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1 doi: /nature20125 Contents Supplementary Information... 1 Stratigraphy... 3 Stratigraphic in situ features... 3 Site formation process... 3 Sediments and Stratigraphic Units... 4 Post depositional disturbances... 4 In situ stone artefacts and limited evidence for vertical displacement of stone artefactual material... 6 Stone Artefact Refits from Square 2C... 7 Chi squared test of independence for Raw Material vs Spit... 8 Distribution of Backed Stone Artefacts... 9 Chronology... 9 Optical dating results and interpretation... 9 Single-grain OSL and TT-OSL properties... 9 Single-grain De results Dose rate assessment Summary of optical ages Radiocarbon ( 14 C) dating Sampling and Contamination Issues Wood charcoal and its identification Egg shell material Bone material Bayesian age modelling Bayesian modelling likelihoods Bayesian age modelling results Residues Evidence of residues on stone artefacts Background Evidence of archaeologically significant residues Artefact No 7. Warratyi RS SQ4D QD Spit 15: Resin Artefact No 14. Warratyi RS SQ2C SC Spit 14: Resin Artefact No 20. Warratyi RS SQ4C QD Spit 18 Red Ochre Evidence of red ochre use at Warratyi Background Gypsum Gypsum analysis

2 White pigment Origin of gypsum Fauna Megafauna Identification of eggshell from Warratyi Rock Shelter as of the putative Genyornis oological material (PGOM) Sample 1. Square 4C, QB, Spit Sample 2. Square 2C, QA, Spit Interpretation and identification of the samples Diprotodon optatum radius Description Morphological comparisons Taphonomy References

3 Stratigraphy Stratigraphic in situ features The stratigraphy exposed in the excavations revealed a slow accumulation of sediment with very little evidence of disturbance. Four stratigraphic units were differentiated according to the degree of disturbance, presence of hearth like features, textural variation (reflecting the amount of roof fall material present), colour variation, and concentrations of white pigment (Figure 2 Main Text). Overall the texture grade of the sediment assessed in the field was fine sandy loam to silty clay loam with a fragile earthy fabric and a subtle range of brown colours that were difficult to identify with colour charts. See Sediments and Stratigraphic Units below for description of these layers. Numerous fine depositional laminae could be traced around the excavation walls, confirming little disturbance in the bulk of the deposit (Extended Data Figure 1a-c and Extended Data Figure 2 a- c). There was no visible evidence for any stratigraphic disconformities. The deposit contained a number of charcoal and ash features that were lenticular in section and interpreted as the remains of small fires or hearths (Extended Data Figure 1). Some individual finds such as the bone point and Diprotodon bone fragment were identified and excavated in situ and bagged separately. Site formation process The shelter has formed on a rocky hill slope by exfoliation and fretting of finely jointed rock within a gentle anticlinal flexure. The roof is a stronger bed than the floor and forms an arch. The shelter contains approximately one metre depth of secondary deposits in which six classes of materials were identified: 1. Flaky roof fall debris (on average mm in size) with occasional larger blocks of dolomitic quartz sandstone at the mouth of the shelter. The roof fall sediment was abundant in all spits and, with the exception of the surface layers that were disturbed by goats, was deposited in laminated sub-horizontal layers that confirmed an absence of burrowing in the bulk of the deposit. 2. Material brought into the shelter by humans, including plant matter, animal bones and emu egg shell, stone artefacts, red ochre and white pigment. 3. Minor accumulations of preserved animal scats from macropods, goats and small rodents that have used the shelter over time. 4. Most units contain a small fraction of wind-blown dust (fine grained red quartz sand), but there is no evidence of any significant quantity of material having been washed into the shelter from adjacent slopes as the physical shape of the shelter prevented this. 5. At the rear of the shelter and on the roof there are thin evaporative layers of calcium carbonate cave coral (identity confirmed by testing with hydrochloric acid). The maximum thickness of these precipitates was 15 mm and some has been incorporated in roof fall debris. The source of this carbonate was the bedrock dolomite and/or from a blanket of aeolian dust that was formerly a main component of the soil on the hill slopes above the shelter. Dissolved carbonate entered the shelter by seepage through the rear wall and open joint planes on the ceiling. These deposits may indicate periods of time when more moisture was available in the soil environment than at present. 6. A very small amount of in situ weathering had occurred in the fractured rock at the base of the deposit. 3

