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Selective hunting of juveniles as a cause of the imperceptible overkill of the Australian Pleistocene 'megafauna'

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Abstract

Overkill by human hunting has been consistently cited as a likely cause of the Pleistocene megafaunal extinctions in Australia, but little archaeological evidence has been found to support the notion of prehistoric Aboriginal people engaging in specialized "big game" hunting more than 40 millennia ago. Here we develop a demographic population model that considers explicitly the possibility of the selective harvest of small, immature (and presumably more vulnerable) individuals of the largest known marsupial, Diprotodon optatum. We show that remarkably low levels of exploitation of juveniles (the equivalent of one or two kills per 10 people per year) would have been sufficient to drive these large species to extinction within centuries, due to their slow life-histories. This conclusion is robust to assumptions regarding the compensatory response of the prey species and declines in the relative efficiency of hunting as the megafaunal populations declined. These findings dispel the idea that evidence of a sophisticated hunting toolkit and massive kill-sites are a necessary adjunct to "blitzkrieg". Ironically, although the extinction event was likely geochronologically instantaneous (given the coarse resolution of dating from that time), on the scale of human (and megafaunal) lifetimes, the unfolding overkill would have been all but imperceptible.
... Young proboscidean remains are rare at South American butchering sites (Fiedel, 2000;Waters et al., 2011;Sanchez et al., 2014). However, hunting vulnerable individuals, such as calves, would not demand a sophisticated toolkit (Brook and Johnson, 2006). None of the Lagoa Santa artifact industry, represented by perforators, spatulas and fishhooks, usually made of wood, bones, stone, or antlers (Prous et al., 1998;Prous, 2009;Araujo et al., 2012), is recognized as typical big-game hunting technology/industry, such as large spears or traps (Waguespack and Surovell, 2003;Waters et al., 2011). ...
... Supplementary data related to this article can be found at https://doi.org/10.1016/j.quascirev.2019.106125. Brook and Johnson (2006) estimated for the Australian Quaternary that exploitation of juvenile individuals of large species, even at low levels (such as one or two kills per 10 people per year) would have been sufficient to drive those species to extinction within a few centuries (i.e., a short temporal span in the Pleistocene/Holocene transition, possibly without enough time to build a well-delineated fossil record; see Mithen, 1993;Nogu es-Bravo et al., 2008). Similarly, humans were present in the Lagoa Santa region during the Pleistocene/Holocene transition, a period long enough to impact d perhaps permanently d the local population of Notiomastodon platensis. ...
Article
The drivers of the global Quaternary megafaunal extinction are constantly being updated and discussed. Most paleoarchaeological sites in South America with proboscideans and humans in association are considered as clear killing sites, an interpretation that might not consider their taphonomic aspects and neglect other ecological interactions. Here we describe a unique example of megafaunal killing by humans in South American, a skull of a young Notiomastodon platensis from Brazil with an artifact embedded in its rostral area. This fossil proboscidean is from Lagoa Santa Karst, the homeland of some of the oldest evidence for humans in South America, the Lagoa Santa culture. The late Pleistocene/early Holocene deposits from Lagoa Santa may record a bottleneck ecological process for megafaunal populations, and the hunting activity of past humans perhaps played an important role in Notiomastodon platensis extinction.
... both, and the changes in Ca isotope composition can be assessed that occur in both the female and her 420 young simultaneously during the nursing and weaning period. Defining the exact offset of the Ca isotope 421 composition of juveniles consuming milk compared to that of the breastfeeding female, not only will 422 provide insight into the nursing and weaning behaviour in wombats, but also aid the reconstruction of such 423 life history changes in extinct fauna, and allow the testing of hypotheses regarding overkill by selective 424 hunting of juveniles (Brook and Johnson, 2006). 425 ...
Article
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.
... Shorter overlap ages are usually used to argue that people played a significant role in the megafauna's disappearance. People allegedly overhunted megafauna, causing population collapse (Brook and Johnson, 2006;Flannery, 1994), or exerted pressure via habitat modification such as increased landscape burning (Bird et al., 2013). ...
