text: A chance discovery at a rock shelter in southern Australia has revealed a human settlement dating back 49,000 years. 
   
   Archaeologist Giles Hamm was surveying the territory in Flinders Ranges with aboriginal elder Clifford Coulthard when his colleague needed a toilet break. 
   
   "Nature called and Cliff walked up this creek bed into this gorge and found this amazing spring surrounded by rock art," Mr Hamm told ABC news. 
   
   "A man getting out of the car to go to the toilet led to the discovery of one of the most important sites in Australian pre-history." 
   
   Image: The finding is crucial in understanding human settlement in Australia. Pic Giles Hamm 
   
   What sparked the archaeologists' interest was a rock shelter with a blackened roof because, Mr Hamm told ABC, "that's people lighting fires inside that rock shelter, that's human activity". 
   
   Sophisticated tools and bone fragments from the largest ever marsupial were found at the site. 
   
   Eventually some 4,300 objects and 200 bone fragments were recovered. 
   
   Scientists working with Mr Hamm's team have determined the age of the site at 49,000 years. 
   
   Aboriginal Australians are the oldest continued civilisation in the world, descending from the first people to leave Africa, according to a genetic study published by the University of Copenhagen in September. 
   
   Image: Scientists determined the age of the site at 49,000 years. Pic Giles Hamm 
   
   But the time of arrival of the first Australians is debated among researchers. The consensus view is they arrived 50,000 years ago. 
   
   But Mr Hamm said their presence 49,000 years ago at a site in southern Australia suggested they must have reached northern parts far earlier. 
   
   "If people did come 50,000 years ago, it doesn't give them much time to move so far south," Mr Hamm said. 
   
   "There could have been colonisation much earlier than the accepted time frame of 50,000 years ago. It could be 55,000 maybe 60,000 years ago." 
   
   Image: Flinders Ranges is 550km north of Adelaide. Pic Giles Hamm 
   
   The site also contained evidence of human interaction with mega fauna, namely the Diprotodon optatum - a marsupial measuring 2m in height and weighing more than 2,500kg. 
   
   Scientists have previously puzzled over how humans had interacted with them. 
   
   But the presence of bones from juvenile animals in a cave on a cliff suggests they were hunted, said Gavin Prideaux, palaeontologist at Flinders University in South Australia. 
   
   "Those animals weren't built to climb up a cliff into the settlement, the only way they could have got there was through human agency," he said. ||||| Excavation methods 
   
   Hand excavation was undertaken within Warratyi rock shelter (Extended Data Fig. 1a–c), using two 2 × 1 m trenches (Extended Data Fig. 1b, c). The first exploratory trench (squares 4C and 4D) was located on the southern side of the shelter to provide a cross-section through potential living areas from east to west (taking in part of the back wall). The second trench (squares 2B and 2C) was positioned in the centre of the shelter floor. Square 2B was only excavated down to spit 6 (30 cm) until obstructed by a large roof fall block. 
   
   Excavation was carried out using a 1-m grid system. This grid was further subdivided into 25 cm square units (quadrats: A–D Extended Data Fig. 1c) to enable greater recording precision. Excavation was undertaken using 5 cm spits, with a trowel and hand shovel and the excavated material was dry-sieved through (8, 5 and 2 mm) sieves. Stratigraphic features, such as charcoal lenses, ash or hearth-like lenses, were all drawn, photographed and noted during the excavation process. Detailed profile drawings were made on completion of the excavation. If possible, stone artefacts, bone and ochre were individually recorded and excavated from their in situ location and bagged separately, rather than being retrieved from the bulk sediment collected from individual spits. To reduce the potential for contamination of the excavated surfaces by loose material falling into the pit, the area surrounding each square (where possible) was covered with plastic sheeting and any loose spoil removed. Excavators were encouraged to wear soft shoes to reduce potential damage to the pit walls. 
   
   Each spit was recorded using a standard excavation sheet, which included making notes of the individual features and conditions encountered within each square and quadrat. A geomorphologist (P.M.) was present during the excavation process to advise excavators on the variability of sedimentary units and the positions of potential depositional changes associated with strata boundaries. When these depositional changes were detected during the excavation, they were noted and new strata were excavated as separate entities within a spit. This process reduced the potential for the sediment of two different strata being mixed. 
   
