- Reviewing EditorYonatan SahleUniversity of Cape Town, South Africa
- Senior EditorGeorge PerryPennsylvania State University, United States of America
Reviewer #1 (Public Review):
I think it is important to note up front that I recognize that the goal of this paper was to announce the discovery of what appear to be intentionally-made marks in Rising Star cave in South Africa. This was not meant to be an in-depth analysis or a declaration of definitive results. With this in mind, I appreciate that the authors did not try to overstate this new discovery, but instead simply reported what had been observed, provided a little bit of background on the current state of the field in regards to the evolution of hominin visual mark-making, made a few tentative identifications, but then clearly acknowledged that a lot more documentation, sampling, and study would be needed before we could understand the full scope and potential importance of this find.
This is a big claim. If it proves to be true, it has the potential to be paradigm-shifting as the identification of intentional engraved marks, made by a small-brained distant human cousin 200,000+ years ago in South Africa, would completely change our understanding of where, when and who made the first graphic marks. Twenty years ago, this claim would probably have been dismissed out of hand as being too far-fetched to be taken seriously, but there have been some major shifts in the field in recent years, in regard to the age of the art and the identity of the artists, that means this is a claim that should be approached with a scientifically cautious, but open mind. There is now mounting evidence for Neanderthals, and potentially other closely related species as well, to have been engaging in similar art-making practices to our own Homo sapiens ancestors. What makes this particular claim so extraordinary is that these marks are some of the oldest in the world and that Homo naledi is a more distant relation with a smaller brain. This is also what makes the further study of this discovery such a fascinating exercise in scientific inquiry.
From a technical and methodological perspective, there is an excellent range of tools and technologies that can be used to study these engravings, so I have no doubt that further studies will help answer some of the "nuts and bolts" questions. Then there is also the opportunity created by this discovery to really open a broader dialogue in the field about who were the first artists and at what point does the hominin brain become "primed" for making visual marks. I look forward to all sorts of lively debates in the future and to seeing the results of further in-depth studies.
Reviewer #2 (Public Review):
Patterns scored into or painted on durable media have long been considered important markers of the cognitive capabilities of hominins. More specifically, the association of such markers with Homo sapiens has been used to argue that our evolutionary success was in part shaped by our unique ability to code, store and convey information through abstract conventions.
That singularity of association has been cast into doubt in the last decade with finds of designs apparently painted or carved by Neanderthals, and potentially by even earlier hominins. Even allowing for these developments, however, extending the capability to generate putatively abstract designs to a relatively small-brained hominin like Homo naledi is contentious. The evidential bar for such claims is necessarily high, and I don't believe that it has been cleared here.
The central issue is that the engravings themselves are not dated. As the authors themselves note, the minimum age constraint provided by U/Th on flowstone does not necessarily relate to the last occupation of the Dinaledi cave system, as the earlier ESR age on teeth does not necessarily document first use of the cave. The authors state that "At present we have no evidence limiting the time period across which H. naledi was active in the cave system". On those grounds though, assigning the age range of presently dated material within the cave system to the engravings - as the current title unambiguously does - is not justifiable.
Because we don't know when they were made, the association between the engravings and Homo naledi rests on the assertion that no humans entered and made alterations to the cave system between its last occupation by Homo naledi, and its recent scientific recording. This is argued on page 6 with the statement that "No physical or cultural evidence of any other hominin population occurs within this part of the cave system".
There is an important contrast between the quotes I have referred to in the last two paragraphs. In the earlier quote, the absence of evidence for Homo naledi in the cave system >335 ka and <241 ka is not considered evidence for their absence before or after these ages. Just because we have no evidence that Homo naledi was in the cave at 200 ka doesn't mean they weren't there, which is an argument I think most archaeologists would accept. When it comes to other kinds of humans, though - per the latter quote - the opposite approach is taken. Specifically, the present lack of physical evidence of more recent humans in the cave is considered evidence that no such humans visited the cave until its exploration by cavers 40 years ago. I don't think many archaeologists would consider that argument compelling. I can see why the authors would be drawn to make that assertion, but an absence of evidence cannot be used to argue in one way for use of the cave by Homo naledi and in another way for use of the cave by all other humans.
