement, but be kept low enough to minimise any additional changes in sensitivity. The same preheat and cutheat will not necessarily be appropriate for each sample, so it is not possible (or desirable) to keep this parameter constant between samples. The most appropriate preheat/cutheat temperature must be determined experimentally, since only a single, optimum, thermal combination may be suitable in some cases. Neglecting to determine the correct combination can result in significant age distortion (typically age shortfalls). There is no a priori physical basis for determining the correct preheat/cutheat combination for any particular sample, owing to wide variability in the structural defects and chemical impurities present in natural grains of quartz. The latter is controlled by, among other factors, the source rock of the quartz grains. This natural variability in quartz composition effectively negates efforts to apply a single preheat/cutheat combination to contemporaneous samples spread across the whole of southern Africa. We have used the dose recovery test (e.g., S39, S40) as an empirical means of determining the most appropriate preheat/cutheat temperature combination for a representative sample from each of the study sites. This test involves the initial emptying of the OSL traps in a natural sample by bleaching at ambient temperature, followed by application of a known laboratory dose to the bleached grains. We used natural, unfiltered sunlight to bleach aliquots composed of ~10 grains, and these aliquots were then given a laboratory dose similar in size to the expected D e value for the sample under investigation. The preheat and cutheat temperatures were varied and up to nine different thermal combinations were used in groups of 6 aliquots each. We found that few 11

13 combinations returned the correct (known) dose for each sample in the majority of cases. Table S2 lists the optimal combinations and the ratios for the measured/given doses, which are consistent with unity at two standard errors. These thermal treatments were subsequently used in the SAR procedure to determine the D e for each sample. The dose recovery test provides a validation of the chosen experimental conditions and lends confidence to the accuracy of the D e estimates. We accept that the chosen preheat/cutheat combination may not be ideal for each and every dated grain, but the use of aliquots composed of only ~10 grains in these dose recovery tests maximises the likelihood of selecting the optimum conditions for the majority of grains. Individual grains that are illsuited to these experimental conditions will likely be discarded during the course of data analysis, on the basis of one or more of the rejection criteria described in the following section. Any remaining grains for which the preheat/cutheat combination was not ideal will simply add to the measured overdispersion in D e values, and may be one of the reasons for overdispersion values of up to 20% being commonly reported for grains that had been sufficiently bleached at the time of deposition (S27, S28, S34). Site name Number of Given/measured Preheat Cutheat aliquots dose ratio Apollo C/10 s 160 C/10 s 1.02 ± 0.04 Diepkloof # C/10 s 220 C/5 s 1.01 ± 0.03 Klasies River C/10 s 160 C/10 s 0.99 ± 0.04 Klein Kliphuis C/10 s 160 C/10 s 1.00 ± 0.07 Melikane C/10 s 160 C/10 s 1.03 ± 0.03 Ntloana Tsoana C/10 s 220 C/5 s 0.95 ± 0.06 Rose Cottage Cave C/10 s 160 C/10 s 0.95 ± 0.03 Sehonghong C/10 s 160 C/10 s 1.01 ± 0.06 Sibudu #* C/10 s 220 C/5 s 0.99 ± 0.05 Umhlatuzana C/10 s 220 C/5 s 0.98 ± 0.05 Table S2: Results obtained for dose recovery tests using the optimal preheat/cutheat combinations for samples at different sites. # For samples from these sites an additional optical stimulation for 40 s at 90% power using the blue light emitting diodes (LEDs) at 280 C was required at the of each measurement cycle. * Results and interpretation published in S40 B.4.d. Data analysis A total of 53,400 individual grains were measured in this study. As has been reported in many previous studies, however, not every grain yields useful information on absorbed dose (S28). We therefore rejected uninformative grains using criteria described and tested elsewhere (S34, S41). These criteria are: (1) if the OSL signals are weak (i.e., T N signal less than 3 times instrumental background); (2) if the recuperation is high (i.e., L X /T X for 0 Gy dose is greater than 5% of L N /T N ); (3) if the recycling ratio is poor (i.e., more than 12

14 two standard errors away from unity); (4) if the sensitivity-corrected natural signal (L N /T N ) is greater than any of the sensitivity-corrected L x /T x ratios (i.e., it does not intersect the dose-response curve); and (5) if exposure to infrared stimulation causes significant loss of OSL signal (i.e., IR OSL depletion ratios smaller than unity by more than two standard errors). Information on the number of single grains measured, the number of rejected D e values and reasons for rejection are provided for each sample in each of the site-specific sections in Section D.1-D.9. The D e values for those grains that were not rejected are displayed for each of the samples measured, on radial plots provided for each samples in each of the site-specific sections in Section D.1-D.9. The overdispersion value (σ d, the relative spread in D e remaining after taking measurement uncertainties into account) was also calculated for each sample from the grains displayed in these radial plots, and these values are listed in the final results table for each site in Sections D.1-D.9. The D e values for individual grains were then combined, using an appropriate statistical model, to give an overall D e for each sample. The choice of model depends on both the shape of the D e distribution, which can be assessed visually from the radial plot, and the overdispersion value (S28). In this study, we used either the central age model (CAM) or finite mixture model (FMM), which were first applied to single-grain D e distributions by (S23) and (S42), respectively. Samples consisting of well-bleached quartz grains commonly have D e distributions that are overdispersed by up to 20% (S43 45). For such samples, we applied the CAM, which takes the measured overdispersion into account when estimating the uncertainty on the weighted mean D e value. Samples with overdispersion values of more than ~20% were considered to be afflicted by variations in the beta dose rate to individual grains (e.g., S46) or by post-depositional mixing of grains with different burial ages (e.g., S20, S47). For these samples, we applied the FMM to the single-grain D e distributions to determine the number of discrete D e components, the relative proportion of grains in each component, and the weighted mean D e value and associated standard error of each component (S42, S44, S48). We ran the FMM using σ d values of between 10 and 20% and identified the minimum number of statistically-supported D e components by means of maximum log likelihood and the Bayesian Information Criterion (BIC). A table containing details about the number of components and their relative proportions for each of the samples measured is provided for each site in Sections D.1-D.9. See (S45, S48 and 13

15 S49) for more information on FMM implementation, and (S28) for further discussion on the interpretation of radial plots and a review of these and other age models. The standard error in D e obtained using the CAM or FMM represents the total uncertainty arising from all sources of random variation arising from OSL measurement. To this experimental error, we added (in quadrature) a systematic uncertainty of 2% to allow for possible bias in D e due to calibration of the 90 Sr/ 90 Y beta source used for laboratory irradiation of all samples. B.4.e. Dose rate (D r ) determination The total dose rate consists of contributions from beta, gamma and cosmic radiation external to the grains, plus a small alpha dose rate due to radioactive decay of U and Th inclusions inside sand-sized grains of quartz. To calculate the optical ages, we have assumed that the measured radionuclide activities and dose rates have prevailed throughout the period of sample burial. An internal alpha dose rate of ± Gy/ka has been assumed for all samples, on the basis of previous measurements on South African quartz grains that had been etched with HF acid (S50). The external beta dose rates were determined for each sample by grinding a portion of dried sample to a fine powder and measuring the total beta counts using a Risø GM-25-5 beta counter (S51). Allowance was made for the effect of grain size (S52) and HF acid etching (S53) on beta-dose attenuation, and the beta dose rates of the Sibudu and Diepkloof samples were also adjusted for the effects of beta-dose microdosimetry, using the procedure described in (S46). This procedure initially involved using the FMM to identify the presence of different D e components in a sample. If a secondary component consisting of low D e values was identified, then the minimum age model (MAM) of (S23) was used to determine the minimum D e value for this component. Its corresponding age was obtained by dividing the minimum D e value by the dose rate with the beta contribution set to zero; the latter amounts to assuming that these grains had received no beta dose during the period of burial, as would be the case if they had been surrounded by 2 mm of material with negligible radioactivity (e.g., carbonates). If the age obtained in this way approximated that obtained from the main D e component and the average beta dose rate, then we inferred that all grains in the sample had been deposited at the same time, but had subsequently experienced a range of beta dose rates. Because the grains in the secondary component had experienced below-average beta dose rates, then the grains in the main component must have received above-average beta dose rates, 14

16 as the sum of the pair results in the average (measured) beta dose rate for the bulk sample. To deduce the beta dose rate for the main D e component requires modeling, since this value is not measured directly. We estimated the latter beta dose rate based on the relative proportion of grains assigned (by the FMM) to the main component in each sample, following the procedures detailed in (S46). To estimate the external gamma dose rate, we generally used the values obtained by in situ gamma-ray spectrometry, which takes account of any spatial heterogeneity in the gamma radiation field around each sample. We were able to obtain such measurements for the majority of samples using a portable gamma spectrometer and the threshold calibration technique (S54) to derive the gamma dose rate from the 238 U and 232 Th decay chains and 40 K. At three of the sites, however, in situ measurements were not feasible. At Klein Kliphuis, the gamma spectrometer could not be inserted into the sections because of the presence of substantial amounts of roof spall, whereas such measurements could not be made at Sibudu because insertion of the spectrometer would have resulted in an unacceptable level of damage to the limited archaeological excavation. At Diepkloof, a reliably calibrated gamma spectrometer was not available at the time of sampling. For these three sites, the gamma dose rates were estimated from a combination of thick source alpha counting (TSAC) and GM-25-5 beta counting. Where samples were collected from a stratigraphic sequence and had gamma radiation fields that overlapped each other, spatial variations in the gamma dose rate were taken into account using the distance data provided by (S29: Appendix H) and (S55). At Klasies River, we also made high-resolution gamma-ray spectrometry (HRGS) measurements to examine the equilibrium conditions of the 238 U and 232 Th decay chains at the time of sample collection (in response to the problems reported for this site by S17), and to obtain independent estimates of 40 K activity. The cosmic-ray dose rates were estimated from the equations provided by S56, taking into account the burial depth of each sample (averaged over the full period of burial), the density of overlying deposit and its water content (S57), the thickness and density of rock overburden, and the geomagnetic latitude and altitude of the site. We have also allowed for the configuration of each cave or rock shelter, by taking into consideration the cos 2 Φ- zenith angular distribution of cosmic rays (S58). The beta and gamma dose rates are based on the conversion factors of S59, and were adjusted for the long-term moisture content of each sample (S29). The latter estimates 15

