Miller et al, 1999

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Pleistocene Extinction of Genyornis newtoni: Human Impact on Australian Megafauna Gifford H. Miller,* John W. Magee, Beverly J. Johnson,† Marilyn L. Fogel, Nigel A. Spooner, Malcolm T. McCulloch, Linda K. Ayliffe‡ 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. Australia suffered a major loss of its largeand medium-sized land mammals in the Late Pleistocene. All marsupials exceeding 100 kg (19 species) and 22 of 38 species between 10 and 100 kg became extinct (1), along with three large reptiles and the ostrich-sized Genyornis newtoni (2); two other large flightless birds, the emu (Dromaius novaehollandiae) and the cassowary (Casuarius casuarius), survived. Dwarfing and range restriction occurred in many other species (1). Collectively, the lost species are often referred to as the Australian megafauna, although most are of modest body mass. For more than a century the cause of this exceptional extinction has been debated without a clear consensus, largely because of the difficulty in dating faunal remains close to the limit of radiocarbon dating (3). The cause of megafauna extinction initially focused on climate change (4) or human predation (5), G. H. Miller and B. J. Johnson, Center for Geochronical Research, Institute of Arctic and Alpine Research (INSTAAR), and Department of Geological Sciences, University of Colorado, Boulder, CO 80309 – 0450, USA. J. W. Magee, Department of Geology, Australian National University, Canberra ACT 0200, Australia. M. L. Fogel, Geophysical Laboratory, Carnegie Institution of Washington, 5251 Broad Branch Road, NW, Washington, DC 20015, USA. N. A. Spooner, M. T. McCulloch, L. K. Ayliffe, Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia. *To whom correspondence should be addressed. Email: gmiller@colorado.edu †Present address: School of Oceanography, Box 357940, University of Washington, Seattle, WA 98195–7940, USA. ‡Present address: Laboratoire des Sciences du Climatet et de l’Environnement (LSCE), Domaine du CRNS– Bt 12, Ave. de la Terrasse, 91198 Gif-sur-Yvette, Cedex, France.

but more recently has included indirect consequences of human activity, particularly ecosystem change resulting from burning practices (6–8). Resolving the debate requires secure dates on the extinction events, on the arrival of humans in Australia, and on major climate and environmental changes. Here we present new dates that constrain the ages of these key events based on amino acid racemization, accelerator mass spectrometry (AMS), 14C and thermal ionization mass spectometry (TIMS) U-series analyses on eggshells, and luminescence dates on associated sediment. The abundance of fossil eggshell reflects, in order of importance, its preservation potential, subsequent exposure potential, and the number of nesting birds. To be preserved, mobile sediment, commonly eolian sand, must be available to bury the eggshell quickly. Eggshell is most frequently collected from natural exposures or deflation hollows. Without recent erosion, eggshell is rarely encountered because it survives only briefly at the surface. Bird populations are controlled primarily by climate, nutrient availability, and predator pressure (including humans). Eggshells of large, flightless birds offer distinct advantages over bone for dating purposes. They are well preserved and surprisingly common across Australia, their dense calcite matrix is resistant to diagenesis, and, from a single fragment, 14C activity, amino acid racemization (AAR), and stable isotope ratios can be measured. By dating eggshells of Genyornis and Dromaius collected from deposits formed during wetter and drier intervals, environmental change may be placed in a secure time frame, and the youngest Genyornis eggshells can hence provide a date

on the bird’s extinction within each region. By dating the extinction event in several regions spanning a range of climates, continental extinction may be evaluated. Most birds incorporate about 3% complex organic compounds in their eggshells as an intracrystalline organic web that is highly resistant to diffusional loss. Epimerization of the common protein amino acid isoleucine, preserved in the proteinaceous residues, follows first-order, reversible kinetics (9, 10). Expressed as the proportion of the non-protein D-alloisoleucine to its protein source, L-isoleucine, D/L increases from essentially zero in modern eggshell to an equilibrium ratio of 1.30 (11). The temperature dependence of isoleucine epimerization in Dromaius eggshell is well known (12). Eggshells of both Genyornis and Dromaius commonly occur together in all regions (13), suggesting that they coexisted and nested in close proximity, contrary to a recent assertion (14). We measured D/L ratios in eggshells of both taxa from three regions (15): (i) an extensive series (1200 analyses) from dune and beach deposits within a 50-km radius of Madigan Gulf (MG) in Lake Eyre, the terminal playa of the Lake Eyre Basin; and modest collections (ii) from a 50-km radius centered on the north end of Lake Frome (LF) and (iii) from a 150-km radius centered on the confluence of the Darling and Murray rivers (DM) (Fig. 1). The MG region is currently arid [21°C, ;150 mm precipitation (16)]; LF is semiarid (19°C, ;400 mm precipitation) and has denser plant cover and thick riparian vegetation; and the DM region is semiarid (17°C, ;400 mm precipitation) with more reliable stream flow. The Darling River drains the summer-dominant precipitation regime of the north, whereas the Murray drains the winter-westerly– dominated precipitation regime of southern Australia. Consequently, the DM sites have one of the most dependable moisture supplies in the interior, and should have been a refugium for fauna during periods of climate stress. In all three regions, precipitation can occur in any season, but summer precipitation dominates in the MG region. Before European settlement, it supported mixed C3 and C4 vegetation. LF and DM support primarily C3 plants. In the MG region, the D/L record is calibrated by 90 paired AAR and calibrated AMS 14 C dates (17) on Dromaius eggshells, 8 luminescence dates between 40 and 120 thousand years ago (ka) on eolian sand from which eggshell has been collected, and 5 TIMS U-series dates on Genyornis eggshell. An age model developed from this calibration set allows calendar ages to be assigned to each D/L ratio for all samples ,130,000 years old (Fig. 2). Frequency histograms for the two taxa derived from the age model document the