   Where a filled burrow (mostly attributable to rabbits) was encountered, the infilling sediment was removed as a discrete unit and bagged separately. These burrows were excavated in each square before the undisturbed enclosing sediments were excavated, thereby minimising potential contamination of the primary sediment by younger and/or mixed burrow infill material. 
   
   All in situ finds larger than 2 cm (including bone) were plotted in plan view within each excavated quadrat (A–D) and their depth ascertained by levelling within each spit (Extended Data Fig. 1b, c). Some of these in situ finds were photographed, however, most were not as their importance at the time of the excavation was not known (for example, bone point and Diprotodon bone fragments). All sediment removed from each spit was weighed. All material remaining on the sieves was bagged for further analysis. Bulk soil samples were removed for sedimentary analyses. At a later stage, sediment residues were wet-sieved through a 1-mm mesh before sorting. All charcoal, artefacts, bone fragments and plant matter recovered from this process were bagged. The location of charcoal samples collected during the excavation was plotted on plans, their depth recorded and then bagged separately. 
   
   A total of 1,070 stone artefacts were tested for refitting from square 2C in order to confirm the integrity of the apparently intact depositional laminae. These artefacts were assessed to see if they could be refitted together as parts of a former piece of stone artefact, on the assumption that their original separation was attributable to stone reduction activity and that they must have originated on a single surface in the shelter. All artefacts from square 2C that were greater than 10 mm in maximum dimension were assessed for refitting. Each refit set comprised artefacts that could be treated analytically as a single knapping episode30. As such, the distance between artefact elevations for each refitting set provides a proxy measure for the vertical displacement of cultural material through the deposit by human trampling and other post-depositional activty31. Refitting was attempted within a 1 × 1 m area, which represents only a sample of the occupied area and therefore is unlikely to capture an entire knapping event. In addition, artefacts will have undoubtedly been laterally dispersed as a result of repeated human and animal occupation; therefore we can predict that the overall percentage of refits (the ‘success rate’) will be low32. 
   
   Optical dating of quartz grains 
   
   Seven optical dating samples were collected from cleaned exposures of excavation square 2C using metal tubes, and wrapped in light-proof bags for transportation and storage. Bulk sediment samples were also collected from the surrounding few centimetres of each sample tube for β-dose rate determination and water content analysis. In the laboratory, quartz grains of 180–212 μm diameter were extracted from the un-illuminated centres of the metal tubes under safe light (dim red LED) conditions and prepared for burial dose estimation using standard procedures33, including etching by 48% hydrofluoric acid for 40 min to remove the α-irradiated external layers. 
   
   Two semi-independent approaches were used to obtain optical age estimates for the Warratyi samples. Single-grain optically stimulated luminescence (OSL) dating of quartz34, 35 was routinely applied to all samples, and was preferred over standard multiple-grain OSL dating because of its ability to identify insufficiently bleached grain populations36, 37, contaminant grains associated with post-depositional mixing38, and aberrant grains displaying inherently unsuitable luminescence properties39, 40. Single-grain TT-OSL dating of quartz41, 42, 43 was applied to the oldest sample in the sequence (ERS-7) as a means of cross-checking the reliability of the OSL-dating approach over dose ranges of 150–200 Gy. TT-OSL dating was applied to individual grains of quartz rather than multi-grain aliquots in this study, following the reliable application of this approach at other archaeological cave and rock shelter sites38, 44, 45. 
   
   OSL and TT-OSL equivalent dose (D e ) measurements were made using experimental apparatus and quality assurance criteria described previously38, 44. Samples were irradiated with a Risø TL-DA-20 90Sr/90Y β source that had been calibrated to administer known doses to multi-grain aliquots and single-grain discs. For single-grain measurements, spatial variations in the β-dose rate across the disc plane were taken into account by undertaking hole-specific calibrations using γ-irradiated quartz. Quartz grains with a diameter of 180–212 μm were measured in standard single-grain aluminium discs drilled with an array of 300 × 300 μm holes. 
   
