87Sr/86Sr Isotope Ratio as a Tool in Archaeological Investigation: Limits and Risks
Round 1
Reviewer 1 Report
Comments and Suggestions for Authors
Overwhelmingly, archaeologists have used radiogenic strontium isotope signatures in human enamel and bone apatite to reconstruct ancient mobility patterns and to distinguish between individuals of local and non-local origins at archaeological sites.
Along this rationale this paper is of value.
Some points should be considered
1) Missing the acknowledgements (please fill in or remove if not thanks given) and supplementary (please remove if not existing)
Acknowledgments: In this section, you can acknowledge any support given which is not covered by the author contribution or funding sections. This may include administrative and technical support, or donations in kind (e.g., materials used for experiments).
Supplementary Materials: The following supporting information can be downloaded at: www.mdpi.com/xxx/s1.
2) Reference style in text is wrong. Use author-date system (e.g. Lugli et al., 2022).
3) References at the end must be in alphabetical order.
4) Refgerences at the end wrong style. It seems the authors had prepared this article for another journal. I urge them to convert to MAA style.
5) Introduction: No citations of past works are given. No goals and aims and novelty at the end of introduction is provided. Write a few lines what the purpose aim novelty and why the reader can not go to a enciclopedia to find all these equations and Sr review? What the present review offers as a new?????
6) These refs must be added. I recommend the general archaeometric overview : Liritzis,I, Laskaris, N , Vafiadou A, Karapanagiotis I , Volonakis, P , Papageorgopoulou, C , Bratitsi, M (2020) archaeometry: an overview. SCIENTIFIC CULTURE, Vol. 6, No. 1, pp. 49-98, DOI: 10.5281/zenodo.3625220. Also, The related work Argyro Nafplioti (2021) Moving forward: strontium isotope mobility research in the aegean: Mediterranean Archaeology and Archaeometry, Vol. 21, No 2, pp. 165-179. DOI:10.5281/zenodo.5057552
Also: Eric J. Bartelink & Lesley A. Chesson (2019) Recent applications of isotope analysis to forensic anthropology, Forensic Sciences Research, 4:1, 29-44, DOI: 10.1080/20961790.2018.1549527.
In general, introduction is not written well. It should include all past works and introduce this article into the wider field of Sr isotopes. If this is a review should be said in the Title. It seems to me a review. So it may change the title: Brief Review of 87Sr/86Sr isotope ratio as a tool in archaeological and environmental investigation: Limits and Risks
7) Isotopes of strontium and rubidium, and decay of 87Rb: Please add a separate section, may be No 2. If introduction is No 1.
8) now retired: remove this and affiliate to the same or other institute. MAA avoids this type of affiliation.
9) Table 1: provide reference source! Owned data?
10) Table 2: which is the ref source? Owned data?
11) Supplementary section is missing though refereed in the text
12) Provide an example of real data using Sr isotopes to determine diet or forensic or other parameter in archaeology.
13) Line 302: Discuss the implications of those results above line 302.
Author Response
Point 1) done.
Points 2),3) and 4) not pertinent.
Point 5) The introduction has been in part changed. The manuscript was submitted as a technical report not as a review. It groups many equations and concepts that is difficult to find all together in one book or encyclopaedia. We ask the referee to suggest us the “encyclopaedia” where we can find all the equations. This will be very useful for us.
Point 6) The manuscript isn’t a review but a technical note on how archaeologist should approach strontium isotope studies.
Point 7) done.
Point 8) affiliation was already indicated.
Point 9) done. See Table
Point 10) Exemplum fictum (see Table), obviously!
Point 11) done
Point 12) We think that is not necessary because there is a rich literature about it.
Point 13) done
Reviewer 2 Report
Comments and Suggestions for AuthorsThe purpose of this paper is to provide archaeologists (and biologists) with a basic knowledge of the natural processes involving strontium isotopes and some suggestions for the proper use of these isotopes. The authors are chemists and consider this knowledge useful to avoid errors in data collection and interpretation.
The first two sections (up to line 303) contain what the authors call "basic knowledge", from their perspective. For an archaeologist, however, this information, loaded with complicated formulas, is far beyond his area of interest. In interdisciplinary research involving isotopes, the archaeologist must know what to ask the chemist and interpret the data correctly. For this, the archaeologist needs a basic knowledge of isotopes to understand how this method works. However, much of the data and formulas in Sections 1-2 go far beyond this basic knowledge. It is the chemist who needs to know the details of the processes involving isotopes, not the archaeologist. There are numerous papers with good presentations for archaeologists of basic information on radiogenic strontium isotopes and their use in archaeology; there is no need to add complex data and details about chemical processes.
