A Late Pleistocene, Holocene, and Anthropocene Continuum

Home , Chendytes, Holocene extinction

Anthropocene 4 (2013) 14–23

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Anthropocene

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Human acceleration of animal and plant extinctions: A Late Pleistocene,

Holocene, and Anthropocene continuum

a, b

Todd J. Braje *, Jon M. Erlandson

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: One of the most enduring and stirring debates in archeology revolves around the role humans played in

Received 6 May 2013

the extinction of large terrestrial mammals (megafauna) and other animals near the end of the

Received in revised form 6 August 2013

Pleistocene. Rather than seeking a prime driver (e.g., climate change, human hunting, disease, or other

Accepted 9 August 2013

causes) for Pleistocene extinctions, we focus on the process of human geographic expansion and

Available online 18 August 2013

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.

Keywords:

Human hunting, population growth, economic intensiﬁcation, domestication and translocation of plants

Extinction

and animals, and landscape burning and deforestation, all contributed to a growing human domination

Megafauna

Anthropocene of earth’s continental and oceanic ecosystems. We explore the deep history of anthropogenic extinctions,

Sixth mass extinction 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.

1. Introduction Cretaceous-Paleogene extinction event (a.k.a. the K-T boundary

event), when 76% of the world’s species went extinct within a few

For many geologists and climate scientists, earth’s fossil record millennia (Renne et al., 2013). Most scientists implicate a large

reads like a soap opera in ﬁve parts. The episodes played out over asteroid impact ca. 65.5 mya as the prime driver for this mass

the last 450 million years and the storylines are divided by ﬁve extinction, characterized by the disappearance of non-avian

mass extinction events, biotic crises when at least half the planet’s dinosaurs and the dawn of the age of mammals.

macroscopic plants and animals disappeared. Geologists have used The Big Five concept has become such an engrained part of the

these mass extinctions to mark transitions to new geologic epochs geologic and other sciences that some scholars use the term ‘‘sixth

(Table 1), and they are often called the ‘‘Big Five’’ extinctions. When extinction’’ to characterize the current crisis of earth’s biological

these extinctions were ﬁrst identiﬁed, they seemed to be outliers resources (e.g., Barnosky et al., 2011; Ceballos et al., 2010; Glavin,

within an overall trend of decreasing extinctions and origination 2007; Leakey and Lewin, 1995). Long before the formal proposal to

rates over the last 542 million years, the Phanerozoic Eon (Gilinsky, deﬁne a new Anthropocene Epoch (Zalasiewicz et al., 2008), a

1994; Raup, 1986; Raup and Sepkoski, 1982). More recent meta- variety of scientists identiﬁed post-industrial humans as the

analyses of large web-based paleontological databases (i.e., Alroy, driving force behind the current and on-going mass extinction

2000, 2008), however, have called into question whether all of (e.g., Glavin, 2007; Leakey and Lewin, 1995). Clearly we are

these mass extinctions are truly outliers and substantially different currently living through a mass extinction event. Calculations

from the continuum of extinctions that have been on-going for suggest that the current rates of extinction are 100–1000 times

hundreds of millions of years. natural background levels (Vitousek et al., 1997b:498; Wilson,

Multiple mass extinctions have occurred over the course of 2002). Some biologists predict that the sixth extinction may result

earth’s history, but they are relatively rare, poorly deﬁned, and in a 50% loss of the remaining plants and animals on earth, which

often played out over millions of years. The one exception is the 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

* Corresponding author. Tel.: +1 415 734 8396; fax: +1 619 594 1150.

propensity for unchecked population growth, pollution, over-

E-mail addresses: [email protected] (T.J. Braje), [email protected]

(J.M. Erlandson). harvesting, 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.

Mass extinction Age mya Extinctions Characteristics

% Families % Genera % Species

Ordovician-Silurian 450–440 27 57 86 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.

Late Devonian 375–360 19 35 75 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.

Permian-Triassic 252 57 56 96 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.

Triassic-Jurassic 200 23 47 80 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.

Cretaceous-Paleogene 65.5 17 40 76 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 Zealand, the Netherlands, Saudi Arabia, Latvia, and the Russian Far

Smith, 2007) refer to as human niche construction. East (Marris, 2009), and scientists are debating the merits of

If we are living during the next great biotic crisis and it is rewilding North America with Old World analog species (Caro,

directly tied to human agency, the question becomes when did this 2007; Oliveira-Santos and Fernandez, 2010; Rubenstein et al.,

mass extinction process begin? Even those who have proposed to 2006).

formally designate an Anthropocene Epoch beginning at the dawn

of the Industrial Revolution (ca. AD 1800) or the nuclear era of the 2. Continental-scale megafaunal extinctions

1960s (e.g. Crutzen, 2002; Steffen et al., 2007, 2011; Zalasiewicz

et al., 2008) acknowledge the evidence for widespread impacts of One enduring debate in archeology revolves around the role of

pre-industrial humans in archeological and historical records. They anatomically modern humans (AMH, a.k.a. Homo sapiens) in the

recognize a wide range of ‘‘pre-Anthropocene Events,’’ including extinction of large continental, terrestrial mammals (megafauna).