4 Sediments and Stratigraphic Units The deposits in Warratyi Rock Shelter comprise four main stratigraphic units that are consistent in depth across all excavated squares Stratigraphic Unit (SU) 1 (divided into sub-units 1A and 1B), SU 2, SU 3 and SU 4 overlying weathered quartzitic sandstone rubble and bedrock (Extended Data Figures 1 and 2). Cultural material principally consisted of stone artefacts and bone material, which were found throughout the deposit. Also present in varying quantities was charcoal, animal scats, red ochre, white gypsum pigment, emu eggshell and plant remains. SU 1A, at a depth of 0 to 5 cm, consists of silty fine sandy loam with a weak earthy fabric and a high organic component made up of goat dung, charcoal, plant material, eggshell, bone and weathered roof fall fragments. This unit has been affected by heavy trampling from goats and possible mixing by Wallaroos/Euros (Macropus robutus). A high density of stone artefacts was found in this unit. SU 1B, at a depth of 5 to 15 cm, consists of very dark grey sandy loam with a weak earthy fabric. It contains charcoal fragments up to 20 mm in length, a spatter of white gypsum pigment in the upper 3 cm, bone, stone artefacts, plant material and red ochre in varying quantities, and roof fall fragments less than 2 cm. SU 2, at a depth of 15 to 40 cm, consists of strong brown earthy fabric silty clay loam with an aeolian dust component. Charcoal fragments, red ochre, plant material, stone artefacts, roof fall fragments less than 2 cm, and white gypsum flecks are scattered throughout. SU 3, at 40 cm to 75 cm, consists of dark brown sandy loam with a high density of charcoal, hearth features and charcoal ash features. Stone artefacts, bone, emu eggshell, plant material and red ochre are found in this unit. SU 4, at 75 cm to 100 cm, consists of yellowish brown fine sandy loam with scattered artefacts, bone, plant material and charcoal.these units overlie the bedrock of the shelter s floor. Post depositional disturbances To ensure reliable interpretation of the stratigraphy we have paid careful attention to identifying all elements of bioturbation and other forms of post-depositional disturbance. As Warratyi is a rock shelter and located in an arid environment, gross disturbance by growing plants and root networks should naturally be limited; indeed, no such patterns of disturbance were identified at the site. SU 1 was, however, mixed by animal trampling and contained abundant goat dung, indicating extensive disturbance by feral goats. These animals were introduced by Europeans in the mid 19 th Century and their effects were confined to the top cm of the deposit. Localised burrowing attributed to rabbits that were introduced to Australia in the 19 th Century is evident in parts of the deeper profile. The main identified burrow contained an infill of loose mixed sediment, some plant material and goat dung from the surface. Importantly, the margins of these burrows are well-preserved and easily distinguishable by colour / texture, which has enabled us to excavate and bag all of the burrow fill separately and eliminate all risk of sample contamination (Supplementary Table S1). There was no evidence of pre-european burrows at Warratyi as could have been dug by large lizards such as goanna (Varanus species) or burrowing marsupials such as Burrowing Bettong( Bettongia lesueur). None of the key cultural or palaeontological finds came from the proximity of any burrow including the bone point, which came from Spit 14 quadrat B of Square 2C (SU 3), the Diprotodon bone, which came from Spit 18 quadrat B of Square 4C (SU 4), lowest backed artefacts which came from Spit 5 quadrat B of Square 2B (SU 3), lowest hafted tools which came from Spit 14, quadrat C of Square 2C and Spit 15 quadrat D of Square 4D (SU 3) and evidence of red ochre use on a stone tool which came from Spit 18 quadrat D of Square 4D (SU 4). Moreover, as Supplementary Table S1 shows, 4

5 visible filled and partly filled burrows were only identified in 26 quadrats between spits 4 and 11, mainly in squares 4C and 4D. All fill material was removed and bagged separately in order to minimize potential contamination of the quadrats by younger or older material. The percentage of disturbance in each quadrat calculated by weight ranged from 1.3% to 29.8%. We are confident that this localised disturbance was properly identified and isolated during excavation. Four of the eggshell 14 C samples discussed in the Radiocarbon Dating section (samples Wk-36234, Wk-36235, Wk and Wk-37316) were collected in association with / in very close proximity to (i.e. within a 5 cm vertical or lateral distance of) the localised burrow features identified in Square 4C spit 4, Square 2C spit 6, Square 4C spit 9 and Square 4C spit 11. These 14 C samples are therefore not considered to be stratigraphically reliable, but we opted to include them in our initial site chronological assessments for completeness (see discussions in Radiocarbon Dating and Bayesian Age Modelling sections. No visible forms of insect bioturbation were evident in the remaining deposits of SU 2, SU 3 and SU 4. The primary micro-layering of sediments in SU 2 to SU 4 remains intact and can be readily traced through the profiles in each excavation trench. Square Spit Quadrats Stratigraphic Unit Wt % burrow fill 4C 4 A C 6 D C 7 A C 7 C C 7 D C 8 B C 8 C C 9 B C 9 D C 9 C C 9 A C 10 B C 10 A C 10 D C 11 A C 11 D D 8 A D 9 A D 9 C D 9 B D 10 A D 10 B D 10 C D 11 D D 11 C C 6 A Supplementary Table S1: Distribution of rabbit burrow fill removed in excavated squares at Warratyi Rock Shelter. 5

