Download Human acceleration of animal and plant extinctions: A Late

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.