the acceleration of plant and animal extinctions associated with As AMH populations spread from their evolutionary homeland in

human colonization of new landscapes (Steffen et al., 2007). In Africa between about 70,000 and 50,000 years ago (Klein, 2008),

their view, however, these impacts are seen as much different in worldwide megafauna began a catastrophic decline, with about 90

scale than those that come later: of 150 genera (Koch and Barnosky, 2006:216) going extinct by

10,000 cal BP (calendar years before present). A variety of scientists

Preindustrial societies could and did modify coastal and

have weighed in on the possible cause(s) of this extinction, citing

terrestrial ecosystems but they did not have the numbers,

natural climate and habitat change, human hunting, disease, or a

social and economic organisation, or technologies needed to

combination of these (Table 2). These extinctions may constitute

equal or dominate the great forces of Nature in magnitude or

the earliest human-induced biotic crisis in earth’s history, with

rate. Their impacts remained largely local and transitory, well

continental extinctions of megafauna (traditionally deﬁned as

within the bounds of the natural variability of the environment

animals weighing more than 44 kg) affecting Australia, North and

(Steffen et al., 2007:615; also see Steffen et al., 2011:846–847).

South America, and Europe during the late Quaternary.

Here, we review archeological and paleoecological evidence In Northern Eurasia and Beringia (including Siberia and Alaska),

for rapid and widespread faunal extinctions after the initial 9 genera (35%) of megafauna (Table 3) went extinct in two pulses

colonization of continental and island landscapes. While the (Koch and Barnosky, 2006:219). Warm weather adapted megafau-

timing and precise mechanisms of extinction (e.g., coincident na such as straight-tusked elephants, hippos, hemionid horses, and

climate change, overharvesting, invasive species, habitat disrup- short-faced bears went extinct between 48,000 and 23,000 cal BP

tion, disease, or extraterrestrial impact) still are debated (Haynes, and cold-adapted megafauna such as mammoths went extinct

2009), the global pattern of ﬁrst human arrival followed by biotic between 14,000 and 11,500 cal BP. In central North America,

extinctions, that accelerate through time, places humans as a approximately 34 genera (72%) of large mammals went extinct

contributing agent to extinction for at least 50,000 years. From the between about 13,000 and 10,500 years ago, including mammoths,

late Pleistocene to the Holocene, moreover, we argue that human mastodons, giant ground sloths, horses, tapirs, camels, bears,

contributions to such extinctions and ecological change have saber-tooth cats, and a variety of other animals (Alroy, 1999;

continued to accelerate. Grayson, 1991, 2007). Large mammals were most heavily affected,

More than simply the naming of geologic epochs, deﬁning the but some small mammals, including a skunk and rabbit, also went

level of human involvement in ancient extinctions may have extinct. South America lost an even larger number and percentage,

widespread ethical implications for the present and future of with 50 megafauna genera (83%) becoming extinct at about the

conservation biology and restoration ecology (Donlan et al., 2005; same time. In Australia, some 21 genera (83%) of large marsupials,

Wolverton, 2010). A growing number of scientists and resource birds, and reptiles went extinct (Flannery and Roberts, 1999)

managers accept the premise that humans caused or signiﬁcantly approximately 46,000 years ago, including giant kangaroos,

contributed to late Quaternary extinctions and, we have the moral wombats, and snakes (Roberts et al., 2001).

imperative to restore and rebalance these ecosystems by In the Americas, Eurasia, and Australia, the larger bodied

introducing species closely related to those that became extinct. animals with slow reproductive rates were especially prone to

Experiments are already underway in ‘‘Pleistocene parks’’ in New extinction (Burney and Flannery, 2005:395; Lyons et al., 2004), a

16 T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23

Table 2

Summary of the major hypotheses proposed to explain Pleistocene megafaunal extinctions around the world.

Hypothesis Details References

Climate driven

Climate change Megafaunal and other animals were unable to adapt to Graham and Grimm (1990) and Guthrie (1984)

changes in climate and vegetation communities at the

Pleistocene–Holocene transition

Drought Rapidly increasing aridity, combined with human hunting, Haynes (1991)

results in North American megafaunal extinctions

Human induced

Overkill Colonizing aboriginal humans rapidly overhunt Alroy (2001) and Martin (1984)

ecologically naı¨ve megafauna

Fire Landscape burning by colonizing humans caused ecological Miller et al. (2005)

changes and megamarsupial extinctions in Australia

Other

Disease Infectious disease brought by colonizing humans rapidly MacPhee and Marx (1997)

affects many megafaunal taxa

Ecological re-organization Loss of megaherbivores, which helped create and maintain Gill et al. (2009), Grayson (1984) and Owen-Smith (1988)

savannahs, triggered ecological changes and increased ﬁre

fuel loads

ET impact An extraterrestrial impact event triggered biomass burning Firestone et al. (2007)

and food shortages that resulted in the North American extinctions

Human-climate dynamics

Multivariant Human hunting, anthropogenic ecosystems alterations, and Barnosky et al. (2004), Burney and Flannery (2005) and

natural climatic/vegetation changes results in increased Doughtry et al. (2010)

ﬁre, landscape transformation, and megafaunal extinctions

Table 3

Summary table of mammalian megafauna extinctions.