6 Several other lines of evidence support the generally intact nature of the deposit, including: Clear sub-horizontal laminations of all the flaky roof fall material and sediments in general in SU 2 to SU 4. (Extended Data Figures 1 and 2 ). If these layers had been disturbed by burrowing or trampling a more random orientation of all material would be expected. The preservation of small hearths with distinct layering of burnt soil, charcoal and an ash surface in SU 2 to SU 3 (Extended Data Figures 1 and 2). Distinctive patterns in artefact and bone fragment size / abundance with depth(extended Data Figure 3). Defined concentration of white pigment (gypsum) between 20 and 80 cm (SU 2 to SU 3), indicating a discrete period of usage and intact preservation of cultural material following burial (Extended Data Figure 8). The general absence of evidence for sedimentary mixing of quartz grains from the singlegrain OSL results of SU 2, SU 3 and SU 4. The latter point merits further discussion as single-grain OSL dating can provide a useful means of assessing stratigraphic integrity on a grain-by-grain basis when undertaken in conjunction with careful sedimentological assessments 1, 2, 3. In addition to providing insights into the presence or absence of small-scale post-depositional disturbance, single-grain equivalent dose (De) datasets can potentially offer insights into the nature and extent of mixing processes when intruded grains from younger or older units are identified as discrete components in De distributions. As detailed in the Chronology section, this appears to be the case for the three single-grain OSL samples collected from SU 1B (samples ERS-1, ERS-3 and ERS-2). These De datasets each contain three to four discrete dose populations and suggest that SU 1B suffered widespread and multi-directional post-depositional grain mixing after its original deposition. In contrast, the single-grain OSL results for SU 2 to SU 4 attest to the generally undisturbed nature of the underlying units at Warratyi. OSL samples ERS-4, ERS-5 and ERS-7, taken from SU 2, SU 3 and SU 4, respectively, each contain a single dose population, confirming the absence of sediment mixing between or within these deposits. The remaining sample (ERS-6) exhibits slightly higher De dispersion related to its proximity to a hearth feature but is similarly devoid of intruded grain populations (see Chronology section for further discussions). These OSL results provide strong evidence for the stratigraphic integrity of the lower horizons in Square 2C and confirm that the grain mixing effects evident in the upper 15 cm of the profile can be reasonable discounted for the key artefact-bearing deposits at Warratyi Rock Shelter. In situ stone artefacts and limited evidence for vertical displacement of stone artefactual material Assessing the vertical displacement of stone artefacts and other material is a useful means of 4, 5, 6, determining whether an archaeological deposit has been subject to a high degree of disturbance 7, 8. Comparisons of archaeological evidence namely bone fragments from Square 2C, which have been identified to be an accumulation from anthropogenic activity rather than animal predation, and flaked stone artefacts in Square 2C indicate that both large and small items are distributed evenly throughout the Warratyi deposit (Extended Data Figure 3a and 3b). A number of large and small stone artefacts were excavated in situ (Extended Data Figure 3a). A graphical plot of the size of in situ stone artefacts (lengths) clearly shows that these stone artefacts have been deposited in a uniform way and were not subject to random vertical displacement by post depositional disturbances. 6

7 Stone Artefact Refits from Square 2C A total of 1070 artefacts were tested for refitting from Square 2C as a test of the integrity of the apparently intact depositional laminae. These artefacts were assessed to see if they could be refitted together as parts of a former piece of stone artefact, under the assumption that their original separation was attributable to stone reduction activity and that they must have originated on a single surface in the shelter. All artefacts from square 2C that were greater than 10 mm in maximum dimension were assessed for refitting. Each refit set comprises artefacts that can be treated analytically as a single knapping episode 9. As such, the distance between artefact elevations for each refitting set provides a proxy measure for the vertical displacement of cultural material throughout the deposit by human trampling and other post-depositional activty 10. Refitting was attempted within a 1 m x 1 m area which represents only a sample of the occupied area and therefore is unlikely to capture an entire knapping event. In addition, artefacts have undoubtedly been laterally dispersed as a result of repeated human and animal occupation, therefore we can predict that the overall percentage of refits (the success rate ) will be low 11. A total of 13 artefacts were found to comprise part of six refit sets. All refits are reconstructed flaking events and do not represent post-depositional breakages. Half of all refit sets (54% of refitting artefacts) contain artefacts that derive from the same spit, demonstrating little to no vertical displacement (< 5cm) across SUs 1-3. There were no refitting artefacts identified within SU 4. Two refit sets within SU 1, comprising four artefacts, were found to be displaced by <10cm, showing some vertical displacement of artefacts (likely due to trampling by goats). These observations are consistent with independent stratigraphic and chronological evidence for widespread mixing of SU 1 (see Postdepositional Disturbance and Optical Dating of Quartz sections). One refit set (Refit No 1), comprising two artefacts that were separated by a vertical distance of <35cm, demonstrates an isolated occurrence of artefact displacement between Spit 8 and Spit 14 of Square 2C within SU 3. We argue that this small single artefact is a rare example of vertical displacement as it comprises only 1/6 of the refit results, and thus does not indicate pervasive mixing of sediments throughout the profile. The artefact was not located near a burrow feature The artefacts in this refit set are small in size, and similar to the emu egg shell fragments in SU 1 (see Radiocarbon Dating Procedures section), could have been separated via localised bioturbation (e.g. insect or minor root activity). Stone artefacts made from raw materials such as chalcedony, (which are predoimantely <20 mm in maximum dimension), are discretely distributed within the top 40 cm of the deposit. The absence of chalcedony at lower depths strongly suggests that widepsread vertical displacement of small artefacts is rare. The minimal artefact displacement exhibited by the majority of the refit sets is indicative of generally high vertical integrity for the deposit, particularly for SUs 2 and 3. The refitted artefacts represent a range of sizes, and thus suggest that the majority of the assemblage is in primary depositional context. These results are in line with analogous studies, which document occasional examples of extensive vertical displacement outliers in an otherwise intact deposit 12, 13. We therefore argue that the general pattern exhibited by the stone artefact refitting results (i.e. low vertical artefact displacement) correlate with the other lines of evidence for site integrity (particularly the single grain OSL results for SU 2, SU 3 and SU 4 and the continous fine laminations in the sediment). 7

