Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Theoretical ecology wikipedia , lookup
Biodiversity wikipedia , lookup
Island restoration wikipedia , lookup
Overexploitation wikipedia , lookup
Assisted colonization wikipedia , lookup
Decline in amphibian populations wikipedia , lookup
Great American Interchange wikipedia , lookup
Habitat conservation wikipedia , lookup
Extinction debt wikipedia , lookup
Pleistocene Park wikipedia , lookup
Anthropocene 4 (2013) 14–23 Contents lists available at ScienceDirect Anthropocene journal homepage: www.elsevier.com/locate/ancene Human acceleration of animal and plant extinctions: A Late Pleistocene, Holocene, and Anthropocene continuum Todd J. Braje a,*, Jon M. Erlandson b a b San Diego State University, Department of Anthropology, San Diego, CA 92182-6040, United States Museum of Natural and Cultural History and Department of Anthropology, University of Oregon, Eugene, OR 97403-1224, United States A R T I C L E I N F O A B S T R A C T Article history: Received 6 May 2013 Received in revised form 6 August 2013 Accepted 9 August 2013 Available online 18 August 2013 One of the most enduring and stirring debates in archeology revolves around the role humans played in the extinction of large terrestrial mammals (megafauna) and other animals near the end of the Pleistocene. Rather than seeking a prime driver (e.g., climate change, human hunting, disease, or other causes) for Pleistocene extinctions, we focus on the process of human geographic expansion and accelerating technological developments over the last 50,000 years, changes that initiated an essentially continuous cascade of ecological changes and transformations of regional floral and faunal communities. Human hunting, population growth, economic intensification, domestication and translocation of plants and animals, and landscape burning and deforestation, all contributed to a growing human domination of earth’s continental and oceanic ecosystems. We explore the deep history of anthropogenic extinctions, trace the accelerating loss of biodiversity around the globe, and argue that Late Pleistocene and Holocene extinctions can be seen as part of a single complex continuum increasingly driven by anthropogenic factors that continue today. ß 2013 Elsevier Ltd. All rights reserved. Keywords: Extinction Megafauna Anthropocene Sixth mass extinction 1. Introduction For many geologists and climate scientists, earth’s fossil record reads like a soap opera in five parts. The episodes played out over the last 450 million years and the storylines are divided by five mass extinction events, biotic crises when at least half the planet’s macroscopic plants and animals disappeared. Geologists have used these mass extinctions to mark transitions to new geologic epochs (Table 1), and they are often called the ‘‘Big Five’’ extinctions. When these extinctions were first identified, they seemed to be outliers within an overall trend of decreasing extinctions and origination rates over the last 542 million years, the Phanerozoic Eon (Gilinsky, 1994; Raup, 1986; Raup and Sepkoski, 1982). More recent metaanalyses of large web-based paleontological databases (i.e., Alroy, 2000, 2008), however, have called into question whether all of these mass extinctions are truly outliers and substantially different from the continuum of extinctions that have been on-going for hundreds of millions of years. Multiple mass extinctions have occurred over the course of earth’s history, but they are relatively rare, poorly defined, and often played out over millions of years. The one exception is the * Corresponding author. Tel.: +1 415 734 8396; fax: +1 619 594 1150. E-mail addresses: [email protected] (T.J. Braje), [email protected] (J.M. Erlandson). 2213-3054/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ancene.2013.08.003 Cretaceous-Paleogene extinction event (a.k.a. the K-T boundary event), when 76% of the world’s species went extinct within a few millennia (Renne et al., 2013). Most scientists implicate a large asteroid impact ca. 65.5 mya as the prime driver for this mass extinction, characterized by the disappearance of non-avian dinosaurs and the dawn of the age of mammals. The Big Five concept has become such an engrained part of the geologic and other sciences that some scholars use the term ‘‘sixth extinction’’ to characterize the current crisis of earth’s biological resources (e.g., Barnosky et al., 2011; Ceballos et al., 2010; Glavin, 2007; Leakey and Lewin, 1995). Long before the formal proposal to define a new Anthropocene Epoch (Zalasiewicz et al., 2008), a variety of scientists identified post-industrial humans as the driving force behind the current and on-going mass extinction (e.g., Glavin, 2007; Leakey and Lewin, 1995). Clearly we are currently living through a mass extinction event. Calculations suggest that the current rates of extinction are 100–1000 times natural background levels (Vitousek et al., 1997b:498; Wilson, 2002). Some biologists predict that the sixth extinction may result in a 50% loss of the remaining plants and animals on earth, which might trigger the collapse of some ecosystems, the loss of food economies, the disappearance of medicinal and other resources, and the disruption of important cultural landscapes. The driving force of this biotic crisis can be directly tied to humans, and their propensity for unchecked population growth, pollution, overharvesting, habitat alteration, and translocation of invasive species T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 15 Table 1 General characteristics of the ‘‘Big Five’’ extinction events as identified by Raup and Sepkoski (1982) from the fossil record.a Mass extinction Age mya % Families % Genera % Species Ordovician-Silurian 450–440 27 57 86 Late Devonian 375–360 19 35 75 Permian-Triassic 252 57 56 96 Triassic-Jurassic 200 23 47 80 17 40 76 Cretaceous-Paleogene a 65.5 Extinctions Characteristics Two extinction pulses, about 1 million years apart. Likely resulted from glacial, interglacial cycles, marine transgressions and regressions, uplift and weathering of Appalachians causing atmospheric and ocean chemistry changes, and CO2 sequestration. Likely marked by several extinctions over 3 million years, the cause is unclear but may include global cooling, spread of anoxic waters, oceanic volcanism, or an extraterrestrial impact. The most severe extinction event that occurred over 1–3 pulses. The earliest pulse was likely the result of gradual environmental change but later pulses may have been triggered by an impact, volcanism, the Siberian Traps, or sea floor methane release. Occurred quickly, in less than 10ky, and allowed dinosaurs to flourish. May have been triggered by gradual climate change, sea-level changes, ocean acidification, an impact, or volcanism. Marked by the extinction of the non-avian dinosaurs and the beginning of the age of mammals. Most scientists point to an asteroid impact as the cause and the extinctions may have occurred over several thousand years. See Barnosky et al. (2011). (Vitousek et al., 1997a,b)—changes Smith and Zeder (2013; also see Smith, 2007) refer to as human niche construction. If we are living during the next great biotic crisis and it is directly tied to human agency, the question becomes when did this mass extinction process begin? Even those who have proposed to formally designate an Anthropocene Epoch beginning at the dawn of the Industrial Revolution (ca. AD 1800) or the nuclear era of the 1960s (e.g. Crutzen, 2002; Steffen et al., 2007, 2011; Zalasiewicz et al., 2008) acknowledge the evidence for widespread impacts of pre-industrial humans in archeological and historical records. They recognize a wide range of ‘‘pre-Anthropocene Events,’’ including the acceleration of plant and animal extinctions associated with human colonization of new landscapes (Steffen et al., 2007). In their view, however, these impacts are seen as much different in scale than those that come later: Preindustrial societies could and did modify coastal and terrestrial ecosystems but they did not have the numbers, social and economic organisation, or technologies needed to equal or dominate the great forces of Nature in magnitude or rate. Their impacts remained largely local and transitory, well within the bounds of the natural variability of the environment (Steffen et al., 2007:615; also see Steffen et al., 2011:846–847). Here, we review archeological and paleoecological evidence for rapid and widespread faunal extinctions after the initial colonization of continental and island landscapes. While the timing and precise mechanisms of extinction (e.g., coincident climate change, overharvesting, invasive species, habitat disruption, disease, or extraterrestrial impact) still are debated (Haynes, 2009), the global pattern of first human arrival followed by biotic extinctions, that accelerate through time, places humans as a contributing agent to extinction for at least 50,000 years. From the late Pleistocene to the Holocene, moreover, we argue that human contributions to such extinctions and ecological change have continued to accelerate. More than simply the naming of geologic epochs, defining the level of human involvement in ancient extinctions may have widespread ethical implications for the present and future of conservation biology and restoration ecology (Donlan et al., 2005; Wolverton, 2010). A growing number of scientists and resource managers accept the premise that humans caused or significantly contributed to late Quaternary extinctions and, we have the moral imperative to restore and rebalance these ecosystems by introducing species closely related to those that became extinct. Experiments are already underway in ‘‘Pleistocene parks’’ in New Zealand, the Netherlands, Saudi Arabia, Latvia, and the Russian Far East (Marris, 2009), and scientists are debating the merits of rewilding North America with Old World analog species (Caro, 2007; Oliveira-Santos and Fernandez, 2010; Rubenstein et al., 2006). 