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REPORTS time dependence of the collection series over the past 130 thousand years (ky) (Fig. 3); the frequency distribution of the 90 14C-dated Dromaius eggshells (Fig. 3) mirrors that of the larger data set of model-derived ages. MG was continually occupied by breeding populations of Dromaius for at least the past 130 ky, even through the stage 2 arid phase. Intervals of greatest Dromaius eggshell abundance reflect peak sediment mobility (preservation) during early stage 5, early stage 3, and at about the stage 2/1 transition. Although the distribution of Genyornis eggshells is similar for the older part of the record, eggshells abruptly disappear about 50,000 years ago. The continuous presence of Dromaius eggshells confirms that the absence of younger Genyornis eggshell is not due to a lack of preservation or exposure potential, but must indicate the actual extinction of the birds in this area. Insufficient age calibration is available for the other two regions to plot frequency distributions in the time domain, but we can evaluate them in the D/L domain (Fig. 4). D/L is a time-dependent quantity, but the epimerization rate exhibits a strong temperature dependency, and Pleistocene temperatures in central Australia were up to 9째C lower than in the Holocene (12); consequently, time is not linearly expressed. Furthermore, because the LF and DM regions are cooler than the MG region, the age for a specific D/L ratio is higher. Within these constraints, D/L histograms for all three regions exhibit similar trends. All three reveal near continuous occupation by Dromaius. The lack of old material at DM simply reflects the poor exposure there of older sediment. In sharp contrast to the continuity of Dromaius histograms, Genyornis displays a distinct termination in all three areas. Because of the temperature differences, the age of the extinction event must be evaluated at each site. To do this, we radiocarbon dated fragments of both Genyornis and Dromaius that straddle the extinction event,

Fig. 1. Locality map showing the Lake Eyre Basin (hatched area), Madigan Gulf sites (MG), Lake Frome sites (LF), and the Darling-Murray sites (DM) at the confluence of the Darling (D) and Murray (M) rivers.

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dated Genyornis eggshells directly by TIMS U-series (18), and dated sediment enclosing the youngest Genyornis eggshell by luminescence (19). At MG, Genyornis became extinct between D/L ratios of 0.46 and 0.50. AMS 14C dates on 11 Dromaius eggshells within that range are all .38,700 14C years before the present (yr B.P.), essentially at the limit of the method. Five luminescence dates from the corresponding eolian unit are between 63 6 5 ka and 44 6 5 ka (20). U-series dates on terminal Genyornis eggshells from two different sites in MG are 47 and 65 ka. Radiocarbon ages of Genyornis eggshell that received only an acid-leaching pretreatment suggest that many of these eggshells are contaminated by younger carbon. For example, three fragments from levels stratigraphically below luminescence dates of 50 to 60 ka produced finite apparent radiocarbon ages between 36,700 and 39,500 14C yr B.P. Using a more rigorous pretreatment (90% acid leach; drilling out all pores), we obtained radiocarbon ages older than 42,000 14C yr B.P. for two fragments of Genyornis that gave the lowest D/L in the MG collections and that previously gave finite radiocarbon ages younger than 40,000 14C yr B.P. with less rigorous pretreatment. We conclude that the extinction event occurred at or beyond the limits of 14C dating. In the DM region Genyornis became extinct at a D/L ratio between 0.28 and 0.32, substantially lower than at MG because average temperatures at DM are 4째C less (21). One Dromaius eggshell slightly younger than the extinction event (D/L 5 0.27) has a radiocarbon

Fig. 2. Age model used to convert D/L ratios to calendar ages based on 90 paired and calibrated (17) AMS 14C dates and D/L ratios, 5 paired TIMS U-series dates and D/L ratios, and 8 luminescence dates on sediment from which eggshell D/L ratios were measured. The two initial linear segments are based on earlier assessments (12), whereas the older two linear segments are simple regressions fit through the data. Other configurations are plausible, but yield similar conclusions. LGM deposits in MG are thin, and the shallow burial, coupled with the low glacial-age temperature, results in poor age resolution for the interval between 16 and 60 ka, but the similar patterns for 14C- and AAR-dated samples (Fig. 3) suggest that any biases in the histograms are minimal.