8 The vertical distribution of raw material used to make stone artefact provides an additional line of evidence for limited localised disturbance. The local stone available to prehistoric stone tool makers at Warratyi was reef quartz. This was available in fist size nodules within a kilometre of the shelter. Silcrete was the next most available raw material being located up to 5 km away from Warratyi Rock Shelter. The least accessible raw materials were the fine grained silcieous material such as chert and chalcedony. Chert is likely to have been brought into Warratyi from distance of between 20 and 50 kms. The appearance of chert as a raw material is consistent with it being used principally to make flakes for backed stone tools. The chert backed tools occur in Warratyi s deposit principally in SU 1 and SU 2, and only very low densities occur below this depth in the upper part of SU 3. The majority of flakes made using chert raw materials are small in size (between 2-3 cm in length). Chert was first used at Warratyi towards the beginning of SU 3 (Spits 7-12). The greatest concentration of chert flakes is found between spits 1 and 4. These patterns are also reflected in the distribution of chert material from the <1 cm size class. Chi squared test of independence for Raw Material vs Spit To quantify whether the raw materials used for stone artefacts significantly differed by spit depth in Warratyi s deposit we undertook a Chi Square analysis. The null hypothesis in this case is that the artefacts from each raw material had an even distribution across all spits. The alternative hypothesis is that there is a significant relationship, meaning that the distribution of the artefacts across spit levels/depth is dependent on the raw material. A total of 2948 (replicates) stone artefacts >1 cm in size from 20 spits were analysed using the R statistical package 14. Due to small sample sizes, it was necessary to remove artefacts made from basalt, chalcedony, river cobble and sandstone from the overall analysis. Thus, quartz, chert, quartzite and silcrete were assessed in the Chi squared test. df SSQ Mean sq. F stat p-value Between <2e-16 Within Supplementary Table S2: Anova Table showing statistical test results for the Chi squared test. Between & Within = show what the sum of squares, degrees of freedom and the mean of squares are being calculated for. (There are no F or p values in the Within section as these are calculated through the use of the sum of squares and the mean of squares from both rows). df = degrees of freedom SSQ = Sum of Squares Mean sq. = Mean of squares F stat = F statistic (test statistic for ANOVA) P-value indicates significance (in the context of testing the specified null hypothesis) 8

9 The distribution of raw material types was highly correlated with depth: X 2 = , df = 19, p-value < 2.2e-16. The null hypothesis is therefore rejected at a very high significance level, meaning that there is extremely strong evidence to suggest that the artefacts do not have a random distribution across spit levels and that there is a relationship between spit level and the stone artefacts made from certain types of raw materials. If there were a high degree of post depositional disturbance in the deposits at Warratyi we would not expect such a strong rejection of the null hypothesis; instead we would expect to observe a more random distribution of stone artefact raw material types across depth. Chalcedony another fine grained imported raw material that is similar to chert exhibits a discrete distribution between Spits 1 and 5. This raw material is not considered to be sourced locally and, like chert, has probably been brought into Warratyi from a considerable distance (i.e km away). The distribution of raw material types confirms that the infill deposits at Warratyi have not been subjected to heavy post-depostional disturbance. If this had been the case we would expect to find a much broader spread of fine grain raw material types such as chert and chalcedony in the lower, as well as the upper, stratigraphic sequence. Distribution of Backed Stone Artefacts The above interpretation of stratigraphic integrity is supported by the depth distribution of backed stone artefacts in Warratyi. Although dated to a much earlier period than previously thought (these modern type backed artefacts are normally associated with occupation no older than 5000 years in the Australian arid zone), seventeen geometric microliths (backed artefacts) have been identified in Warratyi(Extended Data Figure 6). The majority of these modern tool types have been found in Spits 1-4 of SU 1 and SU 2. If there had been considerable vertical disturbance of the deposit in Warratyi, we may expect to find these backed tools throughout the profile and extending into SU 3 and SU 4; this is not the case for any of the excavation squares. Chronology Optical dating results and interpretation Single-grain OSL and TT-OSL properties Between 900 and 1300 individual quartz grains of each sample were measured for equivalent dose (De) determination using the single-aliquot regenerative-dose (SAR) procedures 15 shown in Supplementary Table S3. Of these measured grains, 9-24% were considered suitable for OSL dating 16, 17 purposes after applying the single-grain quality assurance criteria of Arnold et al. (Supplementary Table S4). Only ~4% of measured grains from ESR-7 were accepted for TT-OSL De determination, which reflects the relatively high proportion of non-tt-osl-producing grains (88%) in this sample. Extended Data Figure 4a-b shows representative optically stimulated luminescence (OSL) and thermally transferred OSL (TT-OSL) dose-response/decay curves for grains that passed the SAR quality assurance criteria and were used for dating purposes. The majority of accepted grains display rapidly decaying OSL curves (reaching background levels within 0.5 s), which are characteristic of quartz signals dominated by the most readily bleachable (so-called fast ) OSL component (Extended Data Figure 4a). The single-grain OSL dose-response curves are generally well-represented by either a single saturating exponential function or a saturating exponential plus linear function, as has been widely reported for quartz grains with fast-dominated OSL signals 18, 19, 20. The single-grain TT-OSL dose-response curves are generally characterised by continued signal growth at high doses (