Mass Initial colonization Major extinction # Genera

extinction of AMH (cal BP) interval (cal BP)

Extinct Extinct but surviving elsewhere Holocene survivors % Extinct

Australia 50,000 Æ 5000 80,000–46,000 14 – 2 88

Eurasia 60,000–45,000 48,000–23,000, 4 5 17 35

14,000–11,500

North America 14,500 Æ 5000 13,000–10,500 28 6 13 72

South America 14,500 Æ 5000 13,000–10,500 48 2 10 83

Adapted from Koch and Barnosky (2006:Table 2).

pattern that seems to be unique to late Pleistocene extinctions. have been demonstrated to overlap with humans and that the bulk

According to statistical analyses by Alroy (1999), this late of extinctions occurred prior to human arrival, questioning Roberts

Quaternary extinction episode is more selective for large-bodied et al.’s (2001) terminal extinction date (Field et al., 2008). In the

animals than any other extinction interval in the last 65 million Americas and Eurasia, warming at the end of the Last Glacial

years. Current evidence suggests that the initial human coloniza- Maximum (LGM, ca. 18,000 years ago) resulted in rapid changes to

tion of Australia and the Americas at about 50,000 and 15,000 years climate and vegetation communities during the Pleistocene–

ago, respectively, and the appearance of AMH in Northern Eurasia Holocene transition, creating a set of environmental changes to

beginning about 50,000 years ago coincided with the extinction of which megafauna were unable to adapt (Graham and Grimm,

these animals, although the inﬂuence of humans is still debated 1990; Guthrie, 2003, 2006). Extinctions in the New World may

(e.g., Brook and Bowman, 2002, 2004; Grayson, 2001; Roberts et al., have been further affected by the onset of the Younger Dryas, a

2001; Surovell et al., 2005; Wroe et al., 2004). 1000-year cooling event, which exacerbated shifts in vegetation

communities.

2.1. The climate model Much of the climate change model hinges on dietary assump-

tions about Pleistocene herbivores, and to some degree, carnivores.

Many scholars have implicated climate change as the prime A variety of new studies are testing these assumptions using

13 15

mover in megafaunal extinctions (see Wroe et al., 2006). There are genetic (mtDNA), morphologic, and isotopic (d C and d N) data.

a number of variations on the climate change theme, but the most North American proboscideans (e.g., mammoths, mastodons) and

popular implicates rapid changes in climate and vegetation camelids had very different and specialized diets that may have

communities as the prime driver of extinctions (Grayson, 2007; made them vulnerable to rapid climate change and vegetation

Guthrie, 1984; Owen-Smith, 1988). Extinctions, then, are seen as shifts, for example, but carbon isotope studies of tooth enamel

the result of habitat loss (King and Saunders, 1984), reduced suggest that C4 grasslands that supported large herbivores

carrying capacity for herbivores (Guthrie, 1984), increased generally remained intact during glacial to interglacial transitions

patchiness and resource fragmentation (MacArthur and Pianka, (Connin et al., 1998; Koch et al., 1994, 1998, 2004). Patterns of

1966), or disruptions in the co-evolutionary balance between specialization have also been found with North American

plants, herbivores, and carnivores (Graham and Lundelius, 1984). carnivore species. The species with the greatest extinction

In Australia, extinctions have been linked to a stepwise progression vulnerability tended to be the largest and most carnivorous of

of aridiﬁcation over the last 300,000–400,000 years (Field et al., their families (e.g., dire wolves, saber-tooth cats, short-faced

2002; Kershaw et al., 2003; Wroe et al., 2004). Climate change bears). The smaller, more generalized species (e.g., gray wolves,

proponents argue that only a small number of extinct megafauna puma and bobcats, and black and brown bears) survived into the

T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 17

Holocene (Leonard et al., 2007; Van Valkenburgh and Hertel, megafauna was possible in the Americas and Australia at ﬁrst

1993). human colonization. Questions remain about these models, as

Other studies of environmental changes across the Pleistocene– some simulations that make relatively small adjustments to the

Holocene transition have suggested that climate change is not a model assumptions (i.e., changes to human–prey population

sufﬁcient explanation for megafaunal extinctions. Martı´nez-Meyer dynamics, human population densities, or other input parameters)

et al. (2004) found, for example, that the reduction of habitable do not support the overkill model (see Belovsky, 1998; Choquenot

niches for eight megafauna taxa in North America is insufﬁcient to and Bowman, 1998).

explain their extinction. Pollen records further show that Given that these models disagree in their outcomes and can only

megafaunal extinctions in Eurasia and the Americas coincided provide insights into the relative plausibility of the overkill model,

with rapid vegetational shifts, but the link between vegetation the strongest evidence for overkill comes from the timing of

changes and extinctions in Australia is much less clear (Barnosky megafaunal extinctions and human colonization. In the Americas,

et al., 2004). Although comprehensive studies are needed, current the major megafauna extinction interval coincides with the late

pollen records also suggest that Pleistocene–Holocene changes in Pleistocene arrival of humans about 15,000 years ago (Dillehay,

vegetation were not substantially different from previous glacial– 2000; Meltzer, 2009; Meltzer et al., 1997). Most of the megafauna

interglacial cycles (Koch and Barnosky, 2006:225–226; also see were lost by 10,500 years ago or earlier, generally coincident with

