Australia: The Land Where Time Began

A biography of the Australian continent 

Early Settlement in Central Australia and Cultural Innovation and Megafauna Interaction

In order to understand the adaptability of populations and the potential causes of the extinction of the megafauna 50-40 ka it is essential to elucidate the material culture of the early inhabitants of arid Australia and the nature of their environmental interactions. By 50 ka the continent had been colonised by ancestral Aboriginal people (Veth & O’Connor, 2013; Allen & O’Connell, 2014), though it had been believed that compared to early people in Europe and Africa an apparent lack of cultural innovations had been a barrier to early settlement of the extensive arid zone (Allen & O’Connell, 2014; Mellars, 2006). In this paper evidence is presented that was uncovered from Warratyi rockshelter in the southern interior that indicates that humans had occupied the arid regions of Australia by around 49 ka, which is 10,000 years earlier that had been reported previously (Allen & O’Connell, 2014). The only known reliably dated stratified evidence of extinct Australian megafauna (Roberts et al., 2001; Grellet-Tinner, Spooner & Worthy, 2016) has been preserved at this site, which includes the giant marsupial Diprotodon optatum, alongside artefacts more than 46,000 old. Also reported are the earliest-known use of ochre in Australia and Southeast Asia (at or prior to 49-46 ka), gypsum pigment (40-33 ka), bone tools (40-38 ka), hafted tools (38-35 ka, and backed artefacts (30-24 ka), all of which are up to 10 kyr older than any other known occurrence (Attenbrow, Robertson & Hiscock, 2009; Habgood & Franklin, 2008). It is therefore shown by the evidence presented in this by Hamm et al. that as well as settling the interior an unexpectedly short time after arriving in northern Australia, they had also developed technologies much earlier than had previously been recorded for Australia and Southeast Asia (Habgood & Franklin, 2008).

Previously, 10 archaeological sites dating to between 41 ka and 28 ka had been recorded from the arid regions of Australia (Smith, 2013). Many of these sites lack deposits that are well-stratified and very few span a period of more than 20 kyr. Across the continent the scarcity of sites dating to the Late Pleistocene, especially in the southern arid interior, has continued to prevent reliable interpretations of the nature, timing and implications of human colonisation. Important new evidence for the settlement of arid Australia early in the occupation of the continent by Aboriginal people is provided by deposits at Warratyi rockshelter. The site is an elevated rockshelter in the country of the Adnyamathanha people that is within the present arid zone at the northern end of the Flinders Ranges, southern Lake Eyre Basin, South Australia. Contained in the site is a stratified intact archaeological deposit that is 1 m deep, and is composed of 4 stratigraphic units (SU1-SU4).

The occupation chronology was established by single-grain optical dating (optically stimulated luminescence (OSL) and thermally-transferred OSL (TT-OSL)) of quartz grains and radiocarbon (¹⁴C) dating of charcoal from a hearth and avian eggshells. Calibrated radiocarbon ages of deposition of more than 46 ka and more than 44.7 ka (mean calibrated ages ± 68 % probability ranges = 48.2 ± 1.2 ka and 47.3 ± 1.5 ka) based on an eggshell of a large extinct megapode bird (Grellet-Tinner, Spooner & Worthy, 2016) (see supplementary information: megafauna), and a calibrated radiocarbon age of 49.2-46.3 ka, based on emu eggshell. All are within 2 standard errors of 2 associated optical ages 43.8 ± 3.4 ka and 42.8 ± 2.4 ka. There are 5 radiocarbon ages with a combined span of 41.0-32.7 ka that constrain the age of the overlying SU3, as well as optical ages of 40.5 ± 2.2 ka and 30.3 ± 1.6 ka. The deposition of SU2 is constrained by Bayesian modelling of 1 optical age and 4 radio carbon ages to between 29.8-24.4 ka, while SU1B was revealed by 3 optical ages to have accumulated 11.8-9.9 ka, with younger eggshells being incorporated into this unit by bioturbation. Based on this ages Warratyi rockshelter is shown to be the only site outside tropical northern Australia to have a rich, stratified record of repeated human activity that spanned 50-10 ka.