The second part of the article (Sections 3-5) is useful as it presents the limits and risks of using strontium isotopes and offers several suggestions. However, these limits have been extensively treated in numerous other works, which are not mentioned.
In Section 3, the authors point out that using strontium isoscapes in archaeological and biogeochemical sciences needs great caution because isoscapes generally refer to large-scale grid sampling which does not always correspond to the natural variation. While this is true, they should stress that isoscapes are predictive models, not exact references and that these models are being continuously improved (see, e.g., the mixing model proposed by Lengfelder et al., 2019 with a high success rate). Moreover, it is known that additional sampling is necessary in almost all landscapes for the researchers to achieve their goals (Holt et al., 2021).
The change of mineralogical/isotopic features of the soil over time (Section 4.2) is exemplified by the leaching process or the environmental water. The isotope values of soils and plants could be influenced by other environmental factors, e.g., the presence of sediments such as shell-based sands, sediments transported outside their areas of origin by erosion or glaciers, airborne and atmospheric inputs such as aeolian dust, volcanic ash, rainfall, and sea spray a.o. (Holt et al., 2021). Other factors may lead to covering the prehistoric topsoil, e.g., the formation of peat blankets in upland areas (O’Regan et al., 2023).
The authors state that we can only establish if the analysed individuals may belong to the same group, not that they belong to the same group (Section 4.5.), showing that samples from different areas with similar geological formations exhibit the same isotopic values even if the areas are far one from the other. The equifinality is indeed a problem. However, this topic has been already discussed in other (not cited) papers. One of the approaches is that eliminating possible areas of origin is better than identifying them (e.g., Montgomery, 2010).
Furthermore, it is accepted that strontium isotope analysis alone is usually insufficient to answer research questions, and it should be combined with other proxies. Multi-isotope studies have been found to be more effective than single-isotope studies.
The condition that plants coming from areas with variations of the soil profile with depth must have their roots down to a similar depth (Section 4.6.) is not always necessary. Homogenised sampling can address differences between deep- and shallow-rooted plants, thus reflecting more accurately the strontium in human consumption, as various plant and animal resources are certain to be consumed (Ventresca Miller et al., 2018).
The review format of a paper implies „a comprehensive analysis of the existing literature within a field of study, identifying current gaps or problems” (Instruction for authors). The authors of the present paper do not analyse the literature on the topic. The limits and risks of using strontium isotopes in archaeology have already been discussed in many papers, e.g., Pollard 2011; Holt et al., 2021; Slovak and Paytan, 2012 a.o.
I recommend reducing and simplifying the first part (Sections 1-2) and a thorough evaluation of the literature regarding the limits and risks of using strontium isotopes in archaeological and environmental studies in order to offer an up-to-date image of this topic.
References
Holt et al., 2021. Strontium (87Sr/86Sr) mapping: A critical review of methods and approaches. https://doi.org/10.1016/j.earscirev.2021.103593
Lengfelder et al. 2019. Modelling strontium isotopes in past biospheres – Assessment of bioavailable 87Sr/86Sr ratios in local archaeological vertebrates based on environmental signatures. https://doi.org/10.1016/j.scitotenv.2018.08.014
Montgomery, 2010. Passports from the past: Investigating human dispersals using strontium isotope analysis of tooth enamel. https://doi.org/10.3109/03014461003649297
O’Regan et al., 2023. ‘Why so high?’ Examining discrepancies between the Sr biosphere map and archaeological tooth data from the Peak District, England. https://doi.org/10.1016/j.jas.2023.105826
Pollard, 2011. Isotopes and impact: a cautionary tale. https://doi.org/10.1017/S0003598X00068034
Slovak and Paytan 2012. Applications of Sr Isotopes in Archaeology. https://doi.org/10.1007/978-3-642-10637-8_35
Ventresca Miller et al., 2018. Isotopic investigations of pastoralism in prehistory (Themes in Contemporary Archaeology 4). Abingdon: Routledge; 978-1-138-30858-9
Author Response
“Are the methods adequately described?”
The work does not concern analytical methods. Which methods is the referee referring to?
“The first two sections….”