17 were based on the measured (field) values, the weather conditions prevailing during and shortly before sample collection, the potential impact of any previous excavations in the vicinity of the sampled locations (which could result in desiccation of the sediments), and the probable range of variation due to past climatic changes (averaged over the entire period of sample burial). The extent of such fluctuations is apt to be small at the study sites, because most of the deposits have low moisture contents at the present day and have probably been so for most of the last glacial cycle, owing to their sheltered locations. The uncertainty attached to the total dose rate represents the quadratic sum of all known and estimated sources of random and systematic error. These include an uncertainty sufficient to accommodate all likely variations in sample moisture content throughout the period of burial. The total dose rates decrease (and the optical ages increase) by ~1% for each 1% increase in water content. All dose rates information for each measured sample is provided in the final results tables for each site in Sections D.1- D.9. B.4.f. Optical age determination Optical ages were estimated by dividing each sample D e value by its respective total dose rate. The total uncertainties associated with the final age determinations include all sources of measured and estimated error in D e and D r, as well as the possible bias of ± 2% associated with laboratory beta-source calibration. Because the latter systematic component of variation is common to all samples analysed in this study (because the same instrument was used for all OSL measurements), this value is omitted in our statistical comparisons of optical ages within and between the 10 study sites; only the random component of variation is relevant in such instances (S29: Appendix B). But we have included the systematic uncertainty when comparing our optical ages with all other age estimates (including optical ages reported in previous studies), as recommended by (S29). All ages and associated uncertainties are provided in the final results table for each site in Sections D.1-D.9. 16

18 C. Statistical models and estimates Estimates of the start and end of the HP and SB periods, along with the durations of these periods and of any gaps between them, are based on the following statistical model. The observed (estimated) age y i of sample is given by y i = x i + e i where x i is the unknown true age of the sample and e i is an unobserved random error drawn from a Normal distribution with mean 0 and known standard deviation σ i (which in principle differs for each sample). The values of σ i used were those listed as σ 1 in Fig. 2 in the main text. Within the HP period the values of the x i s are assumed to be randomly drawn between a 1 and a 2 (i.e., uniformly over this range) where a 1 and a 2 are to be estimated. Likewise the x i s from SB are assumed to be uniformly distributed between two unknown values b 1 and b 2 ; the x i s for samples immediately post-hp are randomly sampled between and a 0 and a 1 (the latter coinciding with the end of HP) and those immediately pre-sb are randomly sampled between b 2 (the start of SB) and b 3, where a 0 < a 1 < a 2 < b 1 < b 2 < b 3. Furthermore, the x i s for the samples labelled pre-hp are assumed to be randomly drawn between a 2 and b 3, reflecting the fact that they are prior to HP but not necessarily after SB. The six parameters a 0, a 1, a 2, b 1, b 2 and b 3 are then estimated numerically by maximum likelihood. Of course it is difficult to justify any specific form for the distribution of the true ages x i within a given interval. But the uniform distribution seems to be the simplest reasonable choice given that, in taking samples, an attempt was made to cover the whole range systematically at each site. We also fitted variants of this model using more and fewer intervals, including and excluding data from samples earlier and later. This was partly to answer specific questions and partly to assess the robustness of the method. In particular, the estimates of a 1 and a 2 are practically unaffected by what pre-sb data are included and, likewise, estimates of b 1 and b 2 are largely unaffected by what post-hp data are included. The above statistical model is similar to models that have been used in other studies to estimate ages in a sequence, taking account of information on their ordering using Bayesian prior distributions (e.g., S24). 17

19 Of course, a full Bayesian analysis would require specification of a joint prior distribution for the parameters a 0, a 1, a 2, b 1, b 2 and b 3, as well as for the true age of each sample. This would be vague unless detailed information was available about the values of one or more of these parameters, and the posterior distribution that resulted would represent how these prior beliefs changed in the light of the data. However, for the present purpose (and in scientific reporting generally) it seems more appropriate to use standard statistical methodology based on maximum likelihood model fitting and testing (S60). We are interested in specific questions like: How long did the HP and SB periods last?, Was there a gap in activity between them? and, if so, How long did this last? The statistical model is used here to see what the current data can tell us about these questions, without being combined formally with other data or prior probabilities. Note that we are not attempting to combine or refine individual age estimates and that the true ages, even within a particular period, are not assumed to be equal. In fact, the data are very informative about the HP period, although (understandably) less so about SB. On the basis of this model, the data also fairly clearly support the existence of a gap between SB and HP (see below). Of course, it is possible that future data might suggest otherwise. Fig. S1 is a radial plot of all of the OSL ages shown in Fig. 2 using standard errors σ 1, and subdivided into different categories. Of particular note is that all post-hp symbols fall below the end of the HP (shown as the lower dashed line), and that all pre-hp and earlier symbols fall above the start of the HP (shown as the upper dashed line). Furthermore, all of the HP symbols are statistically consistent with the estimated HP period that is, none fall above the upper grey band or below the lower one. Likewise, all of the pre-sb symbols fall above the start of the SB (shown as the upper dotted line). Fig. S2 compares our OSL ages (filled squares, but plotted using standard errors σ 2 ) with all published independent ages for the pre-sb to immediately post-hp interval, subdivided according to dating method. This figure is similar to Fig. 3 in the main text, but includes pre-sb and post-hp ages also. The grey bands show that all of the independent age estimates are also statistically consistent with our estimates for the relevant time periods, with the possible exception of the two youngest HP estimates (one TL and one OSLi). 18

20 To answer the specific question Was there a hiatus in activity between the SB and HP periods? we fitted the above model, first with a 2 < b 1 and then with a 2 = b 1, and then used a likelihood ratio test. We obtained a small ( significant ) p-value of about which provides quite strong evidence that the data are not consistent with a 2 = b 1 and, hence, in favor of the existence non-zero gap between these two periods. Of course, it is possible that there was activity in this period and that samples from this time were simply not obtained, but based on the present data there is good evidence in favor a gap, which is not contradicted by the other studies cited here (Fig. S2). There is also the possibility (p = 0.02) of a gap between the end of the HP and the start of the post-hp, if the weighted mean age for the 10 oldest post-hp samples is taken to represent the start of the post-hp. Here, the weighted mean was calculated using the common age model of Galbraith et al. (S23), because all 10 ages are consistent with a common value. C.1. Numerical estimates Table S3 gives values of the maximum likelihood estimates and approximate 95% confidence intervals for the various quantities of interest. Age 95% CI a 95% CI b (ka) (ka) (ka) End of HP ( ) Start of HP ( ) Length of HP period ( ) End of SB Start of SB Length of SB period Length of gap between SB and HP ( ) Start of post-hp Length of gap between HP and post-hp ( ) Table S3: Maximum likelihood estimates of parameters. 95% confidence intervals in column 3 (shown with superscript a) do not include the 2% possible bias associated with beta-source calibration, and are the correct values to use for all duration estimates. 95% confidence intervals in column 4 (marked with superscript b) include the 2% calibration uncertainty and are the correct values to use for start and end ages. Italicized estimates (in parentheses) were obtained using a modified model (see text for details). The estimates shown in italics and parentheses were obtained by modifying this model to take account of a possible gap between the end of the HP and the start of the post-hp. In the modified model, parameter a 1 marks the start of the post-hp and the true 19

21 ages of the 10 oldest post-hp samples are assumed to be the same. The parameters of interest were then estimated again by maximum likelihood. The original and modified models give statistically indistinguishable values, but we currently favor the former estimates in the absence of independent archaeological evidence for the existence of a gap between the end of the HP and the start of the post-hp. Note that the estimates of the start of SB (b 2 ) and particularly the duration of SB (b 2 b 1 ) are very uncertain. To test for the presence of a gap between SB and HP: (a) Using just the HP data plus SB and late pre-sb. The general model has four parameters a 1, a 2, b 1, b 2, and the maximum log-likelihood is L 1 = We test the null hypothesis that b 1 = a 2 giving a three-parameter model with maximum log-likelihood L 0 = Thus the test statistic is W = 2(L 1 L 0 ) = 6.93, which gives a p-value of The theory behind this is that under the three parameter model with b 1 = a 2 (i.e., with no gap between SB and HP) W will be a random value from a χ 2 distribution (approximately) with 1 degree of freedom. The p-value is the chance of observing a value from this distribution as large or larger than Since this chance is small, it provides evidence against the hypothesis that b 1 = a 2. (b) Repeating this test, but with data that also include the early post-hp ages, we get L 1 = 83.57, L 0 = 87.06, and hence W = 6.98, again with an approximate p-value of

22 Fig. S1: Radial plot containing all of the OSL ages estimates obtained in this study, presented in a different form in Fig. 2. Upper and lower dashed lines shown the start and end ages of the HP, respectively, and the grey bands indicate ± 2 standard errors for any individual age estimate about each of these lines. Upper and lower dotted lines indicate the start and end ages of the SB, respectively. Different symbols denote different formal and informally-named cultural phases. 21

23 Fig. S2: Radial plots showing the OSL age estimates obtained in this study (filled squares), together with the independent age estimates obtained by various dating methods (denoted by different symbols). Upper and lower dashed (dotted) lines show the start and end ages of the HP (SB) determined from our OSL ages (as in Fig. S1), and the grey bands indicate ± 2 standard errors for any individual age estimate about each of these lines. Note that OSLi refers to independent OSL ages that is, ages obtained in other studies. 22

24 Section D.1: APOLLO 11 (AP) 1. Fig. S3: Site photograph 2. Fig. S4: Stratigraphic drawing, showing OSL sampling locations 23

