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Trophic structures, i.e., the diets, food chain positions, and feeding relationships of species in an ecological community, are a fundamental yet understudied avenue of investigation into Australian megafauna extinction. Calcium (Ca) isotope analysis has been developed as a tool to reconstruct trophic levels in vertebrate palaeobiology and palaeoecology. A baseline of modern marsupial Ca isotope signatures in a single trophic level and dietary niche is required to successfully apply this tool in order to reconstruct Australian faunal food webs. We present Ca isotope data from dental enamel of modern Tasmanian bare-nosed wombats (Vombatus ursinus tasmaniensis) to constrain the Ca isotope composition of this species, an opportunistic grazer, and assess whether sex and environmental variables influence such composition. We compare these data to complementary strontium isotope data from the same samples as a proxy for geographical location. Elodont (ever-growing) wombat teeth allow for a sequential sampling strategy and thus provide high resolution intra-individual variability on a seasonal scale, creating the largest intra-individual and intra-species set of Ca isotope data in a single species so far. We show that the Ca isotope composition of Tasmanian bare-nosed wombats falls within the range for herbivores and is independent of geological substrate. Comparison with carbon and oxygen isotope data from sequential samples within the same individuals highlights that sub-monthly intra-individual variations in Ca isotope compositions may result from change in the proportions in the wombat's diet of C3 and C4 plants, or monocots and dicots. The Ca isotope compositions of male and female wombats suggest that Ca isotopes in marsupials could be used to trace nursing and weaning behaviour. The characterisation of Ca isotope values in marsupial herbivore enamel presented contributes to a modern reference set for reconstructing diet from fossil remains of extinct Australian megafauna herbivores.

The time of arrival of people in Australia is an unresolved question. It is relevant to debates about when modern humans first dispersed out of Africa and when their descendants incorporated genetic material from Neanderthals, Denisovans and possibly other hominins. Humans have also been implicated in the extinction of Australia’s megafauna. Here we report the results of new excavations conducted at Madjedbebe, a rock shelter in northern Australia. Artefacts in primary depositional context are concentrated in three dense bands, with the stratigraphic integrity of the deposit demonstrated by artefact refits and by optical dating and other analyses of the sediments. Human occupation began around 65,000 years ago, with a distinctive stone tool assemblage including grinding stones, ground ochres, reflective additives and ground-edge hatchet heads. This evidence sets a new minimum age for the arrival of humans in Australia, the dispersal of modern humans out of Africa, and the subsequent interactions of modern humans with Neanderthals and Denisovans. Optical dating of sediments containing stone artefacts newly excavated at Madjedbebe, Australia, indicate that human occupation began around 65,000 years ago, thereby setting a new minimum age for the arrival of people in Australia. When did humans first colonize Australia? The date of the initial landing on the continent that is now associated with cold lager and 'Waltzing Matilda' has been highly controversial. Dates from a site called Madjedbebe in northern Australia had put the presence of modern humans in Australia at between 60,000 and 50,000 years ago, but these results have since been hotly contested. Here, the results from a comprehensive program of dating of new excavations at the site confirm that people first arrived there around 65,000 years ago. The results show that humans reached Australia well before the extinction of the Australian megafauna and the disappearance of Homo floresiensis in neighbouring Indonesia.

The mechanisms leading to megafauna (>44 kg) extinctions in Late Pleistocene (126,000—12,000 years ago) Australia are highly contested because standard chronological analyses rely on scarce data of varying quality and ignore spatial complexity. Relevant archaeological and palaeontological records are most often also biased by differential preservation resulting in under-representated older events. Chronological analyses have attributed megafaunal extinctions to climate change, humans, or a combination of the two, but rarely consider spatial variation in extinction patterns, initial human appearance trajectories, and palaeoclimate change together. Here we develop a statistical approach to infer spatio-temporal trajectories of megafauna extirpations (local extinctions) and initial human appearance in south-eastern Australia. We identify a combined climate-human effect on regional extirpation patterns suggesting that small, mobile Aboriginal populations potentially needed access to drinkable water to survive arid ecosystems, but were simultaneously constrained by climate-dependent net landscape primary productivity. Thus, the co-drivers of megafauna extirpations were themselves constrained by the spatial distribution of climate-dependent water sources., Whether Australia’s Pleistocene megafauna extinctions were caused by climate change, humans, or both is debated. Here, the authors infer the spatio-temporal trajectories of regional extinctions and find that water availability mediates the relationship among climate, human migration and megafauna extinctions.

Warratyi rock shelter shows evidence of human occupation approximately 50,000 years ago, development of tool use and cultural innovation, and interaction with now-extinct megafauna in arid Australia. Modern humans had made landfall in Australia by 50,000 years ago. But there has been some doubt as to whether or when they had the technological sophistication to tackle the arid central regions of that driest of continents. The answer is that they had, and that they made short work of it. Giles Hamm et al. report the earliest known occurrence of human occupation in the arid interior of Australia, at a rock shelter in the Flinders Ranges of South Australia around 49,000 years ago. The various layers of rock at the site document the earliest known use in Australia of technologies such as bone tools and backed flakes, and of red ochre and gypsum as pigments. The site also preserves evidence of the presence of the large marsupial Diprotodon optatum and what are thought to be eggshells of the giant bird Genyornis newtoni. This is the only reliably dated, stratified record of extinct Australian megafauna alongside artefacts more than 46,000 years old. Elucidating the material culture of early people in arid Australia and the nature of their environmental interactions is essential for understanding the adaptability of populations and the potential causes of megafaunal extinctions 50–40 thousand years ago (ka). Humans colonized the continent by 50 ka1,2, but an apparent lack of cultural innovations compared to people in Europe and Africa3,4 has been deemed a barrier to early settlement in the extensive arid zone2,3. Here we present evidence from Warratyi rock shelter in the southern interior that shows that humans occupied arid Australia by around 49 ka, 10 thousand years (kyr) earlier than previously reported2. The site preserves the only reliably dated, stratified evidence of extinct Australian megafauna5,6, including the giant marsupial Diprotodon optatum, alongside artefacts more than 46 kyr old. We also report on the earliest-known use of ochre in Australia and Southeast Asia (at or before 49–46 ka), gypsum pigment (40–33 ka), bone tools (40–38 ka), hafted tools (38–35 ka), and backed artefacts (30–24 ka), each up to 10 kyr older than any other known occurrence7,8. Thus, our evidence shows that people not only settled in the arid interior within a few millennia of entering the continent9, but also developed key technologies much earlier than previously recorded for Australia and Southeast Asia8.

