Gamma-ray spectrometric dating of late Homo erectus skulls from Ngandong and Sambungmacan, Central Java, Indonesia Yuji Yokoyama a , Christophe Falgue ` res a, * , François Se ´ mah a , Teuku Jacob b , Rainer Gru ¨n c a De´partement de Pre ´histoire du Muse ´um National d’Histoire Naturelle, UMR 5198CNRS,1, rue rene ´ Panhard, 75013 Paris, France b Department of Bioanthropology and Palaeoanthropology, Faculty of Medicine, Gadjah Mada University, Yogyakarta, Indonesia c Research School of Earth Sciences, The Australian National University, Canberra ACT 0200, Australia article info Article history: Received 19 March 2007 Accepted 4 January 2008 Keywords: Solo man Homo erectus Homo sapiens Indonesia Java Gamma-ray spectrometry abstract Hominid fossils from Ngandong and Sambungmacan, Central Java, Indonesia, are considered to be the most anatomically derived and youngest representatives of Homo erectus. Nondestructive gamma-ray spectrometric dating of three of these Homo erectus skulls showed that all samples underwent uranium leaching. Nevertheless, we could establish minimum age estimates of around 40 ka, with an upper age limit of around 60 to 70 ka. This means that the Homo erectus of Java very likely survived the Toba eruption and may have been contemporaneous with the earliest Homo sapiens in Southeast Asia and Australasia. Ó 2008 Elsevier Ltd. All rights reserved. Introduction Anatomically derived Javanese Homo erectus (Pithecanthropus) were found in the 1930s in the alluvial deposits of a Solo River terrace at Ngandong, Central Java (Fig. 1; Weidenreich, 1951). Similar skulls were later found at Sambungmacan (Jacob, 1973) and Ngawi (Sartono, 1991), also located along the Solo River. The age of these hominids is important in the framework of the study of the settlement of the upper Pleistocene Southeast Asian archipelagos. If the Ngandong and Sambungmacan hominids existed contempo- raneously with early Australian Homo sapiens (which might date back to c. 60 ka, see Thorne et al., 1999), then the archipelagos become a fairly good example of the unique ‘Out of Africa’ origin of modern humans (Cann et al., 1987; Stringer, 1992; Stringer and Gamble, 1992; Rightmire, 1994). Attempts to use U-series dating of fossil mammal teeth and bones from the Ngandong and Sambungmacan sites (Bartstra et al., 1988; van der Plicht et al., 1989) have yielded ages ranging between about 30 and 200 ka. Because all bones uptake uranium during their geological history, any apparent closed system U-series age estimate on bones represents a minimum age estimation (e.g., Pike et al., 2002). Swisher et al. (1996) obtained ESR ages on teeth from Ngandong and Sambungmacan collections, and from teeth recovered in situ from Ngandong, which suggested a surprisingly young age (27 to 53 ka) for the related fossil-bearing layers. If one supposes that such an age range is representative for the hominids from these sites, it would suggest a late survival of Homo erectus, well after the emergence of anatomically modern humans (Homo sapiens) else- where and contemporaneous with modern human settlements in Australasia. In contrast, however, the U-series results of Bartstra et al. (1988) and van der Plicht et al. (1989) suggest that the latest Javanese Homo erectus may be much older and therefore were extinct by the middle Pleistocene, as in other regions. Apart from the dating results, there are several arguments against a young age for the Solo and Sambungmacan hominids: (i) fossils from different locations could have been redeposited in the Ngandong alluvia; as a result, the age of the hominids might not be accurately deduced from the age of the faunal remains (Gru ¨n and Thorne, 1997); (ii) the ages of the faunal re- mains themselves are widely scattered; (iii) the Sambungmacan alluvial series has different layers, and the exact locations of the hominid skulls are unknown; (iv) extinct mammal taxa such as Stegodon still occur in the Ngandong faunal assemblage, although they are not found in any other upper Pleistocene site in the southern part of Java Island (Badoux, 1959; de Vos, 1996; Se ´ mah et al., 2004). To address the question of the age of the Solo hominids, we carried out a direct, nondestructive gamma-ray dating of three * Corresponding author. E-mail address: falguere@mnhn.fr (C. Falgue ` res). Contents lists available at ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol Journal of Human Evolution 55 (2008) 274–277 Contents lists available at ScienceDirect Journal of Human Evolution journal homepage: www.elsevier.com/locate/jhevol 0047-2484/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.jhevol.2008.01.006