25 3. Basic description of stratigraphic units Units A to L represent a heterogeneous and complex stratigraphic sequence. Numerous thin layers of sediment interspersed with large amounts of organic material (animal dung and botanical remains) alternate with sheets of ash, concentrated charcoal and layers containing fine rock debris. The sediments are coloured different shades of grey (Munsell Soil Colour Chart 7.5YR 3/1, 5/1 & 6/1, 10YR 7/1 & 7/2), with the ash lenses being pale yellow to white (2.5Y 8/2). Unit M contains dusty, brown sediments (7.5YR 5/4) interspersed with finely laminated grit layers. Unit N is a densely packed, bouldery deposit, with only small amounts of silty infill (light brownish grey, 10YR 6/2). Unit P consists of a dusty sediment (light olive brown, 2.5Y 5/3) mixed with fine detritus. There are two white ash lenses at the base. Unit S is a homogenous, silty sediment (olive brown, 2.5Y 4/4), very loosely packed. Unit T is a consolidated, brown silt (7.5YR 4/3) mixed with fine, angular debris and some larger slabs (some of which are in an inclined position). Unit U is a horizon of rounded, calcareous concretions, 2 3 mm in diameter. Unit V is a homogeneous horizon of horizontally laminated fine rock debris. Unit W is a heterogeneous mixture of horizontally laminated fine to coarse rock debris. Unit X is, like Unit V, a homogeneous horizon of horizontally laminated fine rock debris. Unit Y is, like Unit W, a heterogeneous mixture of horizontally laminated fine to coarse rock debris, except that the amount and the size of the rock debris increases towards the base and some of the larger slabs are in an inclined position. Unit Z consists of large rock boulders, with Unit Y infiltrating some of the gaps between the boulders. Unit Z probably represents the friable, weathered surface of the hard, black limestone within which the rock shelter has developed. 4. Brief comment on the association between the OSL samples and the artefact assemblages Excavations were made at Apollo 11 by W.E. Wendt in the years 1969 and 1972 (S61 63). We re-excavated the site in 2007, beginning with removal of his backfill. We then excavated 0.5 m 2 of the remaining deposit under controlled conditions from the surface down to the solid bedrock, directly adjacent to Wendt s main trench. All OSL samples were collected from the cleaned faces of in situ deposit exposed in Excavation units were 0.25 m 2 in plan area and 50 mm in depth (spits), but they were further subdivided in the case of sediment changes. We had no problems in correlating the excavated layers with Wendt s stratigraphic sequence from 1969, because the old profile was preserved in near-perfect condition, bearing his original markings and labels. Sample AP-9 was taken from Unit N, which is a massive rockfall horizon that separates the HP Poort (HP) from the final MSA. Unit P corresponds to the HP cultural phase, and the underlying Unit S marks a hiatus between the HP and the SB. An increase of angular debris characterises Unit T, which corresponds to the SB cultural phase. 5. Summary description of the artefact assemblages in the dated portion of the sequence 24

26 Wendt s excavations yielded a total of 20,550 MSA stone artefacts (excluding chips smaller than 1 cm). Of these, 5521 were classified as MSA complex 2 (S64, S65: p.73ff.), which shares many characteristics with the SB. The raw material is dominated (52.4%) by fine-grained quartzite, which is well suited to the production of the typical, very regular blades. The very high proportion of blades (42.3%) justifies the designation of this assemblage as a blade industry. The number of retouched artefacts is high (6.8%) with facial retouch, in particular, being prominent during this phase. Characteristic tool types include all kinds of retouched points: edge retouched points (n = 13), unifacially retouched points (n = 14) and bifacially retouched points (n = 4). Typical core types include single-platform cores and cores with two opposite platforms. Other raw materials were of negligible importance during the MSA at Apollo 11. Among the exceptional finds in complex 2 are three notched rib fragments (of unknown function) and fragments of ostrich eggshell, which bear evidence of having been opened intentionally. Four conventional 14 C dating measurements were made on charcoal (KN- I617, KN-I618, KN-I620, KN-I622), two on unburnt grass and twigs (KN-I615, KN- I623) and two on ostrich eggshell (Pta-507, Pta-505). All eight samples yielded infinite 14 C ages (> 48,000 BP) that is, ages beyond the range of the technique (S66, S67). A total of 10,867 artefacts are associated with MSA complex 3 (S64, S65: p.79f.). This is the largest number of stone artefacts for any of the MSA complexes at Apollo 11, despite the relatively small volume of corresponding deposit. MSA complex 3 corresponds to the HP Poort, as described by (S68 70). The HP from Apollo 11 is interbedded between MSA complex 2 (with SB characteristics) and MSA complex 4, which represents the youngest MSA and includes some blades and unretouched points, but no formal tools. The HP differs in all aspects of stone artefact technology from the preceding MSA complexes. Calcareous mudstone is the dominant raw material (49.1%) instead of quartzite (26.8%), which was previously the most prevalent lithology. All other raw materials decrease in importance also, especially the use of cryptocrystalline silicates (15.4%). The high proportion of flakes (55.3%) and an increase in the relative amount of angular debris (14.0%) distinguish the MSA complex 3 stone artefacts from the underlying assemblages. The proportion of blades (29.1%) is smaller than in all previous complexes, and the low number of complete pieces implies an intentional breakage of blades. The size of medial fragments seems to be standardised, and the length distribution of complete flakes shows a comparable standardisation; they are extremely small, with a mean value of 1.95 cm and a maximum of 3 cm. The proportion of retouched artefacts (7.1%) is higher than in all other assemblages. Backed pieces are characteristic of the HP, and the numerous truncations are mostly steep. The HP has the largest number of different tool types of all the MSA assemblages at Apollo 11. All type forms of the previous complexes occur, but the proportion of edge retouched points is much smaller. Tool types that are exclusive to the HP include large segments (n = 11), straight backed blades (n = 33) and convex backed blades (n = 45). In addition, many pieces have a steep truncation (n = 35), as exhibited also by tools associated with the preceding MSA complex 2. Typical core types are single-platform cores, cores with two opposite platforms, and discoidal cores. The continued appearance of characteristic SB tool types, such as bifacially and unifacially retouched points (n = 3 25

27 and n = 10, respectively), is at odds with the other changes in stone tool technology. At Apollo 11, such continuity could therefore be interpreted as the HP forming part of the general development of the MSA cultural sequence, rather than representing a period of abrupt change. The 4081 ostrich eggshell pieces have a total mass of 3312 g and consist mainly of unworked fragments. Exceptional finds include two small fragments with intentionally engraved lines on the outside, and three pieces with smoothed edges, comparable to LSA ostrich eggshell pendants. All of these fragments are too small, however, to make reliable inferences about any behavioural implications. One conventional 14 C dating measurement was made on charcoal (KN-I616) and another on ostrich eggshell (Pta-1415), but both yielded minimum (infinite) ages of 48,000 BP (S66, S67). 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Apollo 11 are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and sitespecific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). Sample AP9 AP4 AP5 AP6 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S4: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. 26

28 AP9 AP4 AP5 AP6 Fig. S5: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the AP11 samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. 27

29 Table S5: Dose rate data, D e values and optical ages for four sediment samples from Apollo-11 Sample Moisture Dose rates (Gy/ka) Total D e Age model Number of σ d Optical age Code content Beta a Gamma b cosmic c dose rate d,e (Gy) f grains g (%) h (ka) i Post-Howieson s Poort AP9 3 ± ± ± ± ± 6.2 CAM 49 / ± ± 2.6 Howieson s Poort AP4 3 ± ± ± ± ± 3.5 CAM 201 / ± ± 2.3 Pre-Howieson s Poort AP5 3 ± ± ± ± ± 4.8 CAM 64 / ± ± 2.6 Still Bay AP6 3 ± ± ± ± ± 3.4 CAM 150 / ± ± 2.6 a b c d e f g h i Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. Dry dose rates calculated from these activities were adjusted for the water content (expressed as % of dry mass of sample). Measurements made using in situ gamma spectrometry. Wet dose rates measured were adjusted for the water content (expressed as % of dry mass of sample). Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-27.7 S), longitude (17.1 E) and altitude (1050 m). We have also accounted for the different densities of the overlying roof thickness (2.0 g/cm 3 ; limestone and sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. Estimated using single grains of quartz. Preheat and cutheat conditions are given in Table S2. Number of individual grains used for D e determination / total number of grains analysed. Overdispersion (σ d ), the relative standard deviation of the D e distribution after allowing for measurement uncertainties. The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 28

30 Section D.2: DIEPKLOOF ROCK SHELTER (DRS) 1. Fig. S6: Site photograph Diepkloof Rockshelter 2. Fig. S7: Site plan and OSL sampling locations 29

31 Square C6 Connecting trench Square L6 DRS11 DRS12 DRS13 DRS5 DRS9 DRS8 DRS6 DRS4 DRS7 3. Basic description of stratigraphic units Diepkloof Rockshelter is located approximately 180 km north of Cape Town and about 18 km upstream from the mouth of the Verlorenvlei River in the Western Cape province. Since 1998, excavations into the MSA occupations in various parts of the rockshelter (see Fig. S7) have been conducted by a French South African team (John Parkington, Cedric Poggenpoel, Jean-Philippe Rigaud and Pierre-Jean Texier). This team excavated a 12-m long trench, oriented north south, to a depth of ~2 m in the centre of the site (see Fig. S7). The southernmost square in the trench (square L6) extended to a depth of at least 3 m, but bedrock was not reached. Both sides of the trench, and squares C6 and L6 in particular, are relevant to this dating study. The deposits contain more than 50 excavated stratigraphic units (S72), each of which was given a name. Rigaud et al. (S72) also divided the sequence into six Complexes, which were numbered 1 (top) to 6 (bottom). Complex 1 (surface layers to Ced) represents the LSA at the site, which dates to the last 1800 years (S73). Complex 2 (burnt crust to Danny in L6, and First hearth to Anne in C6) represents the post-hp. Complex 3 (Debbie to Glen in L6, and Gavin to George in C6) and Complex 4 (Governor to Kate in L6, and Greg to Iian in C6) both correspond to the HP, with numerous pieces of ostrich eggshell that are engraved in Complex 3 but not in Complex 4. Complex 5 (Kerry to Lauren in L6) is associated with the SB, and Complex 6 with an earlier uncharacterized MSA (S72). Importantly, three layers that cannot be clearly associated with either the SB or the HP occur between Complexes 5 and 4 (S74). Unfortunately, no stratigraphic drawing has been published for this site, and only brief descriptions of the general stratigraphy, artifact assemblages and other details have been published by (S72, S74 and S75). Likewise, detailed technological and typological studies of the stone tool assemblages have yet to be published. Organic and cultural remains are well preserved near the front of the site, including the excavated areas along the northern part of the trench. The HP and upper post-hp layers contain wood pieces and other organic remains (S75), and ashy patches are also clearly defined, resulting in a relatively clear stratigraphy with intense color differences (see square C6 in Fig. S7). Towards the southern part of the trench, in square L6 (the 30