10 Gy) and are typically well-represented by a single saturating exponential function (Extended Data Figure 4a). Single-grain De results The single-grain De distributions of each sample are shown as radial plots in Extended Data Figure 4c. Samples ERS-4, ERS-5 and ERS-7 from SU 2 to SU 4 display relatively homogeneous singlegrain OSL De distributions (Extended Data Figure 4c). These three De datasets are characterised by moderate dose dispersion, De scatter that is well-represented by the weighted mean value (as indicated by the large proportions of grains lying within the 2σ grey bands), and low overdispersion values of 21-26% (Supplementary Table S5). The individual overdispersion estimates of these samples are all consistent with a value of <20% at 2σ, and are therefore in agreement with published single-grain OSL overdispersion datasets for ideal, well-bleached sedimentary samples that have not been affected by post-depositional mixing 21. The single-grain De datasets are not significantly positively skewed (according to the criterion outlined by Arnold and Roberts 22 ) and they do not display distinct leading-edges of low De values or elongated tails of higher De values. Insufficient bleaching prior to burial does not therefore appear to have contributed significantly to the De scatter of these samples, which is consistent with the aeolian origin of the dated quartz grains. Application of the finite mixture model (FMM) 23 confirms the presence of only a single dose population in these De datasets. The absence of multiple dose components confirms that sediment mixing 24 and beta-dose heterogeneity in the natural burial environment are unimportant with these samples. We have therefore used the central age model (CAM) 25 to derive representative burial dose estimates and final ages for these samples. Samples ERS-1, ERS-3 and ERS-2 from SU 1B display highly scattered OSL De distributions (Extended Data Figure 4c) and very high overdispersion values of 42-71% (Supplementary Table S5). A significant proportion of the measured De values do not overlap with the 2σ standardised estimates of the weighted mean burial dose, and application of the FMM confirms the presence of three to four discrete dose populations in the De datasets (Supplementary Table S5). Taking into consideration the similar De characteristics of the three samples from SU 1B, the complicated sedimentary properties of this horizon (i.e. clear visible signs of trampling and bioturbation; see Stratigraphy section), and the fact that the associated egg shell ages from this deposit were also highly scattered (Supplementary Table S7), it seems likely that post-depositional mixing accounts for the discrete dose populations in these D e datasets. Minor dose dispersion arising from other extrinsic sources of De scatter (e.g. beta dose heterogeneity) or from intrinsic sources that cannot be directly assessed in dose-recovery tests (e.g. differences between laboratory and field irradiation, heating and bleaching conditions) cannot necessarily be discounted. However, these factors alone seem unlikely to be the principal cause of the very high dose overdispersion observed for these samples. It is worth noting that the highest and lowest ages obtained using the FMM dose components for these samples are broadly consistent with the widely scattered egg shell ages obtained for radiocarbon samples Wk-37313, Wk-37314, Wk and Wk (Supplementary Table S7). The similar degree of age dispersion between these independent datasets lends further support to our interpretation that SU 1 has suffered from widespread mixing. The De datasets are consistent with multi-directional post-depositional mixing of grains in SU 1B, involving both a downward intrusion of grains that have been optically bleached within the near-surface disturbance zone, and an upward intrusion of grains from the upper marginal zone of SU 2. This two-way vertical movement of grains is borne out by (i) the higher proportion of grains associated with the oldest FMM dose component for the lowermost sample from SU 1B (73% of grains; Extended Data Figure 4c, (ii) agreement between the age of the oldest FMM dose component for the lowermost sample (ERS-2: 26.0 ± 1.5 kyr) and that obtained for an undisturbed sample (ESR4) located in the middle of the underlying unit (ERS-4: 26.4 ± 1.4 kyr), and (iii) the identification of an additional low dose component in the uppermost sample from SU 1B with a very young age of 0.3 ± 0.1 kyr. 10

11 To derive final FMM ages for these samples it is necessary to take into consideration the known sedimentological properties of SU 1, the relevant field-based evidence for localised disturbance, and the collective statistical properties of the three De distributions. In light of the above discussions, we have cautiously derived the final OSL ages using the FMM dose components identified in the middle range of the single-grain De distributions (i.e. those closest to the CAM weighted mean estimate = component k3 for ERS-1, component k2 for ERS-3, and component k2 for ERS-2; shown in bold in Supplementary Table S5), since these components most likely capture the original, non-intruded grain populations. For samples ERS-1 and ERS-3, the chosen FMM components also contain the highest proportions of individual De values (61% of grains in each case). The resultant FMM ages obtained for these three samples are indistinguishable at 1σ (Supplementary Table S5) and suggest that SU 1 was originally deposited around kyr. Sample ERS-6 from the lower part of SU 3 displays moderate overdispersion of 27 ± 3%, in agreement at 2σ with the values obtained for surrounding OSL samples (Supplementary Table S5). However, unlike the other samples from SU 2 to SU 4, the De dataset of ERS-6 exhibits two discrete dose components when fitted with the FMM (Extended Data Figure 4c). The main FMM dose component, which contains the vast majority (88%) of grains, produces a stratigraphically consistent age when compared with the two bracketing OSL samples (ESR-5 and ESR-7), and the bracketing egg shell ages for spits of SU 3 (samples Wk and Wk-36414; Supplementary Table S7). In contrast, the minor, low dose FMM component produces a stratigraphically inverted age at 2σ (according to the statistical test outlined in Galbraith and Roberts 26 ) when compared with the overlying OSL samples from SU 3 (Supplementary Table S5). The origin of this seemingly unreliable low dose component is difficult to ascertain on sedimentological grounds. Postdepositional mixing of younger grains into the horizon seems an unlikely explanation as the immediately overlying deposits in SU 3 are significantly older than the age derived from the low dose FMM component (i.e. there is an absence of sufficiently young overlying deposits from which the ~23.3 kyr intrusive grain populations could have been immediately sourced). Spatial variations in the beta dose rates experienced by individual grains also seem an unlikely explanation for the low dose component because sample ERS-6 was collected from a relatively homogeneous sandy silt horizon and care was taken to avoid roof fall materials / clasts that could have acted as radioactivity cold spots. The origin of the low dose component could perhaps lie with intrinsic rather extrinsic sources of De scatter; i.e. dose dispersion originating from the experimental procedures themselves, such as grain-to-grain variations in luminescence responses due to the fixed SAR conditions or the use of non-identical field and laboratory bleaching, heating and irradiation conditions 27. The proximity of an overlying hearth feature may be significant in this regard because post-burial burning activities could have resulted in significant heat conduction to the underlying horizons and may have potentially exposed some of the grains in sample ESR-6 to different thermal histories. In addition to thermally resetting (partially or completely) the OSL signal of grains in the immediate vicinity of the fire, such post-depositional alterations may have affected the intrinsic luminescence sensitivities of certain grains, resulting in different OSL responses to the chosen SAR conditions. Further work would be needed to ascertain the likelihood of these potential sources of low De scatter. Regardless of its immediate cause, the low dose FMM component of sample ESR-6a comprises a relatively small subset of grains (12%) and it does not appear to yield a stratigraphically consistent age. The final OSL age for ERS-6 (40.5 ± 2.2 kyr) has therefore been derived using the main FMM dose component. It is worth noting that a statistically indistinguishable age of 38.2 ± 2.0 kyr is obtained using the weighted mean (CAM) estimate instead of FMM component k2; hence the final age for this sample is insensitive to our selection of age model. We favour the FMM over the CAM in this instance because the former is considered to provide a more suitable empirical fit to the De dataset on statistical grounds (i.e. according to the maximum log likelihood score criterion outlined by Arnold et al. 28 ). 11