   D e values were determined for individual grains of quartz using the single-aliquot regenerative-dose (SAR) procedures34 shown in Supplementary Table 3. Between 900 and 1,300 individual quartz grains of each sample were measured for D e determination (Supplementary Table 4). Sensitivity-corrected dose–response curves were constructed using the first 0.17 s of each green-laser stimulation after subtracting a mean background count obtained from the last 0.25 s of the signal. A preheat of 260 °C for 10 s was used in the OSL SAR procedure before measuring the natural (L n ) and regenerative dose (L x ) signals, and a cut-heat of 160 °C was applied before undertaking the test-dose OSL measurements (T n and T x ) (Supplementary Table 3). These preheating conditions yielded an accurate measured-to-recovered dose ratio of 1.03 ± 0.03 and a relatively low overdispersion value of 12 ± 3% for a ~130 Gy dose-recovery test performed on individual grains of sample ERS-5 (Extended Data Fig. 6A). The single-grain TT-OSL SAR procedure (Supplementary Table 3) uses a TT-OSL test dose measurement rather than an OSL test-dose measurement (step 11) to correct for sensitivity change, following suitability assessments performed elsewhere40, 44, 45, 46. A dose-recovery test performed on 1,200 individual quartz grains of sample ERS-7 attests to the general suitability of this SAR procedure (Extended Data Fig 6A). The TT-OSL dose-recovery test was performed on a batch of unbleached grains owing to the relatively long periods of light exposure needed to bleach natural TT-OSL signals down to low residual levels47. A known (172 Gy) laboratory dose of similar magnitude to the expected D e was added on top of the natural signals for these grains. The recovered dose was then calculated by subtracting the weighted mean natural D e of sample ERS-7 (168 ± 12 Gy; determined on a separate batch of grains and summarized in Supplementary Table 5) from the weighted mean D e of these unbleached and dosed grains (350 ± 18 Gy). This approach yielded a net (that is, natural-subtracted) recovered-to-given ratio of 1.06 ± 0.09 for sample ESR-7. An overdispersion value of 12 ± 9% was calculated for the D e distribution of the unbleached and dosed batch of grains, which is consistent with that obtained for the single-grain OSL dose-recovery test. 
   
   Individual D e estimates are presented with their 1 standard error ranges (Supplementary Table 5 and Extended Data Fig. 6C), which have been derived from three sources of uncertainty: (i) a random uncertainty term arising from photon-counting statistics for each OSL or TT-OSL measurement, calculated using equation 3 from ref. 48; (ii) an empirically determined instrument-reproducibility uncertainty of 2% for each single-grain measurement; and (iii) a dose–response curve fitting uncertainty determined using 1,000 iterations of the Monte Carlo method implemented in Analyst49. 
   
   Environmental dose rates have been calculated using a combination of in situ field γ-ray spectrometry and high-resolution γ spectrometry of dried and homogenized bulk sediments collected directly from the OSL-sampling positions. Cosmic-ray dose-rate contributions were calculated using the equations in ref. 50 after taking into consideration site altitude, geomagnetic latitude, density, thickness and geometry of the sediment or bedrock overburden. A small, assumed internal (α plus β) dose rate of 0.03 ± 0.01 Gy per kyr has been included in the final dose-rate calculations, based on published 238U and 232Th measurements for etched quartz grains from a range of locations51, 52, 53, 54 and an α efficiency factor (a value) of 0.04 ± 0.01 (refs 55, 56, 57). Radionuclide concentrations and specific activities have been converted to dose rates using published conversion factors58, allowing for β-dose attenuation59, 60 where applicable. 
   
   Radiocarbon (14C) dating of hearth charcoal and eggshell samples 
   
   Seventeen eggshell fragments (15 Dromaius, 2 megapode) and two large charcoal fragments associated with hearth features were used to derive the final 14C chronology of SU1A to SU4. A range of other organic materials were initially submitted for 14C analysis but these were considered unreliable based on stratigraphic or methodological grounds, as detailed in Supplementary Information (radiocarbon dating). Samples were pretreated using acid–base–acid procedures and their 14C contents were measured using accelerator mass spectrometry at the Waikato Radiocarbon Laboratory and the ANSTO Radiocarbon Facility. Uncalibrated eggshell and charcoal 14C ages (Supplementary Table 7) are expressed in 14C years before present (14C yr bp, where bp is defined as 1950 ad) following standard reporting conventions61. Isotopic fractionation has been corrected for by using the measured δ13C value of each sample. The 14C age estimates have been calibrated with the internationally ratified southern hemisphere SHCal13 curve62, using OxCal v4.2.4 (ref. 63). The calibrated 14C age ranges (cal yr bp) are described as 95.4% probability ranges throughout. 
   
