PONE-D-22-05404Homo sapiens lithic technology and microlithization in the South Asian rainforest at Kitulgala Beli-lena (c. 45 – 8 ka)PLOS ONE

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Both of the reviewers offer constructive criticism, with the comments of Reviewer 2 being particularly detailed and suggesting some references and asking for some data sharing/clarifications. 

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This interesting paper describes the lithic assemblages discovered at Kitulgala Beli-Iena, compares them with stone tools found at other sites from the region, and links the findings to other components of the economy of hunter-gatherers living at the sites and in Sri Lanka.

The authors managed to relate their findings to broader concepts such as the relationship between lithic technology and mobility or resource availability, making the reading of the article rather enthralling and thought-provoking.

I would suggest a few additions and the correction of what appears to be a typo:

1) Introduction section

During the early to Late Pleistocene, hominins reached new geographical areas as they expanded out of Africa, populations eventually extending "FROM" the far western [1-5] and eastern edges of Eurasia [6-9].

I believe that the authors meant “to” the edges of Eurasia

2) Materials and methods section

I would suggest adding some schematic drawings to explain visually the terminology used in this study to describe the different knapping methods.

3) Discussion section

-I would suggest adding to the discussion a comparison between the lithic industries from Kitulgala Bali Iena and other sites from Sri Lanka, in particular the question of presence/absence of standardised geometric microliths. These are absent from the assemblages reported in this paper, unlike at other sites from Sri Lanka such as Batadomba-Iena. How can this be explained? What could this mean?

4) Bone points: as the complementarity between lithic and bone tools is mentioned at several places in the manuscript and forms an important idea in the discussion, I would suggest adding a figure showing some of these artefacts.

5) Eventually, as part of the Open Data scheme of the journal, I would suggest adding tables with all the measurements of the individual artefacts and possibly some diacritic diagrams of the knapping techniques identified as Supplementary Material.

Reviewer #2: This is a very interesting paper on the Late Pleistocene-Holocene lithic assemblage of Kitulgala Beli-lena. The corpus of data is robust, the paper is well written and the discussion is interesting. The paper is mainly descriptive but there is not a problem with that.

My apologies for my poor English writing. If there is something not clear on my comments I will be happy to clarify via email. Moreover, I would like to apologize for sending my review one week late, I know as an author how frustrating is to be waiting to the reviewers.

I have some remarks and suggestions, mainly to strengthen this manuscript.

• I have some concerns regarding the stratigraphical research units (divisions) analysed. The description of the stratigraphy is very short, the stratigraphy shown in Figure 1 is quite simple and the decision of merging many layers as units of study for the lithics should be explained and justify. Figure 1 shows in the right-hand size a stratigraphy. The Late Pleistocene seems to have several layers. A better description of the stratigraphy and the decision of merging the lithic analysis in three big chronological phases should be justified and properly explained. First, I would dedicate some part of the introduction on the purely description of the stratigraphy and later on, in the methodology/sample section, I would explain why the authors use such big units. Using these three big chronological groups (Late Pleistocene, Terminal Pleistocene and Holocene) might be masking some diachronic variations (which would change completely the discussion of this paper). Maybe not, but then it must be justify. Moreover, I do not know if I missed it but I would specify what is the surface excavated and the relationship of litres of sediment/artefacts.

• Since the beginning of the manuscript, they use the term ‘microlithism’. In the methodology section they explain that they follow Shea and Pargeter definition. That clarification is pertinent as there is a lot of confusion regarding that term in lithic analyses, but I would explain this before in the manuscript. Because when I started reading, I was wondering what definition are the authors following and I wrote it in my notes. On this topic, in the last paragraph of the Summary, there is no need to mention that there are not backed pieces.

• Regarding the quartz variants, as it is the main raw material I wonder if the authors could differentiate varieties within the groups, as for example suggested by: Martínez Cortizas, A. and C. Llana Rodríguez (1996) Morphostructural variables and the analysis of their effect on quartz blank charecteristics. In: Non-Flint Stone Tools and the Palaeolithic Occupation of the Iberian Peninsula, edited by N. Moloney, L. Raposo and M. Santonja. Pp. 49-53. Tempus Reparatum, 649 Oxford. I have worked quite a bit with quartz and even if quartz is quartz for a geologist, for a stone toolmaker there are very different quality of quartzs depending if it is grainy, if it has flaws, etc which affect a lot on what you can make or not with the raw material. I am not proposing that the authors re-do the analysis, but again, I would explain the categories chosen / divisions made regarding raw material for their analysis. In addition, maybe for future analysis this is an interesting suggestion.