2. Continental-scale megafaunal extinctions One enduring debate in archeology revolves around the role of anatomically modern humans (AMH, a.k.a. Homo sapiens) in the extinction of large continental, terrestrial mammals (megafauna). As AMH populations spread from their evolutionary homeland in Africa between about 70,000 and 50,000 years ago (Klein, 2008), worldwide megafauna began a catastrophic decline, with about 90 of 150 genera (Koch and Barnosky, 2006:216) going extinct by 10,000 cal BP (calendar years before present). A variety of scientists have weighed in on the possible cause(s) of this extinction, citing natural climate and habitat change, human hunting, disease, or a combination of these (Table 2). These extinctions may constitute the earliest human-induced biotic crisis in earth’s history, with continental extinctions of megafauna (traditionally defined as animals weighing more than 44 kg) affecting Australia, North and South America, and Europe during the late Quaternary. In Northern Eurasia and Beringia (including Siberia and Alaska), 9 genera (35%) of megafauna (Table 3) went extinct in two pulses (Koch and Barnosky, 2006:219). Warm weather adapted megafauna such as straight-tusked elephants, hippos, hemionid horses, and short-faced bears went extinct between 48,000 and 23,000 cal BP and cold-adapted megafauna such as mammoths went extinct between 14,000 and 11,500 cal BP. In central North America, approximately 34 genera (72%) of large mammals went extinct between about 13,000 and 10,500 years ago, including mammoths, mastodons, giant ground sloths, horses, tapirs, camels, bears, saber-tooth cats, and a variety of other animals (Alroy, 1999; Grayson, 1991, 2007). Large mammals were most heavily affected, but some small mammals, including a skunk and rabbit, also went extinct. South America lost an even larger number and percentage, with 50 megafauna genera (83%) becoming extinct at about the same time. In Australia, some 21 genera (83%) of large marsupials, birds, and reptiles went extinct (Flannery and Roberts, 1999) approximately 46,000 years ago, including giant kangaroos, wombats, and snakes (Roberts et al., 2001). In the Americas, Eurasia, and Australia, the larger bodied animals with slow reproductive rates were especially prone to extinction (Burney and Flannery, 2005:395; Lyons et al., 2004), a T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 16 Table 2 Summary of the major hypotheses proposed to explain Pleistocene megafaunal extinctions around the world. Hypothesis Climate driven Climate change Drought Human induced Overkill Fire Other Disease Ecological re-organization ET impact Human-climate dynamics Multivariant Details References Megafaunal and other animals were unable to adapt to changes in climate and vegetation communities at the Pleistocene–Holocene transition Rapidly increasing aridity, combined with human hunting, results in North American megafaunal extinctions Graham and Grimm (1990) and Guthrie (1984) Colonizing aboriginal humans rapidly overhunt ecologically naı̈ve megafauna Landscape burning by colonizing humans caused ecological changes and megamarsupial extinctions in Australia Alroy (2001) and Martin (1984) Infectious disease brought by colonizing humans rapidly affects many megafaunal taxa Loss of megaherbivores, which helped create and maintain savannahs, triggered ecological changes and increased fire fuel loads An extraterrestrial impact event triggered biomass burning and food shortages that resulted in the North American extinctions MacPhee and Marx (1997) Human hunting, anthropogenic ecosystems alterations, and natural climatic/vegetation changes results in increased fire, landscape transformation, and megafaunal extinctions Haynes (1991) Miller et al. (2005) Gill et al. (2009), Grayson (1984) and Owen-Smith (1988) Firestone et al. (2007) Barnosky et al. (2004), Burney and Flannery (2005) and Doughtry et al. (2010) Table 3 Summary table of mammalian megafauna extinctions.a Mass extinction Initial colonization of AMH (cal BP) Major extinction interval (cal BP) # Genera Extinct Extinct but surviving elsewhere Holocene survivors % Extinct Australia Eurasia 50,000 5000 60,000–45,000 14 4 – 5 2 17 88 35 North America South America 14,500 5000 14,500 5000 80,000–46,000 48,000–23,000, 14,000–11,500 13,000–10,500 13,000–10,500 28 48 6 2 13 10 72 83 a Adapted from Koch and Barnosky (2006:Table 2). pattern that seems to be unique to late Pleistocene extinctions. According to statistical analyses by Alroy (1999), this late Quaternary extinction episode is more selective for large-bodied animals than any other extinction interval in the last 65 million years. Current evidence suggests that the initial human colonization of Australia and the Americas at about 50,000 and 15,000 years ago, respectively, and the appearance of AMH in Northern Eurasia beginning about 50,000 years ago coincided with the extinction of these animals, although the influence of humans is still debated (e.g., Brook and Bowman, 2002, 2004; Grayson, 2001; Roberts et al., 2001; Surovell et al., 2005; Wroe et al., 2004). 2.1. The climate model Many scholars have implicated climate change as the prime mover in megafaunal extinctions (see Wroe et al., 2006). There are a number of variations on the climate change theme, but the most popular implicates rapid changes in climate and vegetation communities as the prime driver of extinctions (Grayson, 2007; Guthrie, 1984; Owen-Smith, 1988). Extinctions, then, are seen as the result of habitat loss (King and Saunders, 1984), reduced carrying capacity for herbivores (Guthrie, 1984), increased patchiness and resource fragmentation (MacArthur and Pianka, 1966), or disruptions in the co-evolutionary balance between plants, herbivores, and carnivores (Graham and Lundelius, 1984). In Australia, extinctions have been linked to a stepwise progression of aridification over the last 300,000–400,000 years (Field et al., 2002; Kershaw et al., 2003; Wroe et al., 2004). Climate change proponents argue that only a small number of extinct megafauna have been demonstrated to overlap with humans and that the bulk of extinctions occurred prior to human arrival, questioning Roberts et al.’s (2001) terminal extinction date (Field et al., 2008). In the Americas and Eurasia, warming at the end of the Last Glacial Maximum (LGM, ca. 18,000 years ago) resulted in rapid changes to climate and vegetation communities during the Pleistocene– Holocene transition, creating a set of environmental changes to which megafauna were unable to adapt (Graham and Grimm, 1990; Guthrie, 2003, 2006). Extinctions in the New World may have been further affected by the onset of the Younger Dryas, a 1000-year cooling event, which exacerbated shifts in vegetation communities. Much of the climate change model hinges on dietary assumptions about Pleistocene herbivores, and to some degree, carnivores. A variety of new studies are testing these assumptions using genetic (mtDNA), morphologic, and isotopic (d 13C and d 15N) data. North American proboscideans (e.g., mammoths, mastodons) and camelids had very different and specialized diets that may have made them vulnerable to rapid climate change and vegetation shifts, for example, but carbon isotope studies of tooth enamel suggest that C4 grasslands that supported large herbivores generally remained intact during glacial to interglacial transitions (Connin et al., 1998; Koch et al., 1994, 1998, 2004). Patterns of specialization have also been found with North American carnivore species. The species with the greatest extinction vulnerability tended to be the largest and most carnivorous of their families (e.g., dire wolves, saber-tooth cats, short-faced bears). The smaller, more generalized species (e.g., gray wolves, puma and bobcats, and black and brown bears) survived into the T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 Holocene (Leonard et al., 2007; Van Valkenburgh and Hertel, 1993). Other studies of environmental changes across the Pleistocene– Holocene transition have suggested that climate change is not a sufficient explanation for megafaunal extinctions. Martı́nez-Meyer et al. (2004) found, for example, that the reduction of habitable niches for eight megafauna taxa in North America is insufficient to explain their extinction. Pollen records further show that megafaunal extinctions in Eurasia and the Americas coincided with rapid vegetational shifts, but the link between vegetation changes and extinctions in Australia is much less clear (Barnosky et al., 2004). Although comprehensive studies are needed, current pollen records also suggest that Pleistocene–Holocene changes in vegetation were not substantially different from previous glacial– interglacial cycles (Koch and Barnosky, 2006:225–226; also see Robinson et al., 2005). There also is evidence for the Holocene survival of now extinct megafauna in locations that were free from intensive human predation. Wooly mammoths survived on Wrangel Island off northeast Siberia until about 3700 years ago (Stuart et al., 2004; Vartanyan et al., 2008) and on Alaska’s Pribilof Islands until 5000 years ago (Yesner et al., 2005). These animals survived the dramatic climate and vegetation changes of the Pleistocene–Holocene transition, in some cases on relatively small islands that saw dramatic environmental change. Climate change proponents suggest, however, that these cases represent refugia populations in favorable habitats in the far north. Ultimately, additional data on vegetation shifts (studies from pollen and macrofloral evidence) across the Pleistocene–Holocene boundary, including investigation of seasonality patterns and climate fluctuations at decadal to century scales, will be important for continued evaluation of climate change models. 