Michael K. Gagan, Linda K. Ayliffe, Mika R. Puspaningrum, Gerrit D. van den Bergh, Nick Scroxton, Wahyoe S. Hantoro, Heather Scott-Gagan, Scott A. Condie, R. Lawrence Edwards, Hai Cheng, Jian-Xin Zhao, John C. Hellstrom, Alena K. Kimbrough, Matthew J. Gagan, Bambang W. Suwargadi, Joan A. Cowley, Bronwyn C. Dixon, Garry K. Smith, Neil Anderson, Henri Wong, Hamdi Rifai
The cause of the disappearance of the primitive hominin Homo floresiensis from the Indonesian island of Flores about 50,000 years ago is a key question in palaeoanthropology. While the potential roles of climate change and human agency continue to be debated, the history of freshwater availability essential for survival at the type locality, Liang Bua, remains poorly understood. Although speleothem δ18O is widely used to reconstruct monsoon rainfall, variations in summer and winter rainfall, with distinct δ18O values, can complicate interpretations of mean annual rainfall. Here, we combine speleothem Mg/Ca, a proxy for local rainfall, with δ18O to determine annual, summer and winter rainfall amounts concurrent with H. floresiensis and Stegodon, one of its primary prey. Geochemical modelling of the Mg-18O system reveals a sustained decline in mean annual rainfall from ~1560 to 990 mm between 76,000 and 61,000 years ago. Critically, summer rainfall decreased to a record low of ~450 mm at 61,000–55,000 years ago, alongside a marked decline in both the abundance and relative proportion of Stegodon remains in the fossil record. These findings increase the likelihood that progressive landscape aridification, and intensified human-faunal competition for dwindling resources, culminated in abandonment of Liang Bua. © The Author(s) 2025.
Environmental Futures Research Centre, School of Science, University of Wollongong, Wollongong, NSW, Australia; School of the Environment, The University of Queensland, St Lucia, QLD, Australia; Research School of Earth Sciences, The Australian National University, Canberra, Australia; Palaeontology and Quaternary Geology Research Group, Bandung Institute of Technology, Bandung, Indonesia; Irish Climate and Analysis Research Units, Department of Geography, Maynooth University, County Kildare, Maynooth, Ireland; Research Center for Geotechnology, Indonesian Institute of Sciences (LIPI), Bandung, Indonesia; CSIRO Oceans & Atmosphere, Hobart, TAS, Australia; Department of Earth and Environmental Sciences, University of Minnesota, Minneapolis, MN, United States; Institute of Global Environmental Change, Xi’an Jiaotong University, Xi’an, China; State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an, China; School of Geography, Earth and Atmospheric Sciences, The University of Melbourne, Parkville, VIC, Australia; Securing Antarctica’s Environmental Future, University of Wollongong, Wollongong, NSW, Australia; School of Electrical Engineering and Computer Science, The University of Queensland, St Lucia, QLD, Australia; Environmental Research and Technology Group, Australian Nuclear Science and Technology Organisation, Sydney, NSW, Australia; Department of Physics, Universitas Negeri Padang, Padang, Indonesia
