ARTICLES https://doi.org/10.1038/s41559-020-01379-8 Pandanus nutshell generates a palaeoprecipitation record for human occupation at Madjedbebe, northern Australia S. Anna Florin 1,2 ✉ , Patrick Roberts 1,3, Ben Marwick 4, Nicholas R. Patton 5, James Shulmeister2,5,6, Catherine E. Lovelock 7, Linda A. Barry8, Quan Hua 8, May Nango9, Djaykuk Djandjomerr9, Richard Fullagar 10, Lynley A. Wallis 11, Andrew S. Fairbairn 1,2,3 ✉ and Chris Clarkson 1,2,3,10 ✉ Little is known about the Pleistocene climatic context of northern Australia at the time of early human settlement. Here we generate a palaeoprecipitation proxy using stable carbon isotope analysis of modern and archaeological pandanus nutshell from Madjedbebe, Australia’s oldest known archaeological site. We document fluctuations in precipitation over the last 65,000 years and identify periods of lower precipitation during the penultimate and last glacial stages, Marine Isotope Stages 4 and 2. However, the lowest effective annual precipitation is recorded at the present time. Periods of lower precipitation, including the earliest phase of occupation, correspond with peaks in exotic stone raw materials and artefact discard at the site. This pattern is interpreted as suggesting increased group mobility and intensified use of the region during drier periods. adjedbebe is a large sandstone rockshelter located on Pandanus spiralis endocarp (the tough ‘nutshell’ of the pandanus Mirarr country in the Alligator Rivers region, northern drupe, comprised of sclerenchyma tissue; Extended Data Fig. 1). Australia, with evidence for human occupation from at Pandanus has been found in archaeological sites across the trop- M 1 least 65 thousand years ago (ka) to the present (Fig. 1b) . The site ics, including as part of Melanesian and Pacific foraging and agri- provides insights into the behaviour of the first modern humans to cultural systems14–17, and P. spiralis was recovered from almost all reach Sahul (the combined Pleistocene landmass of Australia, New occupation layers at Madjedbebe (Fig. 2)2. We demonstrate that Guinea and the Aru Islands), including evidence for the early use stable carbon isotope analysis of this taxon can provide a reliable of hafted edge-ground axes, grinding stones, reflective pigments palaeoprecipitation proxy, and use it in concert with the analysis of and a broad diet of plant foods1,2. Human use of the site spans sev- soil stable carbon isotopes, and lithic artefact and exotic raw mate- eral periods of substantial global climate change between Marine rial discard rates from Madjedbebe, to investigate the relationship Isotope Stages (MIS) 4 and 1, including the last and penultimate gla- between environmental change and human mobility and settlement cial stages (MIS2 and MIS4, respectively)3, and the formation of the in the past. Kakadu wetlands in the late Holocene4,5. Documenting palaeopre- To test whether stable carbon isotope discrimination in P. spiralis cipitation and subsequent vegetation and resource changes in the endocarp is a useful proxy for the analysis of past fluctuations in Alligator Rivers region is fundamental to our understanding of the mean annual precipitation (MAP), modern P. spiralis drupes were adaptive plasticity of populations entering this region for the first collected from a range of environments in the Northern Territory, time. However, while there are several early (≥45 ka) archaeological and their charred endocarps were analysed for variation in 1,6,7 13 12 13 12 13 sites from this region , the best source of palaeoclimate data for [( C/ C)sample/( C/ C)standard] −1 (δ C) values (Fig. 3; see Extended this early occupation phase is located ~800 km to its east in the Gulf Data Fig. 2 for the results of charring experiments on the δ13C values of Carpentaria (Fig. 1)8,9. This limits our ability to accurately study of P. spiralis endocarp). Figure 3b depicts δ13C variation between local human–environment interaction in this region. different growth environments (floodplain fringe, seasonal flood- In other parts of the world, stable isotope analysis of archaeo- ways, and open forest and woodland environments) found within logical plant material has emerged as a promising way of studying a 10-km radius from Madjedbebe rockshelter. Figure 3c documents changes in past precipitation and temperature in direct association variation in δ13C values with rainfall within the modern range of with records of human occupation and cultural change10–13. Such distribution of P. spiralis, following a >300-km transect along the work has tended to focus on Eurasian crops and tree species, with Stuart Highway from Darwin to Katherine. Both show a significant limited applicability to other regions. Here we report on the results correlation between increasing δ13C values and increased water of stable carbon isotope analysis of modern and archaeological availability (Fig. 3b: one-way analysis of variance, F = 3.572, d.f. = 2, 1School of Social Science, The University of Queensland, Brisbane, Queensland, Australia. 