Dr. Hsun-Ming Hu, a postdoctoral researcher of the Department of Geosciences, National Taiwan University (NTU), along with an international team led by NTU’s Distinguished Professor Shen Chuan-Chou, has made a significant advancement in geochronology by redefining the half-life of uranium-234 with remarkable accuracy. This new measurement extends the range of uranium-thorium dating from 600 to 800 thousand years (ka), greatly enhancing the precision in understanding Earth’s climate history and human evolution. This paper was published on October 1, 2025, in the journal Science Advances (1).
The uranium-thorium dating method determines rock formation ages from the relative amounts of three radioactive isotopes: uranium-238, uranium-234, and thorium-230. Since the 1960s, this method has been crucial for investigating Earth’s history over the past 600 ka, including studies on climate change, tectonic activity, earthquakes, archaeology, and anthropology. One of the main challenges has been accurately measuring the ratio of uranium-234 to uranium-238, as uranium-234 is only one ten-thousandth as abundant as uranium-238, making precise measurements difficult. If the signal of uranium-234 is likened to a junior-high school student, the uranium-238 signal resembles a super-giant as tall as two Mount Everests stacked together. This vast disparity makes mass spectrometric measurement highly challenging. Previous techniques could only determine ages up to about 600 ka, leaving a significant gap between 600-800 ka in understanding the early stages of glacial and interglacial cycles and human evolution.
The NTU team addressed this challenge by employing a multi-collector inductively coupled plasma mass spectrometric method (Figure 1). They modeled the interference of uranium-238 on uranium-234 using thorium isotopes and applied careful corrections, which improved the precision of the uranium-234 to uranium-238 ratio by four times, achieving a 2-sigma precision of ± 0.008%. They recalculated the uranium-234 half-life to be 245,670 years, with an uncertainty of ±260 years, which is about fifty years longer than the previously widely used value. While this adjustment may seem minor, it has significant implications. If outdated numbers continued to be used, dating results for samples older than half a million years could be off by several thousand years. The correction now ensures that reconstructions of Earth’s climate history and the chronology of human evolution are far more reliable.
Importantly, the new method significantly reduces the sample size needed to just one third of what was required by earlier techniques. This advancement enables researchers to study rare or delicate specimens with less risk of damage. Minerals with slow formation rates (Fig. 2), ancient human remains, and precious archaeological artifacts can now be dated more accurately while maintaining the original samples’ integrity.
This improved radiometric clock enables scientists to study the evolution of glacial and interglacial cycles over the past 800 ka and to analyze rapid climate changes. It also enhances the dating of cave deposits and other natural records that indicate the presence of early humans, such as Homo erectus, Neanderthals, and Denisovans. With the updated uranium-234 half-life, researchers can now align evidence from climate science and archaeology on the same timeline, providing a more cohesive understanding of Earth’s history and the story of humanity.
The research was supported by the National Science and Technology Council, the Ministry of Education Higher Education Sprout Project, the NTU Core Research Group Program, and the NTU Center for Advanced Earth System Science. The project was led by NTU and brought together eleven institutions in the United States, Australia, and Asia. NTU contributors included Wei-Yi Chien, Chun-Yuan Huang, and Pei-Yun Lu, in addition to Dr. Hu and Professor Shen.
(1) Hu, H.-M.*, Shen C.-C.*, Cheng H.*, Woodhead J., Edwards R. L., Zhao J.-x., Huang C.-Y., Lu P.-Y., Chien W.-Y., Wang J., Jia X., Yokoyama Y., Cai Y. and Zachariáš J. (2025) Sub-epsilon natural 234U/238U measurements refine the 234U half-life and the U-Th geochronology. Science Advances 11, eadu8117. Oct 1. https://www.science.org/doi/10.1126/sciadv.adu8117
Figure 1. Dr. Hsun-Ming conducting an instrumental experiment in the clean mass spectrometric laboratory of the Department of Geosciences, National Taiwan University.
Figure 2. Prof. Chuan-Chou Shen coring flowstone in an Italian cave. The samples will be precisely dated using uranium–thorium techniques with the new uranium-234 half-life, to reconstruct climate history over the past hundreds of thousands of years.