32 deep sounding), the sediments become relatively more homogeneous and the hearth features more isolated (see Fig. S7). 4. Brief comment on the association between the OSL samples and the artefact assemblages OSL samples were removed from deposits in which characteristic SB, HP and post-hp assemblages had been found. Samples DRS14 and DRS13 were taken from Complex 5 (SB) deposits in square L6 (layers Logan and Kerry, respectively). Sample DRS11 was taken from square L6 (layer John), and samples DRS7, DRS4 and DRS5 were taken from square C6 (layers Helen, Gary and Greg, respectively). The latter four samples are associated with Complex 4 (HP with no engraved ostrich eggshell). Sample DRS10 (square L6, layer Edgar) and sample DRS6 (square C6, layer George) were collected from Complex 3 deposits, which contain both HP tools and engraved ostrich eggshell. Samples DRS8 and DRS9 were both collected from square C6 (layers Anne and Allie, respectively) and correspond to Complex 2 (the post-hp at Diepkloof). 5. Summary description of the artefact assemblages in the dated portion of the sequence The SB industry (Complex 5) contains foliate bifacial points. These double-pointed foliates are the fossile directeur of the SB industry and they occur in 10 different stratigraphic units within square L6. Notched and incised pieces of ochre are found in association with these bifacial points (S72). The HP industry (Complexes 4 and 3) contains numerous, curved backed-blades, side scrapers, notches and denticulates, and end-scrapers (S72). Bright red, worked ochres, as well as numerous fragments of ostrich eggshell, are found in association with both Complexes. The only difference between the two Complexes is that the younger Complex 3 includes ostrich eggshell fragments (more than 80) with deliberate engravings. Parkington et al. (S75) suggested that these engraved eggshells are the remnants of water flasks that had been decorated along their rims and on other parts of the shell also. The post-hp (Complex 2) contains retouched unifacial points and convergent scrapers. 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Diepkloof are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and sitespecific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). 31

33 Sample DRS9 DRS8 DRS6 DRS5 DRS4 DRS7 DRS10 DRS11 DRS13 DRS14 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S6: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. DRS9 DRS8 DRS6 DRS5 32

34 DRS4 DRS7 DRS10 DRS11 DRS13 DRS14 Fig. S8: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the DRS samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S7). The dominant component represented by the largest proportion of grains (Table S7) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to grains that have received a lower than average beta dose rate (e.g., S46). 33

35 Sample σ d (%) N Proportion (%) Proportion (%) Proportion (%) k = 1 k = 2 k = 3 DRS ± 3 70 ± 4 10 ± 3 DRS ± 2 96 ± 2 -- DRS ± 3 67 ± 3 -- DRS ± 1 14 ± 5 84 ± 5 DRS ± 1 98 ± 1 -- DRS ± 1 5 ± 2 94 ± 2 DRS ± 3 12 ± 3 -- DRS ± 1 97 ± 1 -- DRS ± 3 90 ± 3 -- DRS ± 1 91 ± 3 7 ± 2 Table S7: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. 34

36 Table S8 Dose rate data, D e values and optical ages for ten sediment samples from Diepkloof Sample Moisture Radionuclide concentrations a Dose rates (Gy kyr -1 ) Total Number of Optical code content U Th K dose rate e, f D e Age σ i d age j (%) (μg g -1 ) (μg g -1 ) (%) Beta b Gamma c Cosmic d (Gy kyr -1 ) (Gy) model g grains h (%) (kyr) Post-Howieson s Poort DRS9 5 ± ± ± ± ± ± ± ± 1.7 FMM 423 / ± ± 1.7 DRS8 5 ± ± ± ± ± ± ± ± 1.5 FMM 287 / ± ± 2.0 Howieson s Poort DRS6 5 ± ± ± ± ± ± ± ± 1.8 FMM 423 / ± ± 1.9 DRS5 5 ± ± ± ± ± ± ± ± 2.6 FMM 186 / ± ± 2.0 DRS4 5 ± ± ± ± ± ± ± ± 1.4 FMM 342 / ± ± 1.9 DRS7 5 ± ± ± ± ± ± ± ± 1.7 FMM 278 / ± ± 1.9 DRS10 5 ± ± ± ± ± ± ± ± 1.1 FMM 564 / ± ± 1.7 DRS11 5 ± ± ± ± ± ± ± ± 1.8 FMM 276 / ± ± 2.2 Still Bay DRS13 5 ± ± ± ± ± ± ± ± 1.9 FMM 288 / ± ± 2.3 DRS14 5 ± ± ± ± ± ± ± ± 1.3 FMM 342 / ± ± 2.5 a b c d e f g h i j Measurements made on sub-samples of dried, homogenised and powdered samples using thick source alpha counting (TSAC) to obtain U and Th concentrations and a combination of TSAC and GM-25-5 beta counting to obtain K. Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. The measured beta dose rates have been adjusted using the method presented in Jacobs et al. (in press) to compensate for the inhomogeneous distribution of U, Th and K on a beta scale. Dry dose rates calculated were adjusted for the water content (expressed as % of fry mass of sample). Measurements made using a combination of TSAC and GM-25-5 beta counting. In the absence of in situ gamma dose rate measurements, the laboratory-estimated gamma dose rates have been modelled using the distance data provided in S29 (Appendix H) and S55. Dry dose rates calculated were adjusted for the water content (expressed as % dry mass of sample). Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-32.4 S), longitude (18.5 E) and altitude (100 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. The finite mixture model was used to determine the D e for the dose component represented by the highest proportion of grains. Number of individual grains used for D e determination / total number of grains analysed. Relative standard deviation of the D e distribution after allowing for measurement uncertainties. The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 35

37 Section D.3: KLEIN KLIPHUIS (KKH) 1. Fig. S9: Site photograph 2. Fig. S10: Stratigraphic drawing and OSL sampling locations 36

38 3. Basic description of stratigraphic units Klein Kliphuis (KKH) is a rock shelter situated in a small gorge approximately 200 km north of Cape Town and 70 km east-north-east of Diepkloof. The shelter was formed in the gorge wall, approximately 20 m above the Kliphuis River, a tributary of the Olifants River that drains the western portion of the Cederberg Mountain Range. Excavation of the site in 1984, and again in 2006, revealed a sequence of late Holocene material directly overlying Pleistocene sediments. The Pleistocene sediments at KKH are relatively homogenous and do not display fine, well-demarked stratigraphy. Homogenisation likely resulted from a combination of bioturbation and mechanical fragmentation. The two observed bioturbative agents were insects and roots. Insect casings relating to either wasps or solitary bees (S. Van Noort, Iziko Museums of Cape Town, pers. comm.) were encountered at a variety of depths in ~8% of excavated contexts. The burrowing of insects through the deposit necessarily resulted in some vertical redistribution of sediments. Roots activity, observed throughout the excavation, may have had a similar effect of sediment redistribution to insect burrowing, though, with one exception, all roots noted were less than 1mm in diameter. The presence of roots was likely encouraged by moisture introduced into the sediments from cracks in the shelter roof. More than 10 liters of water was collected from beneath one such crack over a wet week in There is probably a relationship between these cracks, the presence of moisture in the shelter rocks, and the high frequency of naturally fractured quartzitic sandstone encountered during excavation. More than 290 kg of naturally fractured rock was recovered from the 0.7 m 3 volume of excavated material. No substantial areas of the excavation were free of roof-spalled material. While the effect of this spalling was tangible in aspects of the archaeology such as the physical disintegration of charcoal, it also strongly diminished the potential for significant vertical distribution of sediment and cultural materials. The stratigraphic Fig. S10 depict only fragments of spalled rock >2 cm, under-representing the total weight of spall by some 32%. Given the persistence of spall at all levels it would have been exceedingly difficult for any material moving under the effect of gravity to have undergone significant vertical relocation. Thus, though the site displays evidence of bioturbation, its effects on stratigraphic integrity are likely to have been limited. Seven stratigraphic units were defined during excavation on the basis of minor changes in sediment colour and composition. All of these are divisions of the Pleistocene component of the sequence, referred to as Zone D (for information on the Holocene component see S76). The seven stratigraphic units within Zone D are denominated by roman numerals; Di, Dii, Diii etc. Excavation proceeded within each unit in 25 mm spits. These allow sub-division of unit Dvi into an upper component (spits 1-7) and a lower component (spits 8-15). The transition from HP to post-hp occurs in spits Dvi7 and Dvi6. Sediments in the units Di Dv were characterized as very fine sandy clay. In the lower spits of unit Dvi the contribution of sand increased, such that by the basal unit (Dvii) sand was more prevalent than clay. In general, sediments became coarser with depth from the upper limits of Dvi through to the base of the deposit. 37

