PONE-D-19-25583

Tooth wear as an indicator of acculturation process in remote Amazonian populations

PLOS ONE

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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?

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Reviewer #1: Partly

Reviewer #2: Partly

Reviewer #3: Partly

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

Reviewer #1: No

Reviewer #2: I Don't Know

Reviewer #3: 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: Yes

Reviewer #3: Yes

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: 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 article is an analysis of the relationship between dental wear and age in an Amazonian Riverine population. The authors correlated the summed score of dental wear of the anterior teeth and premolars against personal age using a linear correlation. The resultant R squared value is intermediate between an urban population (very little relationship) and more isolated indigenous populations. The authors argue that tooth wear can be an indicator of the acculturation process, serving as a tool to assess the loss of cultural identity of traditional Amazonian populations.

There are a series of problems here - theoretical and methodological. Tooth wear is a product of the abrasiveness of food, patterns of occlusion, use of teeth as tools - as the authors point out. However, these are a relatively small part of any acculturation process. The authors use the four field model of acculturation: segregation etc etc. This model points out that there is no single trajectory in acculturation, that individual and group dimensions may vary (people may retain culturally significant values while participating in a broader economy for instance), and more recent work points out acculturation is a two way process between the groups involved. What the dental wear reflects is that as access to different types of food and technology changes so does the relationship between wear and age but this by itself is only part of acculturation and cannot used to assess the loss of cultural identity (as the authors argue in the last line of their article). Effectively the authors are asking a narrower question: does the relationship between age and dental wear alter as diet and technology change. Their data would suggest yes and this falls within the findings from a large series of other studies including extensive studies from the 1950s and 1960s at Yuendumu Central Australia.

However, in demonstrating this the authors need to consider the nature of their sample which includes people born between c2005 and 1957. In other words a population which has undergone extensive change - the younger people in their group have not experienced the same changes as the older individuals. The slope of the line is an artefact of the sample not proof that younger people will experience the same rate of dental wear as they age. In particular if the sample was divided by birth cohorts you will probably find different relationships since in figure 3 the slope for the very youngest individuals is flat. The authors need to look at the distribution of the residuals.

Furthermore their current sample includes older individuals than their comparative samples and in this instance it is the older individuals who seem to be pulling the slope so the R squared values are not strictly comparable given the structure of the sample. I recommend the authors think more carefully about the nature of the samples and the regressions.

The study is an interesting demonstration that the relationship between dental wear and age is population specific and reflects aspects of food availability and technology and that if that relationship is known for a specific population then it might be used as one way of assessing personal age of the unknown dead. However, using dental wear as a measure of acculturation is to ignore the work on acculturation and how it operates upon different dimensions.

Reviewer #2: This manuscript purports to investigate the correlation between tooth wear and chronological age in a riverine population of the Amazon. Valuable aspects of this research include its comparative aspect and the fact that urban and indigenous samples were studied by the same research team that studied the riverine group using the same methodology. This feature of the work enhances reliability and minimizes the possibility that results are impacted by differences in methodology or research protocol.

Some issues discussed in the manuscript would benefit from further consideration include the description of subsistence, use of teeth as tools, and statistical analysis of intra- and inter-observer variation in observing and recording data on tooth wear.

I would like to see a more detailed account of subsistence methods. In the abstract we are informed that the riverine groups rely on nature for subsistence, which is quite general. Later the text states that subsistence includes small-scale fishing and agriculture, plus hunted wild meat. It would be informative for the reader to have estimates of what percent of the diet comes from farming / agriculture; fishing; and hunting. Do the riverine groups forage of collect food?, what kinds? Or does all the vegetarian portion of the diet come from agriculture? Can the type of agriculture be more precisely characterized? Is the farming horticultural? swidden? Are field left fallow? for how long? Please clarify. In the same regard, how similar or variable is the mode of subsistence in different study groups? This is important in understanding inter-group variation in diet and its impact on the degree of occlusal tooth wear.

In terms of methodology, especially the assessment of degree of tooth wear, were all subjects examined by one researcher? If so, was a statistical analysis of intra-observer reliability or repeatability of degree of dental wear conducted? If more than one researcher participated in the observation / scoring of dental wear, was a statistical assessment of concordance or of discordance between observers conducted? This is an important way in which the rigor in dental data collection can be assessed and should be routinely included in such studies.

Less important issues that need attention include redundancy, accuracy of wording, and issues with the references.

Wording & phrases that need reconsideration:

in the abstract and elsewhere the authors say that riverine populations inhabit river borders, this is redundant and should be revised.

p. 3, line 61, for example: is doubly redundant. “..living along the river borders, live the riverine people…” living populations…live; and river borders …riverine. Some revision of the text is required here.

p. 3, line 49: the authors state that mineralization and tooth eruption are inaccurate methods for mature individuals. I contend this should be changed to read that timing of mineralization and tooth eruption cannot be used in estimating the chronological age of mature individuals

p. 3, line 66 (and elsewhere, p. 10, line 207, for example) use of teeth as tools is mentioned, glancing at the references does not provide further information on How teeth are used as tools?

Please provide brief examples. In fact one of the references for use of teeth as tools appears to focus on dental caries prevalence, not tooth wear.

In several places in the References section extraneous information is provided in addition to the journal name. This is unnecessary and should be deleted.

p. 14, line 319: the official journal of the Human Biology Council.

p. 15, line 327: a journal of the Association for Psychological Science.

p. 16, line 346: official publication of the American Association of Orthodontists, its

constituent societies, and the American Board of Orthodontics.

p. 16, line 363: Bericht uber die biologisch-anthropologische Literatur.

additionally multiple references to electronic sources, such as doi, ePub, PubMed, PubMed Central and others are given for the same reference - this seem unnecessary and redundant, a single source for each publication should be sufficient.

p. 16, line 348 (for example): Epub 2016/11/23. doi: 10.1016/j.ajodo.2016.03.033. PubMed PMID: 27871711.

and line 352 (for another example) Epub 2011/09/14. doi: 10.1016/j.jdent.2011.08.014. PubMed PMID: 21911033.

Reviewer #3: Interesting sociological and anthropological article. The authors are quite experts in the field and have already published about these topics in different journals. I just believe that the discussion is a little bit too short concerning the acculturation process. The authors have just cited one (main) book dated from 2003 and one article. May be it could be more developped and put in perspective with other studies (if possible).

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

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Tooth wear as an indicator of acculturation process in remote Amazonian populations

PONE-D-19-25583R1

Dear Dr. Mecenas,

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

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JJ Cray Jr., Ph.D.

Academic Editor

PLOS ONE

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 #3: (No Response)

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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 #3: Yes

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

Reviewer #3: 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 #3: Yes

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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 #3: 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 #3: All the comments I made have been taken into consideration by the authors. I consider this paper acceptable for publication.

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Reviewer #3: No