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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?

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.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: Yes

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

Reviewer #1: Yes

Reviewer #2: Yes

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Reviewer #1: This interdisciplinary study presents some interesting results on faunal and human remains from Nigeria. The text is well written and well structured. The number of human individuals included in this study is low, and more precaution should be taken when the authors generalize the results to produce a population-level interpretation. I believe the nature of the samples chosen to create the strontium baseline is not unanimously approved, and could benefit from being further discussed and argumented by the authors. I agree with the conclusions of the authors regarding the general socio-economic interpretation of the data.

The numbers in front of the comments refer to the lines of the manuscript.

177-179. Is there a reason why this multi-isotope study does not include oxygen isotope analysis, which are very commonly performed alongside strontium isotope analysis in mobility studies? If this is a choice that derives from the initial design of this study, it should be mentioned and explained here.

245-246 Citation needed.

247-249 You should mention why these values are of interest for the reader.

330-333 I assume you analyzed horse cementum either because it was formed while the animals were living at the site, or because it is thought to be more susceptible to diagenesis and would thus represent the local Sr isotopic signature of the soil. Either way, you have to explain why you analyzed this type of tissue to look at variability, as I do not think you mention cementum in the general paragraph about isotopic analyses.

Furthermore, I do not know of any study performing strontium isotope analysis on cementum of archaeological material. If you know of any, it should be cited here. The general consensus is that tooth enamel should be prefered over bones when it comes to strontium isotope analysis of archaeological material, as the latter are more susceptible to suffer from diagenesis. Cementum contains more organic material than enamel, and, therefore, could also be degraded by diagenetic processes. I think you should address these issues here.

401-404 I assume some of these samples are modern and other are from archaeological material; it should be made explicit. The use of snail shells for establishing a local baseline has been criticized recently, it may be good to acknowledge it.

404-408 You should indicate here why you are using soil samples for your baseline, while you also use a probability map that is explicitly based on organic material in order to represent bioavailable strontium signatures over this area. Many authors claim that the relationship between the strontium ratio found in the soils and the bioavailable strontium that characterizes a local system is not strictly linear and can be influenced by a certain number of factors, so it would be useful to acknowledge this fact here.

477 The values are compatible with a local origin, but I do not think they constitute a clear evidence- they could also be consistent with an origin from another place with a similar strontium ratio. It would be better to rephrase.

563-565 Their remains may also have been moved after the site had been abandonned.

629-630 I think this sentence is not very clear- would the local ratio be altered by small quantities of imported salt, or by significant quantities of it? Or unaltered even by significant consumption of salt? That would depend on whether the strontium ratio of the imported foodstuff is different from those locally available, in fine.

626-642 A few studies have tried to provide a quantitative assessment of the amount of salt needed to alter the local strontium ratio of humans, see Fenner 2014 for instance.

658-660 Recent studies also suggest local variations exist within terrestrial landscapes, for instance see Tarrant and Richards 2024.

Fig. 5 You should also include the location of the site and the soil samples on the geological map.

Reviewer #2: The article is an important addition to the literature where there are few written and oral records about the Old Bara site. The authors capture how Archaeology, Zooarchaeology and Bioarchaeology studies have afforded researchers an opportunity to explore past life in the Oyo Empire and its entirety. The abstract and the introduction coherently summarises the article’s research question, key findings, and how the work fits in the existing West African research. The contextualisation of the Oyo Empire and the Old Bara create a baseline to understand/appreciate the authors research investigating the diet of animals and humans at Old Bara and the source of the resources & production centres. To gain these insights into residential mobility, diet and animal management, the authors employ a multiproxy stable isotope ( 13C, 15N, 34S, 87Sr/86Sr), zooarchaeology and Zooarchaeology by Mass Spectrometry (ZooMS) analyses to human and faunal remains excavated and collected from Old Bara between 2018 and 2022. The robust approach of assessing multiple proxies fits the research question and capturing as much data as possible from the limited study material they had available. The authors included methodology backgrounds which shows how they each fit their overall research and the methods are well explained. The tables and the figures align well with the text, the results are well discussed together with the possible limitations and how those shape up the interpretation/manipulation of the data generated. Given the data generated the statistics included in the article is fairly sufficient. A few things the authors could consider are:

- Adding a table that summarises the materials, number and which analysis they were used for (a summary of Pg 13, line 267-271).

- Check “Mores” from Pg 14, line 294, it might be Moorrees.

- Adding a few sub-headings in the methods sections to make it more legible and easier to read.

- Adding points on the Nigerian geological map (figure 5) to clearly show the location of the mentioned 87Sr/86Sr rations.

- The statement on Pg 25, line 522-524 is a bit unclear or incomplete, it might need rephrasing if it is to conclude that “the consistency between bone and tooth values suggests that the remains, with exception of the cranial bone belong to one individual” being individual 1 not 2.

In conclusion the article is well written and shows the extensive research that has been put through to test the historical and oral records with evidence-based results. I believe the article does advance the zooarchaeological, bioarchaeological and biogeochemical fields in understanding past communities in West Africa.

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Reviewer #2: No

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Multiproxy stable isotope analysis provides insights into diet, animal management, and residential mobility in Old Bara, a metropolitan suburb of the Oyo Empire, West Africa

PONE-D-25-64727R1

Dear Dr. Akogun,

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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Enrico Greco

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PLOS One

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