39 Variation in colour was limited, particularly in the upper units. Munsell values for the upper five units varied from 10YR 3/2 (Di) to 10YR 2/1.5 (Dv). Sediments were conspicuously darker in unit Dvi, with Munsell values from 7.5YR 2.5/1 in the upper spits, to 5YR 2.5/1 in the lower spits. The basal spit returned a Munsell value of 7.5YR 3/ Brief comment on the association between the OSL samples and the artefact assemblages Five of eight OSL samples were taken from the north section of the excavation (Fig. S10). KKH8 was placed at the base of unit Di. This unit contained artefacts characteristic of the late Pleistocene microlithic LSA and has been dated by 14 C to ± 103 years BP (Wk-20241). It is possible given the rocky nature of deposit that the sample was taken predominantly from the underlying late MSA unit Div. The single grain OSL data support the suggestion of mixing of ~18 ka and ~33 ka sediment (see Fig. S11), though layer Div has been AMS dated to >35ka (Wk-20243), as has unit Dii (Wk ) which is stratigraphically between Di and Div. Samples KKH4-7 were placed to explore the duration of the HP and the transition from HP to post-hp. Sample KKH4 was taken at the upper limit of unit Dvi, where post- HP technologies are well established. KKH5 was placed in spit Dvi6, at the transition from HP to post-hp technological systems. KKH6 was placed within the HP layers, at a point were artefact density briefly but significantly diminished. KKH7 was placed close to the base of Dvi. Though HP artefacts continued to the base of the excavation, the basal unit was exceptionally rocky, and recovery of a useable sample for OSL considered too difficult. Thus, though KKH7 does not record the earliest HP in the site, it is as close to base in the north section as was feasible. Three further samples were taken in other sections. One of these, KKH1, was placed in relation to an archaeological feature associated with post-hp artefacts in the west section. This sample is stratigraphically intermediate between KKH4 and KKH5. Samples KKH3 and KKH2 were placed at the upper and lower limits of a unit from Van Rijssen s (S77) 1984 excavation at KKH. This unit, denoted D2 by Van Rijssen, yielded a fragment of engraved ochre (cf., S78), and the objective of these samples was thus to provide a bracketing age for this piece. The position of KKH3 is stratigraphically comparable to sample KKH4, while KKH2 is stratigraphically below KKH7, at the base of unit Dvi (Van Rijssen s unit D2 is almost certainly the same as unit Dvi). 5. Summary description of the artefact assemblages in the dated portion of the sequence With the exception of KKH8, all samples were placed in unit Dvi, or the comparable unit from the 1984 excavation. Dvi returned an assemblage of flaked stone artefacts, as well as a sizeable quantity of ochre, both worked and unworked. Spits 8 15 in Dvi contained 67 broken and complete backed artefacts, as well as 30 notched flakes and blades. Among artefacts > 15 mm, material prevalence in these spits was 38

40 predominantly silcrete (74.3%), with quartz the next most common material (9%). On a spit by spit basis, silcrete prevalence varied from ~50% to >90%. Flaking in these spits also produced high edge length to mass values characteristic of the HP at KKH and the nearby site of Diepkloof (cf., S74). Unifacial points occur in the KKH sequence from Dvi1-7. While backed artefacts also occur in Dvi7 and Dvi6, their numbers in these layers are considerably smaller than they are deeper in the sequence. Only two backed artefacts were recorded in Dvi7 and one in Dvi6. This compares with 17 backed artefacts in Dvi8 and 20 in Dvi9. Additionally, only three notched pieces were recovered from these spits, compared with 32 from the underlying spits. While silcrete continued to be the dominant material (70.7% of artefacts > 15 mm), there was a gradual transition from silcrete to quartzite from Dvi7 through to Dvi1. By Dvi1, quartzite was more common than silcrete. Quartzite was the second most common material overall in these spits, accounting for 20.4% of artefacts > 15 mm. The gradual change in material prevalence was mirrored by a change in flaking efficiency, as noted in S Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Klein Kliphuis are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and site-specific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). Sample KKH8 KKH4 KKH3 KKH1 KKH5 KKH6 KKH7 KKH2 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S9: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. 39

41 KKH8 KKH4 KKH3 KKH1 KKH5 KKH6 40

42 KKH7 KKH2 Fig. S11: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the KKH samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S10). The dominant component represented by the largest proportion of grains (Table S10) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to intrusive grains derived from younger deposits. Sample σ d (%) N Proportion (%) Proportion (%) Proportion (%) Proportion (%) k = 1 k = 2 k = 3 k = 4 KKH ± 1 6 ± 2 90 ± 2 3 ± 2 KKH ± 2 92 ± KKH ± 1 96 ± KKH ± 1 9 ± 3 88 ± 3 -- KKH ± 1 96 ± KKH ± 2 91 ± KKH ± 1 91 ± KKH ± 3 90 ± Table S10: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. 41

43 Table S11: Dose rate data, D e values and optical ages for eight sediment samples from Klein Kliphuis Sample Moisture Radionuclide concentrations a Dose rates (Gy kyr -1 ) Total Number of Optical code content U Th K dose rate e, f D e Age σ i d age j (%) (μg g -1 ) (μg g -1 ) (%) Beta b Gamma c Cosmic d (Gy kyr -1 ) (Gy) model g grains h (%) (kyr) Post-Howieson s Poort KKH8 3 ± ± ± ± ± ± ± ± 0.8 FMM 258 / ± ± 1.3 KKH4 3 ± ± ± ± ± ± ± ± 2.0 FMM 190 / ± ± 2.7 KKH3 3 ± ± ± ± ± ± ± ± 1.4 FMM 261 / ± ± 2.0 KKH1 3 ± ± ± ± ± ± ± ± 1.8 FMM 245 / ± ± 2.4 Howieson s Poort KKH5 3 ± ± ± ± ± ± ± ± 1.1 FMM 279 / ± ± 3.0 KKH6 3 ± ± ± ± ± ± ± ± 1.4 FMM 252 / ± ± 2.7 KKH7 3 ± ± ± ± ± ± ± ± 1.4 FMM 213 / ± ± 2.8 KKH2 3 ± ± ± ± ± ± ± ± 1.5 FMM 236 / ± ± 3.4 a b c d e f g h i j Measurements made on sub-samples of dried, homogenised and powdered samples using thick source alpha counting (TSAC) to obtain U and Th concentrations and a combination of TSAC and GM-25-5 beta counting to obtain K. Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. Dry dose rates calculated were adjusted for the water content (expressed as % of fry mass of sample). Measurements made using a combination of TSAC and GM-25-5 beta counting. In the absence of in situ gamma dose rate measurements, the laboratory-estimated gamma dose rates have been modeled using the distance data provided in S29 (Appendix H) and S55. Dry dose rates calculated were adjusted for the water content (expressed as % dry mass of sample). Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-32.4 S), longitude (18.5 E) and altitude (100 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. The finite mixture model was used to determine the D e for the dose component represented by the highest proportion of grains. The preheat and cutheat temperatures used are provided in Table S2. Number of individual grains used for D e determination / total number of grains analysed. Relative standard deviation of the D e distribution after allowing for measurement uncertainties. The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 42

44 Section D.4: KLASIES RIVER (KRM) 1. Fig. S12: Site photograph 2. Fig. S13: Stratigraphic drawing and OSL sampling locations Cave 1A samples (ZKR4, ZKR5 and ZKR6) 43

45 Cave 2 samples (ZKR8, ZKR9 and ZKR10) 3. Basic description of stratigraphic units Main site is 0.5 km east of the mouth of the Klasies River, a small blind river on the Tsitsikamma coast. The deposits, some 20 m thick, accumulated against a cliff in which there are several cave-like openings. The deposits extend into openings, like caves 1 and 2, but main site is an open-air site, once sheltered by dunes and is a single depository. The deposits are well stratified and there are multiple fine layers of alternating occupation and non-occupation. The former are artefact- and fauna-rich and are marked by carbonised material. The latter are light brown sands with clasts of roof rock and other debris and notably inclusions of microfauna. Singer & Wymer (S79) recognised five culture stratigraphic divisions, from the base through the sequence MSA l, ll, with the HP and MSA lll at the top. They mapped a series of numbered layers really thick spits within these divisions. The lithostratigraphic members that are relevant to this paper are the Rock Fall (RF) member, corresponding to Layer 22, immediately underlying the HP and the Upper member that includes the HP and MSA lll. Layer 20 represents the base of the HP and Layer 9 the base of the overlying MSA lll. Erosion has cut off the any connection between the deposits in cave 2 and those in cave 1A but they are lithologically similar and were continuous. The strata containing the HP artefacts are a mass of carbonised horizons of burnt organics and ash with thin nonoccupation inter-beds. A thick YS (field abbreviation for yellow sterile) horizon equivalent to Layer 9 caps the HP and was sampled as ZKR5. Two samples ZKR 9 and 10 were collected from middle of HP, sections less than 1 m in thickness, in the Cutting of S79 and the sieving platform in cave 2. The thickness of the HP layers has been reduced by digenesis, notably the dissolution of shell coupled to compaction. Although exposed sections show a thickness of less than 1.5 m, there is material cemented to the north-west wall cave 2 indicating that the HP artefact bearing deposits were much thicker (S80). Thickness of deposit does not relate simply into time but it does indicate a significant time of accumulation. 44

46 4. Brief comment on the association between the OSL samples and the artefact assemblages The culture stratigraphy of Klasies River main site is well established (S70). The positions of the samples analysed were selected to relate directly to the ages of the layers stratigraphically immediately below, within and immediately above the layers containing the HP assemblage. 5. Summary description of the artefact assemblages in the dated portion of the sequence The presence of backed tools or segments among other elements characterises the HP layers (S70). Such artefacts are essentially absent from the layers above and below in this sequence. The layers 9 and 22, immediately above and below the HP layers are primarily non-occupation deposits and included few artifacts. 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Klasies River are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and site-specific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). Sample ZKR5 ZKR10 ZKR9 ZKR6 ZKR4 ZKR8 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S12: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. Sample σ d (%) N Proportion (%) Proportion (%) Proportion (%) k = 1 k = 2 k = 3 ZKR ZKR ± 2 94 ± 2 -- ZKR ± 2 4 ± 2 -- ZKR ± 2 95 ± 2 ZKR ± 2 93 ± 3 3 ± 2 ZKR ± 1 98 ±