age of 37,600 14C yr B.P., and three eggshells from within the extinction window range between 38,100 and .45,100 14C yr B.P. Two Genyornis eggshells that slightly predate the extinction, based on their D/L ratios, yielded ages of 42,600 and .44,400 14C yr B.P., and five fragments from a single stratigraphic level, all with D/L ratios of 0.34 and therefore slightly older than the extinction, have an average TIMS U-series age of 53 6 3 ka (22). No independent dates are available from LF. The temperature averages 2째C lower there than at MG (21); consequently, the D/L ratio expected of a correlative extinction event is 0.40 6 0.03, midway between those of extinction events at MG and LF. The D/L ratios of the youngest Genyornis at LF are higher (0.46 6 0.02); hence, extinction may have occurred slightly earlier, although the small sample size may mean we failed to locate the youngest Genyornis there. Our dates bracket the timing of Genyornis extinction. Luminescence and U-series dates demonstrate that Genyornis was common as recently as 60 to 50 ka. The radiocarbon evidence from eggshells of both taxa spanning the extinction event collectively demonstrate that it occurred at or beyond the effective limit of 14C dating of carbonates (at least 42,000 14C yr B.P., corresponding to a calendar age of .46 ka). Thus, the extinction

Fig. 3. Age-frequency histograms for Dromaius (above) and Genyornis (below) for the past 130 ky from the MG region, derived from D/L ratios on individual eggshell fragments collected from widely scattered sites that have been converted to calendar ages from the age model shown in Fig. 2. Solid bars in the upper panel represent the AMS 14C-dated eggshells superimposed on the AAR-dated series. The sudden disappearance of Genyornis ;50 ka defines the extinction event in this region. Marine isotope stage boundaries are shown.

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REPORTS occurred 50 6 5 ka. The similar pattern and timing of Genyornis extinction across three different regions, including the DM region that would be expected to serve as a refugium during times of drought, and the continuous occurrence of Dromaius through the extinction event and on to the present at all three sites suggest that extinction was taxonomically selective and on a continental scale. To evaluate whether a change in climate may have led to the extinction, we examined paleoclimate reconstructions that extend through the extinction event in MG (past 150 ky) (20, 23) and DM (past 70 ky) (24), concentrating on changes in available moisture, the limiting variable for vegetation across most of Australia. During arid times, when precipitation is reduced over the Lake Eyre Basin, playa conditions dominate in MG, and groundwater salinity rises because of evaporative concentration. As the watertable is lowered, salts that crystallize at the groundwater capillary fringe within the sediment matrix disrupt the surface and promote deflation, removing sediment and salts from the basin. While disruption and deflation keep pace with watertable lowering, the playa floor is lowered, until the groundwater level reaches equilibrium with the evaporative conditions, and a halite crust develops. Thus, the maximum depth of deflation is a secure proxy for the intensity of an arid phase. Arid-phase deflation excavated the playa floor below its current level (15 m below sea level) about 140 ka, 60 to 50 ka, and between about 30 and 16 ka. Of these, the most extensive excavation occurred at 140 ka, when the playa was eroded to bedrock, as much as 19 m below sea level. Lake Eyre last carried a permanent waterbody ;60 ka; slow drying followed, but the extent of playa deflation, and by direct inference the intensity of aridity, was less

than at 140 ka, and probably less than the arid phase 30 to 16 ka. Eolian sands were deposited adjacent to the lake during the highstand 60 ka and as it subsequently dried. Genyornis eggshells occur throughout the eolian unit, but not in younger deposits, indicating that extinction occurred at the end of a modest drying event or during an immediately subsequent wetter interval. The most complete record of moisture change in the DM region comes from the Willandra Lakes (24). A long period of aridity terminated about 60 ka, with increased moisture supporting abundant vegetation and filling the basin with permanent water. Genyornis and Dromaius eggshells are present in deposits of this age. Beginning at ;40 ka, the climate began to become drier; Dromaius was present, but no Genyornis have been reported in this or any younger units. After an interval of variable conditions, final desiccation occurred shortly after 20 ka, and Lake Mungo has remained dry since. In this region, Genyornis apparently became extinct before the onset of aridity. It thus seems that Genyornis was able to survive through the range of natural environmental changes caused by Pleistocene climate oscillations. At the time of Genyornis extinction, 50 6 5 ka, modest aridity (MG) to slightly wetter-than-present conditions (DM) prevailed. Consequently, climate change as an explanation for Genyornis extinction is unlikely. Genyornis is considered to be an element of the Australian megafauna (1), and its bones are associated with some of the youngest stratigraphic levels containing megafaunal remains. Thus, we argue that extinction of the Australian megafauna in general is likely to be coincident with Genyornis extinction, and that this occurred ;50 ka. Dating the arrival of the first humans to Australia has proven difficult. The most reli-

Fig. 4. D/L-frequency histograms for Dromaius and Genyornis from all three regions. Dromaius D/L ratios have been converted to equivalent Genyornis D/L ratios by dividing by 1.18, their average offset in paired collections of the two taxa, so that within each region the two taxa can be directly compared. Some key radiocarbon dates are indicated at their associated D/L ratio, showing that extinction occurred at or beyond the limit of 14C dating of eggshell.