2.2. The human overhunting model The human overhunting model implicates humans as the primary driver of megafaunal extinctions in the late Quaternary. Hunting, however, does not have to be the principal cause of megafauna deaths and humans do not necessarily have to be specialized, big game hunters. Rather, human hunting and anthropogenic ecological changes add a critical number of megafauna deaths, where death rates begin to exceed birth rates. Extinction, then, can be rapid or slow depending on the forcing of human hunting (Koch and Barnosky, 2006:231). The human overhunting model was popularized by Martin (1966, 1967, 1973, 2005) with his blitzkrieg model for extinction in the Americas. Martin argued that initial human colonization of the New World by Clovis peoples, big game hunting specialists who swept across the Bering Land Bridge and down the Ice Free Corridor 13,500 years ago, resulted in megafaunal extinctions within 500– 1000 years as humans spread like a deadly wave from north to south. Similarly, the initial human colonization of Australia instigated a wave of extinctions from human hunting some 50,000 years ago. According to Martin (1973), this blitzkrieg was rapid and effective in the Americas and Australia because these large terrestrial animals were ecologically naı̈ve and lacked the behavioral and evolutionary adaptations to avoid intelligent and technologically sophisticated human predators (Martin, 1973). Extinctions in Africa and Eurasia were much less pronounced because megafauna and human hunting had co-evolved (Martin, 1966). Elsewhere, Martin (1973) reasoned that since the interaction between humans and megafauna was relatively brief, very few archeological kill sites recording these events were created or preserved. Much of the supporting evidence for the overkill model is predicated on computer simulation, mathematical, and foraging models (e.g., Alroy, 2001; Brook and Bowman, 2004; Mosimann and Martin, 1975). These suggest a rapid, selective extinction of 17 megafauna was possible in the Americas and Australia at first human colonization. Questions remain about these models, as some simulations that make relatively small adjustments to the model assumptions (i.e., changes to human–prey population dynamics, human population densities, or other input parameters) do not support the overkill model (see Belovsky, 1998; Choquenot and Bowman, 1998). Given that these models disagree in their outcomes and can only provide insights into the relative plausibility of the overkill model, the strongest evidence for overkill comes from the timing of megafaunal extinctions and human colonization. In the Americas, the major megafauna extinction interval coincides with the late Pleistocene arrival of humans about 15,000 years ago (Dillehay, 2000; Meltzer, 2009; Meltzer et al., 1997). Most of the megafauna were lost by 10,500 years ago or earlier, generally coincident with the regionalization of Paleoindian projectile points, often interpreted as megafauna hunting technologies, in North America. Similarities are seen in Australia with first human colonization at about 50,000 years ago and the extinction of the continental megafauna within 4000 years on the mainland (Gillespie, 2008; Roberts et al., 2001) and slightly later on Tasmania (Turney et al., 2008). The association of megafauna extinctions and human arrival in Eurasia is more difficult to demonstrate. Hominins (e.g., Homo erectus, H. heidelbergensis, H. neandertalensis) were present in large parts of Eurasia for roughly two million years, so Eurasian mammals should have co-evolved with hominins in a fashion similar to Martin’s African model. With the first AMH arriving in various parts of Eurasia between about 60,000 and 50,000 years ago, apparently with more sophisticated brains and technologies, AMH may have sparked the first wave of megafaunal extinctions at 48,000 years ago (Barnosky et al., 2004). Overkill opponents argue that the small number of documented megafauna kill sites in the Americas and Australia provides no empirical evidence for the model (Field et al., 2008, 2013; Grayson, 1991; Grayson and Meltzer, 2002; Mulvaney and Kamminga, 1999). For North America, Grayson and Meltzer (2003) argued that only four extinct genera of megafauna were targeted by humans at 14 archeological sites. In South America, even fewer megafauna kill sites have been found (see Fiedel and Haynes, 2004:123). Australia has produced no clear extinct megafauna kill sites, save one possible site at Cuddie Springs (Field et al., 2002, 2008, 2013; Mulvaney and Kamminga, 1999). In both Australia and the Americas, these numbers are based on conservative interpretations of archeological associations, however, and other scholars argue for considerably larger numbers of kill sites. Years ago, Martin (1975:670) argued that the dearth of kill sites could be viewed as evidence supporting his blitzkrieg model: Sufficiently rapid rates of killing could terminate a prey population before appreciable evidence could be buried. Poor paleontological visibility would be inevitable. In these terms the scarcity of known kill sites on a landmass which suffered severe megafaunal losses ceases to be paradoxical and becomes a predictable consequence of the special circumstances. . ..’’ Few archeologists have agreed with this assertion, but the lack of evidence may be partly the result of taphonomic biases and differential bone preservation. Waguespack and Surovell (2003), for example, noted that large portions of the United States, particularly the American southeast, have produced precious few archaeofaunal assemblages due to poor preservation. As Grayson (2007) noted, critical to resolving some of these debates will be continued high-resolution dating of the initial human colonization of the Americas and Australia and the extinctions of individual megafauna species. A large-scale and interdisciplinary research program of this type may well resolve the 18 T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 possible linkages between humans and late Quaternary megafauna extinctions. 2.3. Middle ground A number of other models propose that megafauna extinctions resulted from a complex mix of climatic, anthropogenic, and ecological factors (e.g. Lorenzen et al., 2011; Ripple and Van Valkenburgh, 2010). Owen-Smith (1987, 1999) argued, for example, that large herbivores are keystone species that help create and maintain mosaic habitats on which other herbivores and carnivores rely. Loss of these keystone species, such as mammoths, from climate driven vegetational changes or human hunting can result in cascading extinctions. Other models suggest that the reduction of proboscidean abundance from human hunting or other disturbance resulted in a transition from nutrient-rich, grassy steppe habitats to nutrient-poor tundra habitats. With insufficient densities of proboscideans to maintain steppe habitats, cascading extinctions of grassland dependent species such as horses and bison were triggered. Robinson et al. (2005) have identified reduced densities of keystone megaherbivores and changes in vegetation communities in eastern North America by analyzing dung spores. However, continued work will be necessary to evaluate the relative timing of extinctions between megafauna species. Ripple and Van Valkenburgh (2010) argue that human hunting and scavenging, as a result of top-down forcing, triggered a population collapse of megafauna herbivores and the carnivores that relied upon them. In this scenario, Ripple and Van Valkenburgh (2010) envision a pre-human landscape where large herbivores were held well below carrying capacity by predators (a predator-limited system). After human hunters arrived, they vied with large carnivores and the increased competition for declining herbivore megafauna forced both to switch to alternate prey species. With a growing human population that was omnivorous, adaptable, and capable of