47 Table S13: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. ZKR5 ZKR9 ZKR10 ZKR6 ZKR4 ZKR8 46

48 Fig. S14: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the ZKR samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S13). The dominant component represented by the largest proportion of grains (Table S13) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to intrusive grains derived from younger deposits. 47

49 Table S14: Dose rate data, D e values and optical ages for six sediment samples from Klasies River Sample Moisture Dose rates (Gy/ka) Total D e Age model Number of σ d Optical age Code content Beta a Gamma b cosmic c dose rate d,e (Gy) f grains g (%) h (ka) i Post-Howieson s Poort ZKR5 8 ± ± ± ± ± 1.6 CAM 145 / ± ± 2.3 Howieson s Poort ZKR9 15 ± ± ± ± ± 1.4 FMM 256 / ± ± 2.6 ZKR10 8 ± ± ± ± ± 1.4 FMM 151 / ± ± 2.3 ZKR6 15 ± ± ± ± ± 0.9 FMM 220 / ± ± 2.6 Pre-Howieson s Poort ZKR4 15 ± ± ± ± ± 1.3 FMM 113 / ± ± 3.4 ZKR8 15 ± ± ± ± ± 1.7 FMM 126 / ± ± 2.9 a b c d e f g h I Measurements made on sub-samples of dried, homogenised and powdered sample by high resolution gamma spectrometry and GM-25-5 beta counting. The beta dose rate dose rates were calculated from the weighted mean estimate derived from these two methods. Dry dose rates calculated were adjusted for the water content (expressed as % of dry mass of sample) Measurements made using in situ gamma spectrometry. Wet dose rates measured were adjusted for the water content (expressed as % of dry mass of sample). Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (24 24 E), longitude (34 6 S) and altitude (20 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. Estimated using single grains of quartz. Preheat and cutheat conditions are given in Table S2. Number of individual grains used for D e determination / total number of grains analysed. Overdispersion (σ d ), the relative standard deviation of the D e distribution after allowing for measurement uncertainties. The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 48

50 Section D.5: MELIKANE (MLK) 1. Fig. S15: Site photograph Melikane 2. Fig. S16: Stratigraphic drawing and OSL sampling locations MLK4 MLK3 MLK2 MLK1 49

51 3. Basic description of site and stratigraphic units Melikane is a large sandstone rockshelter located in the cliff face high on the south side of the Melikane Valley, a tributary of the Senqu River in the highlands of Lesotho s Qacha s Nek District. Located at S, E and ~1825 m asl, Melikane was excavated between July 14th and August 30th 1974 (S81). All excavated finds are housed in the University Museum of Archaeology and Anthropology, University of Cambridge, United Kingdom. Apart from the briefest descriptions of the stone artefact and faunal assemblages (S81), analysis of the MSA part of the sequence has been limited to a stable carbon isotope study of equid teeth (S82) and reporting of radiocarbon dates (S83). Hobart (S84) has undertaken a more detailed study of the overlying Later Stone Age artefact assemblages. Carter (S81) excavated using 100 mm thick spits that patently crosscut the natural stratigraphy of the site. He did, however, recognise a series of major stratigraphic subdivisions (Layers) and within this examination of unpublished section drawings allows a number of finer-grained stratigraphic units to be identified. Precise correlation between Carter s spits and individual stratigraphic units or layers is not possible. Samples for optical dating were collected from Layers 7 and 6. Layer 7 is a very moist orange to brown (7.5YR4/6) sandy deposit containing few artefacts along with pebbles of rotted bedrock. Distinguishable in colour, but not in texture, from the greenish-yellow rotted bedrock below. Layer 6 is a largely dark brown to black silty sand with sandstone gravels and cobbles which is very moist. The dark colour probably derives from the decomposition of introduced plant and other organic matter associated with the water emanating from the rear wall of the rock shelter some 6 m to the rear of the excavation trench. A partially concreted, gravely band is present midway through the layer in places. MLK 2 is taken from stratigraphic unit 25 (7.5YR2.5/1), the lowest unit within Layer 6, and falls within Carter s Spit 23A. MLK 3 is taken from the overlying stratigraphic unit 24 (7.5YR2.5/2) and within Carter s Spit 22. MLK 4 is taken from stratigraphic unit 23 (7.5YR2.5/1), the uppermost unit within Layer 6, and within Carter s Spits 20 and Brief comment on the association between the OSL samples and the artefact assemblages Stone artefacts are reported to have been "extremely rich" in Layer 6 (S81: p.94), but have not been analysed. As discussed below, MLK 1 and 2 appear to be associated with MSA assemblages of pre-hp age, MLK 3 with a HP assemblage and MLK 4 with a post-hp MSA occurrence. 5. Summary description of the artefact assemblages in the dated portion of the sequence Carter (S81) did not analyse the stone artefacts from Melikane in any detail and they remain unstudied. Thus, no information on patterns of raw material usage, core types or formal tool frequencies exists. However, his unpublished field notes and brief comments in his doctoral thesis indicate that an assemblage with large (mean length ± 100 mm) blades precedes one characterised by small (mean length ± mm) blades and that the latter is associated with many crescents, i.e. backed segments. Carter (S81: p.148) notes that the small blade (assemblage is clearly 50

52 distinct from other highland Lesotho MSA industries and that its segments would pass without comment if placed in many later microlithic assemblages (S81: p.264). Thirty of these segments were noted through the MSA deposits at Melikane. Correlating their provenance, given in Spits, with the stratigraphic information recorded in the site s section drawings suggests that as many as 23 of them are likely to derive from stratigraphic unit 24 in the middle of Layer 6 and are thus dated by the MLK 3 sample. Carter (S81) makes no reference to how his small blade/segment-rich assemblage at Melikane might relate to the broader southern African sequence, but this combination of characteristics has led subsequent authors (S68, S85, S86) to attribute it to the HP industry. It follows that the underlying MSA assemblage dated by MLK 2 belongs to some earlier MSA variant, broadly definable within Volman s (S68) MSA 2, while the overlying assemblages from stratigraphic unit 23 and Layers 3-5 all belong to Volman s (S68) MSA 3. Hopefully, excavations in mid-2008 by Brian Stewart, Cambridge University, will provide a much more detailed and stratigraphically grounded assessment of the cultural sequence at Melikane. 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Melikane are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and site-specific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). Sample MLK4 MLK3 MLK2 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N 6 11 Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S15: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. 51

53 MLK4 MLK3 MLK2 Fig. S17: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the KKH samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S16). The dominant component represented by the largest proportion of grains (Table S16) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to intrusive grains derived from younger deposits. Sample σ d (%) N Proportion (%) Proportion (%) k = 1 k = 2 MLK MLK MLK ± 2 97 ± 2 Table S16: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. 52

54 Table S17: Dose rate data, D e values and optical ages for three sediment samples from Melikane Sample Moisture Dose rates (Gy/ka) Total D e Age model Number of σ d Optical age Code content Beta a Gamma b cosmic c dose rate d,e (Gy) f grains g (%) h (ka) i Post-Howieson s Poort MLK4 19 ± ± ± ± ± 1.8 CAM 103 / ± ± 1.9 Howieson s Poort MLK3 19 ± ± ± ± ± 3.0 CAM 64 / ± ± 2.5 Pre-Howieson s Poort MLK2 19 ± ± ± ± ± 3.8 FMM 251 / ± ± 3.1 a Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. Dry dose rates calculated were adjusted for the water content (expressed as % of dry mass of sample). b Measurements made using in situ gamma spectrometry. Wet dose rates measured were adjusted for the water content (expressed as % of dry mass of sample). c Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-29.6 S), longitude (28.8 E) and altitude (1850 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). d Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. e Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. f Estimated using single grains of quartz. Preheat and cutheat conditions are given in Table S2. g Number of individual grains used for D e determination / total number of grains analysed. h Overdispersion (σ d ), the relative standard deviation of the D e distribution after allowing for measurement uncertainties. I The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 53

55 Section D.1: NTLOANA TSOANA (NT) 1. Fig. S18: Site photograph 2. Fig. S19: Stratigraphic drawing and OSL sampling locations NT2 NT1 54

56 3. Basic description of stratigraphic units Ntloana Tsoana is a medium-sized (~280 m 2 ) rockshelter located at S, E and ~1630 m asl on the south bank of the Phuthiatsana River, Maseru District, Lesotho. No more than 6 m above river level, it is liable to flooding after heavy rains and such flooding events have partly eroded the deposits. The site lies within the catchment of the proposed Metolong Dam and will be completely drowned once this is completed. Excavations took place between July 15th and August 8th 1989 using natural stratigraphic divisions, except where such units exceeded 50 mm in thickness, in which case they were divided into 50 mm spits. Artefacts and other finds are currently stored at the Pitt Rivers Museum, University of Oxford, United Kingdom. The MSA assemblages from Ntloana Tsoana are discussed by S87, overlying LSA assemblages of terminal Pleistocene/early Holocene age by S88. We collected samples for OSL dating from Layers CBS and HBL. Layer CBS is a hard, orange-yellow to brown (7.5YR5/2) coarse, damp sand with some white staining that includes many rotted sandstone fragments. It lies above a very pale brown (10YR8/3) sand with some orange staining and very abundant rotted sandstone fragments that probably represents the rotted bedrock of the shelter. No charcoal or bone is preserved in CBS. Layer HBL is a black (10YR2/1) silty sand. No charcoal or bone is preserved. The layer s boundaries with CBS below it and GWS above it are sharply defined. 4. Brief comment on the association between the OSL samples and the artefact assemblages Sample NT 1 was collected from Layer CBS and sample NT2 was collected from Layer HBL. Stone artefacts are found through these two layers 5. Summary description of the artefact assemblages in the dated portion of the sequence. The MSA artefact assemblages were analysed following the typology used by S89 in their study of the Malan Middle Stone Age collection at Rose Cottage Cave, some 40 km to the west in South Africa. Layer CBS artefacts are predominantly made on opalines (crypto-crystalline silicas) (45%) and tuff (40%), with smaller quantities of siltstone, hornfels and chert; quartz, quartzite, sandstone and petrified wood are present at frequencies of <1%. Cores are predominantly irregular, with rare examples of blade and bladelet cores present. Formal tools are rare (2.1% of all artefacts), with miscellaneously retouched pieces the most frequent category. Backed pieces are more common than points, knives or scrapers and include examples of backed segments, backed blades, backed flakes and obliquely backed blades. Overall, backed artefacts account for 24% of all formal tools, their highest presence in the Ntloana Tsoana sequence. The emphasis on backed pieces, the preference for fine-grained opalines as the main raw material, and the low frequency with faceting was used to prepare flake platforms (<7%) are consistent with attributing the CBS assemblage to the HP and are paralleled at Rose Cottage Cave (S89, S90). Layer HBL artefacts are predominantly made from tuff (50%), followed by opalines (38%) and hornfels (6%); chert, quartz, quartzite and sandstone each account for 55