able dates are luminescence ages of quartz grains enclosing human artifacts. The oldest widely accepted dates are 55 6 5 ka (25, 26), near the time of the extinction; older dates from northwest Australia (27) have been questioned (28, 29), and indirect evidence that has been interpreted as humanly induced, such as changes in fire regime (30, 31), remains tenuous. Humans are known to have had an impact on large birds elsewhere. The extinction of all species of moa (Dinornis spp.) from New Zealand within a few centuries of human colonization is documented to have been a consequence of hunting and fires (32). Genyornis carried about twice the body mass of Dromaius and was presumably less agile. It is plausible that because it was less mobile, or possibly because of a more vulnerable breeding strategy, Genyornis was selectively predated by early hunters. However, evidence of direct predation on Genyornis by humans is limited to a single site (33), and kill sites for other elements of the megafauna are equally rare [for example, (1, 34–36)]. Alternatively, ecosystem disruption as a consequence of early human activity may have impacted the fauna differentially, possibly on the basis of dietary preferences. The gross feeding habits of Genyornis can be reconstructed from the isotopic composition of its eggshells, and its skeletal morphology. The 13C/12C ratio of carbon in a bird’s food source is preserved in the calcite matrix of, and organic compounds within, its eggshells. In modern eggshell of Dromaius, Struthio (ostrich), and Coturnix (quail), the d13C of the organic fraction is enriched by 2 6 1 per mil relative to the diet of the parent; the offset between the organic and inorganic fractions is 9 6 1, 15 6 1, and 14 6 1 per mil, respectively (37, 38). The organic-inorganic offsets are indistinguishable in Late Quaternary eggshell of Dromaius (10 6 2 per mil; n 5 45) and Struthio (14 6 1 per mil; n 5 49). The average isotopic offset between the two fractions for fossil Genyornis (14 6 2 per mil; n 5 74) is similar to that of Struthio and Coturnix. If we assume that the same 2 per mil enrichment of the eggshell organic fraction over dietary d13C measured in our modern controls applies to fossil samples, it is possible to reconstruct dietary d13C for the extinct Genyornis. Dietary d13C reconstructed from 65 Genyornis and 49 Dromaius eggshells that were laid between 60 and 45 ka in MG averages 222 and 218 per mil, respectively. Twenty of 49 Dromaius eggshells are between 213 and 215 per mil, but some individuals have values as light as 226 and as heavy as 29 per mil. Genyornis group more tightly (54 of 65 are between 219 and 225 per mil; none are heavier than 214 per mil), suggesting that Genyornis ate primarily C3 browse, whereas Dromaius had wider dietary tolerances including a signif-

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REPORTS icant component of C4 grasses. In contrast, 25 MG Dromaius eggshells from the last glacial maximum (AMS 14C dates for each are between 28,000 and 14,000 yr B.P.) have a dietary d13C clustered between 219 and 222 per mil, indicating a shift to regional dominance by C3 plants and a corresponding adjustment in the birds’ diet. Genyornis from the DM region apparently ate exclusively C3 plants (d13C 5 226 6 1 per mil; n 5 9). The isotopic data indicate that Dromaius had broader dietary tolerances than did Genyornis and was able to adapt its feeding strategies to a wider variety of ecological conditions. This ability may have contributed to its survival through the extinction event. The cranial morphology of the dromornithids, of which Genyornis is a member, indicates that the beak was used primarily in a shearing motion, a characteristic of browsing animals (39). Consequently, we conclude that Genyornis was primarily a browser and likely to be dependent on extensive shrubland. Fire has exerted a major control on Australian vegetation throughout the Quaternary, but the adaptations to fire are to ignition during a restricted portion of the year and only after sufficient fuel loading had occurred. One possibility is that burning practices of the earliest human immigrants differed enough from that of the natural fire cycle to disrupt ecosystems across the semiarid zone. The ecosystem may have been particularly susceptible as a result of the continent’s geological quiescence; soils in this low-relief landscape were depleted of most nutrients, resulting in a lack of ecosystem resiliency. We postulate that human burning at times of the year and at frequencies to which the vegetation was not pre-adapted resulted in a dramatic decrease in tree and shrub vegetation across the continental interior, which in turn placed unprecedented stress on the dependent fauna (6, 7, 40). This stress, possibly coupled with modest drying that occurred simultaneously and perhaps some direct human predation, led to megafauna extinction. Most of the extinct megafauna were browsers (1). Vegetation over much of their former range is currently desert scrub and spinifex grassland, providing circumstantial evidence in support of major vegetation change. Those taxa with restricted dietary requirements, such as Genyornis, were at greatest risk, whereas more cosmopolitan, opportunistic feeders, such as Dromaius, were able to survive as a new equilibrium was established. Top-level predators were unable to sustain themselves in the face of reduced prey. References and Notes

1. T. F. Flannery, Archaeol. Oceania 25, 45 (1990). 2. P. Vickers-Rich, in The Antipodean Ark: Creatures from Prehistoric Australia, S. Hand and M. Archer, Eds. (Angus and Robertson, Sydney, 1987), pp. 48 –50.