Robinson et al., 2005). There also is evidence for the Holocene the regionalization of Paleoindian projectile points, often inter-

survival of now extinct megafauna in locations that were free from preted as megafauna hunting technologies, in North America.

intensive human predation. Wooly mammoths survived on Similarities are seen in Australia with ﬁrst human colonization at

Wrangel Island off northeast Siberia until about 3700 years ago about 50,000 years ago and the extinction of the continental

(Stuart et al., 2004; Vartanyan et al., 2008) and on Alaska’s Pribilof megafauna within 4000 years on the mainland (Gillespie, 2008;

Islands until 5000 years ago (Yesner et al., 2005). These animals Roberts et al., 2001) and slightly later on Tasmania (Turney et al.,

survived the dramatic climate and vegetation changes of the 2008). The association of megafauna extinctions and human arrival

Pleistocene–Holocene transition, in some cases on relatively small in Eurasia is more difﬁcult to demonstrate. Hominins (e.g., Homo

islands that saw dramatic environmental change. Climate change erectus, H. heidelbergensis, H. neandertalensis) were present in large

proponents suggest, however, that these cases represent refugia parts of Eurasia for roughly two million years, so Eurasian mammals

populations in favorable habitats in the far north. should have co-evolved with hominins in a fashion similar to

Ultimately, additional data on vegetation shifts (studies from Martin’s African model. With the ﬁrst AMH arriving in various parts

pollen and macroﬂoral evidence) across the Pleistocene–Holocene of Eurasia between about 60,000 and 50,000 years ago, apparently

boundary, including investigation of seasonality patterns and with more sophisticated brains and technologies, AMH may have

climate ﬂuctuations at decadal to century scales, will be important sparked the ﬁrst wave of megafaunal extinctions at 48,000 years

for continued evaluation of climate change models. ago (Barnosky et al., 2004).

Overkill opponents argue that the small number of documented

2.2. The human overhunting model megafauna kill sites in the Americas and Australia provides no

empirical evidence for the model (Field et al., 2008, 2013; Grayson,

The human overhunting model implicates humans as the 1991; Grayson and Meltzer, 2002; Mulvaney and Kamminga,

primary driver of megafaunal extinctions in the late Quaternary. 1999). For North America, Grayson and Meltzer (2003) argued that

Hunting, however, does not have to be the principal cause of only four extinct genera of megafauna were targeted by humans at

megafauna deaths and humans do not necessarily have to be 14 archeological sites. In South America, even fewer megafauna kill

specialized, big game hunters. Rather, human hunting and sites have been found (see Fiedel and Haynes, 2004:123). Australia

anthropogenic ecological changes add a critical number of has produced no clear extinct megafauna kill sites, save one

megafauna deaths, where death rates begin to exceed birth rates. possible site at Cuddie Springs (Field et al., 2002, 2008, 2013;

Extinction, then, can be rapid or slow depending on the forcing of Mulvaney and Kamminga, 1999). In both Australia and the

human hunting (Koch and Barnosky, 2006:231). Americas, these numbers are based on conservative interpreta-

The human overhunting model was popularized by Martin tions of archeological associations, however, and other scholars

(1966, 1967, 1973, 2005) with his blitzkrieg model for extinction in argue for considerably larger numbers of kill sites.

the Americas. Martin argued that initial human colonization of the Years ago, Martin (1975:670) argued that the dearth of kill sites

New World by Clovis peoples, big game hunting specialists who could be viewed as evidence supporting his blitzkrieg model:

swept across the Bering Land Bridge and down the Ice Free Corridor

13,500 years ago, resulted in megafaunal extinctions within 500– Sufﬁciently rapid rates of killing could terminate a prey

1000 years as humans spread like a deadly wave from north to south. population before appreciable evidence could be buried. Poor

Similarly, the initial human colonization of Australia instigated a paleontological visibility would be inevitable. In these terms

wave of extinctions from human hunting some 50,000 years ago. the scarcity of known kill sites on a landmass which suffered

According to Martin (1973), this blitzkrieg was rapid and effective in severe megafaunal losses ceases to be paradoxical and becomes

the Americas and Australia because these large terrestrial animals a predictable consequence of the special circumstances. . ..’’

were ecologically naı¨ve and lacked the behavioral and evolutionary

adaptations to avoid intelligent and technologically sophisticated Few archeologists have agreed with this assertion, but the lack of

human predators (Martin, 1973). Extinctions in Africa and Eurasia evidence may be partly the result of taphonomic biases and

were much less pronounced because megafauna and human differential bone preservation. Waguespack and Surovell (2003),

hunting had co-evolved (Martin, 1966). Elsewhere, Martin (1973) for example, noted that large portions of the United States,

reasoned that since the interaction between humans and megafauna particularly the American southeast, have produced precious few

was relatively brief, very few archeological kill sites recording these archaeofaunal assemblages due to poor preservation.