   Bayesian age modelling 
   
   Bayesian age modelling was used to integrate all stratigraphically reliable chronological information within a unified statistical framework and to derive combined age estimates for individual stratigraphic units. The Bayesian age model for Warratyi was constructed using OxCal v4.2.4 (ref. 63). A sequence-deposition model with nested phases of uniform prior duration and associated boundaries was used to derive a combined chronostratigraphic framework for the site, following the approach outlined previously64. The main depositional sequence incorporates the five stratigraphic units found at Warratyi (SU1A–SU4) in an ordered succession according to depth. Units have been represented as nested sequences within the broader depositional column as their overall stratigraphic ordering is sufficiently well preserved. Separate phases have been used to represent groupings of numerical ages within individual units. This approach was deemed necessary for SU2–SU4 because the 14C and optical dating samples were collected from multiple excavation squares that exhibited potentially irregular or spatially heterogeneous stratigraphic relationships. The exact relative ordering of dating samples from each unit could therefore not be directly constrained in a vertical profile. SU1A and SU1B are internally heterogeneous and exhibit signs of inter-horizon mixing, as borne out by the multiple dose components of optical dating samples ERS-1, ERS-2 and ERS-3 (see Supplementary Information: chronology). This has prevented us from making any assumptions about relative chronological ordering of dated horizons within these units, although the relative ordering of SU1A and SU1B remains sufficiently clear. Groupings within SU1A and SU1B were therefore also nested as separate phases rather than sub-sequences. 
   
   Each stratigraphic unit has been represented by a single phase, with the exception of SU3. This unit is significantly thicker than the others at Warratyi and can be differentiated into two broad archaeo–palaeontological phases according to distinct changes in artefact content and bone abundance at a depth of approximately 60–65 cm (Fig. 2). Two separate phases were nested within the SU3 sequence to account for archaeological sub-structuring of the dated horizons. Boundaries were used to delineate the beginning and end of each stratigraphic unit. We have not, however, incorporated any prior depositional gaps in the sequence model as there is no direct evidence of unconformities at Warratyi. The entire site sequence has been constrained with a minimum age of 0 years before 1950 ad and a maximum age of 60 kyr before 1950 ad. The latter represents a conservative upper age estimate for this archaeological sequence and has been chosen to predate sufficiently the earliest existing evidence of human presence in Australia around ≤50 ka, as determined from an assessment of 26 early occupation sites across Sahul65. We note, however, that the Bayesian age model is largely insensitive to our choice of maximum age constraint given the range of likelihoods obtained on the lowest stratigraphic unit. 
   
   The 14C data were input into the model as conventional ages (using the OxCal R_Date function) and were subsequently calibrated using the SHCal13 curve62 as part of the modelling procedure. Modelled posterior 14C age ranges are therefore presented in calendar years before 1950 ad (cal yr bp). To avoid introducing systematic errors in the posterior results, optical dating ages (calculated as kyr before sample collection in 2012 ad) were similarly converted to years before 1950 ad before their incorporation in the model. 
   
   The final Bayesian age model for Warratyi was run using the general outlier function66, which is based on a Student’s t-test distribution with 5 degrees of freedom. Prior outlier probabilities of 5% were equally assigned to all dating samples to identify potentially significant statistical outliers. Likelihood estimates that yielded posterior outlier probabilities >5% were not excluded from the final model but were proportionally down-weighted in the iterative Monte Carlo runs, thereby producing an averaged chronological model66. 
   