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3. Direct dating of megafaunal bone by radiocarbon remains hampered by the poor preservation of collagen, and most dates on faunal remains are close to the radiocarbon limit. Although collagen constitutes 25% by weight in modern bone, under alternately wet and dry conditions in warm regions like Australia it is rapidly denatured into soluble gelatin and leached from the bone (41). Baynes (42) reviewed 91 published radiocarbon dates on megafaunal remains or sediments containing them; ages as young as 6000 14C yr B.P. have been accepted by some authors. After applying rigorous criteria to assess the reliability of a radiocarbon date and its association with faunal remains (43), he rejected most dates, including all those younger than 28,000 14C yr B.P. The few remaining sites with apparent finite 14C ages between 28,000 and 40,000 yr B.P. were not directly on megafaunal remains, and either the association of the megafauna with the dated level remains debated or there are uncertainties in the source of the actual carbon that was dated, leaving the timing of extinction unresolved. 4. R. Tate, Trans. Proc. Philos. Soc. S. Aust. 2, 13 (1879). 5. R. Owen, Researches on the Fossil Remains of the Extinct Mammals of Australia (Erxleben, London, 1877). 6. D. Merrilees, J. R. Soc. West. Aust. 51, 1 (1968). 7. R. Jones, Aust. Nat. Hist. 16, 224 (1969). , Nature 246, 278 (1973). 8. 9. A. S. Brooks et al., Science 248, 60 (1990). 10. G. H. Miller, P. B. Beaumont, A. J. T. Jull, B. J. Johnson, Philos. Trans. R. Soc. London Ser. B 337, 149 (1992). 11. Epimerization rates exhibit systematic offsets between taxa as a result of differences in the amino acid sequences in the protein each bird uses. D/L ratios measured in Dromaius and Genyornis eggshells from the same stratigraphic horizon indicate that isoleucine epimerizes 1.18 times faster in Dromaius; Dromaius D/L ratios have been adjusted by this amount to allow plots comparing the two taxa (Figs. 3 and 4) on a common scale. 12. G. H. Miller, J. W. Magee, A. J. T. Jull, Nature 385, 241 (1997). 13. Dromaius and Genyornis apparently nested in similar habitats; eggshells of both taxa are commonly found at the same stratigraphic level in many eolian deposits, although Genyornis is usually the dominant taxon. Both are occasionally found as crushed whole or partial eggs, more often as concentrations of eggshell fragments. Eggshells of the two genera can be readily distinguished by characteristic macro- and microstructures (44). 14. J. H. Field and W. E. Boles, Alcheringa 22, 177 (1998). 15. The Genyornis analyzed from MG come from 185 different sites, from LF 28 sites, and from DM 17 sites. Dromaius from MG were collected from 198 sites, from LF 30 sites, and from DM 36 sites. 16. Climate data are mean annual temperature and mean annual precipitation calculated with programs described by McMahon et al. (21). 17. In Fig. 2 and in general discussions we have converted radiocarbon ages to calendar ages using the CALIB 3.0 Program (45) for samples ,10,000 14C yr B.P., and the equation CalibAge 5 25.85 3 1026(Conv14CAge)2 1 1.39(Conv14CAge) 2 1807 (E. Bard, unpublished data based on paired U-series and 14C dates). However, when citing specific dates, we leave these in radiocarbon years because most are at or beyond the limits of radiocarbon dating, for which there is no generally accepted terminology or calibration curve. All luminescence and U-series dates are given in calendar years; the U-series dates have 2s uncertainties of about 2%, whereas the luminescence dates have 1s uncertainties of 10 to 15%. 18. We evaluated the potential of TIMS U-series dating using 20 Genyornis eggshell fragments of known AAR. U-series dates are shown to be reproducible among different fragments from the same unit, despite a wide range in U concentrations, but some samples have enough common thorium (232Th) to require correction for unsupported 230Th. Eggshell has discrete pores that allow the developing embryo to exchange gases with the atmosphere, and in some

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19. 20. 21. 22.

23. 24. 25. 26. 27. 28. 29. 30.

31. 32.

33. 34. 35. 36. 37. 38. 39. 40. 41. 42.

43.

44.

45. 46.