events were created or preserved. As Grayson (2007) noted, critical to resolving some of these

Much of the supporting evidence for the overkill model is debates will be continued high-resolution dating of the initial

predicated on computer simulation, mathematical, and foraging human colonization of the Americas and Australia and the

models (e.g., Alroy, 2001; Brook and Bowman, 2004; Mosimann extinctions of individual megafauna species. A large-scale and

and Martin, 1975). These suggest a rapid, selective extinction of 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 over the last 50,000 years, but not the sole mechanism. Climate

extinctions. change alone can explain the extinction of the Eurasian musk ox

and the wooly rhinoceros, for example, but the extinction of the

2.3. Middle ground Eurasian steppe bison and wild horse was the result of both

climatic and anthropogenic inﬂuences. Lorenzen et al.’s (2011)

A number of other models propose that megafauna extinctions ﬁndings demonstrate the need for a species by species approach to

resulted from a complex mix of climatic, anthropogenic, and understanding megafaunal extinctions.

ecological factors (e.g. Lorenzen et al., 2011; Ripple and Van The most powerful argument supporting a mix of humans and

Valkenburgh, 2010). Owen-Smith (1987, 1999) argued, for climate for late Quaternary megafauna extinctions may be the

example, that large herbivores are keystone species that help simplest. Given current best age estimates for the arrival of AMH in

create and maintain mosaic habitats on which other herbivores Australia, Eurasia, and the Americas, a wave of extinctions appears

and carnivores rely. Loss of these keystone species, such as to have occurred shortly after human colonization of all three

mammoths, from climate driven vegetational changes or human continents. In some cases, climate probably contributed signiﬁ-

hunting can result in cascading extinctions. Other models suggest cantly to these extinctions, in other cases, the connection is not as

that the reduction of proboscidean abundance from human obvious. Climate and vegetation changes at the Pleistocene–

hunting or other disturbance resulted in a transition from Holocene transition, for example, likely stressed megafauna in

nutrient-rich, grassy steppe habitats to nutrient-poor tundra North America and South America (Barnosky et al., 2004:74;

habitats. With insufﬁcient densities of proboscideans to maintain Metcalfe et al., 2010). The early extinction pulse in Eurasia (see

steppe habitats, cascading extinctions of grassland dependent Table 3) generally coincides with the arrival of AMH and the later

species such as horses and bison were triggered. Robinson et al. pulse may have resulted from human demographic expansion and

(2005) have identiﬁed reduced densities of keystone megaherbi- the invention of new tool technologies (Barnosky et al., 2004:71).

vores and changes in vegetation communities in eastern North This latter pulse also coincides with warming and vegetation

America by analyzing dung spores. However, continued work will changes at the Pleistocene–Holocene transition. Extinctions in

be necessary to evaluate the relative timing of extinctions between Australia appear to occur shortly after human colonization and are

megafauna species. not clearly linked to any climate events (Roberts et al., 2001),

Ripple and Van Valkenburgh (2010) argue that human hunting although long-term aridiﬁcation may have accelerated the

and scavenging, as a result of top-down forcing, triggered a extinctions (Wroe et al., 2006), and the chronological relationship

population collapse of megafauna herbivores and the carnivores between human colonization and megafaunal extinctions remains

that relied upon them. In this scenario, Ripple and Van controversial (Field et al., 2013).

Valkenburgh (2010) envision a pre-human landscape where large

herbivores were held well below carrying capacity by predators (a 3. Ancient island extinctions

predator-limited system). After human hunters arrived, they vied

with large carnivores and the increased competition for declining The late Quaternary extinctions of continental megafauna will

herbivore megafauna forced both to switch to alternate prey continue to be debated, but extinctions and other ecological

species. With a growing human population that was omnivorous, impacts on island ecosystems around the world shortly after initial

adaptable, and capable of defending themselves from predation human colonization are much more clearly anthropogenic in origin

with ﬁre, tools, and other cultural advantages, Pleistocene (see Rick et al., 2013). These extinctions resulted from direct

megafauna collapsed from the competition-induced trophic human hunting, anthropogenic burning and landscape clearing,

cascade. Combined with vegetation changes and increased and the translocation of new plants and animals. Some of the most

patchiness as the result of natural climatic change, Pleistocene famous and well-documented of these extinctions come from

megafauna and a variety of other smaller animals were driven to Madagascar, New Zealand, and other Paciﬁc Islands.

extinction. In Madagascar, a wide range of megafauna went extinct after

Flannery (1994) and Miller et al. (1999, 2005) argued that human colonization ca. 2300 years ago (Burney et al., 2004). Pygmy

anthropogenic landscape burning after the initial human coloni- hippos, ﬂightless elephant birds, giant tortoises, and large lemurs

zation of Australia contributed to megafaunal extinctions. may have overlapped with humans for a millennium or more, but

Combined with the long-term trend toward increasing aridity, each went extinct due to human hunting or habitat disturbance.