   Use-wear and residue analyses 
   
   Use-wear studies were conducted using a hand-held polarizing Dino-Lite AM4815ZT microscope at magnifications of 30× to 230×. Additional high-power microscopic investigation using an Olympus BX51 at magnifications of 50× and 500× in brightfield and darkfield, were undertaken on seven artefacts. Within the overall study, six small samples of residue (approximately 10–20 μl) were extracted from margins or areas of interest on specific stone artefacts. Samples were extracted with pipettes using distilled water as the lifting medium and transferred to slides that had been pre-cleaned with ethanol. The Dino-lite was used to guide this process. Sample slides were dried under covers for 24 h and then stained with a 0.25% solution of picrosirius red using the protocols described previously67. A Leitz Dialux 22 microscope with polarizing capability was used to examine the stained slides. Residues were photographed in plane, part-polarized and cross-polarized light at a magnification of 400× using a Tucsen ISH 500 camera. 
   
   Data availability 
   
   All elements necessary to allow interpretation and replication of results, including full datasets and detailed experimental procedures are provided in the Supplementary Information. Fossils and archaeological material generated in this study will be deposited at the SA Museum and an Adnyamathanha Traditional Lands Association (ATLA)-keeping place within a 6–12-month time-frame and will be publicly accessible upon request with permission from ATLA and the corresponding author. ||||| Oldest known evidence of Aboriginal settlement in arid Australia found in Flinders Ranges rock shelter 
   
   Updated 
   
   The chance discovery of a rock shelter in the Flinders Ranges has unearthed one of the most important prehistoric sites in Australia. 
   
   Key points: Dating of artefacts and fossils from Warratyi indicates human settlement between 49,000 and 46,000 years ago 
   
   Timing shows people moved through central Australia and used key technologies such as stone axes and ochre much earlier than previously thought 
   
   Archaeological evidence also shows humans lived alongside, and hunted megafauna 
   
   The site, known as Warratyi, shows Aboriginal Australians settled the arid interior of the country around 49,000 years ago — some 10,000 years earlier than previously thought. 
   
   The shelter, about 550 kilometres north of Adelaide, also contains the first reliably dated evidence of human interaction with megafauna. 
   
   Artefacts excavated at the site also push back the earliest-known dates on the development of key bone and stone axe technologies and the use of ochre in Australia. 
   
   Lead author Giles Hamm, a consultant archaeologist and doctoral student at La Trobe University, found the site with local Adnyamathanha elder Clifford Coulthard while surveying gorges in the northern Flinders Ranges. 
   
   "Nature called and Cliff walked up this creek bed into this gorge and found this amazing spring surrounded by rock art," Mr Hamm said. 
   
   "A man getting out of the car to go to the toilet led to the discovery of one of the most important sites in Australian pre-history." 
   
   Mr Hamm said during a survey of the gorge they noticed a rock shelter with a blackened roof about 20 metres above the creek bed. 
   
   "Immediately when we saw that we thought, 'Wow, that's people lighting fires inside that rock shelter, that's human activity'," he said. 
   
   At the time they had no idea how significant the find was, Mr Hamm admitted, and thought maybe it would reach back about 5,000 years. 
   
   Excavations reveal treasure trove of artefacts and bones 
   
   Working with the Adnyamathanha people over the past nine years, Mr Hamm and colleagues recovered from the one-metre-deep excavations around 4,300 artefacts and 200 bone fragments from 16 mammals and one reptile. 
   
   Importantly dating of the artefacts and fossil finds show humans occupied the site from 49,000 to 46,000 years ago. 
   
   Mr Hamm said the significance of the site was the combination of its age and geographic location. 
   
   The previous oldest-known site in the arid zone, located at Puritjarra in western Central Australia, is around 38,000 years old. 
   
   "[This discovery] puts people moving south from the northern part of the continent to the southern interior a lot sooner than we thought," he said. 
   
   However, Mr Hamm said it was likely the climate was more favourable when they arrived. 
   
   "They got there before it became really arid," he said. 
   
   "In one sense they were trapped in the Flinders Ranges because once the climate changed [due to the last glacial maximum] it was too risky to move out of these well-watered ranges that had these permanent springs." 
   
   It was a view supported by palaeoanthropologist Michael Westaway at Griffith University, who was part of a recent genomic study that confirmed modern Aboriginal Australians are the descendants of the first people to inhabit Australia and showed they adapted genetically to survive in the desert. 
   