Terrestrial sedimentary archives that record environmental responses to climate over the last glacial cycle are underrepresented in subtropical Australia. Limited spatial and temporal palaeoenvironmental record coverage across large parts of eastern Australia contribute to uncertainty regarding the relationship between long-term climate change and palaeoecological turnover; including the extinction of Australian megafauna during the late Pleistocene. This study presents a new, high-resolution, calibrated geochemical record and numerical dating framework from Welsby Lagoon, a wetland from North Stradbroke Island that records key periods of late Pleistocene environmental change. Single-grain optically stimulated luminescence and radiocarbon dating are integrated into a Bayesian age-depth model for the sedimentary sequence spanning Marine Isotope Stage (MIS) 5 to the present. Scanning micro X-ray fluorescence (XRF) and bulk sediment XRF assays are used to infer past dust dynamics, with changes in the abundance of silica and potassium interpreted as proxies for aridity across local and regional sources. Variations in dust flux were contemporaneous with hydrological change, concordant with changes in vegetation cover on the island and, relate to deflation events at major dust source regions on the Australian continent. The Welsby Lagoon record supports the notion of a variable MIS4 within which an increased dust flux (71–67 ka), may be indicative of drier climate. Additionally, the record also shows a lower dust flux through the Last Glacial Maximum (LGM) than is evident in other Australian aeolian records. However, this low LGM flux is attributed to the wetland’s evolution, rather than a reduction in total dust flux.

Accurate estimates of the timing of extinctions (θ) are critical for understanding the causes of major die-off events and for identifying evolutionary or environmental transitions. Yet many studies have demonstrated that sampling biases and underlying statistical assumptions affect the accuracy of model-based estimates of extinction times ( θ ˆ ), and the added uncertainty contributed by inherent (laboratory) dating errors has largely been neglected. Here we provide a general guide (model-selection key) for choosing from among eight alternative ‘frequentist sampling’ (i.e., non-Bayesian) methods, differentiated by their treatment of both the probability of record occurrence and uncertainties in record dates, the most appropriate for a given record. We first provide a methodological framework to characterize time series of dated records as a function of the number of records, the size of the interval between successive records, and laboratory dating errors. Using both simulated data and dated Australian megafauna remains, we then assess how the characteristic of a dataset's time series dictates model performance and the probability of misclassification (false extant vs. false extinct). Among the four classic frequentist methods providing highest model performance, Marshall's (1997) and McCarthy's (1998) methods have the highest model precision. However, high model performance did not prevent misclassification errors, such that the Gaussian-resampled inverse-weighted McInerny (GRIWM) approach is the only method providing both high model accuracy and no misclassification issues, because of its unique down-weighting interval procedure and its ability to account for uncertainties in record dates. Applying the guideline to three time series of extinct Australian species, we recommend using Marshall's, McCarthy's and/or GRIWM methods to infer θ of both Thylacinus sp. and Genyornis sp., because each dataset is characterized by many sightings and a low variance of the interval between records, whereas McInerny's method better suits Diprotodon sp. due to an even lower interval variance.

Frédérik Saltré [et al.],. Received 25 June 2015 Accepted 13 December 2015 Published 29 January 2016, Late Quaternary megafauna extinctions impoverished mammalian diversity worldwide. The causes of these extinctions in Australia are most controversial but essential to resolve, because this continent-wide event presaged similar losses that occurred thousands of years later on other continents. Here we apply a rigorous metadata analysis and new ensemblehindcasting approach to 659 Australian megafauna fossil ages. When coupled with analysis of several high-resolution climate records, we show that megafaunal extinctions were broadly synchronous among genera and independent of climate aridity and variability in Australia over the last 120,000 years. Our results reject climate change as the primary driver of megafauna extinctions in the world’s most controversial context, and instead estimate that the megafauna disappeared Australia-wide B13,500 years after human arrival, with shorter periods of coexistence in some regions. This is the first comprehensive approach to incorporate uncertainty in fossil ages, extinction timing and climatology, to quantify mechanisms of prehistorical extinctions.

Recent discussion on the late Pleistocene extinction of the Australian megafauna has revolved around interpretation of several key fossil sites in Tasmania. It has been suggested that humans did not arrive in Tasmania until after the megafauna became extinct, or did not hunt now extinct megafauna, and therefore that humans cannot be implicated in the extinctions. Radiocarbon results from these sites indicate that the youngest extinct megafauna are close to charcoal ages from the oldest archaeological deposits, although difficulties have arisen in establishing chronologies because most relevant sites have ages near the limit for radiocarbon analysis. We report a series of new radiocarbon ages, δ 13 C, δ 15 N and C:N ratios on collagen and dentine fractions from skeletal remains in the Mount Cripps karst area and the Mowbray Swamp, both in northwestern Tasmania, and discuss the reliability of ages from these and other sites. We also report the discovery of an articulated Simosthenurus occidentalis skeleton at Mt Cripps, that represents only the second directly-dated extinct megafaunal taxon with a reliable age Our results suggest that C:N ratios measured on collagen or dentine are not an infallible guide to radiocarbon age reliability. We confirm previous reports of a temporal overlap between the megafaunal and archaeological records in Tasmania, but the presence of archaeological evidence and megafauna with the same age at the same site has not yet been demonstrated. At least two megafaunal taxa—the now-extinct Protemnodon anak and a giant Pleistocene form of the extant Macropus giganteus —were still present in Tasmania after 43 ka, when human crossing of the Bassian landbridge from mainland Australia first became sustainable.

It emerges that people reached Australia earlier than was thought. This finding casts light on the technology used by the travellers, and their possible interactions with animal species that became extinct. See Article p.306 When did humans first colonize Australia? The date of the initial landing on the continent that is now associated with cold lager and 'Waltzing Matilda' has been highly controversial. Dates from a site called Madjedbebe in northern Australia had put the presence of modern humans in Australia at between 60,000 and 50,000 years ago, but these results have since been hotly contested. Here, the results from a comprehensive program of dating of new excavations at the site confirm that people first arrived there around 65,000 years ago. The results show that humans reached Australia well before the extinction of the Australian megafauna and the disappearance of Homo floresiensis in neighbouring Indonesia.

