| 07 Jan 2026
Concurrent hydrological closure and hominin presence in the Early Pleistocene Nihewan Basin (northern China): insights from stable isotopes
Abstract. The Nihewan Basin in northern China contains rich Early Pleistocene Palaeolithic sites, representing one of the earliest locations of hominins outside Africa. Here, we present the first long-term stable oxygen (δ18Oeq.cal) and carbon (δ¹³Ceq.cal) isotope record derived from ostracod shells, preserved in the composite 86.2-m NH-T sediment section at the northeastern part of the basin, with a timeframe between ca. 1.67 and 0.78 Ma. The study aimed at reconstructing the long-term climatic changes and hydrological dynamics of the Early Pleistocene Nihewan Basin and to assess their impact on hominin activities. Unexpectedly, we found a strong covariance of δ18Oeq.cal and δ¹³Ceq.cal values, clearly suggesting that the basin was mostly hydrologically closed. The dominance of evaporation implies that δ18Oeq.cal shifts track the hydrological state at the section location between closed settings with higher water levels (more standing waters) and open settings with low water levels (more flowing waters) instead of regional changes in precipitation/evaporation ratios alone. Moreover, we observed the concurrence of high δ18Oeq.cal and δ¹³Ceq.cal values and the increase in the marine-land temperature gradient (ΔT), indicating enhanced East Asian Summer Monsoon (EASM)-driven precipitation which led to wetter climate and increased biogenic productivity. Conversely, low δ18Oeq.cal and δ¹³Ceq.cal values reflect decreased EASM-driven precipitation and drier climate and reduced biogenic productivity. The new stable isotope data, combined with the synthetic archaeological record, suggest that hominin activities in the Nihewan Basin mostly coincided with periods of higher δ18Oeq.cal and δ¹³Ceq.cal values when more standing waters bodies and wetter climate prevailed in the region.
Moghazi and colleagues present a new stable isotope analysis of deposits from the NH-T section in the Nihewan Basin, northern China. Given that my background is in paleoanthropology and not stable isotopes or ostracod shells I restrict my comments to the general paleoanthropological framework in which the paper is set. My comments are minor and are intended to better set the more up-to-date framework of the study in which the Nihewan Basin sits in Early Pleistocene paleoanthropological research. The paper is clearly acceptable pending minor revisions, depending of course on the stable isotope analysis.
Lines 47-50. Rewrite simply as “Today, it represents one of the densest concentrations of Early Pleistocene Palaeolithic sites outside of Africa”. Here, I would also add Dennell (2009) and Bae (2024) who both spend some time talking about the importance of the Nihewan Basin in their books. I would also recommend citing in here someplace the recent Bae and Manthey (2025) paper as it points out that the Nihewan Basin is no longer considered to be a really “early” region for hominin occupation in eastern Asia. Sites like Xihoudu, Shangchen, and Longgupo are clearly older and the recent dating of the Yunxian Homo erectus site (Tu et al., 2026) is also older than the archaeology sites in the Nihewan Basin.
Lines 50-54. This needs to be rewritten given the evidence from Xihoudu (not very far south of the Nihewan Basin) is dated to 2.43 Ma and Shangchen dates to 2.1 Ma. Mention should also be made someplace in here that most of the Nihewan Basin sites ages are based on relative dating techniques (paleomag, biostrat), while some sites like Xiashagou and Xujiayao (Tu et al., 2022 [cited in paper]; Shao et al., 2026 [not cited in paper]) have been radiometrically dated.
Line 54. Start new paragraph with the first sentence (“Based on their…”).
Lines 68-71. Going out to the third digit seems a bit too overly precise, particularly given that these are likely paleomag dates. Recommend just going out to the second digit as presented in most paleomag studies in eastern Asia.
Line 73. Rewrite “1.3 Ma” to “1.3 millions of years”. Technically, most readers read “Ma” as millions of years ago, but in this context you are only referring to a span of 1.3 millions of years.
Lines 128-130. You should add some justification and clarification as to what revisions you made to the age of the NH-T section in this study. As written, you leave the reader hanging, just saying you did it. But based on what?
Line 285. Provide the age range in brackets for these S and L layers unless it includes the entire time bracket for this section.
Line 296. Provide the age range in brackets for these S and L layers unless it includes the entire time bracket for this section.
Line 308. Ibid.
Section 5.1. It seems that your data crosscut both S and L layers. Is it not possible to determine if there are significant different in isotope ratios between S and L? Given the clear environmental differences between S and L layers, how can you explain then that your data is the same for both S and L?
Line 394. Replace “back from” with “between”. And given that Xujiayao is a part of the Nihewan Basin, this time spread should be pushed back to 160 ka (Shao et al., 2026).
References
Bae, C.J., 2024. The Paleoanthropology of Eastern Asia. University of Hawaii Press.
Bae, C.J. and Manthey, C., 2025. Out of Africa I revisited: Life history, energetics, and the evolutionary capacity for early hominin dispersals. Quaternary Science Reviews, 370, p.109690.
Dennell, R., 2008. The palaeolithic settlement of Asia. Cambridge University Press.
Shao, Q., Wang, F., Ge, J., Bahain, J.J., Voinchet, P., Hu, G., Jin, X., Grün, R., Bae, C.J. and Song, X., 2026. New U-series and coupled ESR/U-series dating of Xujiayao (northern China), the type site for Homo juluensis. Quaternary Science Reviews, 373, p.109742.
Depending on when this paper gets accepted, I can share the Tu et al., 2026 reference as well. It is currently embargoed.