extinctions may have resulted from a complex feedback loop Burney et al. (2003) identiﬁed proxy evidence for population

where the loss of large herbivores increased fuel loads and decreases of megafauna within a few centuries of human arrival by

generated more intense ﬁres that were increasingly ignited by tracking declines in Sporormiella spp., dung-fungus spores that

humans (Barnosky et al., 2004; Wroe et al., 2006). Edwards and grow primarily on large mammal dung. This was followed by

MacDonald (1991) identiﬁed increases in charcoal abundance and dramatic increases of Sporormiella spp. after the introduction of

shifts in pollen assemblages, but arguments still remain over the domesticated cattle a millennium later.

chronological resolution and whether or not these are tied to Shortly after the Maori colonization of New Zealand roughly

natural or anthropogenic burning (Bowman, 1998). Evidence for 1000 years ago, at least eleven species of large, ﬂightless landbirds

anthropogenic burning in the Americas and Eurasia is more (moas), along with numerous smaller bird species, went extinct

ephemeral, although Robinson et al. (2005) reported evidence for (Diamond, 1989:472; Fleming, 1962; Grayson, 2001; Olson and

increased charcoal and human burning in eastern North America in James, 1984). Moa butchery and processing sites are abundant and

the terminal Pleistocene. Similar to some earlier syntheses (e.g., well-documented in the archeological record (Anderson, 1983,

Nogue´s-Bravo et al., 2008), Fillios et al. (2010), argue that humans 1989) and recent radiocarbon dating and population modeling

provided the coup de graˆce in megafaunal extinctions in Australia, suggests that their disappearance occurred within 100 years of ﬁrst

with environmental factors acting as the primary driver. human arrival (Holdaway and Jacomb, 2000). Landbirds across

In a recent study, Lorenzen et al. (2011) synthesized arche- Oceania suffered a similar fate beginning about 3500 years ago as

ological, genetic, and climatic data to study the demographic Lapita peoples and later Polynesians colonized the vast Paciﬁc.

histories of six megafauna species, the wooly rhinoceros, wooly Thirteen of 17 landbird species went extinct shortly after human

mammoth, wild horse, reindeer, bison, and musk ox. They found arrival on Mangaia in the Cook Islands (Steadman and Kirch, 1990),

that climatic ﬂuctuation was the major driver of population change 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.

Island group Island # Species % Extinct Reference

Archeologically identiﬁed Extinct or extirpated

Cook Islands Mangaia 17 13 76 Steadman (1997)

Easter Island 6 6 100 Steadman (1995)

Hawaiian Islands Hawaii 16 5 31 Olson and James (1991)

Hawaiian Islands Kauai 23 13 57 Olson and James (1991)

Hawaiian Islands Maui 37 29 78 Olson and James (1991)

Hawaiian Islands Molokai 23 19 83 Olson and James (1991)

Hawaiian Islands Oahu 35 23 66 Olson and James (1991)

Henderson Island 10 6 60 Wragg and Weisler (1994)

Mariana Islands Aguiguan 9 2 22 Steadman (1999)

Mariana Islands Rota 20 14 70 Steadman (1999)

Mariana Islands Tinian 15 8 53 Steadman (1999)

Marquesas Hiva Oa 7 7 100 Rolett (1998)

Marquesas Nuku Hiva 9 6 67 Rolett (1998)

Marquesas Tahuata 10 7 70 Rolett (1998)

Marquesas Ua Huka 15 13 87 Rolett (1998)

New Caledonia 27 11 41 Balouet and Olson (1989)

New Zealand 93 32 34 Worthy (1999)

Society Islands Huahine 15 10 67 Steadman (1997)

Solomon Islands Anuta 3 0 0 Steadman et al. (1990)

Solomon Islands Tikopia 10 2 20 Steadman et al. (1990)

Tonga Eua 26 14 54 Steadman (1995)

Tonga Lifuka 7 5 71 Steadman (1989)

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 continental and local impacts on ecosystems, recent research

Rollett, 1996), 10 of 15 on Huahine in the Society Islands suggests that the effects may have been larger in scope than

(Steadman, 1997), and six of six on Easter Island (Steadman, scientists once believed. Associated with the extinctions, a number

1995) (Table 4). In the Hawaiian Islands, more than 50% of the of studies have identiﬁed the reorganization of terrestrial

native avifauna went extinct after Polynesian colonization but communities, the appearance and disappearance of no-analog

before Caption Cook and European arrival (Steadman, 2006). These plant communities, and dramatic increases in biomass burning

extinctions likely resulted from a complex mix of human hunting, (Gill et al., 2009; Marlon et al., 2009; Veloz et al., 2012; Williams

anthropogenic ﬁre, deforestation and other habitat destruction, and Jackson, 2007; Williams et al., 2004, 2011). Some studies link

and the introduction of domesticated animals (pigs, dogs, and these no-analog communities to natural climatic changes (e.g.,

chickens) and stowaways (rats). On islands without signiﬁcant terminal Pleistocene changes in solar irradiation and temperature

prehistoric occupation, in contrast, there is little evidence for bird seasonality), but they also may be linked to megafaunal extinctions

extinctions prior to European arrival. In the absence of permanent (Gill et al., 2009; Williams et al., 2001). Gill et al. (2009) used

prehistoric human settlement on Floreana Island in the Gala´pagos Sporormiella spp. and other paleoecological proxies to demonstrate