Stable carbon and oxygen isotope ratios of tooth enamel carbonate were collected from both fossils (50–100 ka) Tammar Wallaby ( Macropus eugeneii ) and Western Grey Kangaroo ( Macropus fuliginosus) from a Late Pleistocene fossil deposit situated on Kangaroo Island, South Australia. δ 13 C and δ 18 O data were also obtained for modern equivalents of both species located proximal to the excavation site. Trace element compositions were collected for Sr, Ba, V, Cu, Zr, Y, La, Ca, Nd, and U for modern and fossil teeth, and for local soils. δ 13 C data for fossil kangaroo and wallaby range between − 5.0 and − 18‰, while less 13 C enriched values between − 18 and − 25‰ are observed in modern tooth enamel. Early-formed molars are 13 C depleted by ∼ 2.5‰ compared to late-formed molars, consistent with isotopic offsets observed in modern molars, and with offsets observed from preservation of original biogenic compositions. Overall, carbon isotopes indicate a shift in diet and environmental conditions from C4-inclusive mixed habitats (woods and open grasslands) during the Late Pleistocene, to C3-only wooded and closed canopy habitats today. δ 18 O values range between 23 and 30‰ and are indistinguishable for fossil and modern tooth enamel. Oxygen isotope compositions of plants and mammals correlate positively with local water compositions, and negatively with relative humidity. Thus, the lack of oxygen isotope differences for the Late Pleistocene vs. modern day teeth may be attributed to combined lower temperatures (decreasing local water δ 18 O) plus decreased relative humidity (increasing plant and mammal δ 18 O) in the Late Pleistocene. Trace element data from fossil and modern teeth and from fossil deposit sedimentary material indicate post burial chemical alteration. Excepting Ba and possibly Cu, concentrations of all other elements analysed (Sr, V, Zr, Y, La, Ce, Nd, and U) increased significantly relative to modern teeth (over an order of magnitude shift, with p ≤ 0.01 for t -tests and Mann–Whitney tests). This diagenetic process may have occurred during the Last Glacial Maximum (LGM), a period of localised wet conditions when significant amounts of soluble soil organic matter accumulated at the fossil site. Trace element analysis of local soils indicates that, relative to soils, teeth strongly prefer Sr and U [ K D (fossil tooth/soil) ∼ 10], and exclude Zr, Cu, and possibly V and Ba [ K D ≤ 0.5]. Surprisingly, Rare Earth Elements (REEs) indicate K D values of ∼ 1. These data imply that Ba is a poor indicator of chemical alteration, while Sr, U, Zr, V, Y, and REEs are particularly sensitive to alteration. Comparisons with other palaeoclimate data suggest that the environmental change on Kangaroo Island from Late Pleistocene to present was greater than on the Nullarbor Plain.

The timing and cause of late Pleistocene faunal extinctions in Australia are subjects of a debate that has become polarised by two vigorously defended views. One contends that the late Pleistocene extinction was a short event caused by humans colonising the Australian continent, whereas the other promotes a gradual demise of the fauna, over a period of at least 10–20 ka, due to a combination of climatic changes and ecological pressures by humans. Cuddie Springs is central to this debate as it is the only site known in continental Australia where archaeological and megafauna remains co-occur. We have analysed more than 60 bones and teeth from the site by laser ablation ICP-MS to determine U, and Th concentrations and distributions, and those with sufficiently high U concentrations were analysed for U-series isotopes. Twenty-nine teeth were analysed by ESR. These new results, as well as previously published geochronological data, contradict the hypothesis that the clastic sediments of Stratigraphic Unit 6 (SU6) are in primary context with the faunal, archaeological and other materials found in SU6, and that all have ages consistent with the optically stimulated luminescence (OSL) estimates of 30–36 ka. These young OSL results were used to argue for a relatively recent age of the extinct fauna. Our results imply that SU6 is either significantly older than the OSL results, or that a large fraction of the faunal material and the charcoal found in SU6 was derived from older, lateral deposits. Our U and Th laser ablation ICPMS results as well as the REE profiles reported by Trueman et al. [2008 . Comparing rates of recystallisation and the potential for preservation of biomolecules from the distribution of trace elements in fossil bones. C.R. Palevol. General Paleontology (Taphonomy and Fossilization) 7, 145–158] contradict the interpretation of previously reported rare earth element compositions of bones, and the argument based thereon for the primary context of faunal material and clastic sediments in SU6 layers.

The nature of late Quaternary megafaunal extinctions has been the subject of intense debate since the 1960s. Traditionally, scientists cite either climatic changes or human predation as the primary reason for worldwide megafaunal extinctions. In many island cases (e.g., Madagascar, New Zealand), scientists have had a tendency to lean toward humans as being the direct or indirect dominant cause for the relatively quick extirpation of indigenous megafaunas. This study evaluates the record for megafaunal (e.g., Palaeoloxodon, Mammuthus, Sinomegaceros) extinctions in the Japanese islands and draw the tentative conclusion that: (1) humans directly and/or indirectly influenced the extinction of some large herbivores; and (2) the megafaunal extinctions likely began earlier than originally proposed; during the marine isotope stage (“MIS”) 3–2 transition (∼30–20 ka) rather than during the MIS 2–1 (∼15–10 ka) shift that roughly coincides with the advent of the Jomon period in Japan. However, we temper our findings due to the current paucity of sites in Japan that have associated archaeology and vertebrate paleontological materials that date to the MIS 3–2 transition.