57 a further 1% of the assemblage. Cores are predominantly irregular, but with a larger sample size than that available from CBS rare examples of prepared cores are present alongside some blade and bladelet examples. Facetted platforms are more common than in CBS. Formal tools, which account for only 0.6% of the entire assemblage, are dominated by unifacial points and knives (together, 40% of the sample), with scrapers (11%) and backed pieces (14%) less common. The assemblage shows clear parallels with the post-hp levels at Rose Cottage Cave in which backed pieces decline, points and knives increase and tuff increases in importance as a raw material relative to opalines (S89, S90). 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Ntloana Tsoana are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and site-specific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). Sample NT2 NT1 Total number of grains measured Grains rejected for the following reasons: T N signal <3xBG Gy dose >5% of L N 6 3 Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S18: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. 56

58 NT2 NT1 Fig. S20: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the NT samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S19). The dominant component represented by the largest proportion of grains (Table S19) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to intrusive grains derived from younger deposits. Sample σ d (%) N Proportion (%) Proportion (%) Proportion (%) k = 1 k = 2 k = 3 NT ± 3 88 ± 4 3 ± 2 NT Table S19: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. 57

59 Table S20: Dose rate data, D e values and optical ages for two sediment samples from Ntloana Tsoana Sample Moisture Dose rates (Gy/ka) Total D e Age model Number of σ d Optical age Code content Beta a Gamma b cosmic c dose rate d,e (Gy) f grains g (%) h (ka) i Post-Howieson s Poort NT2 20 ± ± ± ± ± 2.0 FMM 167 / ± ± 1.8 Howieson s Poort NT1 10 ± ± ± ± ± 4.0 CAM 33 / ± 2.8 a Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. Dry dose rates calculated were adjusted for the water content (expressed as % of dry mass of sample). b Measurements made using in situ gamma spectrometry. Wet dose rates measured were adjusted for the water content (expressed as % of dry mass of sample). c Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-27.8 S), longitude (29.3 E) and altitude (1650 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). d Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. e Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. f Estimated using single grains of quartz. Preheat and cutheat conditions are given in Table S2. g Number of individual grains used for D e determination / total number of grains analysed. h Overdispersion (σ d ), the relative standard deviation of the D e distribution after allowing for measurement uncertainties. i The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 58

60 Section D.7: ROSE COTTAGE CAVE (RCC) 1. Fig. S21: Site photograph 2. Fig. S22: Stratigraphic drawing and OSL sampling locations RCC5 RCC2 RCC3 RCC1 59

61 3. Basic description of stratigraphic units Rose Cottage is five kilometres from Ladybrand in the eastern Free State. The cave is about 20 m long and 10 m wide and has an altitude of approximately 1400 m above mean sea-level. It is a painted cave, but the rock art is now badly faded (S91). It was first excavated in the 1940s by Malan and in the early 1960s by Beaumont; the more recent excavations by Wadley began in 1987 and ended in 1998 (S92). An additional small excavation into the MSA deposits abutting the Malan excavation (S89) was made by Harper (S90) under Wadley supervision and it is in this area that the OSL samples were collected. Deposits are more than 6 m deep and there is a long LSA sequence (S92 98) as well as a long MSA one (S89, S90, S98, S99). Excavations into the LSA were conducted over 32 m 2 and some of the MSA was excavated from 22 m 2 to allow for spatial studies (S95 97, S100). While bone preservation is absent in layers older than about 20 ka, charcoal is present through most of the sequence, except the basal MSA layers (S101). The change in technology from the MSA to the LSA seems to have been a gradual process (S102). Throughout most of the MSA, lithic points have morphologies that imply that they were components of spearheads, but at the top of the MSA sequence small points are more likely to have been arrowheads (S103). Layers containing the HP assemblages These layers are cm thick. They are uniformly dark (almost black) and oily in texture and they are very rich in charcoal. Fifteen very thin layers were identified by S90 based on the occurrence at the top of each thin calcified marker lines. The sequence goes from EMD (Emby (D)) at the base to SUZ (Suzanne) at the top. There are high densities of artifacts in these layers. One OSL sample RCC3 is from EMD another, RCC1, is from ENG (above EMD) and the uppermost of our samples are from BER. Thus RCC3 and RCC1 are from the lower part of the HP and RCC2 from the upper part. The upper HP is in layers BER to SUZ. Layers containing the post-hp assemblages The post- HP layers (BYR to KAR) are clearly distinguishable from the HP layers by their texture, which is often quite sandy and light in color, especially BYR and THO. Between BYR and THO, the layers PAN, CLI, LIN and ANN were rich in charcoal and brown to dark-brown in color. OSL sample RCC5 is from LIN. Charcoal was preserved, but there was no other organic material. The sediments, with high densities of stone artifacts, are heavily compacted. 4. Brief comment on the association between the OSL samples and the artefact assemblages OSL samples RCC3 (from EMD) and RCC1 (from ENG) are associated with numerically rich and typical HP backed tools and blades from the oldest part of the HP sequence. OSL sample RCC2 (from BER) is also associated with the HP, but S99 observed a decline in the quality of blade production during this phase of the HP. OSL sample RCC5 is from layer LIN, associated with a post-hp assemblage with scrapers, points and flakes. 60

62 5. Summary description of the artefact assemblages in the dated portion of the sequence The HP Industry. A rich HP Industry with many backed tools made on small blades is sandwiched between the earliest MSA occupations and later ones with point and scraper industries. The backed tools and blades are made on the same opaline and tuffaceous rocks that were used throughout the MSA sequence and which occur as nodules in the Caledon River, about 8 km from the site (S90, S92, S99). More than 90% of all blades and flakes are of opaline; the opaline frequency for debitage varies from 96.8% in layer EMD at the base to 92.5% in layer SUZ at the top (S99). Other rock types include volcanic tuff and fine-grained sandstone. The HP Industry at Rose Cottage is innovative because of its technique of direct marginal percussion using a soft stone hammer in layers EMD to MAS (S99). The technique did not disappear rapidly at this site, but was progressively abandoned during the course of the HP Industry itself (S99). The first Levallois flakes and cores appear in ETH and SUZ, at the top of the HP sequence, where percussion for blade production became non-marginal and backed pieces decreased. Thus HP technology is not a single, unchanging entity. Backed tools have ochre and plant residues on their backed portions, suggesting that they were hafted (S104). The post-hp industry. Side scrapers and convergent scrapers are the most common forms, followed by unifacial and partly bifacial points (S90, S99). Blade production diminishes until the more recent MSA layers, LYN and KAR, where blades increase and are more common than flakes (S90, S98, S99). Layer THO is differentiated by the fairly regular use of the bipolar anvil technique and by a predominance of flake production (S99). Opaline continues to be the most important rock type, but fine sandstone and tuff are used particularly for large scrapers. 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Rose Cottage Cave are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and site-specific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order. Sample RCC5 RCC1 RCC2 RCC3 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values

63 Table S21: The number of single grains that were measured and rejected after being subjected to the rejection criteria proposed by S34, S41 and those that were accepted for inclusion in the calculation of the combined D e estimate for age calculation. RCC5 RCC2 RCC1 RCC3 Fig. S23: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the RCC samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S22). The dominant component represented by the largest proportion of grains (Table S22) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to intrusive grains derived from younger deposits. 62

64 Sample σ d (%) N Proportion (%) Proportion (%) Proportion (%) k = 1 k = 2 k = 3 RCC RCC ± 2 96 ± 2 3 ± 2 RCC RCC Table S22: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. 63

65 Table S23: Dose rate data, D e values and optical ages for four sediment samples from Rose Cottage Cave Sample Moisture Dose rates (Gy/ka) Total D e Age model Number of σ d Optical age Code content Beta a Gamma b cosmic c dose rate d,e (Gy) f grains g (%) h (ka) i Post-Howieson s Poort RCC5 12 ± ± ± ± ± 3.1 CAM 50 / ± ± 2.3 Howieson s Poort RCC2 12 ± ± ± ± ± 2.0 FMM 194 / ± ± 2.3 RCC1 12 ± ± ± ± ± 2.1 CAM 98 / ± ± 2.3 RCC3 12 ± ± ± ± ± 3.7 CAM 92 / ± ± 3.0 a Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. Dry dose rates calculated were adjusted for the water content (expressed as % of dry mass of sample). b Measurements made using in situ gamma spectrometry. Wet dose rates measured were adjusted for the water content (expressed as % of dry mass of sample). c Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-29.2 S), longitude (27.5 E) and altitude (1700 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ- zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). d Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. e Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. f Estimated using single grains of quartz. Preheat and cutheat conditions are given in Table S2. g Number of individual grains used for D e determination / total number of grains analysed. h Overdispersion (σ d ), the relative standard deviation of the D e distribution after allowing for measurement uncertainties. i The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 64

