Griffith Centre for Social and Cultural Research, Griffith University, Southport, Australia; Australian Research Centre for Human Evolution, Griffith University, Southport, Australia
Manish Arora
Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, United States
Christine Austin
Department of Environmental Medicine and Public Health, Icahn School of Medicine at Mount Sinai, New York, United States
Griffith Centre for Social and Cultural Research, Griffith University, Southport, Australia; School of the Environment, The University of Queensland, Brisbane, Australia
Mathieu Duval
Australian Research Centre for Human Evolution, Griffith University, Southport, Australia; Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Burgos, Spain; Palaeoscience Labs, Department of Archaeology and History, La Trobe University, Melbourne, Australia
Tze Tshen Lim
Department of Geology, Universiti Malaya, Kuala Lumpur, Malaysia
Philip J Piper
School of Archaeology and Anthropology, The Australian National University, Canberra, Australia
Griffith Centre for Social and Cultural Research, Griffith University, Southport, Australia; Australian Research Centre for Human Evolution, Griffith University, Southport, Australia; School of Archaeology and Anthropology, The Australian National University, Canberra, Australia
John de Vos
Department of Geology, Naturalis Biodiversity Center, Leiden, Netherlands
Ian S Williams
Research School of Earth Sciences, The Australian National University, Canberra, Australia
Jian-xin Zhao
Radiogenic Isotope Facility, School of the Environment, The University of Queensland, Brisbane, Australia
Daniel R Green
Australian Research Centre for Human Evolution, Griffith University, Southport, Australia; Department of Human Evolutionary Biology, Harvard University, Cambridge, United States
Studies of climate variation commonly rely on chemical and isotopic changes recorded in sequentially produced growth layers, such as in corals, shells, and tree rings, as well as in accretionary deposits—ice and sediment cores, and speleothems. Oxygen isotopic compositions (δ18O) of tooth enamel are a direct method of reconstructing environmental variation experienced by an individual animal. Here, we utilize long-forming orangutan dentitions (Pongo spp.) to probe recent and ancient rainfall trends on a weekly basis over ~3–11 years per individual. We first demonstrate the lack of any consistent isotopic enrichment effect during exclusive nursing, supporting the use of primate first molar teeth as environmental proxies. Comparisons of δ18O values (n=2016) in twelve molars from six modern Bornean and Sumatran orangutans reveal a high degree of overlap, with more consistent annual and bimodal rainfall patterns in the Sumatran individuals. Comparisons with fossil orangutan δ18O values (n=955 measurements from six molars) reveal similarities between modern and late Pleistocene fossil Sumatran individuals, but differences between modern and late Pleistocene/early Holocene Bornean orangutans. These suggest drier and more open environments with reduced monsoon intensity during this earlier period in northern Borneo, consistent with other Niah Caves studies and long-term speleothem δ18O records in the broader region. This approach can be extended to test hypotheses about the paleoenvironments that early humans encountered in southeast Asia.
