Australia: The Land Where Time Began

A biography of the Australian continent 

Earliest Hominin Occupation in Sulawesi, Indonesia

Sulawesi is the largest island in Wallacea, the large zone of oceanic islands that separates continental Asia from Sahul, the combined landmass of Australia, including Tasmania, and New Guinea in the Pleistocene at times of low sea levels during glacial periods. An unknown hominin lineage had colonised Flores by 1 million years ago, which is immediately to the south (Brumm et al., 2010), and by about 50,000 BP modern humans had crossed to Sahul (Clarkson et al., 2015; O’Connor, 2015). Van den Bergh et al. suggest that Sulawesi was probably pivotal in these dispersals, on the basis of ocean currents, position and biogeographical context (Morwood & Van Oosterzee, 2007). It is indicated by rock art in the limestone karst region of Maros, southwest Sulawesi, where speleothems have been dated by uranium series, revealed that humans were present on the island at least 40,000 BP (Aubert et al., 2014). In this paper  van den Bergh et al. report new excavations at Talepu in the Walanae Basin to the northeast of Maros, where stone artefacts have been found in situ that are associated with fossil remains of megafauna (Bulbalus sp., Stegodon and Celebochoerus) were recovered from stratified deposits that had accumulated from prior to 200,000 BP to about 100,000 BP. Sulawesi is suggested by these findings to have hosted a long-established population of archaic hominins, as did Flores, though their ancestral origins and taxonomic status has remained elusive.

The discovery in the late 1940s in Walanae Basin, south Sulawesi of ‘Palaeolithic’ stone artefacts associated with fossil fauna dating to the Pleistocene (Van Heekeren, 1949) led to a considerable amount of speculation about the time depth of human occupation of the island (Bartstra, Keates, Basoeki & Kallupa, 1991; Van Heekeren, 1972). The lithic assemblages that were comprised of cores, choppers and flakes, the ‘Cabenge Industry’, and derived from surface collections that were not dated from along the eastern side of the Walanae River (Van Heekeren, 1949;  Bartstra, Keates, Basoeki & Kallupa, 1991; Van Heekeren, 1972), which follows the Walanae Depression, an elongated basin that is fault-bounded and trends north-south. Van den Bergh et al. recovered from the same unstratified contexts (Hooijer, 1948; Hooijer, 1974) the fossils of several extinct species, such as 2 pygmy proboscideans, a giant tortoise, and a large endemic suid, Celebochoerus, as well as in excavations at various sites (van den Bergh, 1999). The stratigraphic context and the time range of the ‘Cabenge Industry’ was still unresolved because in situ stone artefacts were still lacking (van den Bergh, 1999), in spite of protracted investigations.

Surveys were conducted in the Cabenge area between 2007 and 2012 to clarify these issues which led to the discovery of 4 new sites that contained in situ stone artefacts in their stratigraphic context. Deep-trench excavations were undertaken at Talepu, one of the sites that were newly discovered. This site is located 3 km to the southeast of Cabenge and 13 km downstream from the point at which the Walanae River leaves the valley that confines it and enters a widening floodplain that is subsiding actively towards the north. East-west compression and wrench faulting along the Walanae fault zone resulted in uplift of the Sengkang anticline and the southern part of the Walanae Depression (Grainge & Davies, 1983; Sukamto, 1975). The folded sedimentary sequences from the Pliocene-Pleistocene of the Walanae Formation are now exposed in the uplifted areas (van den Bergh, 1999). Accumulations of fluvio-lacustrine sediments, dating to the Pleistocene to recent times, were facilitated in the northern part of the Walanae Depression by compressional down-folding. The Talepu site (4o 22’ 6.5” S, 119o 59’ 7” E) is situated near the hinge line between the southern part of the Walanae Depression, which is uplifted, and the northern part, which is subsiding.