12 The single-grain TT-OSL De distribution for ERS-7 (Extended Data Figure 4c (h) is consistent with that obtained for this sample using single-grain OSL measurements (Extended Data Figure 4c (g). The TT-OSL De dataset is characterised by a similar amounts of dose dispersion and an indistinguishable overdispersion value of 24 ± 8% (Supplementary Table S5). The majority of De values lie within 2σ of the weighted mean burial dose and form a single dose population when fitted with the FMM. These De characteristics attest to a sample that was sufficiently bleached prior to burial and has remained undisturbed thereafter. As such, we have calculated the final TT-OSL age of ESR-7 using the CAM. The single-grain TT-OSL age of 43.8 ± 3.4 kyr is statistically indistinguishable from the single-grain OSL age of 42.8 ± 2.4 kyr for this sample, underscoring the reliability of the optical chronologies for SU 4. The agreement between these two semi-independent dating techniques also confirms that the OSL age of the lowermost sample is not limited by the effects of dose saturation (as also suggested by the low proportion of rejected saturated grains in this sample; (Supplementary Table S3) or inaccurate De estimation over dose ranges of Gy. Dose rate assessment Supplementary Tables S5 provides a summary of the environmental dose rates, De values and optical ages obtained for each of the seven quartz samples. The present-day sediment water contents of the Warratyi samples are very low, and range between 1.8% and 3.0% (Supplementary Table S5). These values are not considered to be representative of those prevailing throughout the sample burial periods because the samples were collected one and a half years after the excavation pits had been dug; hence the sediment exposures would have partially dried out prior to sampling. To estimate suitable long-term sediment moisture contents, we have therefore taken a proportional estimate of the calculated saturated water content for each sample, following the approach outlined in Aitken 29. Preservation of secondary carbonates (in parts of SU 2 to SU 4, and on the surfaces of several bone specimens), buried flowstones (SU 3) and speleothems on the back wall of the shelter attest to higher sediment water contents during parts of the burial period. These sedimentological properties are consistent with several documented phases of increased effective precipitation in the Flinders Ranges during the last 40 kyr, particularly around kyr, kyr, ~11.5 kyr, and 8-6 kyr 30, 31, 32, 33, 34. Nevertheless, the sedimentary profile at Warratyi displays limited signs of weathering, there is no evidence of surface wash processes or water lain sediment deposition, and the site is situated well above the groundwater table; indicating that the average long-term water contents are not likely to have been considerably higher in the past. We have therefore opted to correct the beta, gamma and cosmic-ray dose rates of each sample using a moderate estimate equivalent to 30% of the measured saturated water contents. A 1σ relative uncertainty of 20% has been assigned to all measured water contents to accommodate likely variations in hydrologic conditions during burial. This approach yielded long-term sediment moisture contents of % for samples ESR1 to ESR7, which overlap with published values for similar types of rock shelters and shallow caves from the arid zone of Australia 35, 36, 37, 38, 39 and elsewhere 40, 41, 42. The high-resolution gamma spectrometry data collected for these samples provides insights into the state of equilibrium in the 238 U and 232 Th decay series. The specific activities of 238 U (determined from 235 U and 234 Th emissions after correcting for 226 Ra and 228 Ra interference, respectively), 226 Ra (derived from 214 Pb and 214 Bi emissions), 210 Pb, 228 Ra (derived from 228 Ac emissions), 228 Th (derived from 212 Pb and 208 Tl emissions) and 40 K obtained for dried and homogenised, bulk sediment subsamples are summarised in Supplementary Table S6. The isotopic ratios for 228 Th: 228 Ra are consistent with unity at 1σ or 2σ for all samples, indicating that a condition of secular equilibrium currently exists in the 232 Th decay series of these sediments. However, there is evidence for minor disequilibrium in the 238 U decay series for all samples apart from ERS-6. The 210 Pb/ 226 Ra ratios of samples ERS-1 and ERS-3 indicate an 11% loss of daughter isotopes towards the base of the 238 U series, as noted elsewhere in Australian cave / rock shelter settings 36, 22. This leaching of 210 Pb with 12