Islands, for example, Steadman et al. (1991) identiﬁed 18 bird that the decline in large herbivores may have altered ecosystem

species four of which are now extinct, but all probably survived structure in North America by releasing hardwoods from predation

into historic times. pressure and increasing fuel loads. Shortly after megafaunal

In the Paciﬁc, many island extinctions were probably caused by declines, Gill et al. (2009) identiﬁed dramatic restructuring of plant

the accidental introduction of the Polynesian rat (Rattus exulans) communities and heightened ﬁre regimes.

from mainland southeast Asia. This stowaway on Polynesian sailing In Australia, Flannery (1994:228–230) identiﬁed a link between

vessels has been implicated in the extinction of snails, frogs, and the arrival of the ﬁrst Aboriginals and a change in vegetation

lizards in New Zealand (Brook, 1999), giant iguanas and bats in communities toward a ﬁre-adapted landscape. While some

Tonga (Koopman and Steadman, 1995; Pregill and Dye, 1989), and a scientists implicate anthropogenic burning, Flannery (1994:229)

variety of birds across the Paciﬁc (Kirch, 1997; Kirch et al., 1995; suggested that there are ample natural lightning strikes in

Steadman, 1989; Steadman and Kirch, 1990). The staggering story of Australia to consume vegetation. If humans began systematically

deforestation, competitive statue building, and environmental burning after they arrived, this would diminish the effects of ﬁre as

deterioration on Easter Island (Rapa Nui), often used as a cautionary lighting more ﬁres increases their frequency but lowers their

tale about the dangers of overexploitation (Bahn and Flenley, 1992; intensity, since fuel loads are not increased. Flannery (1994:230)

Diamond, 2005; but see also Hunt and Lipo, 2010), may be as much a suggested that the extinction of large herbivores preceded large

story about rats as it is humans. Flenley (Flenley, 1993; Flenley et al., scale burning in Australia and the subsequent increase in fuel loads

1991) identiﬁed Polynesian rat gnaw-marks on the seeds of the now from unconsumed vegetation set the stage for the ‘‘ﬁre-loving

extinct Easter Island palm, suggesting that these rodents played a plant’’ communities that dominate the continent today.

signiﬁcant role in the extinction of this species, the decreased A similar process may have played out much later in

richness of island biotas, and subsequent lack of construction Madagascar. Burney et al. (2003) used methods similar to Gill

material for ocean-going canoes and other purposes. et al. (2009) to demonstrate that increases in ﬁre frequency

postdate megafaunal decline and vegetation change, and are the

4. Post extinction transformations: plant communities and ﬁre direct result of human impacts on megafauna communities.

regimes Human-assisted extinctions of large herbivores in Madagascar,

North America, and Australia, may all have resulted in dramatic

While the extinction of large herbivores and other megafauna shifts in plant communities and ﬁre regimes, setting off a cascade

around the world in the late Quaternary and the Holocene had 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 In our view, the acceleration of plant and animal extinctions

extinction that swept the globe beginning after about 50,000 years ago is part

of a long process that involves climate change, the reorganization

With the advent of agriculture, especially intensive agricultural of terrestrial ecosystems, human hunting and habitat alteration,

production, anthropogenic effects increasingly took precedence and, perhaps, an extraterrestrial impact near the end of the

over natural climate change as the driving forces behind plant and Pleistocene (see Firestone et al., 2007; Kennett et al., 2009).

animal extinctions (Smith and Zeder, 2013). Around much of the Whatever the causes, there is little question that the extinctions

world, humans experienced a cultural and economic transforma- and translocations of ﬂora and fauna will be easily visible to future

tion from small-scale hunter–gatherers to larger and more scholars who study archeological and paleoecological records

complex agricultural communities. By the Early Holocene, worldwide. If this sixth mass extinction event is used, in part, to

domestication of plants and animals was underway in several identify the onset of the Anthropocene, an arbitrary or ‘‘fuzzy’’ date

regions including Southwest Asia, Southeast Asia, New Guinea, and will ultimately need to be chosen. From our perspective, the

parts of the Americas. Domesticates quickly spread from these deﬁned date is less important than understanding that the mass

centers or were invented independently with local wild plants and extinction we are currently experiencing has unfolded over many

animals in other parts of the world (see Smith and Zeder, 2013). millennia. We believe one of the most interesting aspects of

With domestication and agriculture, there was a fundamental deﬁning the Anthropocene is striving toward a broader under-

shift in the relationship between humans and their environments standing of how humans have shaped and modiﬁed earth’s

(Redman, 1999:53–126; Smith and Zeder, 2013; Zeder et al., 2006). ecosystems and biological resources over the longue dure´e.