The excavations were focused on the northernmost hill of an elongated ridge near the village of Talepu that was about 600 m to the west of the Walanae River. The summit of Talepu Hill is 32 m above sea level and 18 m above the adjacent floodplain of the Walanae River. There are deposits exposed along this ridge comprised of a sequence of sub-horizontal fluvio-lacustrine layers of sand and silt, which coarsens upwards, which is overlain by alluvial cobble gravels. At Talepu 2 deep excavations were carried out, trenches T2 and T4, which provided a combined length of 18.7 m long stratigraphic section that exposed 5 main sedimentary units: in descending order of depth, units A-E.

The first evidence of in situ stone artefacts to be found in Walanae Basin in stratified and dated contexts were revealed by these excavations. Van den Bergh et al. recovered 270 stone artefacts from between the surface and a depth of 4.2 m, which were associated with the high-energy fluvial gravel deposits of unit A by the T2 excavation. Most are therefore water-rolled to various degrees, though 21 % are still in relatively fresh condition. Silicified limestone cobbles that are coarse- to medium grained that have a diameter of up to 130 mm, are the main source of raw material. Most are flakes of medium- to large size, with cores that comprise 13 % of the assemblage. Hard hammer blows to one face (42 %) were used to reduce cores or bifacially (58 %) from striking platforms that were unprepared. Reduction of cores was not intensive, though 7 cobbles were rotated and multiplatform cores that were formed by subsequent reduction. Flakes that were struck from the cobbles were then reduced to 1 face (60 %) or bifacially (40 %). There is little evidence that the stoneworkers were constructing tools of a specific form; rather sharp-edged flakes were produced by stone flaking for use or a source for additional flakes, though there is patterning in the flaking techniques.

From T4 the topsoil and colluvium to a depth of 120 cm contained 41 artefacts. There were, however, 4 silicified limestone artefacts in situ in older strata that were exposed within the silt of subunit E2, that provide the earliest stratigraphic evidence at Talepu of human activity. 2 unmodified flakes, at 2.2-2.4 m depth, were recovered and there are 2 that are angular scatter fragments at a depth of 3.0-3.1 m, which van den Bergh et al. suggest are probably the results of percussion flaking. The scatter fragments are made from distinctive mottled silicified limestone which appears to have been removed from the same core. There is no evidence on the artefacts of them undergoing transport by water, unit E not yielding any clasts that are indicative of high-energy water flow.

There was only 1 fossil that was identified from T2: a lower molar fragment of a bovid that was recovered from a depth of 4 m that is just above the size range of the lowland anoa, Bubalus depressicornis, which is extant. 8 Celebochoerus dental elements, e.g., a lower canine and 3 fragments of bone that were not identifiable, were recovered from the silty interval of subunit E2 between 3.1 and 4.0 m below the surface and just beneath the deepest stone artefacts. Van den Bergh et al. suggest at least some of these fossil remains can be ascribed to a single individual. A fragment of a milk molar from a Stegodon was recovered from a depth of 1.9-2.0 m and a dermal scute from a crocodile was recovered from a depth of 3.9-4.0 m.

Teeth and bones that had been recovered from subunit E2 were dated by uranium series by the laser ablation inductively coupled plasma mass spectroscopy (LA-ICP-MS) methods (Grün et al., 2014), to constrain the age of the deposits at Talepu. Sequential laser spot analyses were carried out on cross-sections of 8 fossils of Celebochoerus that had been recovered from a depth of between 0.2-0.5 m below the deepest known stone artefacts in the same silty unit. For each sample data sets were combined and a single age estimate was calculated by use of the diffusion-absorption-decay model (Sambridge, Grün & Eggins, 2012). There were infinite error bounds for most of the age results, so minimum ages were all that was possible (Grün et al., 2014). The fossil samples are indicated by the combined uranium-series results to be older than 200,000 BP. Silty layers of units A, C and E have normal magnetic polarities at all levels sampled based on palaeomagnetic samples. Taken together with the results of uranium series analysis the fossils therefore have an age of more than 200 ka and less than 780 ka.