   "Our DNA paper suggested the arid centre at 50,000 years ago was not really a barrier to the movement of people, and this seems to be what Giles is suggesting — people were able to migrate south quite quickly," Dr Westaway said. 
   
   Among the other significant artefact finds at the site was the earliest-known use of ochre in Australia and South-East Asia around 49,000-46,000 years ago. 
   
   Mr Hamm said they had pushed back the dates on the development of technologies such as bone needles (40,000-38,000 years ago), wood-handled stone tools (at least 24,000 years ago) and gypsum use (40,000-33,000 years ago). 
   
   The site also provided reliably dated evidence of hafted axe technology about 38,000 years ago. 
   
   Evidence dates cohabitation with megafauna 
   
   Co-author Professor Gavin Prideaux pointed to the discovery of bones from the extinct giant wombat-like Diprotodon optatum and eggs from an ancient giant bird as important evidence of interaction with ancient humans which would have an impact on the debate over the extinction of megafauna. 
   
   Professor Prideaux, from Flinders University's School of Biological Sciences, said the only previous site in Australia where megafauna remains and human artefacts had been found together was Cuddie Springs in NSW, which had become the subject of controversy over the accuracy of dating. 
   
   "One good thing about this study ... is there's no doubt there are megafauna remains in the form of Diprotodon and a giant bird in that rock shelter in a well-dated, well-stratified context sometime between 45,000 and 50,000 years ago," Professor Prideaux said. 
   
   "The only way those bones and shells got there [because of the steep incline up to the rock shelter] is because people brought them there [to eat] ... in terms of megafauna that's the really significant finding." 
   
   Professor Prideaux said the discovery was an important milestone in the debate over whether humans or climate change drove the extinction of megafauna. 
   
   "[The find] undermines one of the supposed pillars of support for climate change, not humans, causing the extinctions because [the Warrayti site shows] humans lived alongside these animals and hunted them," he said. 
   
   Professor Prideaux said the paper, published yesterday in Nature, "smashed several paradigms about Indigenous Australians". 
   
   "People ... were set up in arid southern Australia by about 50,000 years ago and they had all these amazing technologies much earlier than what we've thought." 
   
   Dr Westaway supported this view. 
   
   "There is a Eurocentric view that material culture in Australia is quite simplistic and backward, but this helps rewrite that story," he said. 
   
   Elders told stories of shelters 
   
   Mr Coulthard, of the Adnyamathanha Traditional Lands Association, said he had worked on the property where Warratyi was located when he was a teenager. 
   
   The elders he had worked with had told him their people had lived in the area and had pointed out a lot of the shelters. 
   
   He had forgotten the information until he teamed up with Mr Hamm and believed "the spirits showed me the road" to the site. 
   
   He said the Adnyamathanha people were proud and happy about the discovery and interested to know how it would be received. 
   
   Topics: science-and-technology, indigenous-aboriginal-and-torres-strait-islander, archaeology, sa 
   
   First posted ||||| Humans arrived in the arid interior of Australia some 10,000 years earlier than we thought, archaeologists suggest, with the discovery of ancient artefacts in a South Australian cave that have been dated to as far back as 49,000 years ago. 
   
   That means once humans first set foot on the Australian coastline, it took a mere 1,000 years for them to expand out into its dry interior - further evidence of the ingenuity of what now stands as the oldest continuous civilisation on Earth. 
   
   The site, which is a newly discovered cave in the Flinders Ranges, about 550 km north of Adelaide, is known as the Warratyi rock-shelter. 
   
   Archaeologist Giles Hamm from La Trobe University in Melbourne led the excavations at the cave, finding what appear to be some of the oldest bone and quartz tools ever found in Australia, plus the earliest known use of the pigment ochre in the country’s history. 
   
   Artefacts that have been found so far include burnt eggshells, sharpened stone and bone tools, red ochre and gypsum pigments, and the team says this is evidence that these early technologies were developed locally. 
   
   "The old idea is that people might have come from the East, from the Levant, out of Africa, and these modern humans may have come with a package of innovative technologies," Hamm told Nicola Davis at The Guardian. 
   