Stone artefacts were recovered from throughout this deposit with concentrations being present at depths of 5-20 cm (corresponding to SU1-upper part SU2) and 60-80 cm (SU3). The composition of the lithic assemblage is mostly of whole flakes, broken flakes and waste material. A range of raw materials were used in the manufacture of stone artefacts, which reflects a change in rock types that were preferred over time. Changes in tool types also reflect this pattern; in the upper parts of SU2 and in SU1, chert and silcrete become major components. Changes in tool types was also reflected in this pattern; SU1  and SU2 contained predominantly backed and small hafted tools, while SU3 and SU4 contained whole and retouched flakes. The antiquity of backed and hafted tools in Australia is greatly extended by the chronology that has been revealed by Bayesian modelling of all stratigraphically reliable ages that were available for Warratyi. In SU2 3 geometric microliths that were found at a depth of 25 cm, are the oldest backed artefacts, based on Bayesian modelled deposition ages of 30-24 ka. Prior to the finds at Warratyi the oldest confirmed ages of deposition were 4 ka in the arid zone (Smith, 2013) and 8.5 ka on the east coast (Attenbrow, Robertson & Hiscock, 2009). There was a possible occurrence at the GRE8 rockshelter site in the Carpentarian Gorges of northern Queensland that was dated to 15 ka, but the interpretation of its stratigraphy has been questioned (Smith, 2013; Slack et al., 2004). Resin within SU3 (70-75 cm depth) was identified by residue analysis which has shown that some flakes had been hafted (see Extended Data Fig. 8A and Supplementary Information: residues in source). A deposition age of 40-33 ka for SU3 unit, which was produced by the modelling, carried out by Hamm et al.¹, which has shown that this is the earliest-known evidence by far of hafting technology in Australia and Southeast Asia. Previously the oldest ages were from the Early Holocene at 10-9 ka (Mulvaney & Kamminga, 1999; Barton et al., 2009).

 At depths of 20-75 cm in SU2-SU3 (40-24 ka) white spheroids were found which have diameters of 2-30 mm. The material in the spheres was identified by X-ray diffraction analysis as gypsum (see Extended Data Fig. 8B and Supplementary Information: gypsum), the closest known source of which is 12-15 km to the north. This gypsiferous material was interpreted as having been brought back to the rockshelter to make white pigment. Red ochre was also confirmed to be present by X-ray analysis, and the deepest sample was found in SU4 associated with artefacts and bone material dating to ≥49-46 ka (see Extended Data Fig. 2 and Supplementary Information: red ochre). The presence of red ochre that had been worked was confirmed by residue analysis on a silcrete stone tool in SU4 at 90 cm depth (see Supplementary Information: residues). Carpenters Gap Rockshelter is the site of the finding of the previous earliest evidence of the use of ochre in Australia and Southeast Asia which dated to 42.8 ka (O’Connor & Franklin, 2001; Aubert et al., 2014). Archaeological evidence for the pre-modern use of gypsum has not been reported to date in Australia.

In a representative sub-sample of the Warratyi bone assemblage there were at least 16 mammal species and 1 species of reptile (see Supplementary Information: fauna). Among the 2,000 fragments that were assessed there was a predominance of medium-sized macropodids. No evidence of the bones being gnawed or breakage patterns that are caused by the teeth of scavengers was found, which supports the interpretation of the bones being a result of human activity. A sharpened bone point was recovered from a depth of 65-70 cm, SU3, which had been ground from the cylindrical portion of the proximal end of the fibula of a macropodid, which was similar to a yellow-footed rock wallaby, Petrogale xanthopus. Elsewhere, single-point tools have been interpreted as being used for fine needle of awl work on animal skins (Webb & Allen, 1990). Bone tools have been considered to be an innovation from the Late Pleistocene by humans in Australia and East Timor, though they only appeared in the last 11 ky in the remainder of Southeast Asia (O’Conner, Robertson & Aplin, 2014; Rabett, 2005). It is indicated by the stratigraphic position of this tool that has a date of more than 38 kyr, substantially earlier than the next youngest examples that were recovered from Warreen Cave in Tasmania that dated to 29 ka (Cosgrove, 1999) and Devils Lair in southwestern Australia that dated to 26 ka.