Human arrival in Sahul – Pleistocene Australia and New Guinea – has long been argued as the catalyst in the decline and disappearance of a suite of extinct animals referred to as megafauna. The debate concerning causality in Sahul is highly polarised, with climate change often cited as the alternative explanatory model. On continental Australia, there are few datasets available with which to explore the likely processes leading to the extinction events. At the present time, there is one site in New Guinea (Nombe Rockshelter) and one on continental Australia (Cuddie Springs) where the coexistence and temporal overlap of humans and megafauna has been identified. The Cuddie Springs Pleistocene archaeological site in southeastern Australia contains an association of fossil extinct and extant fauna with an archaeological record through two sequential stratigraphic units dating from c. 36 to c. 30 ka ago. A taphonomic study of the fossil fauna has revealed an accumulation of bone in a primary depositional context, consistent with a waterhole death assemblage. Overall the faunal assemblage studied here (n: 8146; NISP: 1355) has yielded little direct evidence of carnivore damage or human activities. Post depositional factors such as physical destruction incurred by trampling, compaction of sediments, and/or the hydrological status of the lake at that time have played important roles. As the only known site on continental Australia where megafauna and humans co-occur, the Cuddie Springs faunal assemblage yields equivocal evidence for a significant human role in the accumulation of the fauna here. At the present time there is no evidential basis to the argument that humans had a primary role in the extinction of the Australian megafauna. The first colonisers are likely to have preyed upon those few species known to have persisted to this time, but their impact may have been restricted to the tail end of a process that had been underway for millennia prior to human arrival.

The timing of the extinction of the Australian Megafauna and whether it was simultaneous and widespread has been a much researched topic in Quaternary geoscience. The Black Creek Swamp Megafauna site on Kangaroo Island was thought to be a refugium for Megafauna; however, recent and multidiscipline age determinations have established that the fossils are considerably older than the well-quoted extinction age of 45 kyr. Further radiocarbon age determinations, δ13C isotope analysis and 13C-NMR spectroscopy of the fossil containing organic matter demonstrates that it is highly soluble and accumulated as recently as 31–18 cal. kyr BP. These radiocarbon ages are much younger than the 100–50 kyr age bracket ascertained for the fossil material itself, implying separate episodes of death, deposition and burial. The soluble nature of the organic matter and increasing radiocarbon ages with depth suggests lateral accumulation, probably transported by subsurface waters from elevated areas proximal to the low-lying swamp. Such depositional conditions and 14C age range implies that the site may have experienced an unusually wet Last Glacial Maximum, due maybe to its proximity to the continental shelf and thus to maritime conditions. C3 vegetation dominates the Black Creek Swamp and its organic matter (δ13C; −30‰ and −23‰); however, variations in δ13C may indicate climatic shifts. 13C-enrichment and an abundance of salt-tolerant gastropods within the site's final phase of sediment accumulation (

In recent years, there has been much debate about the timing of the Late Pleistocene extinction of the Australian megafauna. Some studies postulated a rapid, continental-wide extinction at around 46 000 years ago and that the arrival of humans in Australia, rather than climatic fluctuations, was the main cause for the demise of the megafauna. We have applied electron spin resonance (ESR) dating to a series of teeth from megafauna sites in South Australia, where young ages were expected. During this study, a number of unexpected problems were encountered. These were mainly related to the fact that ESR age assessments on fossil teeth are critically dependent on a realistic reconstruction of the post-mortem uranium uptake into the dental tissues. At virtually all sites, conventional, routine ESR dating, based on the parametric early and linear U-uptake models, would have led to grossly erroneous results. Most teeth were analysed for U-series isotopes with laser ablation ICP-MS, and the results were used to c...

We report radiocarbon ages on cellulose isolated from the gut contents of a Diprotodon found at Lake Callabonna, South Australia. The maximum age obtained corresponds to a minimum age of >53,400 BP for this extinct giant marsupial. This is older than, and hence consistent with, the generally accepted Australian megafauna extinction window. We argue that dichromate and other strong oxidants are less selective than chlorite for lignin destruction in wood, and our results suggest that ages approaching laboratory background can be obtained using a repeated pretreatment sequence of chlorite-alkali-acid and measurement of the sometimes discarded 330°C combustion fraction.

The extinction of large-bodied taxa from the Pleistocene in Southeast Asia is examined. Although the chronological resolution of these extinctions is poor, and number of excavations in the region relatively few, broad characteristics of these extinctions can be described. Many taxa which became extinct appear to have been endemic to regions within Southeast Asia, while some taxa which experienced extinction or severe range reduction occurred in several regions. Members of the latter group include proboscideans (Stegodon and Palaeloxodon), the pygmy hippopotamus (Hexaprotodon), the orangutan (Pongo), hyenas (Crocuta and Hyaena), the giant panda (Ailuropoda), tapirs (Tapirus and Megatapirus), rhinoceroses (Rhinoceros), and the giant Asian ape Gigantopithecus. The loss of these species cannot be assigned to a single cause. Rather their disappearance is likely tied to both climatic and human agents. Unlike other regions which experienced megafauna extinctions, eustatic changes in sea level in Southeast Asia seems to have been an important factor.

Arguments that megafaunal extinctions in Australia were anthropogenically mediated have focused on establishing terminal appearance ages. This approach has been underpinned by three principle tenets: (1) if megafauna disappeared before significant climate change, but after human colonisation, then it can be inferred that extinctions were human mediated; (2) climate change within the last glacial cycle was unremarkable relative to previous cycles; and (3) all or most Pleistocene megafauna were present when people arrived on the continent. We review the evidence for human causation and note mounting evidence suggesting that the last 400–300 ka in Australia has been characterised by escalating aridity and climatic variability, culminating in the breach of a hydrological threshold within the last glacial cycle. Only 21 species (35%) of megafauna whose disappearance has been attributed to human activity are known to have persisted after the Penultimate Glacial Maximum, a time of undoubtedly severe climate change. Thus, 39 species of megafauna (65%) cannot be reliably placed within 85,000 years of firm evidence for human arrival, ca 50–43 ka. At most eight species (13%) were clearly present at this time. Four or more persisted until the onset of full glacial conditions at ca 30 ka. We argue for a falsifiable model of staggered extinction in which most megafaunal extinctions predated human arrival and with the influence of people as a minor superimposition on broader trends in train since middle Pleistocene times.