fossil samples these have been infilled with clay, a carrier of thorium. We thus restrict our discussion to samples with 230Th/232Th activity ratios .30. Supplementary material for 14C, TIMS U-series, and OSL data is available at www.sciencemag.org/ feature/data/985798.shl. J. W. Magee, thesis, Australian National University, Canberra (1997). J. P. McMahon, M. F. Hutchinson, H. A. Nix, K. D. Ord, Centre for Resource and Environmental Studies, Australian National University, Canberra (1995). Although the 230Th/232Th activity ratios of these samples are below our preferred threshold, the reproducibility between many samples from a single level with large differences in U concentrations suggests that the ages are reliable. J. W. Magee, J. M. Bowler, G. H. Miller, D. L. G. Williams, Palaeogeogr. Palaeoclimatol. Palaeoecol. 113, 3 (1995). J. M. Bowler, Archaeol. Oceania 33, 120 (1998). R. G. Roberts, R. Jones, M. A. Smith, Nature 345, 153 (1990). R. G. Roberts et al., Quat. Geochronol. 13, 575 (1994). R. L. K. Fullagar, D. M. Price, L. M. Head, Antiquity 70, 751 (1996). N. A. Spooner, ibid. 72, 173 (1998). R. G. Roberts et al., Nature 393, 358 (1998). G. Singh, A. P. Kershaw, R. Clark, in Fire and Australian Biota, A. M. Gill, R. A. Groves, I. R. Noble, Eds. (Australia Academy of Science, Canberra, 1981), pp. 23– 54. A. P. Kershaw, G. M McKenzie, A. McMinn, Proc. Ocean Drilling Prog. Sci. Results 133, 107 (1993). M. M. Trotter and B. McCulloch, in Quaternary Extinctions: A Prehistoric Revolution, P. S. Martin and R. G. Klein, Eds. (Univ. of Arizona Press, Tucson, 1984), pp. 708 –727. M. Smith, G. Miller, G. Van Tets, Rec. S. Aust. Mus. 27, 228 (1994). D. R. Horton, Archaeol. Phys. Anthropol. Oceania 15, 86 (1980). T. F. Flannery, The Future Eaters (Reed Books, Melbourne, 1994). J. L. Kohen, Aboriginal Environmental Impacts (Univ. of New South Wales Press, Sydney, 1995). B. J. Johnson, thesis, University of Colorado (1995). , M. L. Fogel, G. H. Miller, Geochim. Cosmochim. Acta 62, 2451 (1998). P. Murray and D. Megirian, Rec. S. Austr. Mus., in press. A. P. Kershaw, Nature 322, 47 (1986). T. W. J. Stafford, P. E. Hare, L. Currie, A. J. T. Jull, D. Donahue, J. Archaeol. Sci. 189, 35 (1991). A. Baynes, in Taphonomy Symposium 95, Canberra, 28 –29 April 1995 (Department of Anthropology and Archaeology, Australian National University, Canberra, 1995), pp. 12–14. D. J. Meltzer and J. I. Mead, in Environments and Extinctions: Man in Late Glacial North America, J. I. Mead and D. J. Meltzer, Eds. (University of Maine Center for the Study of Early Man., Orono, 1985), pp. 145–173. D. L. G. Williams and P. V. Rich, in Vertebrate Paleontology of Australasia, P. V. Rich, J. M. Monaghan, R. F. Baird, T. H. Rich, Eds. (Pioneer Design Studio, Lilydale, Victoria, Australia, 1992), pp. 871– 891. M. Stuiver and P. Reimer, Radiocarbon 35, 215 (1993). Supported by the U.S. National Science Foundation, Division of Atmospheric Sciences (G.H.M., B.J.J., and M.L.F.), the Australian National University (J.W.M., M.T.M., L.K.A., and G.H.M.), and the University of Colorado Faculty Fellowship Program (G.H.M.). We thank J. Bowler for initiating our study of the Lake Eyre Basin; A. Baynes, J. Chappell, A. Chivas, P. Clark, P. DeDekker, T. Flannery, P. Latz, P. Murray, M. Smith, and S. Webb for discussions; C. Hart for lab assistance; G. Atkin, O. Miller, and M. Miller for field assistance; and the station owners and aboriginal community leaders in our field areas for land access and logistical assistance.

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9 October 1998; accepted 24 November 1998

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Pleistocene Extinction of Genyornis newtoni: Human Impact on Australian Megafauna Gifford H. Miller, John W. Magee, Beverly J. Johnson, Marilyn L. Fogel, Nigel A. Spooner, Malcolm T. McCulloch, and Linda K. Ayliffe

