Unit 3 accumulated below the hanging remnants of the Unit 2 debris cone near the entry shaft, and also extends along the current, sloping cave floor to the SW end of the chamber (Figures 2c and 8). We appreciate that this is difficult to accept, but we can find no evidence to refute this claim. The assignment of the bone as hominin in this cartoon figure was unintentional (a mistake), and we are grateful to the reviewer to point this out to us. This core is surrounded by a ~23 mm-thick central zone that consists of more coarsely layered (3–10 mm-thick), cream to grey-white coloured calcite with layering preserved as subtle colour variations, which at its base shows replacement by radiating sheaves of aragonite needles. Nevertheless, analyses were carried out as part of the due diligence process, and the results of these tests are presented here. B) Note that the explanation would have probably been easier to read if the oldest unit was called Unit 1, the second oldest Unit 2 etc. Also, text only refers to Units, table refers to Facies, and they are not comparable! This should have a different header. Likewise, we have introduced two sub-units to describe Unit 1 sediments along the cave floor. (2013), and we propagate uncertainty on tracer (spike) isotope concentrations. Need an explanation as to why they were undatable in the last publication, but are now magically all datable. For example, flowstone group 1c does provide a minimum age for the specimen that is stuck underneath it, and the ESR ages do provide a maximum age for the 2 teeth. The lower phase (phase A) is interstratified with visible clastic laminations. It is also a little confusing and not entirely convincing to argue that Unit 2 is probably older than Unit 1 and was sourced from sediments that look like Unit 1 – there is very little actual evidence to back up this claim. In other words we know that the ages for Unit 1 as currently preserved in the cave are younger that the ages of Unit 2, and we also know that there are other deposits of unit-1 like material higher in the cave that may be the source for the fragments in Unit 2, and that we have not been able to test in this study (please note that the fractures in which these sediments occur are extremely hard to access). As one reviewer points out, we effectively throw the kitchen sink at dating the fossils and this is the sole focus of the study. Other suggested edits are added in an attached text version of the paper. Together these scenarios provide our best estimate for the age range of the fossil teeth. See text for detailed discussion. Nevertheless, we have expanded the discussion, especially by focusing more on the quality of the data presented as recommended by the reviewer, and we have added a summary of what the ages mean for hominin evolution. - Line 426: There is no data on Sample 1841 in Table 7. This has been extensively reworded. Results have been calculated for the two scenarios (Table 7): (1) 80% Rn loss in the sediment; and (2) post-Rn equilibrium in dental tissue and sediment (i.e., no radon degassing). Should just stick to the ESR data. C'est son frère aîné, Thierry Séchan, qui reprend le flambeau paternel en publiant plusieurs ouvrages à l'âge adulte. The results from this phase have the highest mean maximum angular deviation (MAD) values (Table 9) due to the small and oddly shaped nature of the samples that provide less consistent measurements between each spin in the magnetometer. So, as it stands this paper reads as a technical report of the different dating techniques, the type of document circulated between member of a large project to share information. The debris cone of mud clast breccia was subsequently eroded leaving behind hanging erosion remnants of Unit 2 below a flowstone apron (Figures 2b and 3l). The cave system comprises several kilometres of mapped passageways (Figure 1a) that are stratigraphically bound to a 20–30 m-thick, chert-poor dolomite horizon capped by a 1–1.3 m-thick chert unit that forms the roof to the cave system (Dirks et al., 2015). Text says RS18 overlies Unit 3, Table says RS18 overlies Facies 2b (=Unit2?). Views are: (a) buccal, (b) occlusal, (c) lingual, and (d) internal. Normalised dose response curves (DRC’s) are shown in Figure 11. RS13 was sampled from the outermost part of the outer zone (Figure 3g). This age provides the best minimum age estimate for sub-unit 3b, and by extension a minimum age for the H. naledi fossils. On the whole, there seems little leeway for significant changes in external dose rate. Similarly, their assertion that facies 1c (as opposed to 1a or 1b) must have been the unit that provided the source material to Unit 2 (now 3?) The most important one is that sample RS18 is said to overly Unit 3 (hominin-bearing) in the text, but Unit 2 in the Table. However, this clearly causes confusion with the reviewers who question how Unit 1 sediments that appear to be younger than Unit 2 (and physically lower down in the cave stratigraphy) can possibly be incorporated in Unit 2. 