The extinction of the Australian megafauna is presently one of the most hotly contested debates in Australian Quaternary sciences. [Roberts et al., 2001. U-series and ESR analyses of bones and teeth relating to the human burials from Skhul. Journal of Human Evolution. 49, 316–334.] proposed contentiously that the megafauna went extinct within a short time period somewhere in the range of 39,000–52,000 years ago. Being tucked away at the continental fringe, Kangaroo Island offers an ideal refuge for the megafauna for survival. Initial radiocarbon analyses of soil organic matter, ESR of teeth and OSL of quartz provided consistent age assessments, which strongly suggested that the site could be as young as 20,000 years. However, it turned out that the sediments contained extreme disequilibria in the U-decay chain, with 230 Th/ 238 U ratios in the range of 0.3 and 210 Pb/ 238 U ratios around 0.1. Furthermore, in situ laser ablation analysis revealed that uranium migrated into the teeth at a very late stage during the Holocene. Contrary to expectations, insoluble organic matter was considerably younger than the soluble fraction. After combining all analytical results, a complex geochemical history can be reconstructed, implying that organic matter and large amounts of uranium were injected into the megafauna-bearing layers around the Last Glacial Maximum. When combined U-series/ESR dates are calculated, they all turn out older than the proposed extinction window. This was confirmed by a subsequent OSL study. The Black Creek Swamp site is another example that the parametric early (EU) and linear U-uptake (LU) ESR age models, particularly when applied to teeth with high-U concentrations, may provide completely unreliable age results.

The juxtaposition of stone tools, charcoal and bones at Cuddie Springs has been used to support claims that people were butchering now-extinct animals, and grinding seeds about 30,000 BP. Statistical analysis of dates for the site shows significant sediment disturbance, and the anomalous presence of hair residues in the absence of bone collagen suggests that bones and stone tools are not the same age. We argue that the published studies on the Cuddie Springs claypan deposits do not show a stratified and undisturbed Late Pleistocene archaeological site, as proposed by the excavators, instead revealing a palimpsest of Late Holocene and European occupational debris superimposed on a much longer-term record of Quaternary landscape evolution. There is no reliable evidence that extinct Australian megafauna coexisted with people using seed-grinding technology at Cuddie Springs, nullifying the excavators' support for climate change models of extinction and dietary choice.

[Roberts et al. 2001a. New ages for the last Australian megafauna: continent-wide extinction about 46,000 years ago. Science 292, 1888–1892] concluded that the extinction of Australia's late Pleistocene megafauna was an abrupt event that took place about 46 ka ago throughout the continent. By placing the extinctions soon after the arrival of people in Australia but before climate changes associated with the Last Glacial Maximum, this study implicated human impact as cause. However, the study was controversial because it excluded evidence, mainly from archaeological sites containing disarticulated megafauna remains, for survival of some megafauna well past 46 ka ago. Here, I ask how our interpretation of the extinctions would be changed if this evidence were accepted. Contrary to climate-change models of extinction, the young megafauna sites are not concentrated in mesic refuges around the coast. These sites do suggest that relatively small-bodied megafauna species were the last to disappear, as predicted by a version of the overkill hypothesis. More work is needed to test the evidence for late survival of megafauna species in Australia, but at present this evidence supports overkill, not climate change, as the cause of the extinctions.

We investigated, using meta-analysis of empirical data and population modelling, plausible scenarios for the cause of late Pleistocene global mammal extinctions. We also considered the rate at which these extinctions may have occurred, providing a test of the so-called ‘blitzkrieg’ hypothesis, which postulates a rapid, anthropogenically driven, extinction event. The empirical foundation for this work was a comprehensive data base of estimated body masses of mammals, comprising 198 extinct and 433 surviving species > 5 kg, which we compiled through an extensive literature search. We used mechanistic population modelling to simulate the role of human hunting efficiency, meat off-take, relative naivety of prey to invading humans, variation in reproductive fitness of prey and deterioration of habitat quality (due to either anthropogenic landscape burning or climate change), and explored the capacity of different modelling scenarios to recover the observed empirical relationship between body mass and extinction proneness. For the best-fitting scenarios, we calculated the rate at which the extinction event would have occurred. All of the modelling was based on sampling randomly from a plausible range of parameters (and their interactions), which affect human and animal population demographics. Our analyses of the empirical data base revealed that the relationship between body mass and extinction risk relationship increases continuously from small- to large-sized animals, with no clear ‘megafaunal’ threshold. A logistic ancova model incorporating body mass and geography (continent) explains 92% of the variation in the observed extinctions. Population modelling demonstrates that there were many plausible mechanistic scenarios capable of reproducing the empirical body mass–extinction risk relationship, such as specific targeting of large animals by humans, or various combinations of habitat change and opportunistic hunting. Yet, given the current imperfect knowledge base, it is equally impossible to use modelling to isolate definitively any single scenario to explain the observed extinctions. However, one universal prediction, which applied in all scenarios in which the empirical distribution was correctly predicted, was for the extinctions to be rapid following human arrival and for surviving fauna to be suppressed below their pre-‘blitzkrieg’ densities. In sum, human colonization in the late Pleistocene almost certainly triggered a ‘blitzkrieg’ of the ‘megafauna’, but the operational details remain elusive.

It is generally known that during the Quaternary there were wide spread extinctions of fauna on all continents except for Antarctica. The coinciding of these extinction events with the arrival of humans on each of the respective continents has led to the hypothesis that humans hunted this fauna into extinction (Flannery 1994). Termed the blitzkrieg or overkill hypothesis (Martin 1984), such was invoked by Flannery (1994) to explain the extinction of the megafauna in Australia. However, the applicability of the overkill hypothesis to Australia was brought under intense and serious scrutiny due to problems with the timing of the extinctions and human arrival (Grayson 1990), and the lack of any mass-kill sites such as has been found in New Zealand and North America (Owen-Smith 1989). Opponents to the human caused extinction have often cited the fluctuating climate characteristic of the Pleistocene as the causal agent in the demise of the Australian megafauna (Horton 1977). Problems with correlating extinction events with severe climatic conditions have produced incongruence in the climateinduced hypothesis (Flannery 1994). Consequently, a third hypothesis, the anthropogenic disruption hypothesis, which states that Aboriginal burning modified habitats enough to bring about a change in the ecology of the megafauna and their eventual demise, has been put forward (Miller et al. 1999). Due to the fact that the megafaunal extinction debate in Australia has reached a certain stalemate relative to the debate in other regions of the world, a rather different, if not heuristic, hypothesis is proposed here to stimulate an alternative line of inquiry. The hypothesis has been largely developed from recent advancements in the study of system complexity. I propose that an increase in immigration of fauna from south-east Asia and speciation of the existing local fauna in response to the increasing aridity of the Pliocene led the faunal assemblage of Australia to a level of self-organised instability, as defined by Sole et al. (2002a). The arrival of humans into Australia increased significantly the level of connectivity between the faunal elements in the Australian faunal system. Subsequently, the fauna of Australia was inherently susceptible to an extinction event. The purpose of this paper is to outline the logic behind this hypothesis, from here to be termed the self-organised instability (SOI) hypothesis of megafaunal extinctions, and the conditions that allow it to be applicable to Australia.