13 respect to 226 Ra may be related to the disturbed nature of the upper sediment horizons in SU1B. With the exception of ESR-6, all samples exhibit relatively high 238 U activities with respect to 226 Ra ( 226 Ra: 238 U deviations of 12-33%). This disequilibrium may reflect the incorporation of bones within the sediment samples and the subsequent uptake of unsupported 238 U by these bones following their burial. Alternatively, since we have used the post-radon daughter emissions of 214 Pb and 214 Bi to derive 226 Ra activities, this 238 U excess with respect to 226 Ra may reflect loss of radon ( 222 Rn) gas to the atmosphere. Regardless of the cause of this 238 U excess (or 226 Ra deficiency), it should be noted that numerically modelled isotopic disequilibria of similar magnitudes have been shown to have negligible effects (2-3%) on the total dose rate of quartz 43, 44, 45. Such systematic biases would be significantly less than the existing error ranges on our final dose rate estimates. Any 238 U disequilibrium effects will be further diminished for these samples because: (i) the 238 U decay series contributes to only 17-20% of the total quartz dose rate; and (ii) the gamma and beta dose rates have been derived using emission counting techniques that measure post-radon decays in the 238 U chain instead of parent nuclide concentrations 43, 44. To calculate the luminescence ages of these samples, we have assumed that the measured daughter-to-parent nuclide ratios in the 238 U and 232 Th decay chains prevailed throughout the burial period. Summary of optical ages Single-grain OSL dating of three quartz samples from SU 1B indicates that extensive sediment mixing took place in this horizon after its original deposition at kyr, consistent with sedimentological interpretations. The single-grain OSL results for SU 2 to SU 4 provide much greater confidence in the stratigraphical integrity of the lower horizons in Square 2C. Three stratigraphically consistent single-grain OSL ages of 26 ± 1 kyr to 41 ± 2 kyr were obtained for SU 2 and SU 3 (Supplementary Tables S5). SU 4, which contains the earliest archaeological remains and an associated Diprotodon bone, yielded a single-grain OSL age of 43 ± 2 kyr and a replicate single-grain TT-OSL age of 44 ± 3 kyr. In comparative archaeological terms, Warratyi Rock Shelter is one of only a handful of Pleistocene Australia archaeological sites that has now been comprehensively dated using the single-grain OSL method. 13

14 A: OSL SAR procedure B: TT-OSL SAR procedure Step Treatment Signal Step Treatment Signal 1 Dose (natural or laboratory) 1 Dose (natural or laboratory) 2 Preheat 1 (PH 1 = 260ºC for 10 s) 2 Preheat 1 (PH 1 = 260ºC for 10 s) 3 Single-grain OSL stimulation (125ºC for 2 s) L n or L x 3 Single-grain OSL stimulation (125ºC for 3 s) 4 Test dose (10 Gy) 4 Preheat 2 (PH 2 = 260ºC for 10 s) 5 a IRSL stimulation (50ºC for 60 s) 5 Single-grain TT-OSL stimulation (125ºC for 3 s) L n or L x 6 Preheat 2 (160ºC for 0 s) 6 OSL stimulation (280ºC for 400 s) 7 Single-grain OSL stimulation (125ºC for 2 s) T n or T x 7 Test dose (150 Gy) 8 Repeat measurement cycle for different sized 8 Preheat 3 (PH 3 = 260ºC for 10 s) regenerative doses 9 Single-grain OSL stimulation (125ºC for 3 s) 10 Preheat 4 (PH 4 = 260ºC for 10 s) 11 Single-grain TT-OSL stimulation (125ºC for 3 s) T n or T x 12 OSL stimulation (290ºC for 400 s) 13 Repeat measurement cycle for different sized regenerative doses Supplementary Table S3: Single-aliquot regenerative-dose (SAR) procedures used for dose-recovery measurements and De determination. a Step 5 is only included in the single-grain SAR procedure when measuring the OSL IR depletion ratio 46. Each of these SAR measurement cycles was repeated for the natural dose, 3 5 different-sized regenerative doses and a 0 Gy regenerative dose (to measure OSL signal recuperation). The first regenerative dose cycle was repeated at the end of the TT-OSL SAR procedure to assess the suitability of the test-dose sensitivity correction. Both the smallest and second-largest non-zero regenerative dose cycles were repeated at the end of the OSL SAR procedure to assess the suitability of the test-dose sensitivity correction. In the case of the single-grain OSL SAR procedure, the smallest regenerative-dose cycle was also repeated a second time with the inclusion of step 5 to check for the presence of feldspar contaminants using the OSL IR depletion ratio 46. For single-grain TT-OSL D e measurements, feldspar contamination was checked by measuring the OSL IR depletion ratio separately and in the standard manner shown for single-grain OSL measurements. L x = regenerative dose signal response; L n = natural dose signal response; T x = test dose signal response for a laboratory dose cycle T n = test dose signal response for the natural dose cycle. 14

15 Sample name ERS1 ERS3 ERS2 ERS4 ERS5 ERS6 ERS7 ERS7 SAR protocol SG OSL SG OSL SG OSL SG OSL SG OSL SG OSL SG OSL SG TT-OSL Total measured grains Reason for rejecting grains from D e analysis Standard SAR rejection criteria: % % % % % % % % T n <3σ background Low-dose recycling ratio 1 at ±2σ High-dose recycling ratio 1 at ±2σ OSL-IR depletion ratios <1 at ±2σ Gy L x/t x >5% L n/t n Additional rejection criteria: Non-intersecting grains (L n/t n > dose response curve saturation) Extrapolated grains (L n/t n > highest L x/t x at ±2σ) Saturated grains (L n/t n dose response curve I max at ±2σ) Anomalous dose response / unable to perform Monte Carlo fit Sum of rejected grains (%) Sum of accepted grains (%) Supplementary Table S4: Single-grain OSL and TT-OSL classification statistics for the Warratyi Rock Shelter samples. The proportion of grains that were rejected from the final De estimation after applying the various SAR quality assurance criteria of Arnold et al. 47, 48 are shown in rows