Supplementary Material Table 1.14C Data Table Madigan Gulf region (MG) Genus

D/L

AAL Lab-ID

14

C age

14

C Lab-ID

Dromaius 0.024

7608

Fm:1.160±0.007

AA-20890

Dromaius 0.018

7176

Fm:1.186±0.007

AA-12620

Dromaius 0.042

8236

1145±45

AA-22892

Dromaius 0.074

7117

1405±65

AA-12611

Dromaius 0.122

7130

1565±50

AA-12618

Dromaius 0.067

7828

1620±50

AA-19012

Dromaius 0.107

7130

1725±50

AA-13042

Dromaius 0.102

7122

1770±60

AA-12616

Dromaius 0.248

7118

2985±85

AA-12612

Dromaius 0.209

7479

3585±60

AA-15138

Dromaius 0.233

7190

3730±55

AA-13046

Dromaius 0.218

7129

4420±75

AA-15668

Dromaius 0.430

7512

5600±80

AA-15665

Dromaius 0.360

8119

6010±65

AA-25248

Dromaius 0.337

7128

6175±75

AA-12617

Dromaius 0.352

8111

7240±55

AA-25249

Dromaius 0.314

7120

7525±80

AA-12613

Dromaius 0.335

7511

7725±120

AA-15664

Dromaius 0.342

7355

8175±70

AA-15408

Dromaius 0.342

7355

8510±70

AA-15134

Dromaius 0.278

6914

9475±75

AA-15144

Dromaius 0.284

6914

9520±80

AA-10239

Dromaius 0.384

7452

9635 ± 65

AA-16397

Dromaius 0.407

6878

10,070±90

AA-10234

Dromaius 0.464

8000

10,370±85

AA-20897

Dromaius 0.541

8233

10,620±70

AA-22891

Dromaius 0.510

7931

11,300±85

AA-20894

Dromaius 0.478

7341

11,370±75

AA-14032


Dromaius

0.570 7341

11,390±105

AA-17269

Dromaius

0.500 8144

11,400±70

Dromaius

0.350 8230

11810±110

AA-25257

Dromaius

0.338 7605

11,850±120

AA-17274

Dromaius

0.429 6877

11,875±115

AA-10232

Dromaius

0.375 7214

11,905±90

AA-15141

Dromaius

0.403 8231

12,055±75

AA-25254

Dromaius

0.486 7186

12,220±155

AA-25258

Dromaius

0.468 7930

12,275±150

AA-20887

Dromaius

0.490 8313

12,350±125

AA-25253

Dromaius

0.504 7187

12,425±95

AA-13045

Dromaius

0.381 7951

12,440±90

AA-20893

Dromaius

0.461 7827

12,480±110

AA-19013

Dromaius

0.540 7186

12,555±80

AA-25259

Dromaius

0.246 7219

12,680±125

AA-15145

Dromaius

0.560 7120

13,880±190

AA-12614

Dromaius

0.753 7224

16,490±120

AA-13049

Dromaius

0.541 7344

17,310±125

AA-15135

Dromaius

0.529 7583

18,405±115

AA-22899

Dromaius

0.558 7121

18,450±165

AA-12615

Dromaius

0.502 8268

19,815±190

AA-25251

Dromaius

0.510 8268

19,845±140

AA-25250

Dromaius

0.590 5533

20,230±150

AA-16396

Dromaius

0.559 7803

20,660±265

AA-19005

Dromaius

0.554 8233

20,915±155

AA-22890

Dromaius

0.555 8280

22,520±180

AA-25255

Dromaius

0.597 7514

23,275±325

AA-15666

Dromaius

0.524 8237

23,315±180

AA-22895

Dromaius

0.556 8038

23,430±215

AA-20892

Dromaius

0.556 8157

23,585±190

AA-22905

Dromaius

0.494 8140

23,615±210

AA-22887

Dromaius

0.565 8140

23,720±245

AA-22888

Dromaius

0.541 7123

24,030±245

AA-20896

Dromaius

0.544 7123

24,055±245

AA-13041

Dromaius

0.514 7694

24,835±240

AA-17276

Dromaius

0.539 8000

25,055±280

AA-20881

Dromaius

0.494 8235

25,680±230

AA-22894

Dromaius

0.518 8232

25,705±350

AA-22889

Dromaius

0.510 8260

26,195±245

AA-22893

Dromaius

0.533 7806

26,750±475

AA-19006

Dromaius

0.739 7843

27,345±530

AA-19014

AA-22903


Dromaius

0.515

8280

27,500±290

AA-25256

Dromaius

0.517

8149

27,625±325

AA-23256

Dromaius

0.606

7830

29,440±640

AA-19011

Dromaius

0.545

8417

29,970±380

AA-25316

Dromaius

0.562

7683

30,605±435

AA-17275

Dromaius

0.546

7592

31,720±490

AA-17272

Dromaius

0.549

7137

32,355±570

AA-13044

Dromaius

0.541

8045

32,990±550

AA-20884

Dromaius

0.552

7592

33,035±705

AA-17273

Dromaius

0.584

7137

33,455±580

AA-20889

Dromaius

0.551

8302

34,035±590

AA-25252

Dromaius

0.540

8045

34,600±1900

AA-20885

Dromaius

0.543

8160

34,815±765

AA-22886

Dromaius

0.605

8048

38,760±2320

AA-20886

Dromaius

0.527

8160

39,585±1190

AA-22885

Dromaius

0.569

8285

41,700±1450

AA-25247

Dromaius

0.588

7524

42,600±1650

AA-20891

Dromaius

0.535

8145

42,970±1800

AA-22904

Dromaius

0.596

7513

43,400±1900

AA-01900

Dromaius

0.591

7808

43,500±3800

AA-19007

Dromaius

0.546

8043

>37,240

AA-20883

Dromaius

0.608

6920

>39,700

AA-10237

Dromaius

0.592

7694

41,650

AA-20882

Genyornis 0.460

8161

42,830±880

CAMS-43987

Genyornis 0.460

8161

42,930±720

CAMS-43986

Genyornis 0.460

8161

31,070±450

AA-25239