A partial right juvenile radius of Diprotodon optatum and possibly burnt and unburnt fragments of eggshell of a large ground-nesting bird, and the shell type has been identified as Genyornis newtoni were recovered from 85-90 cm depth (see Extended Data Figs. 9,10). Deposition age of ≥49-46 ka has been found by direct radiocarbon dating of shell and optical dating of host sediments. The co-occurrence of these taxa with humans who were probably involved in the accumulation of their remains is indicated by the age of these fossils, as well as no evidence of tooth marks made by carnivores and the location of the shelter on a steep escarpment that is not suitable for D. optatum individuals to climb (see Supplementary Information: stratigraphy).

Warratyi Rockshelter has been found to be the earliest known occupation site in the arid zone of Australia and one of the earliest known on the entire continent. It is suggested by the presence of people in the southern interior of the continent at or before 49-46 ka that the first arrivals must have spread more rapidly across the continent than previously believed. Hamm et al. suggest a more direct route from north to south may have been taken by the first settlers instead of exclusively along the coast. Hamm et al. say the evidence supports the model that Aboriginal people settled the arid zone long before the conditions in the arid zone became extremely arid during the Last Glacial Maximum, and the associated expansion of major environmental barriers such as sandy deserts (Hiscock & Wallis, 2005).

It is indicated by the repeated, ephemeral occupation of the site that the Aboriginal people may have used Warratyi as a refuge at a time when the lowlands and plains that surround the site were so arid that they couldn’t be exploited and as a temporary camp site when environmental conditions improved and became more stable regionally (Smith, 2013).

It is shown by such things as worked bone technology that had been developed by at least 40-38 ka, and by at least 35 ka hafted tools, and backed artefacts by at least by 24 ka that the people at Warratyi were early innovators of modern technological adaptations that have been found in the Late Pleistocene of Australia and Southeast Asia. Hamm et al. suggest this refutes views that were previously held concerning the timing of cultural and technological innovation in Late Pleistocene Australia.

Stratified archaeological data and chronology is also provided by Warratyi the link directly humans to megafauna in Australia. The extinction of large vertebrates from the continents marks the Late Pleistocene (Barnosky et al., 2008; Field et al., 2013; Wroe et al., 2013). In Australia and New Guinea there at least 22 species that overlapped temporarily with humans, but went extinct later (Barnosky et al., 2008), though there are only 2 sites, Cuddie Springs in eastern Australia and Nombe rockshelter in New Guinea, that have been reported to have contained cultural and megafauna materials within the same stratigraphic layers (Barnosky et al., 2008; Wroe et al., 2013). Evidence of direct association between megafauna and humans at these sites have, however, been challenged based on formation of the site, climatic, stratigraphic and chronological grounds (Brook et al., 2013; Cohen et al., 2015; Grün et al., 2010).

Hamm et al. suggest that the discovery of bones of megafauna and directly dated eggshell in Warratyi that was well-stratified and that has been dated reliably in an archaeological context shows that these taxa were contemporary with humans, and also provides the only direct evidence of humans interacting with some megafauna in Australia. It is also important that Warratyi is located in northern South Australia for the valuation of causes of megafauna extinction over the entire continent, as it confirms the temporal overlap of humans and extinct species between 50 ka and 40 ka across a much broader geographic area of Australia than was previously believed. Direct evidence for the co-existence of humans and megafauna for the arid interior, a major region of the continent, had been lacking until now.

It is rare in Australia and southern Asia to find an archaeological site to contain evidence of modern human colonisation, unique cultural innovation and interaction with species of megafauna that are now extinct. It is rarer still to find sites that preserve records of human occupation going back 50 ka. Warratyi rockshelter, as well as these landmark discoveries, reveals evidence of the development of modern human behaviour in Australia and Asia. A dynamic, adaptive culture existed in arid Australia within as little as a few thousand years of settlement of the continent, are revealed by important technological innovations and early symbolic behaviour (Hiscock & Wallis, 2005; Balme et al., 2009).

Sources & Further reading

1. Hamm, G., P. Mitchell, L. J. Arnold, G. J. Prideaux, D. Questiaux, N. A. Spooner, V. A. Levchenko, E. C. Foley, T. H. Worthy, B. Stephenson, V. Coulthard, C. Coulthard, S. Wilton and D. Johnston (2016). "Cultural innovation and megafauna interaction in the early settlement of arid Australia." Nature advance online publication.