This paper has been motivated by a desire to put some numbers beside the label of sustainability as is currently applied to water related issues. Of particular interest is a general estimate of the water balance and environmental flows during the time intervals before Aboriginal arrival, when the land was being managed in an environmentally sustainable manner by the Aboriginals, and most recently following European settlement. This will be considered in an Australia-wide context, because the continent is geographically diverse, being mostly arid desert, with limited areas of fertile soils. Climate variation ranging from a hot tropical north to a cool temperate south will also be discussed. Attention will be given to the major factors that have influenced the water balance, including the extinction of Australian megafauna, the effects of “fire-stick” farming and the clearance of land for European agriculture with its consequences. It is hoped that the findings will increase our understanding of Australian water resources, and promote a greater appreciation of the fragility of this ancient landscape on which we dwell.

All Australian land mammals, reptiles, and birds weighing more than 100 kilograms, and six of the seven genera with a body mass of 45 to 100 kilograms, perished in the late Quaternary. The timing and causes of these extinctions remain uncertain. We report burial ages for megafauna from 28 sites and infer extinction across the continent around 46,400 years ago (95% confidence interval, 51,200 to 39,800 years ago). Our results rule out extreme aridity at the Last Glacial Maximum as the cause of extinction, but not other climatic impacts; a “blitzkrieg” model of human-induced extinction; or an extended period of anthropogenic ecosystem disruption.

New dating confirms that people occupied the Australian continent before the earliest time inferred from conventional radiocarbon analysis. Many of the new ages were obtained by accelerator mass spectrometry 14C dating after an acid–base–acid pretreatment with bulk combustion (ABA-BC) or after a newly developed acid–base–wet oxidation pretreatment with stepped combustion (ABOX-SC). The samples (charcoal) came from the earliest occupation levels of the Devil's Lair site in southwestern Western Australia. Initial occupation of this site was previously dated 35,000 14C yr B.P. Whereas the ABA-BC ages are indistinguishable from background beyond 42,000 14C yr B.P., the ABOX-SC ages are in stratigraphic order to ∼55,000 14C yr B.P. The ABOX-SC chronology suggests that people were in the area by 48,000 cal yr B.P. Optically stimulated luminescence (OSL), electron spin resonance (ESR) ages, U-series dating of flowstones, and 14C dating of emu eggshell carbonate are in agreement with the ABOX-SC 14C chronology. These results, based on four independent techniques, reinforce arguments for early colonization of the Australian continent.

The Cuddie Springs site in south-eastern Australia provides the first evidence of an unequivocal association of megafauna with humans for this continent. Cuddie Springs has been known as a fossil megafauna locality for over a century, but its archaeological record has only recently been identified. Cuddie Springs is an open site, with the fossil deposits preserved in a claypan on the floor of an ancient ephemeral lake. Investigations revealed a stratified deposit of human occupation and fossil megafauna, suggesting a temporal overlap and an active association of megafauna with people in the lead up to the Last Glacial Maximum, when conditions were more arid than the present day. Two distinct occupation phases have been identified and are correlated to the hydrology of the Cuddie Springs lake. When people first arrived at Cuddie Springs, sometime before 30,000 BP, the claypan on the lake floor was similar to a waterhole, with five species of megafauna identified. Flaked stone artefacts were found scattered through this level. After the lake dried, there was human occupation of the claypan. The resource base broadened to include a range of plant foods. Megafauna appear to be just one of a range of food resources exploited during this period. A return to ephemeral conditions resulted in only periodic occupation of the site with megafauna disappearing from the record around 28,000 BP. The timing of overlap and association of megafauna with human occupation is coincident with the earliest occupation sites in this region. The archaeological evidence from Cuddie Springs suggests an opportunistic exploitation of resources and no specialised strategies for hunting megafauna. Disappearance of megafauna is likely to be a consequence of climatic change during the lead up to the Last Glacial Maximum and human activities may have compounded an extinction process well under way.

The worldwide extinction of large terrestrial mammals in the late Pleistocene has been attributed to climate change, overkill by human populations colonizing new continents, or some combination of these two processes. Lack of precision in chronologies for human colonization and mega- faunal extinction suggests that the role of overkill will be difficult or impossible to resolve from the archaeological and fossil record. In this study, we used a simple two species predator-prey model to examine the population density and hunting efficiency of a colonizing Aboriginal population necessary for overkill to have led to extinction (equilibrium density=0), of a range of different sized megafauna (250–1000 kg bodyweight) inhabiting an hypothetical tract of north Australian Eucalyptus savanna. We referred our modelling to this region because estimates of contemporary Aboriginal population density arguably set an upper limit for those occurring during the Pleistocene, and data are available on harvesting rates of large introduced mammals such as buffalo. Modelling results indicated a compensatory trade-off between the effect of Aboriginal population density and hunting efficiency (measured as the rate of effective search for prey) on equilibrium megafauna densities. The modelling also demonstrated that although intrinsic rate of population increase and density at carrying-capacity for mammals increase with declining body size, smaller megafauna would have been more readily exterminated than larger megafauna because they would have been harvested at a higher rate to satisfy the demand for meat. However, while at contemporary Aboriginal densities it appears plausible that over-harvesting could have affected the fate of smaller megafauna (

The most enduring and high-profile scientific debate in Australian prehistory is that surrounding the loss of more than 50 species of endemic, large-bodied vertebrates (megafauna) and the timing of these extinctions (1). Wroe et al. (2) present a personal perspective on some of the available literature to reject the scenario of rapid, continent-wide losses, and downplay any role for human agency. They contend that different species of megafauna went extinct progressively during the Middle and Late Pleistocene, with many “disappearing” long before human hunters arrived, leaving climate change as the alternative explanation. However, these conclusions rely on a biased selection of data and disregard several underlying geochronological …

This chapter introduces the animals: who they were, where they lived and as far as possible when they lived. It dissects the groups in terms of whether some should be called megafauna at all and describes those both aquatic and terrestrial forms that were and went extinct. The purpose here is to also map out the demography of these animals although that may not be complete. That is carried out to determine the continental distribution of megafauna but also species distribution and from there the size limitations of the populations as a whole from the pattern of its demography. The chapter also goes where few have bothered to before: to the exposed continental shelves that emerged during the long Ice Ages and discusses how these may not have been ideal places to occupy.