A second problem is with what Homo naledi might have made engravings. The authors state that "The lines appear to have been made by repeatedly and carefully passing a pointed or sharp lithic fragment or tool into the grooves". The authors then describe one rock with superficial similarities to a flake from the more recent site of Blombos to suggest that sharp-edge stones with which to make the engravings were available to Homo naledi. Blombos is considered relevant here presumably because it has evidence for Middle Stone Age engravings. The authors do not, however, demonstrate any usewear on that stone object such as might be expected if it was used to carve dolomite. Given that it is presented as the only such find in the cave system so far, this seems important.
My greater concern is that the authors did not compare the profile morphology of the Dinaledi engravings with the extensive literature on the morphology of scored lines caused by sharp-edge stone implements (e.g., Braun et al. 2016, Pante et al. 2017). I appreciate that the research group is reticent to undertake any invasive work until necessary, but non-destructive techniques could have been used to produce profiles with which to test the proposition that the engravings were made with a sharp edge stone.
One thing I noticed in this respect is that the engravings seem very wide, both in absolute terms and relative to their depth. The data I collected from the Middle Stone Age engraved ochre from Klein Kliphuis suggested average line widths typically around 0.1-0.2 mm (Mackay and Welz 2008). The engraved lines at Dinaledi appear to be much wider, perhaps 2-5 mm. This doesn't discount the possibility that the engravings in the Dinaledi system were carved with a sharp edge stone - the range of outcomes for such engravings in soft rock can be quite variable (Hodgskiss 2010) - only that detailed analysis should precede rather than follow any assertion about their mode of formation.
None of this is to say that the arguments mounted here are wrong. It should be considered possible that Homo naledi made the engravings in the Dinaledi cave system. The problem is that other explanations are not precluded.
As an example, the western end of the Dinaledi subsystem has a particular geometry to the intersection of its passages, with three dominant orientations, one vertical (which is to say, north-south), and two diagonal (Figure 1). The major lines on Panel A have one repeated vertical orientation and two repeated diagonal orientations (Figure 16), particularly in the upper area not impacted by stromatolites. The lines in both the cave system and engravings in Panel A appear to intersect at similar angles. Several of the cave features appear, superficially at least, to be replicated. In fact, scaled, rotated, and super-imposed, Figure 16 is a plausible 'mud map' of the western end of the Dinaledi system carved incrementally by people exploring the caves. A figure showing this is included here:
Of course, there are problems with this suggestion. The choice of the upper part of Panel A is selective, the similarity is superficial, and the scales are not necessarily comparable. (Note, btw, that all of those caveats hold equally well for the comparison the authors make between the unmodified rock from Dinaledi and the flake from Blombos in Figure 19). However, the point is that such a 'mud map hypothesis' is, as with the arguments mounted in this paper, both plausible and hard to prove.
Having read this paper a few times, I am intrigued by the engravings in the Dinaledi system and look forward to learning more about them as this research unfolds. Based on the evidence presently available, however, I feel that we have no robust grounds for asserting when these engravings were made, by whom they were made, or for what reason they were made.
Braun, D. R., et al. (2016). "Cut marks on bone surfaces: influences on variation in the form of traces of ancient behaviour." Interface Focus 6: 20160006.
Hodgskiss, T. (2010). "Identifying grinding, scoring and rubbing use-wear on experimental ochre pieces." Journal of Archaeological Science 37: 3344-3358.
Mackay, A. & A. Welz (2008). "Engraved ochre from a Middle Stone Age context at Klein Kliphuis in the Western Cape of South Africa." Journal of Archaeological Science 35: 1521-1532.
Pante, M. C., et al. (2017). "A new high-resolution 3-D quantitative method for identifying bone surface modifications with implications for the Early Stone Age archaeological record." J Hum Evol 102: 1-11.