In order to constrain the age of artefacts van den Bergh et al. used a multi-elevated-temperature post-infrared infrared stimulated luminescence (MET-pIRIR) dating procedure (Li & Li, 2011; Li, Jacobs Roberts & Li, 2014) was applied to feldspar grains that were rich in potassium that had been extracted from 5 sediment samples that spanned the entire sequence. The ages in stratigraphic order obtained for the 4 samples from T2 that were analysed are 103 ±  9 ka at a depth of 3 m to 156 ± 19 ka at 10 m depth. The Talepu cultural sequence ends at about 100 ka, or possibly earlier, as suggested by these results. Sediments dating to 156 ± 19 ka were deposited near the top of unit D, which lies above the sedimentary layer unit E from which the deepest artefacts were recovered, more than 3 m below. The oldest evidence for stone artefacts from Talepu that is securely dated therefore has an age of 194 to 118 ka at the 95 % confidence interval (2σ), though it is clear that the site was occupied earlier given the recovery of artefacts from the greater stratigraphic depths.  In the lower trench, T4, a sample recovered from a depth of 8 m was found to have a minimum age of about 195 ka. This estimate of age is stratigraphically consistent with the MET-pIRIR ages for the T2 and with the minimum uranium ages of about 200 ka for the T4 fossil remains from subunit E2.

It is suggested by the results of the Talepu excavation that it is now possible to conclude that the initial occupation of Sulawesi occurred at least 118 ka. As earlier assumptions had Sulawesi being only colonised by H. sapiens, which are believed at present to have arrived in the region by about 50,000 BP, the identity of these earlier inhabitants is of great interest. In island Southeast Asia the earliest skeletal remains of H. sapiens are from about 45,000 BP (Barker et al., 2007; Grün et al., 2005), though in the Levant (Grün et al., 2005) the earliest modern skeletal human remains have been recovered that date to about 120 ka, and possibly a similar time in Southeast Asia (Westaway, 2007). It appears possible, though controversial, that soon after H. sapiens evolved in Africa they spread to Sunda, the easternmost tip of continental Asia and by about 120 ka they crossed to Wallacea. However, by 1 million years ago early hominins had already reached Flores, which is far smaller and more remote than Sulawesi, van den Bergh et al. suggesting that they possibly arrived on Flores on debris from a tsunami (Morwood & Van Oosterzee, 2007). Therefore it is conceivable that the first humans on Sulawesi could possibly have arrived in a similar manner at around the same time or earlier or later.

The findings from Talepu attest to the presence on Sulawesi of early tool makers by the Middle Pleistocene, though a definitive answer as to which species of hominin was the first to arrive is precluded by the lack of human fossils dating to the Pleistocene. Van den Bergh et al. say there are at least 3 candidates in the region of potential island colonisers: the known and inferred distributions of H. floresiensis on Flores, about 190 ka or earlier (Brumm et a;., 2010), on the southern margin of Sunda (Java of the present), H. erectus, about 1.5 million years ago to about 140 ka (Zaim et al., 2011; Indriati et al., 2011), and ‘Denisovans’, who are suggested by van den Bergh et al. to have possibly extended into Wallacea (Cooper & Stringer, 2013). When the currents of the Indonesian through-flow that are predominantly southerly flowing (Sprintall, 2014), van den Bergh et al. speculate that Borneo to the west, which was part of mainland Asia at times of low sea level is the most likely point of origin for the colonisers of Sulawesi, and to the north the Philippines, the northern extremity of Wallacea, with the implication that there may be records of archaic hominins on other islands in the region that are still to be discovered.

Sources & Further reading

  1. van den Bergh, G. D., B. Li, A. Brumm, R. Grün, D. Yurnaldi, M. W. Moore, I. Kurniawan, R. Setiawan, F. Aziz, R. G. Roberts, Suyono, M. Storey, E. Setiabudi and M. J. Morwood (2016). "Earliest hominin occupation of Sulawesi, Indonesia." Nature 529(7585): 208-211.


Author: M. H. Monroe
Last updated: 07/05/2016
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