Genyornis 0.471

8161

>37,000

AA-25240

Genyornis 0.483

7517

34,275±715

AA-16398

Genyornis 0.489

7136

39,740±1400

AA-13043

Genyornis 0.493

7516

34,800±755

AA-15667

Genyornis 0.494

8284

39,285±1200

AA-25242

Genyornis 0.496

7519

35,130±830

AA-25245

Genyornis 0.504

7518

41,300±1500

AA-25244

Genyornis 0.549

7525

45,440±1200

CAMS-43988

Genyornis 0.549

7525

36,700±960

AA-17271

Genyornis 0.550

5534

40,740±2100

AA-04248

Genyornis 0.588

7615

37,700±930

AA-25243

Genyornis 0.588

7615

38,500±1200

AA-25243

Genyornis 0.590

6875

39,500±1100

AA-25246

Genyornis 0.594

8141

41,100±1400

AA-25241


Lake Frome region (LF) Genus

D/L

AAL Lab-ID

Dromaius

0.034

5531

455±50

AA-04247

Dromaius

0.115

5530

2025±60

AA-04246

Dromaius

0.260

7942

6490±70

AA-19692

Dromaius

0.427

7943

6575±80

AA-19688

Dromaius

0.364

7943

7000±75

AA-19694

Dromaius

0.369

6889

10,790±105

AA-10236

Dromaius

0.449

7811

14,545±100

AA-19008

Dromaius

0.450

7936

19,780±190

AA-19693

Dromaius

0.507

6894

23,005±200

AA-15407

14

C age

14

C Lab-ID

Darling-Murray Rivers confluence (DM) Genus

D/L

AAL Lab-ID

Dromaius

0.023

6807

Fm:1.2663

AA-19015

Dromaius

0.232

7509

11,160±115

AA-15671

Dromaius

0.288

7197

13,045±85

AA-13047

Dromaius

0.204

8326

13,680±100

AA-25260

Dromaius

0.272

6919

13,835±110

AA-10240

Dromaius

0.307

6806

17170±130

AA-25262

Dromaius

0.24

6755

17,995±205

AA-08722

Dromaius

0.254

6755

18,050±240

AA-08725

Dromaius

0.309

6750

19,255±200

AA-08721

Dromaius

0.321

6779

21,140±190

CAMS-1929

Dromaius

0.347

7508

21,360±235

AA-15670

Dromaius

0.319

5604

37,600±1000

AA-04251

Dromaius

0.346

5608

38,100±1100

AA-04252

Dromaius

0.350

8318

40,520±1280

AA-25261

Dromaius

0.376

6887

42,100±1700

AA-10235

Dromaius

0.358

6761

>45,100

AA-08723

Genyornis 0.348

5609

42,600±1900

AA-04253

Genyornis 0.396

7200

>44,400

AA-13048

14

C age

14

C Lab-ID


Table 2. TIMS U-series data Table. TIMS U-series data 230

D/L Uppm

Th/232Th activity

230

Th/238U activity

234

U

Age (ka)

Age (ka) before correction for unsupported Th

Sample

Locality

1A

Bullysandhill

0.91

0.29

120.0

0.72696

199.18 97.9±1.2

1E

Bullysandhill

0.92

5.48

1360.0

0.67553

190.25 88.6±1.1

2D

Williams Point

0.5

0.15

31.9

0.56906

236.00 65.6±1.6

3B

Kutjitara West Bluff

0.6

0.08

43.14

0.59395

235.00 69.6±0.8

7E

Eric Island

0.57

0.12

31.43

0.45507

257.48 48.0±0.4

A1*

Perry Sand Hills

0.34

0.23

18.35

0.50340

203.00

56±2

58.0±1.1

A2-a*

Perry Sand Hills

0.34

0.75

2.52

0.61340

287.00

52±2

68.5±2.6

A2-b*

Perry Sand Hills

0.34

0.90

2.23

0.61320

266.00

51±15

70.1±5.2

A2-c*

Perry Sand Hills

0.34

0.91

3.95

0.53000

264.00

50±8

57.9±4.3

A2-d*

Perry Sand Hills

0.34

0.74

3.15

0.57990

187.00

58±9

71.4±2.1

All samples are eggshell of Genyornis newtoni; samples 1, 2, 3, and 7 are from the Madigan Gulf Region, whereas samples A1 and A2 are from the Perry Sand Hills at the confluence of the Darling and Murray rivers. Errors given are ±2 sigma. *Samples A2 (a-d) are from different fragments of the same egg; Sample A1 is from a different egg at the same stratigraphic level.

Table 3.OSL Data Table. OSL Data Palaeodose (Gy)

Dose rate (Gy/ka)

Age (ka)

D/L

WM Pt 11

84.9 ± 4.2

1.348 ± 0.077

63.0 ± 4.7

0.57

WmPt 13

64.8 ± 3.4

1.319 ± 0.075

49.1 ± 3.8

0.49

LDom 8

94.6 ± 5.4

0.832 ± 0.037 113.7 ± 8.3 1.00

Dul 1

31.1 ± 1.4

0.658 ± 0.043

47.3 ± 3.8

0.50

TBM 92/1 1

63.2 ± 4.2

0.750 ± 0.045

84.3 ± 7.6

0.81

TBM 92/1 2

58.2 ± 5.1

0.755 ± 0.039

77.1 ± 7.9

0.81

M95 TL2

121.0 ± 6.3

1.043 ± 0.038 116.0 ± 7.4 0.98

M95 TL5

30.4 ± 1.7

0.691 ± 0.042

Sample

44.0 ± 5.1

0.51

OSL DataTable. Optically-stimulated luminescence (OSL) dates on quartz sand from Magee (1997) that were used to calibrate the D/L-age relationship for the Madigan Gulf region of the Lake Eyre Basin, Australia. D/L is the proportion of D-alloisoleucine to L-isoleucine in eggshell from the same or correlative deposits of Genyornis or Dromaius (converted to equivalent Genyornis ratios). Uncertainty is one sigma.


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