Reviewer #3 (Public Review):
Lee Berger and colleagues argue here that markings they have found in a dark isolated space in the Rising Star Cave system are likely over a quarter of a million years old and were made intentionally by Homo naledi, whose remains nearby they have previously reported. As in a European and much later case they reference ('Neanderthal engraved 'art' from the Pyrenees'), the entangled issues of demonstrable intentionality, persuasive age and likely authorship will generate much debate among the academic community of rock art specialists. The title of the paper and the reference to 'intentional designs', however, leave no room for doubt as to where the authors stand, despite avoidance of the word art, entering a very disputed terrain. Iain Davidson's (2020) 'Marks, pictures and art: their contributions to revolutions in communication', also referenced here, forms a useful and clearly articulated evolutionary framework for this debate. The key questions are: 'are the markings artefactual or natural?', 'how old are they?' and 'who made them?, questions often intertwined and here, as in the Pyrenees, completely inseparable. I do not think that these questions are definitively answered in this paper and I guess from the language used by the authors (may, might, seem etc) that they do not think so either.
First, a few referencing issues: the key reference quoted for distinguishing natural from artefactual markings (Fernandez-Jalvo et al. 2014), whilst mentioned in the text, is not included in the references. In the acknowledgements, the claim that "permits to conduct research in the Rising Star Cave system are provided by the South African National Research Foundation" should perhaps refer rather to SAHRA? In the primary description of their own markings from Rising Star and their presumed significance, there are, oddly, several unacknowledged quotes from the abstract of one of the most significant European references (Rodriguez-Vidal et al. 2014). These need attention.
Before considering the specific arguments of the authors to justify the claims of the title, we should recognise the shift in the academic climate of those concerned with 'ancient markings' that has taken place over the past two or three decades. Before those changes, most specialists would probably have expected all early intentional markings to have been made by Homo sapiens after the African diaspora as part of the explosion of innovative behaviours thought to characterise the 'origins of modern humans'. Now, claims for earlier manifestations of such innovations from a wider geographic range are more favourably received, albeit often fiercely challenged as the case for Pyrenean Neanderthal 'art' shows (White et al. 2020). This change in intellectual thinking does not, however, alter the strict requirements for a successful assertion of earlier intentionality by non-sapiens species. We should also note that stone, despite its ubiquity in early human evolutionary contexts, is a recalcitrant material not easily directly dated whether in the form of walling, artefact manufacture or potentially meaningful markings. The stakes are high but the demands are no less so.
Why are the markings not natural? Berger and co-authors seem to find support for the artefactual nature of the markings in their location along a passage connecting chambers in the underground Rising Star Cave system. The presumption is that the hominins passed by the marked panel frequently. I recognise the thinking but the argument is weak. More confidently they note that "In previous work researchers have noted the limited depth of artificial lines, their manufacture from multiple parallel striations, and their association into clear arrangement or pattern as evidence of hominin manufacture (Fernandez-Jalvo et al. 2014)". The markings in the Rising Star Cave are said to be shallow, made by repeated grooving with a pointed stone tool that has left striations within the grooves and to form designs that are "geometric expressions" including crosshatching and cruciform shapes. "Composition and ordering" are said to be detectable in the set of grooved markings. Readers of this and their texts will no doubt have various opinions about these matters, mostly related to rather poorly defined or quantified terminology. I reserve judgement, but would draw little comfort from the similarities among equally unconvincing examples of early, especially very early, 'designs'. Two or even three half-convincing arguments do not add up to one convincing one.
The authors draw our attention to one very interesting issue: given the extensive grooving into the dolomite bedrock by sharp stone objects, where are these objects? Only one potential 'lithic artefact' is reported, a "tool-shaped rock [that] does resemble tools from other contexts of more recent age in southern Africa, such as a silcrete tool with abstract ochre designs on it that was recovered from Blombos Cave (Henshilwood et al. 2018)", also figured by Berger and colleagues. A number of problems derive from this comparison. First, 'tool-shaped rock' is surely a meaningless term: in a modern toolshed 'tool-shaped' would surely need to be refined into 'saw-shaped', 'hammer-shaped' or 'chisel-shaped' to convey meaning? The authors here seem to mean that the Rising Star Cave object is shaped like the Blombos painted stone fragment. But the latter is a painted fragment, not a tool and so any formal similarity is surely superficial and offers no support to the 'tool-ness' of the Rising Star Cave object. Does this mean that Homo naledi took (several?) pointed stone tools down the dark passageways, used them extensively and, whether worn out or still usable, took them all out again when they left? Not impossible, of course. And the lighting?