We disagree with the referee. Formulas are not complicated at all. All students before following university have experience in this elementary mathematics. The formulas cannot be out of interest of an archaeologist. Does he use scientific results without knowing their scientific meaning? For our experience, the geochemist and geologist participate to the archaeological research on the field, organise appropriate sampling, and interpret the geochemical data together with archaeologists, thus archaeologists must have basic knowledge on geochemistry and geologist and geochemist must have basic knowledge of the archaeological research. The geochemists working in archaeology are not only analysts: the opinion that the data-providing geochemist is purely a technical tool and not a cultural one is part of a humanistic presumption that we thought had long been outdated (see CP Snow, The two cultures and the scientific revolution, Cambridge University Press 1959). Moreover, without knowing the geological processes (as, for instance, mineral dissolution processes) the archaeologist can fall in error, as sometimes occurs. “The second part of the article…”We agree with the referee. However, in general, we prefer to avoid any redundance of citations. In our opinion, citations cannot be a plethoric list of articles. Frequently, in archaeological papers, the citations are so abundant to make the text illegible, plethoric, and boring. “In Section 3, the authors…”Isoscapes are descriptive, and, at the same time, a generic (not statistical) predictive tool. We know well this! Isoscapes may be used to have an idea of the isotopic features of the area of interest. In our opinion, the work of Lengfelder et al. (2019) only gives suggestion to facilitate the isotopic description of an area at present. The extrapolation to the past is not allowed in general.
“I recommend reducing and simplifying …”
See answer referred to “The first two sections ...”
Most of the references indicated by the reviewer have been reported in the present form manuscript.
Reviewer 3 Report
Comments and Suggestions for AuthorsA very interesting topic for archaeologists who date historical levels based on absolute ages determined by Sr and Rb isotope ratios, biochemists interested in correlations with the biological environment in studies, but also for those interested in interdisciplinary research.
The conclusions of the study are particularly valuable and supported by mathematical calculations, explained clearly enough even for people who do not have a background in geology. It would have been very helpful for them to have 1-2 practical examples, which would include geological, archaeological information and the determination of absolute ages on unique (or selected) pieces compared to random selection.
However, the mathematical details are relatively easy to understand as a sequence, outlining the scientific aspect of the article. Very useful are the examples of minerals with natural content of radioactive isotopes and the information regarding the magnitude of strontium and rubidium concentration in some common rock-forming minerals, to support in the research the specialists who recognize these minerals in the analyzed artifacts.
Selective mineral dissolution and sorption/desorption processes were included and detailed. The use of strontium isoscapes in archaeological and biogeochemical sciences offer specific information, important at least for a better interpretation of the obtained values.
The conclusions offer clear application value, both by summarizing the information presented, and by the indications for their use.
Author Response
Referee 3 (17 Oct 2023)
“It would have been very helpful to have 1-2 practical examples …”
We did not report examples because the literature is very rich of examples.
“Are the methods adequately described?” “Can be improved”.
The work does not concern with all the analytical methods. Which methods is the referee referring to?
Round 2
Reviewer 1 Report
Comments and Suggestions for AuthorsI accept more explanations but I found the authors stubborn in what they had in mind. The reviewer and readers should ideally easily delve into their presentation and comprehend the "technical" points as the authors maintain and make correlations with other works in archaeology related to their critical evaluation (se eg rib and fumur in the time of belonging).. Equations surely are found in Books, ppt presentation , articles on Sr isotope geochemistry/geology/ancient diet!
But the importance of referring to recent works of archaeological applications on Sr isotopes which shed light on the nuances of migrations for the social groups involved, is necessary and fair.
The authors should reconsider and read the suggested article by Nafplioti , A (2021) Moving forward: strontium isotope mobility research in the Aegean.: Mediterranean Archaeology and Archaeometry, Vol. 21, No 2, pp. 165-179. DOI:10.5281/zenodo.5057552.
Author Response
Reviewer 1
Sentence. “I accept more explanations, but I found the authors stubborn in what they have in mind.”
Answer. In this we resemble the Reviewer.
Sentence. “Equations surely are found in books…”
Answer. This may be partly true. However, we point out that too many archaeologists have not informed themselves in depth through books, the internet, and so on.
Sentence. “But the importance of referring …”
Answer. It is our opinion that citing recent articles cannot and should not be done out of kindness but only if it is useful as a comparison with one's own results or as a pioneering article on a given topic. We want to underline the fact that many archeological articles using isotopes are not sufficiently clear in the use of the isotopes themselves.
Sentence. “The authors should reconsider and read the suggested article …”
Answer. Many thanks for the suggestion.
Thank you very much for taking the time to review our manuscript
Reviewer 2 Report
Comments and Suggestions for AuthorsThe revised manuscript meets the threshold for publication.
Author Response
Thank you very much for taking the time to review our manuscript