defending themselves from predation with fire, tools, and other cultural advantages, Pleistocene megafauna collapsed from the competition-induced trophic cascade. Combined with vegetation changes and increased patchiness as the result of natural climatic change, Pleistocene megafauna and a variety of other smaller animals were driven to extinction. Flannery (1994) and Miller et al. (1999, 2005) argued that anthropogenic landscape burning after the initial human colonization of Australia contributed to megafaunal extinctions. Combined with the long-term trend toward increasing aridity, extinctions may have resulted from a complex feedback loop where the loss of large herbivores increased fuel loads and generated more intense fires that were increasingly ignited by humans (Barnosky et al., 2004; Wroe et al., 2006). Edwards and MacDonald (1991) identified increases in charcoal abundance and shifts in pollen assemblages, but arguments still remain over the chronological resolution and whether or not these are tied to natural or anthropogenic burning (Bowman, 1998). Evidence for anthropogenic burning in the Americas and Eurasia is more ephemeral, although Robinson et al. (2005) reported evidence for increased charcoal and human burning in eastern North America in the terminal Pleistocene. Similar to some earlier syntheses (e.g., Nogués-Bravo et al., 2008), Fillios et al. (2010), argue that humans provided the coup de grâce in megafaunal extinctions in Australia, with environmental factors acting as the primary driver. In a recent study, Lorenzen et al. (2011) synthesized archeological, genetic, and climatic data to study the demographic histories of six megafauna species, the wooly rhinoceros, wooly mammoth, wild horse, reindeer, bison, and musk ox. They found that climatic fluctuation was the major driver of population change over the last 50,000 years, but not the sole mechanism. Climate change alone can explain the extinction of the Eurasian musk ox and the wooly rhinoceros, for example, but the extinction of the Eurasian steppe bison and wild horse was the result of both climatic and anthropogenic influences. Lorenzen et al.’s (2011) findings demonstrate the need for a species by species approach to understanding megafaunal extinctions. The most powerful argument supporting a mix of humans and climate for late Quaternary megafauna extinctions may be the simplest. Given current best age estimates for the arrival of AMH in Australia, Eurasia, and the Americas, a wave of extinctions appears to have occurred shortly after human colonization of all three continents. In some cases, climate probably contributed significantly to these extinctions, in other cases, the connection is not as obvious. Climate and vegetation changes at the Pleistocene– Holocene transition, for example, likely stressed megafauna in North America and South America (Barnosky et al., 2004:74; Metcalfe et al., 2010). The early extinction pulse in Eurasia (see Table 3) generally coincides with the arrival of AMH and the later pulse may have resulted from human demographic expansion and the invention of new tool technologies (Barnosky et al., 2004:71). This latter pulse also coincides with warming and vegetation changes at the Pleistocene–Holocene transition. Extinctions in Australia appear to occur shortly after human colonization and are not clearly linked to any climate events (Roberts et al., 2001), although long-term aridification may have accelerated the extinctions (Wroe et al., 2006), and the chronological relationship between human colonization and megafaunal extinctions remains controversial (Field et al., 2013). 3. Ancient island extinctions The late Quaternary extinctions of continental megafauna will continue to be debated, but extinctions and other ecological impacts on island ecosystems around the world shortly after initial human colonization are much more clearly anthropogenic in origin (see Rick et al., 2013). These extinctions resulted from direct human hunting, anthropogenic burning and landscape clearing, and the translocation of new plants and animals. Some of the most famous and well-documented of these extinctions come from Madagascar, New Zealand, and other Pacific Islands. In Madagascar, a wide range of megafauna went extinct after human colonization ca. 2300 years ago (Burney et al., 2004). Pygmy hippos, flightless elephant birds, giant tortoises, and large lemurs may have overlapped with humans for a millennium or more, but each went extinct due to human hunting or habitat disturbance. Burney et al. (2003) identified proxy evidence for population decreases of megafauna within a few centuries of human arrival by tracking declines in Sporormiella spp., dung-fungus spores that grow primarily on large mammal dung. This was followed by dramatic increases of Sporormiella spp. after the introduction of domesticated cattle a millennium later. Shortly after the Maori colonization of New Zealand roughly 1000 years ago, at least eleven species of large, flightless landbirds (moas), along with numerous smaller bird species, went extinct (Diamond, 1989:472; Fleming, 1962; Grayson, 2001; Olson and James, 1984). Moa butchery and processing sites are abundant and well-documented in the archeological record (Anderson, 1983, 1989) and recent radiocarbon dating and population modeling suggests that their disappearance occurred within 100 years of first human arrival (Holdaway and Jacomb, 2000). Landbirds across Oceania suffered a similar fate beginning about 3500 years ago as Lapita peoples and later Polynesians colonized the vast Pacific. Thirteen of 17 landbird species went extinct shortly after human arrival on Mangaia in the Cook Islands (Steadman and Kirch, 1990), for example, five of nine on Henderson Island (Wragg and Weisler, T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 19 Table 4 A sample of landbird extinctions on Pacific Islands after Late Holocene human colonization.a Island group Island Cook Islands Easter Island Hawaiian Islands Hawaiian Islands Hawaiian Islands Hawaiian Islands Hawaiian Islands Henderson Island Mariana Islands Mariana Islands Mariana Islands Marquesas Marquesas Marquesas Marquesas New Caledonia New Zealand Society Islands Solomon Islands Solomon Islands Tonga Tonga Mangaia Hawaii Kauai Maui Molokai Oahu Aguiguan Rota Tinian Hiva Oa Nuku Hiva Tahuata Ua Huka Huahine Anuta Tikopia Eua Lifuka # Species Archeologically identified Extinct or extirpated 17 6 16 23 37 23 35 10 9 20 15 7 9 10 15 27 93 15 3 10 26 7 13 6 5 13 29 19 23 6 2 14 8 7 6 7 13 11 32 10 0 2 14 5 % Extinct Reference 76 100 31 57 78 83 66 60 22 70 53 100 67 70 87 41 34 67 0 20 54 71 Steadman (1997) Steadman (1995) Olson and James (1991) Olson and James (1991) Olson and James (1991) Olson and James (1991) Olson and James (1991) Wragg and Weisler (1994) Steadman (1999) Steadman (1999) Steadman (1999) Rolett (1998) Rolett (1998) Rolett (1998) Rolett (1998) Balouet and Olson (1989) Worthy (1999) Steadman (1997) Steadman et al. (1990) Steadman et al. (1990) Steadman (1995) Steadman (1989) a After Grayson (2001); Jones et al. (2008) also noted a gradual extinction of a flightless duck (Chendytes lawi) on California’s Channel Islands after human colonization with Chendytes hunting beginning at least 11,700 years ago (Erlandson et al., 2011). 1994), seven of 10 on Tahuata in the Marquesas (Steadman and Rollett, 1996), 10 of 15 on Huahine in the Society Islands (Steadman, 1997), and six of six on Easter Island (Steadman, 1995) (Table 4). In the Hawaiian Islands, more than 50% of the native avifauna went extinct after Polynesian colonization but before Caption Cook and European arrival (Steadman, 2006). These extinctions likely resulted from a complex mix of human hunting, anthropogenic fire, deforestation and other habitat destruction, and the introduction of domesticated animals (pigs, dogs, and chickens) and stowaways (rats). On islands without significant prehistoric occupation, in contrast, there is little evidence for bird extinctions prior to European arrival. In the absence of permanent prehistoric human settlement on Floreana Island in the Galápagos Islands, for example, Steadman et al. (1991) identified 18 bird species four of which are now extinct, but all probably survived into historic times. In the Pacific, many island extinctions were probably caused by the accidental introduction of the Polynesian rat (Rattus exulans) from mainland southeast Asia. This stowaway on Polynesian sailing vessels has been implicated in the extinction of snails, frogs, and lizards in New Zealand (Brook, 1999), giant iguanas and bats in Tonga (Koopman and Steadman, 1995; Pregill and Dye, 1989), and a variety of birds across the Pacific (Kirch, 1997; Kirch et al., 1995; Steadman, 1989; Steadman and Kirch, 1990). The staggering story of deforestation, competitive statue building, and environmental deterioration on Easter Island (Rapa Nui), often used as a cautionary tale about the dangers of overexploitation (Bahn and Flenley, 1992; Diamond, 2005; but see also Hunt and Lipo, 2010), may be as much a story about rats as it is humans. Flenley (Flenley, 1993; Flenley et al., 1991) identified Polynesian rat gnaw-marks on the seeds of the now extinct Easter Island palm, suggesting that these rodents played a significant role in the extinction of this species, the decreased richness of island biotas, and subsequent lack of construction material for ocean-going canoes and other purposes. 