Article
Understanding of Late Pleistocene megafaunal extinctions in Australia and New Guinea (Sahul) suffers from a paucity of reliably dated bone deposits. Researchers are divided as to when, and why, large-bodied species became extinct. Critical to these interpretations are so-called ‘late survivors’, megafauna that are thought to have persisted for tens of thousands of years after the arrival of people. While the original dating of most sites with purported late survivors has been shown to have been erroneous or problematic, one site continues to feature: Cloggs Cave. Here we report new results that show that Cloggs Cave’s youngest megafauna were deposited in sediments that date to 44,500–54,160 years ago, more than 10,000 years older than previously thought, bringing them into chronological alignment with the emerging continental pattern of megafaunal extinctions. Our results indicate that the youngest megafauna specimens excavated from Cloggs Cave datedate to well before the Last Glacial Maximum (LGM), and their demise could not have been driven by climate change leading into the LGM, the peak of the last Ice Age.
... A role for people in the extinction of Sahul megafauna through their direct extirpation has been previously proposed. However, with no evidence of butchery or kill sites, it has been proposed that extinction occurred rapidly across Sahul shortly after human arrival [12][13][14]22,[52][53][54][55] . In the absence of evidence for direct extirpation, indirect human-mediated factors such as landscape burning have been proposed but are difficult to differentiate from non-human factors 15,16,21,56,57 . ...
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Explanations for the Upper Pleistocene extinction of megafauna from Sahul (Australia and New Guinea) remain unresolved. Extinction hypotheses have advanced climate or human-driven scenarios, in spite of over three quarters of Sahul lacking reliable biogeographic or chronologic data. Here we present new megafauna from north-eastern Australia that suffered extinction sometime after 40,100 (±1700) years ago. Megafauna fossils preserved alongside leaves, seeds, pollen and insects, indicate a sclerophyllous forest with heathy understorey that was home to aquatic and terrestrial carnivorous reptiles and megaherbivores, including the world’s largest kangaroo. Megafauna species diversity is greater compared to southern sites of similar age, which is contrary to expectations if extinctions followed proposed migration routes for people across Sahul. Our results do not support rapid or synchronous human-mediated continental-wide extinction, or the proposed timing of peak extinction events. Instead, megafauna extinctions coincide with regionally staggered spatio-temporal deterioration in hydroclimate coupled with sustained environmental change. The causes of the Upper Pleistocene megafauna extinction in Australia and New Guinea are debated, but fossil data are lacking for much of this region. Here, Hocknull and colleagues report a new, diverse megafauna assemblage from north-eastern Australia that persisted until ~40,000 years ago.
... In ecological terms, humans have burned savannah and prairie alike in order to ensure constant and renewed grazing by large herbivores to make for easier hunting. Particularly vulnerable megafauna (e.g. on islands, flightless birds, slow reproducing) have been hunted to extinction by humans (Stuart, 1991;Holdaway and Jacomb, 2000;Brook and Johnson, 2006). Humans are ecological mega-disruptors on an order of magnitude comparable to natural catastrophes (Zalasiewicz, 2010;and Revkin, 2011) with no abating in sight. ...