Aboriginal people have exploited European and Asian cattle as a food resource since the introduction of these animals to Australia. Butchering techniques are usually simple and efficient and involve minimum disarticulation of the carcass or artefactual damage to bones. Subsequent residues often show little or no direct evidence of being a product of human activity. Similar 'optimum butchering' strategies may well have applied to the butchering of extinct Australian megafauna, particularly the Diprotodontidae , and would provide one explanation for the inconclusive evidence for human exploitation of megafauna. This paper comments on the Aboriginal hunting and butchering of cattle for non-commercial use. The descriptions provided are derived, firstly, from field observations over several years of Aboriginal hunting and the butchering of two buffalo and nine European cattle from several spatially separate regions of northern Australia; secondly, from interviews with Aboriginal informants; and, thirdly, from discussions with other field researchers. This description relies on qualitative data. Observations of hunting and butchering events were usually fortuitous, occurring in the course of other work, and collection of more detailed data suitable for quantitative analysis was simply not possible. Therefore, rather than describe the specifics of the limited number of observations, the observation and interview data have been combined to provide a summary of the general strategy. It is hoped that these notes will stimulate discussion, firstly, about the status of cattle in Aboriginal social and economic life and, secondly, about exploitive models applicable to certain species of Australian megafauna. Â

The origins, evolution and palaeodiversity of Australia’s unique marsupial fauna are reviewed. Australia’s marsupial fauna is both taxonomically and ecologically diverse comprising four extant orders (Dasyuromorphia, Peramelemorphia, Notoryctemorphia and Diprotodontia) and one extinct order (Yalkaparidontia). Molecular divergence dates estimate a Palaeocene origin for the Australian marsupial orders yet ordinal differentiation is obscured by significant gaps in the fossil record with a single terrestrial mammal-bearing deposit known between the late Cretaceous and the late Oligocene. This deposit, the 55 million-year-old early Eocene Tingamarra Local Fauna of southeastern Queensland, contains Australia’s oldest marsupial (Superorder Australidelphia) as well as taxa tentatively interpreted to represent South American groups (Order Polydolopimorphia). Palaeobiogeographic hypotheses regarding the distribution and interordinal relationships of Australian and South American marsupials are discussed. Dasyuromorphia and Peramelemorphia were possibly also present in the early Eocene, Diprotodontia in at least the late Oligocene and Notoryctemorphia and Yalkaparidontia in the early Miocene. Palaeobiodiversity was highest during the early to middle Miocene as evidenced by a spectacular array of marsupial groups in the rainforest assemblages of the Riversleigh World Heritage Area. The onset of icehouse conditions during the middle Miocene saw significant faunal turnover with loss of many archaic groups and the emergence of a range of modern lineages. Few deposits of late Miocene age are known. Development of Australia’s first grasslands and arid habitats occurred in the Pliocene, accompanied by an explosive radiation of grazing kangaroos. The Pleistocene was characterised by severe and unpredictable climatic conditions and the extinction of the Australian megafauna. Lowered sea levels allowed faunal interchange between mainland Australia and neighbouring New Guinea as well as the arrival of the first humans. Resolution of the role of humans and/or climate change in megafaunal extinction requires more precise dating of late Pleistocene deposits. We reflect on the predictive power of the fossil record to enhance understanding of the effects of climate change and humans on the future of the Australian marsupial fauna.

The date at which people entered Australia has important implications for the debate on modern human origins. Thermoluminescence dates of 50–60 ka, reported for initial occupation of the Malakunanja II site in northern Australia, have been used as a means of calibrating the rate of mitochondrial and nuclear DNA evolution in modern humans. Optical dating of unburnt quartzose sediments from a rock shelter site (Nauwalabila I, Lindner Site) in Deaf Adder Gorge, 70 km south of Malakunanja II, provides new evidence for the timing of the colonisation of the continent. Optical dates were determined for several stratigraphic levels within a 3 m deep excavation, in which flaked stone artefacts and ground pigments were found in primary depositional setting. The lowest human occupation levels are bracketed by dates of 53.4 ± 5.4 ka and 60.3 ± 6.7 ka, while the upper levels show good agreement between optical and calibrated 14C age estimates. High-quality haematite with ground facets and striations is associated directly with the 53 ka level and indicates the use of pigments by these early Australians. The optical dates independently confirm evidence for the colonisation of northern Australia shortly after 60 ka and should be seen in the context of this region as having been a likely entry route for the first human movements into Sahul.

A unifying, predictive hypothesis is developed that explains many facets of late Quaternary biotic change in Australia. Pleistocene faunal extinction (commonly called megafaunal extinction) is envisaged as the precipitating mechanism for much environmental change. The extinction is thought to be of the “blitzkrieg” type as presented by Martin (1973), and was followed by suppression through human hunting of the remaining large herbivores. Much vegetation was left uneaten because of these events, resulting in an increased standing crop of fuel. Increased fuel continuity and mass ensured that fires could become much larger and hotter than was usually possible previously. The changed fire regime eventually eliminated fire sensitive Gondwanan rainforest elements from almost all parts of the continent that were not protected. Aborigines responded to the changed fire regime with firestick farming. This maintained a high diversity as it ameliorated the worst effects of fires on medium-sized mammals and possibly some plants. Twentieth century Australian mammal extinctions are the result of a trophic cascade that followed the cessation of firestick farming.

Most of Australia's largest mammals became extinct 50,000 to 45,000 years ago, shortly after humans colonized the continent. Without exceptional climate change at that time, a human cause is inferred, but a mechanism remains elusive. A 140,000-year record of dietary δ 13 C documents a permanent reduction in food sources available to the Australian emu, beginning about the time of human colonization; a change replicated at three widely separated sites and in the marsupial wombat. We speculate that human firing of landscapes rapidly converted a drought-adapted mosaic of trees, shrubs, and nutritious grasslands to the modern fire-adapted desert scrub. Animals that could adapt survived; those that could not, became extinct.