4. Post extinction transformations: plant communities and fire regimes While the extinction of large herbivores and other megafauna around the world in the late Quaternary and the Holocene had continental and local impacts on ecosystems, recent research suggests that the effects may have been larger in scope than scientists once believed. Associated with the extinctions, a number of studies have identified the reorganization of terrestrial communities, the appearance and disappearance of no-analog plant communities, and dramatic increases in biomass burning (Gill et al., 2009; Marlon et al., 2009; Veloz et al., 2012; Williams and Jackson, 2007; Williams et al., 2004, 2011). Some studies link these no-analog communities to natural climatic changes (e.g., terminal Pleistocene changes in solar irradiation and temperature seasonality), but they also may be linked to megafaunal extinctions (Gill et al., 2009; Williams et al., 2001). Gill et al. (2009) used Sporormiella spp. and other paleoecological proxies to demonstrate that the decline in large herbivores may have altered ecosystem structure in North America by releasing hardwoods from predation pressure and increasing fuel loads. Shortly after megafaunal declines, Gill et al. (2009) identified dramatic restructuring of plant communities and heightened fire regimes. In Australia, Flannery (1994:228–230) identified a link between the arrival of the first Aboriginals and a change in vegetation communities toward a fire-adapted landscape. While some scientists implicate anthropogenic burning, Flannery (1994:229) suggested that there are ample natural lightning strikes in Australia to consume vegetation. If humans began systematically burning after they arrived, this would diminish the effects of fire as lighting more fires increases their frequency but lowers their intensity, since fuel loads are not increased. Flannery (1994:230) suggested that the extinction of large herbivores preceded large scale burning in Australia and the subsequent increase in fuel loads from unconsumed vegetation set the stage for the ‘‘fire-loving plant’’ communities that dominate the continent today. A similar process may have played out much later in Madagascar. Burney et al. (2003) used methods similar to Gill et al. (2009) to demonstrate that increases in fire frequency postdate megafaunal decline and vegetation change, and are the direct result of human impacts on megafauna communities. Human-assisted extinctions of large herbivores in Madagascar, North America, and Australia, may all have resulted in dramatic shifts in plant communities and fire regimes, setting off a cascade of ecological changes that contributed to higher extinction rates. 20 T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 5. Domestication, agriculture, and colonialization: a legacy of extinction With the advent of agriculture, especially intensive agricultural production, anthropogenic effects increasingly took precedence over natural climate change as the driving forces behind plant and animal extinctions (Smith and Zeder, 2013). Around much of the world, humans experienced a cultural and economic transformation from small-scale hunter–gatherers to larger and more complex agricultural communities. By the Early Holocene, domestication of plants and animals was underway in several regions including Southwest Asia, Southeast Asia, New Guinea, and parts of the Americas. Domesticates quickly spread from these centers or were invented independently with local wild plants and animals in other parts of the world (see Smith and Zeder, 2013). With domestication and agriculture, there was a fundamental shift in the relationship between humans and their environments (Redman, 1999:53–126; Smith and Zeder, 2013; Zeder et al., 2006). Sedentary communities, human population growth, the translocation of plants and animals, the appearance and spread of new diseases, and habitat alterations all triggered an accelerating wave of extinctions around the world. Ecosystems were transformed as human subsistence economies shifted from smaller scale to more intensified generalized hunting and foraging and to the specialized and intensive agricultural production of one or a small number of commercial products. In many cases, native flora and fauna were seen as weeds or pests that inhibited the production of agricultural products. In tropical and temperate zones worldwide, humans began clearing large expanses of natural vegetation to make room for agricultural fields and grazing pastures. As carrying capacities increased and urban centers grew ever larger, habitat destruction, land clearance, and human-environmental impacts grew from local to regional and continental scales. New competitors and predators were introduced from one end of the globe to the other, including rodents, weeds, dogs, domesticated plants and animals, and everything in between (Redman, 1999:62). Waves of extinction mirrored increases in human population growth and the transformation of settlement and subsistence systems. By the 15th and 16th centuries AD, colonialism, the creation of a global market economy, and human translocation of biota around the world had a homogenizing effect on many terrestrial ecosystems, disrupting both natural and cultural systems (Lightfoot et al., 2013; Vitousek et al., 1997b). Quantifying the number and rates of extinctions over the past 10,000 years is challenging, however, as global extinction rates are difficult to determine even today, in part because the majority of earth’s species still remain undocumented. 6. Summary and conclusions The wave of catastrophic plant and animal extinctions that began with the late Quaternary megafauna of Australia, Europe, and the Americas has continued to accelerate since the industrial revolution. Ceballos et al. (2010) estimated that human-induced species extinctions are now thousands of times greater than the background extinction rate. Diamond (1984) estimated that 4200 (63%) species of mammals and 8500 species of birds have become extinct since AD 1600. Wilson (2002) predicted that, if current rates continue, half of earth’s plant and animal life will be extinct by AD 2100. Today, although anthropogenic climate change is playing a growing role, the primary drivers of modern extinctions appear to be habitat loss, human predation, and introduced species (Briggs, 2011:485). These same drivers contributed to ancient megafaunal and island extinctions – with natural forces gradually giving way to anthropogenic changes – and accelerated after the spread of domestication, agriculture, urbanization, and globalization. In our view, the acceleration of plant and animal extinctions that swept the globe beginning after about 50,000 years ago is part of a long process that involves climate change, the reorganization of terrestrial ecosystems, human hunting and habitat alteration, and, perhaps, an extraterrestrial impact near the end of the Pleistocene (see Firestone et al., 2007; Kennett et al., 2009). Whatever the causes, there is little question that the extinctions and translocations of flora and fauna will be easily visible to future scholars who study archeological and paleoecological records worldwide. If this sixth mass extinction event is used, in part, to identify the onset of the Anthropocene, an arbitrary or ‘‘fuzzy’’ date will ultimately need to be chosen. From our perspective, the defined date is less important than understanding that the mass extinction we are currently experiencing has unfolded over many millennia. We believe one of the most interesting aspects of defining the Anthropocene is striving toward a broader understanding of how humans have shaped and modified earth’s ecosystems and biological resources over the longue durée. The degree of human involvement in late Quaternary continental extinctions will continue to be debated, but humans clearly played some role over many thousands of years. We view the current extinction event as having multiple causes, with humans playing an increasingly significant role through time. Ultimately, the spread of highly intelligent, behaviorally adaptable, and technologically sophisticated humans out of Africa and around the world set the stage for the greatest loss of vertebrate species diversity in the Cenozoic Era. As Koch and Barnosky (2006:241) argued: ‘‘. . .it is time to move beyond casting the Pleistocene extinction debate as a simple dichotomy of climate versus humans. Human impacts were essential to precipitate the event, just as climate shifts were critical in shaping the expression and impact of the extinction in space and time.’’ Viewing the current extinction crisis as an outgrowth of a long and continuing process facilitated by humans may help foster an understanding of the full range of factors that shaped today’s ecosystems and focus conservation efforts on practical solutions to preserve and restore biodiversity in various regions around the world. Let us not fiddle as Rome burns. So far, the Anthropocene has been defined, primarily, by significant and measurable increases in anthropogenic greenhouse gas emissions from ice cores and other geologic features (Crutzen and Steffen, 2003; Ruddiman, 2003, 2013; Steffen et al., 2007). Considering the acceleration of extinctions over the past 50,000 years, in which humans have played an increasingly important role over time, we are left with a number of compelling and difficult questions concerning how the Anthropocene should be defined: whether or not extinctions should contribute to this definition, and how much humans contributed to the earlier phases of the current mass extinction event. We agree with Grayson (2007) and Lorenzen et al. (2011) that better chronological and contextual resolution is needed to help resolve some of these questions, including a species by species approach to understanding their specific demographic histories. On a global level, such a systematic program of coordinated interdisciplinary research would contribute significantly to the definition of the Anthropocene, as well as an understanding of anthropogenic extinction processes in the past, present, and future. Acknowledgments We are grateful for the thoughtful comments of Torben Rick and two anonymous reviewers on earlier drafts of this paper, as well as the editorial assistance of Anne Chin, Timothy Horscraft, and the editorial staff of Anthropocene. This paper was first presented at the T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 2013 Society for American Archaeology meetings in Honolulu. We are also indebted to the many scholars who have contributed to the ongoing debate about the causes of Late Pleistocene and Holocene extinctions around the world. References Alroy, J., 1999. Putting North America’s end-Pleistocene megafaunal extinction in context: large-scale analyses of spatial patterns, extinction rates, and size distributions. In: MacPhee, R.D.E. (Ed.), Extinctions in Near Time: Causes, Contexts, and Consequences. Kluwer Academic, New York, pp. 105–143. Alroy, J., 2000. New methods for quantifying macroevolutionary patterns and processes. Paleobiology 26, 707–733. Alroy, J., 2001. A multispecies overkill simulation of the end-Pleistocene megafaunal mass extinction. Science 292, 1893–1896. Alroy, J., 2008. Dynamics of origination and extinction in the marine fossil record. Proc. Natl. Acad. Sci. U.S.A. 105, 11536–11542. Anderson, A., 1983. Faunal depletion and subsistence change in the early prehistory of southern New Zealand. Archaeol. Ocean. 18, 1–10. Anderson, A., 1989. Mechanics of overkill in the extinction of New Zealand moas. J. Archaeol. Sci. 16, 137–151. Bahn, P.G., Flenley, J., 1992. Easter Island, Earth Island: A Message from Our Past for the Future of Our Planet. Thames & Hudson, New York. Balouet, J.C., Olson, S.L., 1989. Fossil Birds from Late Quaternary Deposits in New Caledonia. Smithsonian Contributions to Zoology, No. 469. . Barnosky, A.D., Koch, P.L., Feranec, R.S., Wing, S.L., Shabel, A.B., 2004. Assessing the causes of late Pleistocene extinctions on the continents. Science 306, 70–75. Barnosky, A.D., Matzke, N., Tomiya, S., Wogan, G.O.U., Swartz, B., Quental, T.B., Marshall, C., McGuire, J.L., Lindsey, E.L., Maguire, K.C., Mersey, B., Ferrer, E.A., 2011. Has the earth’s sixth mass extinction already arrived? Nature 471, 51–57. Belovsky, G.E., 1998. An optimal foraging-based model of hunter–gatherer population dynamics. J. Anthropol. Archaeol. 7, 329–372. Bowman, D.M.J.S., 1998. The impact of Aboriginal landscape burning on the Australian biota. New Phytol. 140, 385–410. Briggs, J.C., 2011. Marine extinctions and conservation. Mar. Biol. 158, 485–488. Brook, F.J., 1999. Changes in the landsnail fauna of Lady Alice Island, northeastern New Zealand. J. R. Soc. N. Z. 29, 135–157. Brook, B.W., Bowman, D.M.J.S., 2002. Explaining the Pleistocene megafaunal extinctions: models, chronologies, and assumptions. Proc. Natl. Acad. Sci. U.S.A. 99, 14624–14627. Brook, B.W., Bowman, D.M.J.S., 2004. The uncertain blitzkrieg of Pleistocene megafauna. J. Biogeogr. 31, 517–523. Burney, D.A., Robinson, G.S., Burney, L.P., 2003. Sporormiella and the late Holocene extinction in Madagascar. Proc. Natl. Acad. Sci. U.S.A. 100, 10800–10805. Burney, D.A., Burney, L.P., Godfrey, L.R., Jungers, W.L., Goodman, S.M., Wright, H.T., Jull, A.J.T., 2004. A chronology for late prehistoric Madagascar. J. Hum. Evol. 47, 25–63. Burney, D.A., Flannery, T.F., 2005. Fifty millennia of catastrophic extinctions after human contact. Trends Ecol. Evol. 20, 395–401. Caro, T., 2007. The Pleistocene re-wilding gambit. Trends Ecol. Evol. 22, 281–283. Ceballos, G., Garcia, A., Ehrlich, P.R., 2010. The sixth extinction crisis. J. Cosmol. 8, 180–185. Choquenot, D.M., Bowman, J.S., 1998. Marsupial megafauna, Aborigines and the overkill hypothesis: application of predator–prey models to the question of Pleistocene extinction in Australia. Glob. Ecol. Biogeogr. Lett. 7, 167–180. Connin, S.L., Betancourt, J., Quade, J., 1998. Late Pleistocene C4 plant dominance and summer rainfall in the southwestern United States from isotopic study of herbivore teeth. Quat. Res. 50, 179–193. Crutzen, P.J., 2002. Geology of mankind. Nature 415, 23. Crutzen, P.J., Steffen, W., 2003. How long have we been in the Anthropocene Era? Clim. Change 61, 251–257. Diamond, J.M., 1984. Historic extinctions: a Rosetta Stone for understanding prehistoric extinctions. In: Martin, P.S., Klein, R.D. (Eds.), Quaternary Extinction: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 824–862. Diamond, J.M., 1989. The present, past and future of human-caused extinctions. Phil. Trans. R. Soc. Lond. 325, 469–477. Diamond, J.M., 2005. Collapse: How Societies Choose to Fail or Succeed. Penguin Group, New York. Dillehay, T.D., 2000. The Settlement of the Americas: A New Prehistory. Basic Books, New York. Donlan, J., Greene, H.W., Berger, J., Bock, C.E., Boch, J.H., Burney, D.A., Estes, J.A., Foreman, D., Marin, P.S., Roemer, G.W., Smith, F.A., Soulé, M.E., 2005. Re-wilding North America. Nature 436, 913–914. Doughtry, C.E., Wolf, A., Field, C.B., 2010. Biophysical feedbacks between the Pleistocene megafauna extinction and climate: the first human-induced global warming? Geophys. Res. Lett. 37, 1–5. Edwards, K.J., MacDonald, G.M., 1991. Holocene palynology. II. Human influences and vegetation change. Prog. Phys. Geogr. 15, 364–391. Erlandson, J.M., Rick, T.C., Braje, T.J., Casperson, M., Culleton, B., Fulfrost, B., Garcia, T., Guthrie, D.A., Jew, N., Kennett, D.J., Moss, M.L., Reeder, L., Skinner, C., Watts, J., Willis, L., 2011. Paleoindian seafaring, maritime technologies, and coastal foraging on California’s Channel Islands. Science 331, 1181–1185. Fiedel, S., Haynes, G., 2004. A premature burial: comments on Grayson and Meltzer’s Requiem for overkill. J. Archaeol. Sci. 31, 121–131. 21 Field, J.H., Dodson, J.R., Prosser, I.P., 2002. A late Pleistocene vegetation history from Australian semi-arid zone. Quat. Sci. Rev. 21, 1023–1037. Field, J., Fillios, M., Wroe, S., 2008. Chronological overlap between humans and megafauna in Sahul (Pleistocene Australia-New Guinea): a review of the evidence. Earth-Sci. Rev. 89, 97–115. Field, J., Wroe, S., Trueman, C.N., Garvey, J., Wyatt-Spratt, S., 2013. Looking for the archaeological signature in Australian megafaunal extinctions. Quat. Int. 285, 76–88. Fillios, M., Field, J., Charles, B., 2010. Investigating human and megafauna cooccurrence in Australian prehistory: mode and causality in fossil accumulations at Cuddie Springs. Quat. Int. 211, 123–143. Firestone, R.B., West, A., Kennett, J.P., Becker, L., Bunch, T.E., Revay, Z.S., Schultz, P.H., Belgya, T., Kennett, D.J., Erlandson, J.M., Dickenson, O.J., Goodyear, A.C., Harris, R.S., Howard, G.A., Kloosterman, J.B., Lechler, P., Mayewski, P.A., Montgomery, J., Poreda, R., Darrah, T., Que Hee, S.S., Smith, A.R., Stich, A., Topping, W., Wittke, J.H., Wolbach, W.S., 2007. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proc. Natl. Acad. Sci. U.S.A. 104, 16016–16021. Flannery, T.F., 1994. The Future Eaters: An Ecological History of the Australasian Lands and People. Grove Press, New York. Flannery, T.F., Roberts, R.G., 1999. Late Quaternary extinctions in Australasia: an overview. In: MacPhee, R.D.E. (Ed.), Extinctions in Near Time: Causes, Contexts, and Consequences. Plenum, New York, pp. 239–255. Fleming, C.A., 1962. History of the New Zealand land bird fauna. Notornis 9, 270–274. Flenley, J.R., 1993. The paleoecology of Easter Island, and its ecological disaster. In: Fischer, S.R. (Ed.), Easter Island Studies: Contributions to the History of Rapanui in Memory of William T. Mulloy. Oxbow Monograph No. 32. Oxbow Books, Oxford, pp. 27–45. Flenley, J.R., King, A.S.M., Jackson, J., Chew, C., 1991. The late Quaternary vegetational and climatic history of Easter Island. J. Quat. Sci. 6, 85–115. Gilinsky, N.L., 1994. Volatility and the Phanerozoic decline of background extinction rates. Paleobiology 20, 445–458. Gill, J.L., Williams, J.W., Jackson, S.T., Lininger, K.B., Robinson, G.S., 2009. Pleistocene megafaunal collapse, novel plant communities, and enhanced fire regimes in North America. Science 326, 1100–1103. Gillespie, R., 2008. Updating Martin’s global extinction model. Quat. Sci. Rev. 27, 2522–2529. Glavin, T., 2007. The Sixth Extinction: Journeys Among the Lost and Left Behind. Thomas Dunne Books, New York. Graham, R.W., Grimm, E.C., 1990. Effects of global climate change on the patterns of terrestrial biological communities. Trends Ecol. Evol. 5, 289–292. Graham, R.W., Lundelius, E.L.J., 1984. Coevolutionary disequilibrium and Pleistocene extinction. In: Martin, P.S., Klein, R.D. (Eds.), Quaternary Extinction: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 223–249. Grayson, D.K., 1984. Nineteenth-century explanations of Pleistocene extinctions: a review and analysis. In: Martin, P.S., Klein, R.G. (Eds.), Quaternary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 5–39. Grayson, D.K., 1991. Late Pleistocene extinctions in North America: taxonomy, chronology, and explanations. J. World Prehist. 