8) Figure 8: With the addition of another unit, it is very challenging to differentiate the little sliver of Unit 2 (below Flowstone 1a) and Unit 3 upper because of the similarity in color, especially in the upper panel. I'm glad there are finally some dates out for the chamber now so that speculation is no longer needed. Iscriviti a. No age calculations were carried out for U concentrations of ≤0.5 ppm or U/Th ≤250 (indicated in red and underlined). During the consultation process, other reviewers highlighted the importance of these points given the interdependence of most of the age/depositional models on those interpretations. An alternative explanation is that Unit 1a/b is older than Unit 2 and the OSL dates are incorrect (aliquots as opposed to single grain). (2005). Indeed we have been very lucky to have the help of many World-class collaborators on this project. Of the known factors, the only possible problem with the dating lies in the evaluation of the external dose rate. These are the main sources of uncertainty for the age estimates, and we treat them as three sources of uncorrelated uncertainty. In the absence of volcanic deposits, it is generally difficult to obtain accurate ages for the fossils, not just because reliable techniques are few, but mostly because the stratigraphic sequences in the caves are complex, discontinuous and frequently reworked (e.g., Brain, 1993; Pickering et al., 2011a; Bruxelles et al., 2014; Stratford et al., 2014). To overcome some of this issue and make the principles of the dating techniques more accessible to a general reader, we added a general description of each technique at the start of each methodology dating section, These were all written by the same person (PD) and edited and approved by the individual labs. If the teeth were not fully covered by sediment up to a depth of about 30 cm (which is the average attenuation length of gamma-rays in material with a density of ~2.5 g/cm3) an estimate has to be made for the burial history of the teeth as well as the more general background radiation in the cave. Ages were calculated assuming closed system behaviour (CS), and compared with age results assuming continuous diffusion models (after Sambridge et al., 2012). In one area below the entrance to the chamber, these drip points repeatedly formed flowstone aprons over cave sediments that dip towards the deeper part of the chamber. The use of enamel fragments in measuring the dose allows us to differentiate between the relative contributions of non-oriented CO2- radicals (NOCOR’s) versus anisotropic radicals (AICOR’s) (e.g., Grün et al., 2008b). I disagree that there is much of a difference in writing style across the results sections; we are dealing with a range of very different techniques that require a different approach when being explained. That is not actually what the errors mean. Dose evaluations were carried out at the CENIEH using a sub-exponential dose step distribution (Grün and Rhodes, 1992) for the following gamma doses (6.705 Gy/min): 0, 13.4, 40.2, 93.9, 201.2, 415.7, 844.8, 1649, 3058, 5471, 8690, 12713, 17943, 25989, 34861 and 61412 Gy. However, we also wish to highlight that the caves mentioned by the reviewer are mature excavation sites with extensive excavation histories and multiple dating and stratigraphic studies. RS22 and RS23 are two samples from an eroded rim of Flowstone 1a near the entry shaft into the Dinaledi Chamber (Figure 1b). H. naledi shared several traits with the most primitive of our ancient relatives, including its small brain. (2015), and this work is clearly cited throughout. Should at least use consistent maps between papers. See our explanation under point 2 above. Papio) that had been recovered from sub-unit 3a below the hominin-bearing horizon (Figures 2d and 7). We disagree with this. Some micromorphology of these sediments (resin impregnated blocks then cut to make thin sections) would be very useful. 1993: Traditional music album of the year award for "Renaud cante el' Nord", 2003: Three awards given for: Album of the Year, Artist of the Year, and Song of the Year (for, This page was last edited on 21 February 2021, at 12:58. However, the results are consistent with the interpreted stratigraphy and other dating in the chamber, and highlight the potential for additional work. As explained in the text carbon dating was done “as due diligence to obtain an indication if carbon dating should be further pursued”. Overdispersion in De ranges from 50–70%, which is much higher than would be expected for a well-bleached sample (Galbraith et al., 1999), and is a reflection of the cave environment from which the samples were taken (Duller, 2008). The flowstone overlies sediments of Unit 3 that are partly eroded from underneath the flowstone leaving a 5–10 cm gap between the flowstone sheet and the current floor (Figure 3c). Or perhaps the 1a looking material was brought into the chamber from elsewhere where similar depositional environments also produced laminated orange mud. We have clearly explained this in the text (and have now expanded on this explanation in the new version). Lithofacies may be grouped into lithofacies associations or assemblages, which are characteristic of particular depositional environments". The reviewer may have missed this section? Several isolated, non-hominin bone fragments in hanging erosion remnants of Unit 2 and a single baboon tooth in floor sediments in sub-unit 3a were deposited prior to the entry of the hominin remains. CO2 produced from the sample was introduced into a reaction vessel containing an aliquot of cobalt metal catalyst. These changes also go a long way in addressing some of the concerns raised by the reviewers regarding