Understanding of the Pleistocene megafaunal extinctions has been advanced recently by the application of simulation models and new developments in geochronological dating. Together these have been used to posit a rapid demise of megafauna due to over-hunting by invading humans. However, we demonstrate that the results of these extinction models are highly sensitive to implicit assumptions concerning the degree of prey naivety to human hunters. In addition, we show that in Greater Australia, where the extinctions occurred well before the end of the last Ice Age (unlike the North American situation), estimates of the duration of coexistence between humans and megafauna remain imprecise. Contrary to recent claims, the existing data do not prove the “blitzkrieg” model of overkill.

More than 85 percent of Australian terrestrial genera with a body mass exceeding 44 kilograms became extinct in the Late Pleistocene. Although most were marsupials, the list includes the large, flightless mihirung Genyornis newtoni . More than 700 dates on Genyornis eggshells from three different climate regions document the continuous presence of Genyornis from more than 100,000 years ago until their sudden disappearance 50,000 years ago, about the same time that humans arrived in Australia. Simultaneous extinction of Genyornis at all sites during an interval of modest climate change implies that human impact, not climate, was responsible.

1 Wroe, S. et al. (2005) Megafaunal extinction: climate, humans andassumptions. Trends Ecol. Evol.,21.doi: 10.1016/j.tree.2005.11.0122 Burney, D.A. and Flannery, T.F. (2005) Fifty millennia ofcatastrophic extinctions after human contact. Trends Ecol. Evol.20, 395–4013 Diamond, J. (1984) Historical extinctions: a Rosetta Stonefor understanding prehistoric extinctions. In Quaternary Extinc-tions: A Prehistoric Revolution (Martin, P.S. and Klein, R.G., eds),pp. 824–862, University of Arizona Press4 Burney, D.A. et al. (2004) A chronology for late prehistoricMadagascar. J. Hum. Evol. 47, 25–635 Flannery, T.F. (1995) Mammals of New Guinea, Reed Publishing6 Miller, G.H. et al. (1999) Pleistocene extinction of Genyornis newtoni:human impact on Australian megafauna. Science 283, 205–2087Roberts, R.G.et al. (2001) New ages for the last AustralianMegafauna: continent-wide extinction about 46,000 years ago. Science292, 1888–18928 Steadman et al. (2005) Asynchronous extinction of late Quaternarysloths on continents and islands. Proc. Natl. Acad. Sci. U. S. A. 102,11763–117689 Robinson, G.S. et al. (2005) Landscape paleoecology and megafaunalextinction in southeastern New York State. Ecol. Monogr. 75, 295–31510 Burney, D.A. et al. (2003) Sporormiella and the late Holoceneextinctions in Madagascar. Proc. Natl. Acad. Sci. U. S. A. 100,10800–1080511 Martin, P.S. (2005) Twilight of the Mammoths; Ice Age Extinctions andthe Rewilding of America, University of California Press

A rich source of fossils recently discovered in caves beneath the arid, treeless Nullarbor Plain of western Australia offers a rare glimpse of life in the continent in the Middle Pleistocene (between around 800,000 and 200,000 years ago), long before humans arrived. Despite the remarkable diversity of animals and plants, including eight previously unknown kangaroo species, two of them tree kangaroos, the climate was similar to that of today. This means that climate change alone is unlikely to have been responsible for the subsequent wave of extinctions that swept away most of the Australian megafauna.

Excavations into the Australian swamp of Lancefield show that a bone bed dated at 26,000 years ago contains perhaps 10,000 giant extinct animals. Associated artifacts suggest that humans were in the area, but the direct cause of death of the animals is, on present evidence, not explicable. Such a recent date for the classic megafauna shows that it was living together with humans for at least 7000 years in southeast Australia. This enduring association argues against a catastrophic and rapid overkill in the Australian Pleistocene.

To understand the current biodiversity crisis, it is crucial to determine how humans have affected biodiversity in the past. However, the extent of human involvement in species extinctions from the Late Pleistocene onward remains contentious. Here, we apply Bayesian models to the fossil record to estimate how mammalian extinction rates have changed over the past 126,000 years, inferring specific times of rate increases. We specifically test the hypothesis of human-caused extinctions by using posterior predictive methods. We find that human population size is able to predict past extinctions with 96% accuracy. Predictors based on past climate, in contrast, perform no better than expected by chance, suggesting that climate had a negligible impact on global mammal extinctions. Based on current trends, we predict for the near future a rate escalation of unprecedented magnitude. Our results provide a comprehensive assessment of the human impact on past and predicted future extinctions of mammals.

A critical comment on 'A review of the evidence for a human role in the extinction of Australian megafauna and an alternative explanation' by S. Wroe and J. Field is presented. The authors have highlighted a range of ideas under consideration, and provided a selective interpretation which does not come to terms with biology and ignores or misinterprets current evidence. They rely heavily on the ages reported by Roberts et al. (2001) to argue for a gradual attenuation of the megafauna. They propose a staggered series of extinctions throughout the Middle and Late Pleistocene, with many taxa lost during the Penultimate Glacial Maximum (PGM) 140 130 ka, and relatively few species persisting. They ignore measurement uncertainties associated with the ages, which, when properly considered, means that 20, rather than eight of the species they list have last appearance ages consistent with 45 ka.

THE oldest secure date for human occupation in Greater Australia is 40kyr from eastern Papua New Guinea1, whereas slightly younger dates have been reported from southern Australia2. We now report thermoluminescence (TL) dates that suggest the arrival of people between 50 and 60 kyr in northern Australia. TL dates were obtained from sandy footslope deposits at two former occupation sites that yielded a range of stone artefacts in their primary depositional setting. Artefacts terminated mid-way down one profile, which had a basal age of about 100 kyr. Confidence in the TL dates is given by their close correspondence with radiocarbon dates obtained from the upper occupation levels. These TL dates are not only the oldest yet proposed for Aboriginal occupation but also may mark the time of initial human arrival on the Australian continent.

Roberts et al . ([1][1]) suggested an age date of around 46.4 thousand calendar years ago (ka) for extinction of at least six genera of Australian megafauna based on dated articulated remains. Since the exploitation of animals by people inherently involves the disarticulation of faunal remains, this