The authors rightly note that the circumstance of the markings "makes it challenging to assess whether the engravings are contemporary with the Homo naledi burial evidence from only a few metres away" and more pertinently, whether the hominins did the markings. Despite this honest admission, they are prepared to hypothesise that the hominin marked, without, it seems, any convincing evidence. If archaeologists took juxtaposition to demonstrate authorship, there would be any number of unlikely claims for the authorship of rock paintings or even stone tools. The idea that there were no entries into this Cave system between the Homo naledi individuals and the last two decades is an assertion, not an observation, and the relationship between hominins and designs no less so. In fact, the only 'evidence' for the age of the markings is given by the age of the Homo naledi remains, as no attempt at the, admittedly very difficult, perhaps impossible, task of geochronological assessment, has been made.
The claims relating to artificiality, age and authorship made here seem entangled, premature and speculative. Whilst there is no evidence to refute them, there isn't convincing evidence to confirm them.
Davidson, I. 2020. Marks, pictures and art: their contribution to revolutions in communication. Journal of Archaeological Method and Theory 27: 3 745-770.
Henshilwood, C.S. et al. 2018. An abstract drawing from the 73,000-year-old levels at Blombos Cave, South Africa. Nature 562: 115-118.
Rodriguez-Vidal, J. et al. 2014. A rock engraving made by Neanderthals in Gibralter. Proceedings of the National Academy of Sciences.
White, Randall et al. 2020. Still no archaeological evidence that Neanderthals created Iberian cave art.
Reviewer #4 (Public Review):
This is potentially a landmark study with far-reaching consequences for archaeology, palaeoanthropology, and more widely. The antiquity of intentional human mark marking is a hot topic but this study – understood as initial – has as yet incomplete sources of evidence and methods; and it will be interesting to follow how the study develops in subsequent studies.
Strengths and points to build on:
* Heuristic potential: As knowledge advances it poses a risk to accepted knowledge – and we should accept that one such risk is moving on from long-held disciplinary tenets. In this case, there has been a growing quantum of evidence – all hotly debated – for the deep antiquity of mark-making and even symbolism by species other than ourselves. Most researchers now accept Neanderthal symbolic capacity actualised in burials, intentional mark-making and the like. The evidence here presented is not unequivocal but is very suggestive and an ideal test case for applying multi-disciplinary techniques of analysis and interpretation beyond the expertise of the listed authors *see comments in 'weaknesses'). This work by itself may be equivocal but when taken together with other such work, points to a 'human' sensu lato past that is as complex as it is long. This work then helps all researchers to at least be alive to the possibility of things like anthropic marks and residues in a context not normally thought to have it.
* Decentering speciesism: As per the above comment, I appreciate empirical studies that erode speciesism – in particular studies that open up our minds to the possibility that multiple members of the Genus Homo were capable of intentional mark-making and even 'symbolic' behaviour, though this latter term is not well understood or uniformly used. This is probably because of continuous unconscious bias on our part as currently the only exemplar of our genus living - in contrast to most of the past in which different species and genera co-existed - if not on the same landscape and/or at exactly the same time, then with enough overlap that people would have realised 'others' were about either by sight and/or by encountering their physical remains and artefacts.
* Problematising 'firsts' and deep time: A strength – but which needs to be developed in this manuscript – is our understanding of time and change. We have a plethora of dating techniques but relatively few substantive monographs, articles, and think tanks on time – and especially on how change comes about and what causes it. This leads us to privilege 'firsts' and the 'oldest' finds in 'deep' time above those that are more recent and in 'shallow' time. I would suggest in addition to the claims for the oldest of the reported marks, the authors develop nascent remarks on the possibility the suite of marks may have been made over time. This will help counter criticism that these marks – if established to be anthropic – were not just a singularity, but part of patterned behaviour, which would move it towards the realm of 'symbolic' cognitive behaviour. And indeed, it would be good to hear more about why in this place, these marks were made to establish a replicable model for identifying early anthropic marks.
Ultimately, this manuscript presents evidence that those who are pro the deep antiquity of intentional mark-making by Homo (and possibly even other genera) will find enough evidence to support; while those sceptical of such claims will find enough methodological flaws and evidential limits to refute those claims. The next decade of work will likely be definitive and this article makes a key contribution to the debate.