consistent bracketing of age ranges for the fossils. Ages are reported relative to 1950. Lines 304-315 (and elsewhere): Again, until other ages are generated for facies 1c subfacies or its stratigraphic relationship/contacts with other units can be observed/demonstrated, the time-transgressive explanation for Unit 1, and the relationship between Units 1 and 2 are just a hypothesis. - Line 200: How can Unit 2 sediments be derived both from local erosion/reworking of Unit 1 and as a debris cone below a vertical fracture system? The Dinaledi Chamber contains deposits of fine-grained, muddy sediments intercalated with flowstone drapes. We have retained Facies 3c, but we have expanded the descriptions of the different facies and we have included bed-form characteristics that clearly differentiate Facies 1c from Facies 1a and 1b. We have now expanded the section in which we explain our dating approach and this has been made clear. All the detailed descriptions of the U-Th samples in the paper are based on thin-section work and extensively discuss recrystallization textures, sample by sample. This value is expected to vary over time, but not by much given that the Dinaledi Chamber occurs deep inside the cave, close to the water table, where sediments are expected to have always been close to water saturated. - Line 202: Why is there no mention of the baboon tooth in Unit 2 here? Further support was provided by ARC (DP140104282: PHGMD, ER, JK, HHW; FT 120100399: AH). This zone is mantled by a ~22 mm-thick outer zone of white calcite preserving only remnants of internal layering. The Unit 1 sediments in this location are partly covered by Unit 3 sediments and a cascade of Flowstone Group 2 (Figure 3k). Good points; we have expanded discussion on the OSL somewhat to reflect the preliminary nature of the work, and the challenges with obtaining good dates by OSL. Also, the yellow box in figure 14 is not 200-300 ka, but more like 200-340 ka. Dating protocol – Chemical procedures largely follow Horwitz et al. Originally the results provided by the two labs varied significantly, largely because each lab had made different à priori model assumptions (as a result of this being a double blind experiment), which would have been hard to spot by any non-specialist. The flowstone layer is ~25 mm thick and comprises a 6 mm thick, basal unit of grey to brown calcite that is recrystallized into fine (sub-mm scale), equigranular grains of calcite overgrowing an older acicular texture. 2) The overall synthesis/analysis of the various dating results is too limited at present, and choices on what results are highlighted at various points in the manuscript seem arbitrary at times. Thicknesses are μm, not mm and according to the table, 100 μm was removed from the dentine and the sediment, not enamel and dentine, due to misplaced headers. In both scenarios the water content has been taken as 25 ± 10%. However, in response to reviewer 4, all of the previous concerns raised with respect the use of facies, units and sub-units have now been addressed. Although the age constraints for sub-units 1a and 1b are imprecise they do suggest that Unit 1 in this part of the chamber is younger than Unit 2, and that the red mud clasts forming Unit 2 sediment were derived from source material matching our description of sub-unit 1a, but positioned higher up in the cave. sub-unit 3b), we conducted U-Th dating of flowstones that directly overlie Unit 3. Most of the U concentrations in the enamel are too low to provide a meaningful age. This seems rather arbitrary when in fact it is something that could be either modeled or calculated statistically. In addition, at the end of the Abstract, it may be better to simply state that "These dating results indicate a much younger age for the H. naledi fossils than have previously been hypothesized based on their morphology.". This luminescence signal is related to the environmental radiation dose the mineral has received since the last exposure to sunlight. The variable U-Th disequilibrium ages are a clear indication that U uptake events took place, and provide a minimum age estimate for the true age of the teeth. Additionally, fibrous aragonite needles are widely distributed in sheaf-like patterns. The U-Th dating technique has an upper age limit of ~600 ka, determined by the half-life of 230Th, and by the precision with which the various isotopes can be measured in the laboratory (Cheng et al., 2013). This is now clearly and repeatedly described in the text and is what forms the basis for our interpretation of repeated reworking. Additional measurements were taken across each tooth in areas away from the ESR fragment to assess U variability and diffusion gradients. The mud is mostly the product of the cave formation process, representing the insoluble residue left over when cavities develop via dissolution in dolomite (Dirks et al., 2015).”