   "But the development of these fine stone tools, the bone technology, we think that happened as a local innovation, due to a local cultural evolution." 
   
   That’s significant, adds one of the team, Gavin Prideaux from Flinders University in Adelaide, because it challenges certain assumptions that Indigenous Australians were not as innovative as similar populations elsewhere in on the globe. 
   
   "There is a Eurocentric view that material culture in Australia is quite simplistic and backward, but this helps rewrite that story," he told ABC News. 
   
   Until now, the oldest human tool found in Australia’s vast, arid interior has been a tiny axe fragment found earlier this year in the Carpenter's Gap rock-shelter of the Kimberley region of northwest Australia. 
   
   While the Carpenter’s Gap site is not far from the northwest coast of Australia - thought to be one of the earliest settled parts of Australia - the Warratyi rock-shelter sits more than 2,000 km from the early settlement of Lake Mungo in southeasten New South Wales, making it a much more difficult trek. 
   
   The tools have been dated based on a couple of estimates - quartz grains from the site have been dated to 44,000 years ago, but radiocarbon dating of the burnt eggshells, which are thought to be evidence of human cooking, revealed them to be between 45,000 and 49,000 years old. 
   
   The shells are thought to have come from emus and a large, extinct flightless bird from the Genyornis genus. Together with discovery of bones of a huge, extinct wombat-like species, Diprotodon optatum, this suggests that early humans were actually interacting with Australia’s legendary megafauna. 
   
   Diprotodon reconstruction. Credit: Dmitry Bogdanov/Wikimedia 
   
   This doesn’t necessarily mean they were hunting them, but they were at least living in close enough quarters that they could find bones and eggs and bring them back to the cave. 
   
   "One good thing about this study ... is there's no doubt there are megafauna remains in the form of Diprotodon and a giant bird in that rock shelter in a well-dated, well-stratified context sometime between 45,000 and 50,000 years ago," Prideaux told the ABC. 
   
   "The only way those bones and shells got there is because people brought them there ... in terms of megafauna that's the really significant finding." 
   
   The find is, of course, controversial, because that tiny axe fragment we mentioned earlier has been dated to around the same time period - 44,000 to 49,000 years ago. The problem is these estimates are all fairly rough, and still up for interpretation - Hamm's team, for example, insists that the axe is no more than 48,000 years old. 
   
   "[E]veryone is keen to make their site sound older," Sue O'Connor from the Australian National University, who was not involved in either find, told Marcus Strom at The Sydney Morning Herald. But she did add that "the Hamm discovery was likely older". 
   
   "The methodology of this study is as good as it gets," she said. "It's a very important site and a really significant find." 
   
   Debate will likely rage among archaeologists for some time, but the most important thing is that we're finally seeing real evidence of just how widespread the Indigenous Australians were within just 1,000 years of hitting the coast. 
   
   The study has been published in Nature.
target: – "A man getting out of the car to go to the toilet led to the discovery of one of the most important sites in Australian pre-history," archaeologist Giles Hamm tells ABC News. Hamm was surveying a section of Australia's Flinders Ranges when his partner, aboriginal elder Clifford Coulthard, had to go to the bathroom. "Nature called and Cliff walked up this creek bed into this gorge and found this amazing spring surrounded by rock art," Hamm says. At the time, Hamm thought the newly discovered human settlement, a site called Warratyi, was only 5,000 years old. It turns out it's closer to 49,000 years old, and that has huge ramifications for our knowledge of ancient Australian civilization, Sky News reports. Hamm and his team published a study on Warratyi this week in Nature. The discovery of Warratyi in the arid interior of the continent means humans either arrived in Australia up to 10,000 years earlier than previously believed—or they expanded across the continent at a much quicker rate, Science Alert reports. Researchers at the site found 4,300 objects, including tools, and 200 bone fragments from multiple animals, including a 5,500-pound marsupial. The bones help explain how early Australians interacted with megafauna, including hunting them. The tools show Australians were using bone and stone axes earlier than believed and are evidence that early Australians developed some technologies on their own rather than adopting them from other peoples as previously believed. (Ninety rocks in Australia could rank up there with Stonehenge.)