**5. Conclusions**

This study evaluated humeral biomechanical asymmetry across complete humeral diaphysis based on high-resolution micro-CT, and by quantifiable visualization and statistical methods. Using specimens from three Chinese archaeological populations that varied in geographic location, chronological age, and subsistence pattern, the pattern of humeral asymmetry in East Asian modern humans was investigated. Distinct humeral asymmetry patterns are observed on the mean morphometric map, but are not statistically significant. Analogous distributions of highly asymmetrical regions and CV are observed across nearly all the sexes and populations, indicating possible universality of the humeral asymmetry pattern in East Asian modern humans. These highly asymmetrical regions correspond with major muscle attachments. The diaphyseal regions that are highly varied in bilateral asymmetry tend to present a low asymmetrical level. Although J35 and J50 asymmetry are related to the overall humeral asymmetry, it can only explain about half of the total variation. These findings sugges<sup>t</sup> that the overall biomechanical asymmetry of humeral diaphysis is more complicated than previously assumed. This study complements previous findings on humeral asymmetry, and accumulate data and knowledge for future works in this area.

**Author Contributions:** Conceptualization, Y.Z.; methodology, Y.Z.; software, Y.Z.; validation, Y.Z., S.X.; formal analysis, Y.Z.; investigation, Y.Z.; resources, M.Z., H.L., J.H.; data curation, Y.Z., S.X.; writing—original draft preparation, Y.Z.; writing—review and editing, P.W., S.X.; visualization, Y.Z.; supervision, S.X.; project administration, S.X.; funding acquisition, H.L., S.X. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB26000000), the National Natural Science Foundation of China (41872030), and the National Social Science Fund of China (19BKG039, 19VJX066).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data supporting this study are available from the corresponding author on reasonable request.

**Acknowledgments:** The authors thank Yemao Hou, Pengfei Yin, and Jiawei Ma for their help in scanning and image processing. The authors also thank Xiujie Wu and Mackie O'Hara Ali for optimizing the manuscript.

**Conflicts of Interest:** The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

**Appendix A**

**Figure A1.** Morphometric maps exhibiting SMA asymmetry values of all specimens.