5, 193–232. Grayson, D.K., 2001. The archaeological record of human impacts on animal populations. J. World Prehist. 15, 1–68. Grayson, D.K., 2007. Deciphering North American Pleistocene extinctions. J. Archaeol. Res. 63, 185–212. Grayson, D.K., Meltzer, D.J., 2002. Clovis hunting and large mammal extinction: a critical review of the evidence. J. World Prehist. 16, 313–359. Grayson, D.K., Meltzer, D.J., 2003. A requiem for North American overkill. J. Archaeol. Sci. 30, 585–593. Guthrie, R.D., 1984. Mosaics, allelochemicals and nutrients: an ecological theory of Late Pleistocene megafaunal extinctions. In: Martin, P.S., Klein, R.G. (Eds.), Quaternary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 259–298. Guthrie, R.D., 2003. Rapid body size decline in Alaskan Pleistocene horses before extinction. Nature 426, 169–171. Guthrie, R.D., 2006. New carbon dates link climatic change with human colonization and Pleistocene extinctions. Nature 441, 207–209. Haynes, C.V., 1991. Geoarchaeological and paleohydrological evidence for a Clovis-age drought in North America and its bearing on extinction. Quat. Res. 35, 438–450. Haynes, G. (Ed.), 2009. American Megafaunal Extinctions at the End of the Pleistocene. Springer, New York. Holdaway, R.N., Jacomb, C., 2000. Rapid extinction of the moas (Aves: Dinornithiformes): model, test, and implications. Science 287, 2250–2254. Hunt, T.L., Lipo, C.P., 2010. Ecological catastrophe, collapse, and the myth of ecocide on Rapa Nui (Easter Island). In: McAnany, P.A., Yoffee, N. (Eds.), Questioning Collapse: Human Resilience, Ecological Vulnerability, and the Aftermath of Empire. Cambridge University Press, Cambridge, pp. 21–44. Jones, T.L., Porcasi, J.F., Erlandson, J.M., Dallas Jr., H., Wake, T.A., Schwaderer, R., 2008. The protracted Holocene extinction of California’s flightless sea duck (Chendytes lawi) and its implications for the Pleistocene overkill hypothesis. Proc. Natl. Acad. Sci. U.S.A. 105, 4105–4108. Kennett, D.J., Kennett, J.P., West, A., Mercer, C., Que Hee, S.S., Bement, L., Bunch, T.E., Sellers, M., Wolbach, W.S., 2009. Nanodiamonds in the Younger Dryas boundary sediment layer. Science 323, 94. Kershaw, P., Moss, P., Van Der Kaars, S., 2003. Causes and consequences of long-term climatic variability on the Australian continent. Freshw. Biol. 48, 1274–1283. 22 T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 King, J.E., Saunders, J.J., 1984. Environmental insularity and the extinction of the American mastodont. In: Martin, P.S., Klein, R.D. (Eds.), Quaternary Extinction: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 315–359. Kirch, P.V., 1997. Microcosmic histories: island perspectives on global change. Am. Anthropol. 99, 30–42. Kirch, P.V., Steadman, D.W., Butler, V.L., Hather, J., Weisler, M.I., 1995. Prehistory and human ecology at Tangatatau Rockshelter, Mangaia, Cook Islands. Archaeol. Ocean. 30, 47–65. Klein, R.G., 2008. Out of Africa and the evolution of human behavior. Evol. Anthropol. 17, 267–281. Koch, P.L., Barnosky, A.D., 2006. Late Quaternary extinctions: state of the debate. Annu. Rev. Evol. Syst. 37, 215–250. Koch, P.L., Diffenbaugh, N.S., Hoppe, K.A., 2004. The effects of Pleistocene climate and pCO2 change on C4 plant abundance in the south-central United States. Palaeogeogr. Palaeoclim. Palaeoecol. 207, 331–357. Koch, P.L., Fogel, M.L., Tuross, N., 1994. Tracing the diets of fossil animals using stable isotopes. In: Lajtha, K., Michener, R.H. (Eds.), Stable Isotopes in Ecology and Environmental Science. Blackwell, Oxford, pp. 63–92. Koch, P.L., Hoppe, K.A., Webb, S.D., 1998. The isotopic ecology of late Pleistocene mammals in North America – Part 1, Florida. Chem. Geol. 152, 119–138. Koopman, K.F., Steadman, D.W., 1995. Extinction and Biogeography of Bats on ‘Eua, Kingdom of Tonga. American Museum Novitates No. 3125. . Leonard, J.A., Villà, C., Fox-Dobbs, K., Koch, P.L., Wayne, R.K., Van Valkenburgh, B., 2007. Megafaunal extinctions and the disappearance of a specialized wolf ecomorph. Curr. Biol. 17, 1146–1150. Leakey, R.E., Lewin, R., 1995. The Sixth Extinction: Patterns of Life and the Future of Humankind. Doubleday, New York. Lightfoot, K.G., Panich, L.M., Schneider, T.D., Gonzalez, S.L., 2013. Anthropogenic transformations and European colonialism: the effects of early historical globalization in western North America. Anthropocene (in press). Lorenzen, E.D., Nogués-Bravo, D., Orlando, L., Weinstock, J., Binladen, J., Marske, K.A., Ugan, A., Borregaard, M.K., Gilbert, M.T.P., Nielsen, R., Ho, S.Y.W., Goebel, T., Graf, K.E., Byers, D., Stenderup, J.T., Rasmussen, M., Campos, P.F., Leonard, J.A., Koepfli, K.P., Froese, D., Zazula, G., Stafford Jr., T.W., Aaris-Sørensen, K., Batra, P., Haywood, A.M., Singarayer, J.S., Valdes, P.J., Boeskorov, G., Burns, J.A., Davydov, S.P., Haile, J., Jenkins, D.L., Kosintev, P., Kuznetsova, T., Lai, X., Martin, L.D., McDonald, H.G., Mol, D., Meldgaard, M., Munch, K., Stephan, E., Sablin, M., Sommer, R.S., Sipko, T., Scott, E., Suchard, M.A., Tikhonov, A., Willerslev, R., Wayne, R.K., Cooper, A., Hofreiter, M., Sher, A., Shapiro, B., Rahbek, C., Willerslev, E., 2011. Species-specific responses of late Quaternary megafauna to climate and humans. Nature 479, 359–364. Lyons, S.K., Smith, F.A., Brown, J.H., 2004. Of mice, mastodons and men: humanmediated extinctions on four continents. Evol. Ecol. Res. 6, 339–358. MacArthur, R.H., Pianka, E.R., 1966. On optimal use of a patchy environment. Am. Nat. 100, 603–609. MacPhee, R.D.E., Marx, P.A., 1997. The 40,000-year plague. In: Goodman, S.M., Patterson, B.D. (Eds.), Natural Change and Human Impacts in Madagascar. Smithsonian Institution Press, Washington, DC, pp. 169–217. Marlon, J.R., Bartlein, P.J., Walsh, M.K., Harrison, S.P., Brown, K.J., Edwards, M.E., Higuera, P.E., Power, M.J., Anderson, R.S., Briles, A., Carcaillet, C., Daniels, M., Hu, F.S., Lavoie, M., Long, C., Minckley, T., Richard, P.J.H., Scott, A.C., Shafer, D.S., Tinner, W., Umbanhowar Jr., C.E., Whitlock, C., 2009. Wildfire responses to abrupt climate change in North America. Proc. Natl. Acad. Sci. U.S.A. 106, 2519–2524. Martin, P.S., 1966. Africa and Pleistocene overkill. Nature 212, 339–344. Martin, P.S., 1967. Prehistoric overkill. In: Martin, P.S., Wright, Jr., H.E. (Eds.), Pleistocene Extinctions: The Search for a Cause. Yale University Press, New Haven, pp. 75–120. Martin, P.S., 1973. The discovery of America. Science 179, 969–974. Martin, P.S., 1975. Palaeolithic players on the American stage: man’s impact on the Late Pleistocene megafauna. In: Ives, J.D., Berry, R.G. (Eds.), Arctic and Alpine Environments. Methuen, London, pp. 669–700. Martin, P.S., 2005. Twilight of the Mammoths: Ice Age Extinctions and the Rewilding of America. University of California Press, Berkeley. Martin, P.S., 1984. Prehistoric overkill: the global model. In: Martin, P.S., Klein, R.G. (Eds.), Quaternary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 354–403. Martı́nez-Meyer, E., Peterson, A.T., Hargrove, W.W., 2004. Ecological niches as stable distributional constraints on mammal species, with implications for Pleistocene extinctions and climate change projects for biodiversity. Glob. Ecol. Biogeogr. 13, 305–314. Marris, E., 2009. Reflecting the past. Nature 462, 30–32. Meltzer, D.J., 2009. First Peoples in a New World: Colonizing Ice Age America. University of California Press, Berkeley. Meltzer, D.J., Grayson, D.K., Ardila, G., Barker, A.W., Dincauze, D.F., Haynes, C.V., Mena, F., Núñez, L., Stanford, D.J., 1997. On the Pleistocene antiquity of Monte Verde, Southern Chile. Am. Antiq. 