16 Sample Unit Sample depth (cm) Grain size (μm) Water Content (%) a Beta dose rate b,c Environmental dose rate (Gy/kyr) Gamma dose rate c,d Cosmic dose rate c,e Total dose rate c,f De type g No. of grains h Equivalent dose (De) data Overdispersion (%) i Age model j,k ERS-1 1B ± 0.6 / 10.1 ± ± ± ± ± 0.12 SG OSL 219 / ± 3 FMM comp ± 0.2 De (Gy) c Final age (kyr) l,m 0.32 ± 0.08 FMM comp ± ± 0.4 FMM comp ± ± 0.6 FMM comp ± ± 1.6 ERS-3 1B ± 0.3 / 10.2 ± ± ± ± ± 0.13 SG OSL 191 / ± 3 FMM comp ± ± 0.5 FMM comp ± ± 0.8 FMM comp ± ± 1.9 ERS-2 1B ± 0.5 / 11.2 ± ± ± ± ± 0.13 SG OSL 168 / ± 4 FMM comp ± ± 0.4 FMM comp ± ± 1.6 FMM comp ± ± 1.5 ERS ± 0.4 / 10.1 ± ± ± ± ± 0.14 SG OSL 119 / ± 3 CAM 92 ± ± 1.4 ERS ± 0.6 / 9.8 ± ± ± ± ± 0.13 SG OSL 119 / ± 3 CAM 103 ± ± 1.6 ERS ± 0.4 / 8.1 ± ± ± ± ± 0.12 SG OSL 122/ ± 3 FMM comp ± ± 2.2 FMM comp ± ± 2.2 ERS ± 0.4 / 7.1 ± ± ± ± ± 0.13 SG OSL 78 / ± 4 CAM 164 ± ± 2.4 SG TT-OSL 39 / ± 8 CAM 168 ± ± 3.4 Supplementary Table S5: Dose rate data, single-grain equivalent doses and quartz optical ages for the Warratyi Rock Shelter samples. a Present-day water content, expressed as % of dry mass of mineral fraction / Long-term water content, calculated as 30% of the present-day saturated water contents and expressed as % of dry mass of mineral fraction. A relative uncertainty of ±20% is assigned to the present-day and long-term water content values. b Beta dose rates were calculated on dried, powdered sediment samples using high resolution gamma spectrometry, after making allowance for beta dose attenuation due to grain-size effects and HF etching 49. c Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. d Gamma dose rates were calculated from in situ measurements made at each sample position with a NaI:Tl detector, using the energy windows approach

17 e Cosmic-ray dose rates were calculated using the approach of Prescott and Hutton 50 and assigned a relative uncertainty of ±10%. f Total dose rate includes an assumed internal dose rate of 0.03 Gy / kyr with an assigned relative uncertainty of ±30% (±0.01 Gy / kyr), based on intrinsic 238 U and 232 Th contents published by Mejdahl 51, Bowler et al. 52 Jacobs et al. 53 and Pawley et al. 54, and an a-value of 0.04 ± , 56, 57. g SG OSL = single-grain optically stimulated luminescence; SG TT-OSL = single-grain thermally transferred OSL. h Number of D e measurements that passed the SAR rejection criteria and were used for D e determination / total number of grains analysed. i The relative spread in the D e dataset beyond that associated with the measurement uncertainties of individual D e values, calculated using the central age model (CAM) 25. j Age model used to calculate the sample-averaged D e value for each sample. FMM = finite mixture model 23. k The FMM was fitted by varying the common overdispersion parameter (σ k) between 5 and 30% and incrementally increasing the specified number of k n components. The FMM parameter values shown here were obtained from the optimum FMM fit (i.e. the fit with the lowest BIC score 50 ), which corresponded to a σ k value of 15% for sample ERS6, 20% for sample ERS3, and 25% for samples ERS1 and ERS2 (all consistent with the empirical overdispersion value obtained for well-bleached, unmixed D e datasets at this site at 2σ). Using this approach, the D e distributions of samples ERS1, 2, 3 and 6 are shown to contain between two and four discrete dose populations (k 1 to k 4). All other samples contain a single dose component when fitted with the FMM. l Total uncertainty includes a systematic component of ±2% associated with laboratory beta-source calibration. m The preferred ages are shown in bold for each sample (see text for further details). 17

18 Sample Unit Sample depth (cm) Radionuclide specific activities (Bq/kg) a, b Daughter: parent isotopic ratio 238 U 226 Ra 210 Pb 228 Ra 228 Th 40 K 226 Ra: 238 U 210 Pb: 226 Ra 228 Th: 228 Ra ERS-1 1B ± ± ± ± ± ± ± ± ± 0.02 ERS-3 1B ± ± ± ± ± ± ± ± ± 0.02 ERS-2 1B ± ± ± ± ± ± ± ± ± 0.02 ERS ± ± ± ± ± ± ± ± ± 0.03 ERS ± ± ± ± ± ± ± ± ± 0.02 ERS ± ± ± ± ± ± ± ± ± 0.02 ERS ± ± ± ± ± ± ± ± ± 0.02 Supplementary Table S6: High-resolution gamma spectrometry results and daughter-to-parent isotopic ratios for selected samples from Warratyi Rock Shelter. a Measurements made on dried and powdered sediment sub-samples of ~120 g. b Mean ± total uncertainty (68% confidence interval), calculated as the quadratic sum of the random and systematic uncertainties. 18