• “We first tested the normality of the data using Shapiro- Wilk tests, and, then, we employed a non-parametric test” I suppose this is because all the data were not normal distributions, but where is the table showing these results? This should be provide somewhere in the paper (Supplementary material or in a table). In this regard, I wonder if the authors are sharing their whole database. When I have published in PlosOne I am always encouraged to share my data and I think the authors should do it.

• “Following the demonstration of the bimodal distribution of blade sizes in southern India [113], we employ a 40mm size threshold and describe flakes, blades (bladelets), and retouched tools smaller than 40mm as microlithic (see [38])” I suppose it is okay to compare with other data, but I would rather show the distribution in length and width of the different blanks (maybe with simple histograms) and asses if the distribution is continuous or there are ‘breaks’ on it. This seems particularly relevant being so homogeneous all the groups selected.

• The anvil rested modality I think it was firstly defined by Callahan. I think it should be referenced (the work I am referring is a special monograph on the Neolithic of Sweden, If I remember correctly) In one of their groups they recognize this type of knapping, it would be convenient to specify how they recognize this, what are the stigma? Also, I would add some photos, etc I have been working on bipolar knapping for a while and I do not think the identification of this type of knapping/variant is straightforward, there is very little experimentation. I ask because I am curious and I am working on it indeed.

• A figure explaining the different types of cores is needed the variants vertical, horizontal, bipolar+unid., unidirectional, etc. In lithic technology every analyst use slightly different categories and for the shake of clarity and future comparisons I recommend this is better explained. In the same vein, what do the authors mean by ‘core-edge’ flakes? Also, regarding ‘debris’ I think I have not seen an explanation of how the authors define this category (well, where they put the measure cut to consider a flake chips or debris).

• I also have a problem with the use of the term ’splintered pieces’ , particularly in an assemblage with a lot of bipolar knapping. It seems the authors are referring to a type of blank (which is not its original definition which was typological). The authors need to give clarity in this regard too. Splitered pieces or pieces esquillees was originally a typological category defined by Sonneville-Bordes, later on was problematic, thus they eliminated it from the type-list of the Upper Palaeolithic because it was considered an a posteiori tool…It is problematic since long time ago but researchers keep using it I do not know why. I would dedicate some explanation too to the different blanks considered in this analysis from bipolar knapping: what is a flake-splinter? How is that category different to what they call splintered flake? I would show all this in methodology, particularly because I Imagine in the future they will do a comparative analysis with other sites in Sri Lanka and it is important to explain all these categories better. I cannot remember if these are the categories used in : Mourre V. Les Industries en Quartz au Paléolithique. Terminologie, Méthodologie et Technologie. Paléo. 1996;8:205-23. Regarding this publication I think to reference it is interesting but the authors must bear in mind that the type of knapping defined by Mourre in that work is to flake big blanks, whereas the type of bipolar knapping they have is towards the production of small things, which is slightly different. To distinguish variants within bipolar knapping is the future as finally researchers are opened to identify it.

• Regarding the comparison of the three groups of lithics analysed I would try to do some comparative statistical test beyond figure 5 and 9, although these two are quite eloquent.

• Finally, how did they differ between crystal and milky bipolar cores when the cores were very reduced/exhausted? By the presence of facets? Translucency? I am curious as I have this problem often.

Finally, I would like to say that I enjoyed the reading a learning from this fascinating assemblage.

Paloma de la Peña

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Reviewer #1: No

Reviewer #2: Yes: Paloma de la Peña

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Homo sapiens lithic technology and microlithization in the South Asian rainforest at Kitulgala Beli-lena (c. 45 – 8,000 years ago)

PONE-D-22-05404R1

Dear Dr. Picin,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Additional Editor Comments (optional):

Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: All comments have been addressed

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: Yes

Reviewer #2: Yes

**********

4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

**********

6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: (No Response)

Reviewer #2: All the comments and suggestions that I pointed out have been addressed. As I said in my previous review I have enjoyed and learned from this work.

For the question: "Have the authors made all data underlying the findings in their manuscript fully available?'' I have answer no, because I do not think the attribute analysis/database has been included in the manuscript as SM. I think this is desirable. The databases should be share for future analyses, archaeological comparissons, etc. When I have published in this journal the editors have encouraged me to do so and I think the authors should do the same in this case. Lithic analyses should be as more transparent and clear as possible.

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Reviewer #1: No

Reviewer #2: Yes: Paloma de la Peña

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