62, 659–663. Metcalfe, J.Z., Longstaffe, F.J., Zazula, G.D., 2010. Nursing, weaning, and tooth development in woolly mammoths from Old Crow, Yukon, Canada: implications for Pleistocene extinctions. Palaeoecology 298, 257–270. Miller, G.H., Fogel, M.L., Magee, J.W., Gagan, M.K., Clarke, S.J., Johnson, B.J., 2005. Ecosystem collapse in Pleistocene Australia and a human role in megafaunal extinction. Science 309, 287–290. Miller, G.H., Magee, J.W., Johnson, B.J., Fogel, M.L., Spooner, N.A., McCulloch, M.T., Ayliffe, L.K., 1999. Pleistocene extinction of Genyornis newtoni: human impact on Australian megafauna. Science 283, 205–208. Mosimann, J.E., Martin, P.S., 1975. Simulating overkill by paleoindians. Am. Sci. 63, 304–313. Mulvaney, D.J., Kamminga, J., 1999. Prehistory of Australia. Smithsonian Institution Press, Washington, DC. Nogués-Bravo, D., Rodrı́guez, J., Hortal, J., Batra, P., Araújo, M.B., 2008. Climate change, humans, and the extinction of woolly mammoth. PLoS Biol. 6, e79. Oliveira-Santos, L.G.R., Fernandez, F., 2010. Pleistocene rewilding, Frankenstein ecosystems, and an alternative conservation agenda. Conserv. Biol. 24, 4–5. Olson, S.L., James, H.F., 1984. The role of Polynesians in the extinction of the avifauna of the Hawaiian Islands. In: Martin, P.S., Klein, R.G. (Eds.), Quaternary Extinctions: A Prehistoric Revolution. University of Arizona Press, Tucson, pp. 768–780. Olson, S.L., James, H.F., 1991. Descriptions of Thirty-two New Species of Birds from the Hawaiian Islands: Part 1. Non-passeriformes. Ornithological Monographs, No. 45. American Ornithologists Union, Washington, DC. Owen-Smith, N., 1987. Pleistocene extinctions: the pivotal role of megaherbivores. Paleobiology 13, 351–362. Owen-Smith, N., 1988. Megaherbivores: The Influence of Very Large Body Size on Ecology. Cambridge University Press, Cambridge. Owen-Smith, N., 1999. The interaction of humans, megaherbivores, and habitats in the late Pleistocene extinction event. In: MacPhee, R.D.E. (Ed.), Extinctions in Near Time: Causes, Contexts, and Consequences. Kluwer Academic, New York, pp. 57–70. Pregill, K.P., Dye, T., 1989. Prehistoric extinction of giant iguanas in Tonga. Copeia 1989, 505–508. Raup, D.M., 1986. Biological extinction in earth history. Science 231, 1528–1533. Raup, D.M., Sepkoski Jr., J.J., 1982. Mass extinctions in the marine fossil record. Science 215, 1501–1503. Redman, C.L., 1999. Human Impact on Ancient Environments. University of Arizona Press, Tucson. Renne, P.R., Deino, A.L., Hilgen, F.J., Kuiper, K.F., Mark, D.F., Michell III, W.S., Morgan, L.E., Mundil, R., Smit, J., 2013. Time scales of critical events around the Cretaceous-Paleogene boundary. Science 339, 684–687. Rick, T.C., Kirch, P.V., Erlandson, J.M., Fitzpatrick, S., 2013. Archaeology, deep history, and the human transformation of island ecosystems. Anthropocene, http:// dx.doi.org/10.1016/j.ancene.2013.08.002. Ripple, W.J., Van Valkenburgh, B., 2010. Linking top-down forces to the Pleistocene megafaunal extinctions. Bioscience 60 (7) 516–526. Roberts, R.G., Flannery, T.F., Ayliffe, L.K., Yoshida, H., Olley, J.M., Prideaux, G.J., Laslett, G.M., Baynes, A., Smith, M.A., Jones, R., Smith, B.L., 2001. New ages for the late Australian megafauna: continent-wide extinction about 46,000 years ago. Science 292, 1888–1892. Robinson, G.S., Burney, L.P., Burney, D.A., 2005. Landscape paleoecology and megafaunal extinction in southeastern New York state. Ecol. Monogr. 75, 295–315. Rolett, B.V., 1998. Hanamiai: Prehistoric Colonization and Cultural Change in the Marquesas Islands (East Polynesia). Yale University Publications in Anthropology, No. 81. . Ruddiman, W.F., 2003. The anthropogenic greenhouse era began thousands of years ago. Clim. Change 61, 261–293. Rubenstein, D.R., Rubenstein, D.I., Sherman, P.W., Gavin, T.A., 2006. Pleistocene park: does re-wilding North America represent sound conservation for the 21st century? Biol. Conserv. 132, 232–238. Ruddiman, W.F., 2013. The Anthropocene. Annu. Rev. Earth Planet. Sci. 41, 45–68. Smith, B.D., 2007. Niche construction and the behavioral context of plant and animal domestication. Evol. Anthropol. 16, 188–199. Smith, B.D., Zeder, M.A., 2013. The onset of the Anthropocene. Anthropocene, http:// dx.doi.org/10.1016/j.ancene.2013.05.001. Steadman, D.W., 1989. Extinction of birds in eastern Polynesia: a review of the record, and comparisons with other Pacific Island groups. J. Archaeol. Sci. 16, 177–205. Steadman, D.W., 1995. Prehistoric extinctions of Pacific Island birds: biodiversity meets zooarchaeology. Science 267, 1123–1131. Steadman, D.W., 1997. Extinctions of Polynesian birds: reciprocal impacts of birds and people. In: Kirch, P.V., Hunt, T.L. (Eds.), Historical Ecology in the Pacific Islands: Prehistoric Environmental and Landscape Change. Yale University Press, New Haven, pp. 51–79. Steadman, D.W., 1999. The prehistory of vertebrates, especially birds, on Tinian, Aguiguan, and Rota, Northern Mariana Islands. Micronesica 31, 319–345. Steadman, D.W., 2006. Extinction and Biogeography of Tropical Pacific Birds. University of Chicago Press, Chicago. Steadman, D.W., Kirch, P.V., 1990. Prehistoric extinction of birds on Mangaia, Cook Islands, Polynesia. Proc. Natl. Acad. Sci. U.S.A. 87, 9605–9609. Steadman, D.W., Pahlavan, D.S., Kirch, P.V., 1990. Extinction, Biogeography, and Human Exploitation of Birds on Tikopia and Anuta, Polynesian Outliers in the Solomon Islands. Bernice P. Bishop Museum Occasional Papers, No. 30. , pp. 118–153. Steadman, D.W., Rollett, B.V., 1996. A chronostratigraphic analysis of landbird extinction on Tahuata, Marquesas Islands. J. Archaeol. Sci. 23, 81–94. Steadman, D.W., Stafford Jr., T.W., Donahue, D.J., Jull, A.J.T., 1991. Chronology of Holocene vertebrate expansion in the Galápagos Islands. Quaternary Research 36, 126–133. Steffen, W., Crutzen, P.J., McNeill, J.R., 2007. The Anthropocene: are humans now overwhelming the great forces of nature? Ambio 36, 614–621. Steffen, W., Grineval, J., Crutzen, P., McNeill, J., 2011. The Anthropocene: conceptual and historical perspectives. Phil. Trans. R. Soc. 369, 842–867. T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 Stuart, A.J., Kosintsev, P.A., Higham, T.F.G., Lister, A.M., 2004. Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth. Nature 431, 684–689. Surovell, T., Waguespack, N., Brantingham, P.J., 2005. Global archaeological evidence for proboscidean overkill. Proc. Natl. Acad. Sci. U.S.A. 102, 6231–6236. Turney, C.S.M., Flannery, T.F., Roberts, R.G., Reid, C., Fifield, L.K., Higham, T.F.G., Jacabs, Z., Kemp, N., Colhoun, E.A., Kalin, R.M., Ogle, N., 2008. Late-surviving megafauna in Tasmania, Australia, implicate human involvement in their extinction. Proc. Natl. Acad. Sci. U.S.A. 105, 12150–12153. Van Valkenburgh, B., Hertel, F., 1993. Tough times at La Brea: tooth breakage in large carnivores of the late Pleistocene. Science 261, 456–459. Vartanyan, S., Arslanov, K.A., Karhu, J.A., Possnert, G., Sulerzhitsky, L.D., 2008. Collection of radiocarbon dates on the mammoths (Mammuthus primigenius) and other genera of Wrangel Island, northeast Siberia, Russia. Quat. Res. 70, 51–59. Veloz, S.D., Williams, J.W., Blois, J.L., He, F., Otto-Bliesner, B., Liu, Z., 2012. No-analog climates and shifting realized niches during the late Quaternary: implications for 21st-century predications by species distribution models. Glob. Change Biol. 18, 1698–1713. Vitousek, P.M., D’Antonio, C.M., Loope, L.L., Rejmánek, M., Westbrooks, R., 1997a. Introduced species: a significant component of human-caused global change. N. Z. J. Ecol. 21, 1–16. Vitousek, P.M., Mooney, H.A., Lubchenco, J., Melillo, J.M., 1997b. Human domination of earth’s ecosystems. Science 277, 494–499. Waguespack, N.M., Surovell, T.A., 2003. Clovis hunting strategies, or how to make out on plentiful resources. Am. Antiq. 68, 333–352. Williams, J.W., Blois, J.L., Shuman, B.N., 2011. Extrinsic and intrinsic forcing of abrupt ecological change: case studies from the late Quaternary. Journal of Ecology 99, 664–677. Williams, J.W., Jackson, S.T., 2007. Novel climates, no-analog communities, and ecological surprises. Front. Ecol. Environ. 5, 475–482. 23 Williams, J.W., Shuman, B.N., Webb III, T., 2001. Dissimilarity analysis of lateQuaternary vegetation and climate in eastern North America. Ecology 82, 3346– 3362. Williams, J.W., Shuman, B.N., Webb III, T., Bartlein, P.J., Leduc, P.L., 2004. LateQuaternary vegetation dynamics in North America: scaling from taxa to biomes. Ecol. Monogr. 74, 309–334. Wilson, E.O., 2002. The Future of Life. Vintage, New York. Wolverton, S., 2010. The North American Pleistocene overkill hypothesis and the rewilding debate. Divers. Distrib. 16, 874–876. Worthy, T.H., 1999. What was on the menu? Avian extinction in New Zealand. N. Z. J. Archaeol. 19, 126–160. Wragg, G.M., Weisler, M.I., 1994. Extinctions and new records of birds from Henderson Island, Pitcairn Group, South Pacific Ocean. Notornis 41, 61–70. Wroe, S., Field, J., Fullagar, R., Jermin, L.S., 2004. Megafaunal extinction in the Late Quaternary and the global overkill hypothesis. Alcheringa 28, 291–331. Wroe, S., Field, J., Grayson, D.K., 2006. Megafaunal extinction: climate, humans, and assumptions. Trends Ecol. Evol. 21, 61–62. Yesner, D., Veltre, D., Crossen, K., Graham, R., 2005. 5700-Year-old mammoth remains from Qagnax Cave, Pribilof Islands, Alaska. In: World of Elephants. Short Papers and Abstracts of the 2nd Int. Congress, Mammoth Site Scientific Papers 4. Mammoth Site of Hot Springs Publication, Hot Springs, SD, pp. 200– 204. Zalasiewicz, J., Williams, M., Smith, A., Barry, T.L., Coe, A.L., Bown, P.R., Brenchley, P., Cantrill, D., Gale, A., Gibbard, P., Gregory, F.J., Hounslow, M.W., Kerr, A.C., Pearson, P., Knox, R., Powell, J., Waters, C., Marshall, J., Oates, M., Rawson, P., Stone, P., 2008. Are we now living in the Anthropocene? GSA Today 18, 4–8. Zeder, M.A., Bradley, D.G., Emshwiller, E., Smith, B.D. (Eds.), 2006. Documenting Domestication: New Genetic and Archaeological Paradigms. University of California Press, Berkeley.