Weaknesses and points to attend to:
* Definitions: The term 'rock engraving' is used rather uncritically and also the term 'etching' – and it would be useful to have a short definition of how the authors understand the term. Rock art scholars regularly debate these terms and whether they are or are not 'rock art' with its overwhelmingly visual bias; which this discovery may usefully help overthrow and advance.
* Dating: There is no evidence provided for dating the marks found in the cave system. They could, for example, have been made more recently than the dates claimed – and by another species (if we accept their anthropogenic authorship). This is a perennial problem of much rock art research – especially when it comes to understanding the wider archaeological/palaeoanthropological context. More crucially, accurate dating allows a more reliable understanding of authorship and who/what was responsible for a particular artefact or feature. This has not been demonstrated in this case, though we do have fossil evidence of Homo naledi in the cave system. The article title is this incorrect / and unsupported claim as the marks, if they are anthropic, have not been dated and are of unknown age. The authors allow that there may have been multiple episodes, but not that the marks can belong to a time other than they posit – either earlier, later, or distributed over a long period as the authors allow for in their concluding remarks.
* Authorship: The study does not utilise either a geoscientist as one of the authorial team, or a rock art specialist. These are key oversights as the former would help better contextualise the dating of the marks reported on, as well as explore alternative non-anthropogenic agents that may have created the marks reported on. For example, the marks and 'pitting' etc may be the result of water bringing abrasive agents during times of flooding, hitting prominent rock features in the cave system. Some explanation is given from lines 114-124, but are uncited. The overlying 'sediment' may be similar to the mondmilch found in cave systems and which is of natural origin. It may be that these non-anthropogenic causes are easy to discount; but the arguments do need to be made. Or, that the polishing was made by Homo naledi brushing against the surfaces as they moved in the cave system, independent of any mark-making. A Table showing the pros and cons of intentional anthropic versus natural authorship would be very effective - as well as showing some of the natural linear marks in the cave system to avoid any confirmation or similar bias. FTIR analysis of the panel A-C would be more than useful to determine whether an additional layer of material has been added. This is mentioned for future work, but this seems a rather post-hoc research programme.
* Use-wear analysis: If the marks are anthropic in origin; they are likely to have been made by a stone tool, which would leave characteristic marks, directionality and sequencing, distinct from natural causes. It is vital this work – such as was done on the Blombos engraved ochre – is done here – for example, linking to the chert and other tools described on lines 152-158. Note Figure 19, of such a tool, is very hard to make out. The Blombos – and Klasies River Mouth engraved ochres (curiously not referenced) – have very similar geometric markings and there is a real opportunity to compare these in securely dated contexts of 70-120 kya –which could support the argument made here for Homo naledi's cognitive capacity. On figure 16 it would be good to know on what basis some marks were selected as anthropic – and why others were not; this would help demonstrate the methodology and ability to distinguish between the two kinds of marks.
* Viewshed: The rock art specialist would have added essential expertise on how to study anthropic marks. For example, the images of the marks shown are all of individual or small collections of motifs rather than showing each panel as well as all panels together, to help understand the iconographic context as an ensemble – a 'feature' rather than isolated 'artefacts' or 'motifs'. Line 60 mentions being able to see these as a 'triptych' but the reader is not able to have this view in this manuscript. From the cave map, it is not clear whether all three 'panels' (an unfortunate art historical term that suggests a framed entity - better to use a term like 'cluster') can be viewed simultaneously or in sequence. The view shed in relation to the area where the bodies were recovered is vaguely stated as 'only a few metres away' and is worth developing. I understand 3D scans have been made so it would be useful to have a version showing the marks in relation to where the bodies were recovered and as a 3-cluster ensemble.
* Image enhancements: Also, in addition to polarised images, have colour enhancement tools like DStretch been tried to see if, for example, attempts at colouring with different coloured sands were made? Similarly, a 3D scan of the motif and panel – (Metashape is mentioned but not shown) – might assist in understanding how the marks and the rock they are on might relate to each other- as research in European upper Palaeolithic contexts has shown. Here, experimenting with different kinds of lighting - or in the absence of lighting, of tactility and how these marks and their rock support may have been experienced by those who may have made and interacted with them? As a note, it would be useful to have a scale in each image of the 'engravings' and it is a pity the one in situ photograph with the scale is not a standard rock art colour-corrected scale as is commonly used in rock art research.