Conference Paper
Ecological Panarchy, as described by Gunderson et al, (1995), Holling et al, (2002a), and Holling et al, (2002b), builds up on and extends traditional frameworks for understanding ecological dynamics. It adds to phenology a more realistic emphasis on processes of destruction and organization in addition to the traditional ecological foci on growth and conservation. Their framework adds two additional functions, release and reorganization. Ecological Panarchy, as described by Gunderson et al, (1995), Holling et al, (2002a), and Holling et al, (2002b), builds up on and extends traditional frameworks for understanding ecological dynamics. It adds to phenology a more realistic emphasis on processes of destruction and organization in addition to the traditional ecological foci on growth and conservation. Their framework adds two additional functions, release and reorganization. Ecological Panarchy is theoretically malleable and can be applied to questions in economics and sociology, to name just two areas, while focusing on problems of resilience and sustainability. Likewise, it is here proposed that this framework might be useful in understanding psycho-ecological systems. Specifically, “a sense of place,” defined both in personal and historical terms, might be understood as a phenology in and of the psyche with respect to changing environmental occurrences and circumstances. Key Terms: Panarchy, ecopsychology, phenology, psycho-phenology
... In ecological terms, humans have burned savannah and prairie alike in order to ensure constant and renewed grazing by large herbivores to make for easier hunting. Particularly vulnerable megafauna (e.g. on islands, flightless birds, slow reproducing) have been hunted to extinction by humans (Stuart, 1991;Holdaway and Jacomb, 2000;Brook and Johnson, 2006;Metcalf, et al, 2016). Humans are ecological mega-disruptors on an order comparable to natural catastrophes (Zalasiewicz, 2010;and Revkin, 2011) with no abating in sight. ...
Book
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Ecopsychology Revisited is a critique of and deconstructive approach to several trends termed “ecopsychology.” This work attempts to bring light to some of the misconceptions that have hardened as “ecopsychology,” as these ideas have been reinterpreted and sometimes oversimplified by the general public and some professionals outside mainstream psychology. Part of the confusion arose when “ecopsychology” became inadequately amalgamated with other ideas. Nevertheless, within the social and behavioral sciences, at least, there is great value in devising and applying evidence-based strategies that track the normative ramifications dealing with cognition, emotion and behavior, exploring how or why humans relate to natural processes in a wide range of ways.
... Although the extinction of mammalian taxa is documented throughout the Cenozoic fossil record, the rapid and large global species losses without functional replacements at the end of the Pleistocene are unusual. Identifying the drivers of the global extinctions of these megafauna (animals with average weights N 44 kg) remains controversial (Barnosky, 2008), with climate fluctuations (Wroe and Field, 2006;Webb, 2008;Wroe et al., 2013;Cooper et al., 2015), human impact through hunting (Brook and Johnson, 2006;Johnson, 2006;Brook et al., 2007), habitat alteration , and/or a synergistic combination of climate and humans (Miller et al., 2005;Metcalf et al., 2016;Saltre´et al., 2016), the commonly cited causes. Currently about 60% of the large extant herbivorous animals are now threatened with possible extinction (Ripple et al., 2015). ...
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... Yet cutmarking is very scarce or absent on megafaunal bone in those sites and when it appears around 1200 y ago it is confined to bone from small extant taxa. This observation, together with the virtual absence of megafaunal bones in southwestern settlement sites [29]; and in middens dating 1400-1000 y B.P. [47], suggests that the role of human predation in regional extirpation of megafauna did not exceed "imperceptible overkill" [48], reflecting the vulnerability of generally conservative (K-selected), megafaunal life histories to modest increases in death rates by continual low-level hunting that left few traces in the sedimentary record. The youngest megafaunal dates~1350-1000 cal B.P. at all three sites, in our data (Table G in S1 File), are consistent with the youngest ages on four genera of extinct lemur, 1460-1010 y B.P. [28], and semiquantitative evidence of plummeting population decline in large megafauna around 1000 y B. P. [26] in the southwestern region. ...
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One Pleistocene mystery is why early North Americans eradicated their large, potentially domesticable animals (e.g., horses), whereas early Europeans did not. A commonly-held hypothesis is that European species were evasive due to co-evolution with hominids, whereas North American animals were naÔve and unable to adapt quickly enough when experienced human hunters arrived from Eurasia. We explore this hypothesis with a paleoeconomic model of co-evolution that integrates human hunting investments and wildlife population responses. We find that investments in hunting ability, based on the relative scarcity of prey species, could have mattered more than wildlife 'naivety' in explaining the extinction. Copyright (c) Scottish Economic Society 2003,.