Previous excavations at Mata Menge and Boa Lesa in the Soa Basin of Flores, Indonesia, recovered stone artefacts in association with fossilized remains of the large-bodied Stegodon florensis florensis1,2,3,4,5,6,7,8,9. Zircon fission-track ages from these sites indicated that hominins had colonized the island by 0.88 ± 0.07 million years (Myr) ago6. Here we describe the contents, context and age of Wolo Sege, a recently discovered archaeological site in the Soa Basin that has in situ stone artefacts and that lies stratigraphically below Mata Menge and immediately above the basement breccias of the basin. We show using 40Ar/39Ar dating that an ignimbrite overlying the artefact layers at Wolo Sege was erupted 1.02 ± 0.02 Myr ago, providing a new minimum age for hominins on Flores. This predates the disappearance from the Soa Basin of ‘pygmy’ Stegodon sondaari and Geochelone spp. (giant tortoise), as evident at the nearby site of Tangi Talo, which has been dated to 0.90 ± 0.07 Myr ago10. It now seems that this extirpation or possible extinction event and the associated faunal turnover were the result of natural processes rather than the arrival of hominins9. It also appears that the volcanic and fluvio-lacustrine deposits infilling the Soa Basin may not be old enough to register the initial arrival of hominins on the island.
The 2005 excavations in the Soa Basin were funded by a Discovery Project grant from the Australian Research Council (ARC) to M.J.M. The Soa Basin research was authorized by D. Sukarna and D. Kosasih. The Ngadha excavation team was led by K. Podhi and consisted of H. Bele, P. Carpus, J. Dadi, A. Djo, S. Gholo, M. Lalu, M. Lebe and M. Rani. Other participants included Dadang and Ngaliman. R. G. Roberts, K. Westaway and D. Phillips are acknowledged for their initial contributions to dating the site; R. G. Roberts, in particular, is thanked for his assistance and support. G. Barker and N. Ashton are also acknowledged, and M. W. Moore is thanked for preparing images of the artefacts. The 2005 fieldwork of A.B. at Wolo Sege was supported by an Australian National University PhD co-funded stipend scholarship, and follow-up research was funded by an ARC Discovery postdoctoral research fellowship based at the University of Wollongong and a postdoctoral research fellowship at the McDonald Institute for Archaeological Research, University of Cambridge. A grant from the D. M. McDonald Grants and Awards Fund is also acknowledged. The Quaternary Dating Laboratory at Roskilde University is funded by the Villum Kann Rasmussen Foundation. G.M.J. is supported by a PhD stipend co-funded by the Villum Kann Rasmussen Foundation, Roskilde University and The Danish Agency for Science, Technology and Innovation. We thank O. Stecher for technical assistance and J. Saxton and A. Deino for discussions on multi-collector noble-gas mass spectrometry.
Author Contributions A.B. located and excavated the Wolo Sege site and analysed the stone artefacts. G.D.v.d.B. mapped, described and interpreted the stratigraphic units and prepared Fig. 5 (with M.J.M.), and I.K. supervised the excavation. G.M.J. identified and sampled Wolo Sege ash layers suitable for dating and carried out the mineral separation. M.S. carried out the 40Ar/39Ar multi-collector dating experiments. M.J.M. and F.A. are the Chief Investigator and the Australian and Indonesian Institutional Counterpart in this ARC project, respectively, and provided support and advice for the Wolo Sege excavation.
This file contains Supplementary Table 1 in two parts, Table 1a gives the hornblende fusion results (relative Ar isotopic abundances and derived ages) for the 40Ar/39Ar dating. Table 1b gives monitor ACs-2 relative isotropic abundances and calculated J value.