Abstract
Asia’s exceptional biodiversity is reflected in the Hengduan Mountains fossil record in eastern Tibet, yet the timing and drivers of mammalian diversification remain enigmatic. Here we combine U–Pb dating of mammalian bone-cavity calcite and palaeosol nodules from the Relu Basin with stable-isotope palaeoaltimetry of fossil tooth enamel. We show that the Relu mammal assemblage was buried at 39.2–38.1 Ma, making it the oldest directly dated Cenozoic mammal fauna reported from the Tibetan Plateau, and that herbivores inhabited near-modern habitat elevations of 3463 m (+819/−869). This directly dated Eocene mammalian assemblage coincided with diversification of high-elevation forests, implying that a montane biodiversity hotspot had emerged by ~39 Ma. Mediterranean-type false-ring signals in 41.5-Ma fossil wood and climate-model simulations are consistent with Eocene surface uplift contributing to a strongly seasonal, bimodal-rainfall regime that predated the modern Asian monsoon and provided environmental conditions favourable for early high-elevation biotic diversification. These results refine Tibetan mammalian chronology and provide a benchmark linking mountain-building, rainfall seasonality and biodiversity.
Acknowledgements
We are grateful to the scientists and students who participated in the fieldwork and to the local residents of Relu, Maiwa, Labo and Gemu for their generous local assistance and support. We also thank Yinli Qin (ITPCAS) for assistance with sample preparation for clumped-isotope analyses and Hongwei Li (IGGCAS) for help with carbon and oxygen isotope analyses.
Funding
This work was supported by the National Natural Science Foundation of China (42402223); the Excellent Research Group Program for Tibetan Plateau Earth System (42588201); and the National Natural Science Foundation of China (92355002). Open Access funding enabled and organized by Projekt DEAL.
Author information
Authors and Affiliations
Corresponding author
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Supplementary information
Transparent Peer Review file (download PDF )
Supplementary Information (download PDF )
Description of Additional Supplementary Files (download PDF )
Supplementary Data 1 (download XLSX )
Supplementary Data 2 (download XLSX )
Supplementary Data 3 (download XLSX )
reporting-summary for COMMSENV-26-1461C (download PDF )
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Reprints and permissions
About this article
Cite this article
He, S., Ding, L., Mulch, A. et al. Origins of biodiversity in eastern Tibet revealed by Eocene mammals and fossil tree rings.
Commun Earth Environ (2026). https://doi.org/10.1038/s43247-026-03967-1
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s43247-026-03967-1
Source: Ecology - nature.com