66 Section D.8: SEHONGHONG (SEH) 1. Fig. S24: Site photograph 2. Fig. S25: Stratigraphic drawing and OSL sampling locations SEH4 SEH3 SEH2 SEH1 65

67 3. Basic description of stratigraphic units Sehonghong is a large sandstone rockshelter on the south side of the river of the same name, a tributary of the Senqu River in the highlands of Lesotho s Thaba Tseka District. Located at S, E and ~1800 m asl, Sehonghong was first excavated between July 14th and August 30th All finds from this excavation are housed in the University Museum of Archaeology and Anthropology, University of Cambridge, United Kingdom. A brief description of the artefact and faunal sequences is given by Carter (S81), with a more extended discussion of the former provided by S105. The site s upper deposits were subsequently reinvestigated in 1992 by S106, but his excavations ceased in layers equivalent to Carter s Layers VI, VII and VIII, which produced artefact assemblages transitional between Middle Stone Age and Later Stone Age technologies (S107). Carter (S81) excavated using 100 mm thick spits that patently crosscut the natural stratigraphy of the site. He did, however, recognise a series of major stratigraphic subdivisions (Layers) and within these examinations of unpublished section drawings allows a number of finer-grained stratigraphic units to be identified. Precise correlation between Carter s spits and individual stratigraphic units or layers is not possible. We have collected the OSL samples from Layers II, III and IV Layer I, the lowest layer, consists mostly of partially cemented slabs of sandstone roof fall in a dark brown (10YR3/3) rotted sandstone matrix. The layer appears to consist of a single stratigraphic unit. Sample SEH1 was collected from Layer II, which is a dark greyish brown (10YR3/2) sandy loam. Layer II contains some bone and charcoal, as well as stone artefacts. Sediment is only lightly moist, even at this depth, in keeping with the overall dryness of the Sehonghong deposits compared to those at Melikane. The layer appears to consist of a single stratigraphic unit. Samples SEH2 and SEH3 were collected from Layer III, which is a yellowish to darker brown (10YR5/4) sand with large tabular sandstone slabs and smaller angular fragments and spalls, within which only sporadic artefacts and bone fragments occur. Some of the slabs are up to 1 x 1 m in size and 10 cm thick. Three stratigraphic units are visible in section, with the middle one separated from those above and below it by otherwise undescribed pink horizons. On the south side of the excavation trench the upper of these pink horizons marks the boundary between Layers III and IV. SEH 2 comes from the lowest of these three stratigraphic units, SEH 3 from the uppermost of them. Sample SEH4 was collected from Layer IV, which consists of a set of darker ashy lenses within a dark brown (10YR 3/3) loamy sediment that contains some smaller, angular sandstone slabs and fragments, but is free from rotted sandstone matrix. Seven stratigraphic units are identifiable in section, with SEH 4 coming from toward the base of the Layer. 4. Brief comment on the association between the OSL samples and the artefact assemblages Carter (S81) undertook only a limited analysis of the artefact assemblages from his excavations and his breakdown of their content is not differentiated by raw material. 66

68 Subsequent study attempted to compensate for Carter s use of 100 mm thick spits in excavation by limiting analysis to those spits that appeared to come entirely from within one or other Layer. However, sample sizes were small and the typology used does not conform to that employed in studying other MSA assemblages in southern Africa (S105). More detailed information can therefore only come from stratigraphically conducted reexcavation of the MSA part of the Sehonghong deposits. As discussed below, SEH 1-4 are all probably associated with MSA assemblages of post-hp character. 5. Summary description of the artefact assemblages in the dated portion of the sequence Carter et al. (S105) combined the artefact assemblages from Layers I, II and III, informally labelling them MSA 3. Artefact assemblages from Layers IV and V were also combined and informally labelled MSA 5. SEH 1, 2 and 3 - Opalines (55%) are the most common raw material used in the MSA 3, with hornfels accounting for a further 40% of the total assemblage (N = 1435). Quartzite (6%) is the only other material present. Almost all cores are irregular, although a couple of cylindrical blade cores occur. No bladelet or prepared cores are present. In the very small (N = 8) sample of formal tools observed by S105 two backed flakes and one segment were noted. Carter s (S81) earlier analysis noted the presence of several segments, but an absence of points. The presence of these segments and the enhanced frequency of opalines in Layers I, II and III tentatively suggested to S105 (p.193, 237) the possibility of a connection between this assemblage and the HP, but the number of artefacts present is really too limited to be sure. SEH 4 Carter et al. s (S105) MSA 5 assemblage is characterised by a much higher usage of hornfels (57%) compared to opalines (36%). Quartzite accounts for 11% of the total assemblage, with trace contributions from basalt and crystal quartz. This larger assemblage (N = 13331) includes a few blade, bladelet and Levallois cores, although the majority are irregular. Artefacts classifiable as scrapers and (probably) knives (sensu S89) are the most common formal tool types identified by (S105). In the absence of more detailed analysis of better provenanced assemblages from Layer IV, it seems reasonable to conclude that the artefacts recovered from it by Carter (S81) belong within Volman s (S68, S86) MSA 3 stage of the southern African Middle Stone Age (S85). 6. Optical dating results Summary tables and radial plots of the results obtained from the single-grain optical dating analysis for the samples from Sehonghong are provided below. Details about the measurement and analysis of the samples are discussed in section B. Sample and site-specific details are provided in table and figure captions or in the footnotes to the tables, where necessary. All data are presented in stratigraphic order (top to bottom). 67

69 Sample SEH4 SEH3 SEH2 SEH1 Total number of grains measured Grains rejected for the following reasons T N signal <3xBG Gy dose >5% of L N Poor recycling ratio No L N /T N intersection Depletion by IR Sum of rejected grains Acceptable individual D e values Table S24: The number of single grains that were measured, rejected after being subjected to the rejection criteria proposed by S34, S41 and accepted for inclusion in the calculation of the combined D e estimate for age calculation. Sample σ d (%) N Proportion (%) Proportion (%) k = 1 k = 2 SEH ± 3 94 ± 3 SEH SEH SEH Table S25: The number of grains (N) included in the finite mixture model, together with the number of dose components (k) and the value of overdispersion (σ d ) for which the optimum Bayesian Information Coefficient (BIC) and maximum likelihood (llik) values were obtained. Also shown is the proportion of grains consistent with each component. The final D e value was calculated for the component with the largest proportion of grains. SEH4 SEH3 68

70 SEH2 SEH1 Fig. S26: Radial plots (S71) of the equivalent dose (D e ) estimates obtained from individual grains of quartz from each of the KKH samples. The equivalent dose for a grain is read by drawing a line from the origin of the y-axis ( Standardised Estimate ) through the data point of interest, until the line intersects the radial axis (log scale) on the right-hand side. The measurement error on this equivalent dose is obtained by extending a line vertically to intersect the x-axis. The latter has two scales: the relative standard error and its reciprocal ( Precision ). Hence, the most precise estimates fall furthest to the right of the plot, and the least precise estimates fall furthest to the left. If the equivalent doses are statistically consistent with a common dose (i.e., the spread in values is due solely to measurement error), then 95% of the data points should be captured by a band ± 2 units in width projecting from the standardised estimate axis. Using the finite mixture model (S42, S45), the plotted data for all samples can be resolved into two or more dose components (see Table S25). The dominant component represented by the largest proportion of grains (Table S25) is shown by a shaded band and is centered on the central D e value calculated for that component. This value is believed to provide the most accurate estimate of the D e. The central values for the other secondary components are shown as solid lines. We attribute the secondary components to intrusive grains derived from younger deposits. 69

71 Table S26: Dose rate data, D e values and optical ages for four sediment samples from Sehonghong Sample Moisture Dose rates (Gy/ka) Total D e Age model Number of σ d Optical age Code content Beta a Gamma b cosmic c dose rate d,e (Gy) f grains g (%) h (ka) i Post-Howieson s Poort SEH4 10 ± ± ± ± ± 1.5 FMM 84 / ± ± 1.4 SEH3 6 ± ± ± ± ± 7.3 CAM 12 / ± ± 3.4 SEH2 6 ± ± ± ± ± 4.8 CAM 39 / ± ± 2.5 SEH1 10 ± ± ± ± ± 3.0 CAM 64 / ± ± 2.3 a Measurements made on sub-samples of dried, homogenised and powdered samples by GM-25-5 beta counting. Dry dose rates calculated were adjusted for the water content (expressed as % of dry mass of sample). b Measurements made using in situ gamma spectrometry. Wet dose rates measured were adjusted for the water content (expressed as % of dry mass of sample). c Cosmic dose rates have been calculated using the equations provided by S56 taking into account the latitude (-29.7 S), longitude (28.8 E) and altitude (1785 m). We have also accounted for the different densities of the overlying roof thickness (2.5 g/cm 3 ; sandstone) and sediment (2.0 g/cm 3 ) and for the cos 2 Φ-zenith angle dependence (see S58). Dry dose rates calculated were also adjusted for the water content (expressed as % dry mass of sample) (see S57). d Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. e Includes an assumed internal alpha dose rate of 0.03 Gy kyr -1, with an assigned relative uncertainty of ± 25%. f Estimated using single grains of quartz. Preheat and cutheat conditions are given in Table S2. g Number of individual grains used for D e determination / total number of grains analysed. We acknowledge that the number of grains measured for sample SEH3 is small, but its age consistency with that of SEH4 and with an unpublished 14 C age of c. 32 ka BP gives us confidence that the age is accurate within its associated uncertainty. h Overdispersion (σ d ), the relative standard deviation of the D e distribution after allowing for measurement uncertainties. I The total uncertainty includes a systematic component of ± 2% associated with laboratory beta-source calibration. 70

72 Section D.9: SIBUDU CAVE (SIB) 1. Fig. S27: Site photograph 2. Fig. S28: Stratigraphic drawing and OSL dating locations 71