. If based on ESR dates, then need to explain/justify why settled on 200-300 ka specifically as opposed to the ESR range of ~150-425 Ma? Although true, this is well outside the scope of this particular paper, and it would be inappropriate to discuss this here without more work. The flowstone consists of a 12–25 mm thick layer of carbonate overlying an irregular surface of consolidated mud clast breccia similar to sediments of Unit 2 in the Dinaledi Chamber. The remains are exceptionally well preserved and represent the largest collection of fossils from a single primitive hominin species ever discovered in Africa. In this location, Flowstone 1c covers the erosional remains of a mud clast breccia containing a long bone consistent with the H. naledi assemblage (Figure 3g), and interpreted as Unit 3. Not just refer to figures that don't contain the information either (e.g., Figures 5, 8). Nous sommes ravis de pouvoir vous annoncer que DavidDC ainsi que Renaud ont repris du poil de la bête et ont relancé un nouveau serveur skyblock revisité par leurs soins !. The dose response curves (DRC’s) were obtained by averaging the T1-B2 ESR intensities recorded for all the angles at a given irradiation dose. Prime Carrello. Docteur Renaud Serum Lift & Lumiere - Sérum Anti-âge - 30 ml - Nota: 0.5 / 20 The laminations are locally recrystallized and overgrown by radiating, elongated crystals of calcite growing from the base to the top of the flowstone layer. 5) Similarly detailed treatment for reporting the radiocarbon methods and results, as the other dating methods, should be provided. For the two samples that were measured by both laboratories, the SCU procedure systematically provides higher DE results. The combined analytical data for dentine from GU-ANU in samples 1810A and 1810B yield apparent U-Th ages of 80.1 ± 2.5 ka and 82.1 ± 2.7 ka respectively, coupled with consistent initial 234U/238U activity ratios (Table 5). The flowstone groups (i.e., Flowstone Groups 1, 2 or 3), sample numbers, and ages (2σ uncertainty), as listed in Table 1, are shown below each sample. (2015) has caused confusion because it shows a bone with the caption assigning all bones to Hominin, including a bone drawn under flowstone 1a. ME would like to thank Stephan Woodborne (iThemba LABS, Gauteng) for his help in unravelling the spectrometer results related to OSL and ESR dating. Renaud Rahard. Nevertheless, the preliminary results are consistent with the range of ages suggested for Unit 3 by ESR and U-Th analyses on capping flowstones (Figure 14). We have now treated the radiocarbon dating in the same way as the other techniques; but we have not explained things to the same amount of detail, because we only did some preliminary testing with 14C, and then decided not to pursue things further. The age groupings also indicate that episodic wet periods in the Dinaledi Chamber alternated with periods during which no flowstone was deposited. Reported δ13C was measured relative to the PDB-1 on the sample itself. (2015)), with the one big difference that Unit 2 and Unit 3 sediments have been oxidized and affected by Fe-Mn oxy-hydroxide infiltration. Perhaps better to say they were deposited or transported. In this case, this would constrain the minimum age of Unit 2. In 2006, he published Les Bobos, as a satire on the Parisian lower bourgeoisie. Which is it? ESR intensities were extracted from T1-B2 peak-to-peak amplitudes of the ESR signal of enamel (Grün, 2000a). In the previous submission, Unit 2 was under the flowstone and underneath the hominid fossils on the cave floor. In situ gamma ray spectrometer measurements yielded K and Th values broadly in agreement with analysed concentrations, but did not detect U. The changes will make it much easier for people to read and understand. Methodologies and approaches taken by each laboratory that has contributed to this paper are described in detail in the methodology section." Reference to kyr BP has been removed from the text. The remaining sediment was treated with 33% hydrochloric acid and 20% hydrogen peroxide to remove carbonate and organic components. These are very valid concerns and we have tried to address this as follows: A) We realise that the time-transgressive nature of Unit 1 can be somewhat confusing, more so because it includes different facies and erosional remnants that have been preserved at different topographic levels in the cave. They are not C-14 ages. C) The text and figures been reworked to reflect the above changes. The inclination was accounted for by marking the sample on a completely flat surface of the block. Dating protocols: U series analysis – Laser ablation U-series analyses were carried out at the Australian National University (ANU), using a custom-built laser sampling system interfaced between an ArF Excimer laser and a Finnigan Neptune MC-ICP-MS (Eggins et al., 2003, 2005), following principles and procedures described in Grün et al. Apparent U-Th ages were calculated with Isoplot 3.75 (Ludwig, 2012), and uncertainties are reported as 2σ. The flowstone age groupings indicate that episodic wet periods in the Dinaledi Chamber alternated with periods during which no flowstone was deposited. So does panel C of Figure 3 and all of Figure 4. As a result the paper is easier to read, ages are now better and more consistently constrained, and it has been easier to explain how the age results place constraints on the ages of the sediments and fossils. It was clear from preliminary tests that this could not be achieved with 14C, and instead combined ESR and U-Th disequilibrium dating techniques (US-ESR; Grün et al., 1988) were applied to three H. naledi teeth that were freshly collected from near the site of the original excavation (Figures 1, 2, 4 and 6), as well as a single baboon tooth (cf.
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