2Australian Research Council Centre of Excellence for Australian Biodiversity and Heritage, University of Wollongong, Wollongong, New South Wales, Australia. 3Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany. 4Department of Anthropology, University of Washington, Seattle, WA, USA. 5School of Earth and Environment, University of Canterbury, Christchurch, New Zealand. 6School of Earth and Environmental Sciences, The University of Queensland, Brisbane, Queensland, Australia. 7School of Biological Sciences, The University of Queensland, Brisbane, Queensland, Australia. 8Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales, Australia. 9Gundjeihmi Aboriginal Corporation, Jabiru, Northern Territory, Australia. 10Centre for Archaeological Science, School of Earth, Atmospheric and Life Sciences, University of Wollongong, Wollongong, New South Wales, Australia. 11Griffith Centre for Social and Cultural Research, Griffith University, Nathan, Queensland, Australia. ✉e-mail: [email protected]; [email protected]; [email protected] NATURE ECOLOGY & EVOLUTION | VOL 5 | March 2021 | 295–303 | www.nature.com/natecolevol 295 ARTICLES NATURE ECOLOGY & EVOLUTION a G4-K12P1 b G4-K4P1 G4-K4P3 Arafura Sea Van Diemen Gulf Beagle Gulf G5-2-056P G5-2-053P Indonesia Darwin Madjedbebe Papua New G5-4-107P Timor Sea Guinea Nauwalabila I Timor-Leste Arafura Sea G5-6-149P2 Nawarla Gabarnmang G6-4 G6-2 Timor Sea Coral Sea G6-2 Alligator Rivers Girraween region MD98-2167 Lagoon Gulf of Carpentaria Stuart Highway Katherine Arnhem Land Escarpment Black Springs transect Lake Euramoo ODP820 Lynch’s Crater P.spiralis modern extent Australia Elevation (m) 650 km km N 0 325 650 N 0 0 60 120 Fig. 1 | The geographical location of the study area. a, A map showing the location of Madjedbebe (star) and all Pleistocene-age environmental records for the monsoonal tropics of northern Sahul (crosses)29,59–61. b, The location of the modern and archaeological study sites, including Madjedbebe and other early (≥45ka) archaeological sites (white dots), within and near the Alligator Rivers region (dashed line)1,6,7; the Stuart Highway transect from Darwin to Katherine (white line); and the modern extent of the southern distribution of P. spiralis (slashed line)62. Credit: Esri, DigitalGlobe, GeoEye, Earthstar, Geographics, CNES/ Airbus DS, USDA, USGS, AeroGRID, IGN, and the GIS User Community (a); panel b adapted with permission from ref. 63, Geoscience Australia a d 0 b c 0.2 Phase 7 0.4 sl 0.6 Phase 6 0.8 7.1 1.0 Phase 5 (endocarp) 9.7 1.2 (mesocarp) Age (ka) Phase 4 1.4 26.7 1.6 P. spiralis Phase 3 P. spiralis vb 1.8 51.6 vb 2.0 2.2 Phase 2 65.0 Depth (m) 0 0.5 1.0 1.5 0 0.5 Fragments per litre Fragments per litre Fig. 2 | Modern and archaeological P. spiralis. a, P. spiralis trees on the Magela Creek floodplain near Madjedbebe in October 2017, with an inset displaying the cephalium, or aggregate fruit of the tree, comprising ~20 polydrupes (see Supplementary Section 1). b, A scanning electron micrograph of an archaeological fragment of P. spiralis endocarp from Phase 7 (C3/5). sl, seed locule; vb, vascular bundle. Scale bar, 1 mm. c, A scanning electron micrograph of an archaeological fragment of P. spiralis mesocarp from Phase 7 (C3/6). Scale bar, 200 µm. See Florin et al.2 for a detailed identification proof. d, The numbers of fragments of P. spiralis endocarp and P. spiralis mesocarp recovered per litre of soil floated from Madjedbebe, versus increasing depth (m) and decreasing archaeological phase. The dark grey area indicates the numbers of P. spiralis endocarp and mesocarp by litres floated, respectively, and the light grey area indicates the numbers of cf. P. spiralis endocarp and mesocarp by litres floated, respectively. The age estimates are based on the modelled mid-point value of the 95% confidence interval for the start date of each phase1. 296 NATURE ECOLOGY & EVOLUTION | VOL 5 | March 2021 | 295–303 | www.nature.com/natecolevol NATURE ECOLOGY & EVOLUTION ARTICLES a b Alligator Rivers –26 region P. spiralis modern Van Diemen Gulf extent –27 Beagle Gulf June mean daily –28 evaporation (mm) (‰) 6.75 Darwin VPDB 229, 230 C 13 –29 231, 232 δ 4.90 Madjedbebe MAP (mm) 235, 236, 237 –30 238, 239 1,750 950 Elevation (m) –31 650 Open Seasonal Floodplain 240 woodland floodways fringe 243, 245, 246 0 Madjedbebe environments 247, 248, 249 c –25 y = –37.52 + 0.0058(x) R 2 = 0.43 250 253 251, 252 254, 255 –26 RMSE = 0.75‰ P < 0.0001 268, 269, 270 –27 256 267 264, 265, 266 (‰) –28 263 VPDB C –29 262 13 261, 260 δ 257, 258, 259 –30 Katherine –31 –32 km N 1,000 1,100 1,200 1,300 1,400 1,500 1,600 1,700 0 40 80 MAP (mm) Fig.