Sedentary communities, human population growth, the translo- The degree of human involvement in late Quaternary conti-

cation of plants and animals, the appearance and spread of new nental extinctions will continue to be debated, but humans clearly

diseases, and habitat alterations all triggered an accelerating wave played some role over many thousands of years. We view the

of extinctions around the world. Ecosystems were transformed as current extinction event as having multiple causes, with humans

human subsistence economies shifted from smaller scale to more playing an increasingly signiﬁcant role through time. Ultimately,

intensiﬁed generalized hunting and foraging and to the specialized the spread of highly intelligent, behaviorally adaptable, and

and intensive agricultural production of one or a small number of technologically sophisticated humans out of Africa and around

commercial products. In many cases, native ﬂora and fauna were the world set the stage for the greatest loss of vertebrate species

seen as weeds or pests that inhibited the production of agricultural diversity in the Cenozoic Era. As Koch and Barnosky (2006:241)

products. argued:

In tropical and temperate zones worldwide, humans began

‘‘. . .it is time to move beyond casting the Pleistocene extinction

clearing large expanses of natural vegetation to make room for

debate as a simple dichotomy of climate versus humans.

agricultural ﬁelds and grazing pastures. As carrying capacities

Human impacts were essential to precipitate the event, just as

increased and urban centers grew ever larger, habitat destruction,

climate shifts were critical in shaping the expression and

land clearance, and human-environmental impacts grew from

impact of the extinction in space and time.’’

local to regional and continental scales. New competitors and

predators were introduced from one end of the globe to the other, Viewing the current extinction crisis as an outgrowth of a long and

including rodents, weeds, dogs, domesticated plants and animals, continuing process facilitated by humans may help foster an

and everything in between (Redman, 1999:62). Waves of extinc- understanding of the full range of factors that shaped today’s

tion mirrored increases in human population growth and the ecosystems and focus conservation efforts on practical solutions to

transformation of settlement and subsistence systems. By the 15th preserve and restore biodiversity in various regions around the

and 16th centuries AD, colonialism, the creation of a global market world. Let us not ﬁddle as Rome burns.

economy, and human translocation of biota around the world had a So far, the Anthropocene has been deﬁned, primarily, by

homogenizing effect on many terrestrial ecosystems, disrupting signiﬁcant and measurable increases in anthropogenic greenhouse

both natural and cultural systems (Lightfoot et al., 2013; Vitousek gas emissions from ice cores and other geologic features (Crutzen

et al., 1997b). Quantifying the number and rates of extinctions over and Steffen, 2003; Ruddiman, 2003, 2013; Steffen et al., 2007).

the past 10,000 years is challenging, however, as global extinction Considering the acceleration of extinctions over the past 50,000

rates are difﬁcult to determine even today, in part because the years, in which humans have played an increasingly important role

majority of earth’s species still remain undocumented. over time, we are left with a number of compelling and difﬁcult

questions concerning how the Anthropocene should be deﬁned:

6. Summary and conclusions whether or not extinctions should contribute to this deﬁnition, and

how much humans contributed to the earlier phases of the current

The wave of catastrophic plant and animal extinctions that began mass extinction event. We agree with Grayson (2007) and

with the late Quaternary megafauna of Australia, Europe, and the Lorenzen et al. (2011) that better chronological and contextual

Americas has continued to accelerate since the industrial revolution. resolution is needed to help resolve some of these questions,

Ceballos et al. (2010) estimated that human-induced species including a species by species approach to understanding their

extinctions are now thousands of times greater than the background speciﬁc demographic histories. On a global level, such a systematic

extinction rate. Diamond (1984) estimated that 4200 (63%) species program of coordinated interdisciplinary research would contrib-

of mammals and 8500 species of birds have become extinct since AD ute signiﬁcantly to the deﬁnition of the Anthropocene, as well as an

1600. Wilson (2002) predicted that, if current rates continue, half of understanding of anthropogenic extinction processes in the past,

earth’s plant and animal life will be extinct by AD 2100. Today, present, and future.

although anthropogenic climate change is playing a growing role,

the primary drivers of modern extinctions appear to be habitat loss, Acknowledgments

human predation, and introduced species (Briggs, 2011:485). These

same drivers contributed to ancient megafaunal and island We are grateful for the thoughtful comments of Torben Rick and

extinctions – with natural forces gradually giving way to anthropo- two anonymous reviewers on earlier drafts of this paper, as well as

genic changes – and accelerated after the spread of domestication, the editorial assistance of Anne Chin, Timothy Horscraft, and the

agriculture, urbanization, and globalization. editorial staff of Anthropocene. This paper was ﬁrst presented at the

T.J. Braje, J.M. Erlandson / Anthropocene 4 (2013) 14–23 21

Field, J.H., Dodson, J.R., Prosser, I.P., 2002. A late Pleistocene vegetation history from

2013 Society for American Archaeology meetings in Honolulu. We

Australian semi-arid zone. Quat. Sci. Rev. 21, 1023–1037.

are also indebted to the many scholars who have contributed to the

Field, J., Fillios, M., Wroe, S., 2008. Chronological overlap between humans and

ongoing debate about the causes of Late Pleistocene and Holocene megafauna in Sahul (Pleistocene Australia-New Guinea): a review of the evi-

dence. Earth-Sci. Rev. 89, 97–115.

extinctions around the world.

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,

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