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ANTHROPOLOGY
Campo Laborde: A Late Pleistocene giant ground sloth
kill and butchering site in the Pampas
Gustavo G. Politis1*, Pablo G. Messineo2, Thomas W. Stafford Jr3, Emily L. Lindsey4
The extinction of Pleistocene megafauna and the role played by humans have been subjects of constant debate
in American archeology. Previous evidence from the Pampas region of Argentina suggested that this environ-
ment might have provided a refugium for the Holocene survival of several megamammals. However, recent ex-
cavations and more advanced accelerator mass spectrometry radiocarbon dating at Campo Laborde site in the
Argentinian Pampas challenge the Holocene survival of Pleistocene megamammals and provide original and high-
quality information documenting direct human impact on the Pleistocene fauna. The new data offer definitive
evidence for hunting and butchering of Megatherium americanum (giant ground sloth) at 12,600 cal years BP and
dispute previous interpretations that Pleistocene megamammals survived into the Holocene in the Pampas.
INTRODUCTION
The late Quaternary megafaunal extinctions at the end of the Pleistocene,
resulting in the loss of between 35 and 90% of large-bodied animal
species on ice-free continents (excluding Africa), represented the most
profound faunal transition that Earth’s ecosystems experienced during
the Cenozoic, but the cause or causes of this event remain hotly debated
(14). In the New World, the causes and dynamics of the extinctions
have proved especially challenging to elucidate because they coin-
cided closely both with end-Pleistocene climate changes and with
the invasion of a new predator—Homo sapiens (2,3,5,6). Under-
standing this extinction in South America, both in archeology and
paleontology, has suffered primarily from a lack of chronological
control for the disappearance of megafauna taxa, as well as data on
the extent of their temporal overlap and interactions with humans
(3,4,79).
South America is particularly important for investigations of late
Quaternary extinctions because the continent lost more megafauna
taxa than any other continent during this event (2,3,9,10). The an-
swer to the questions of the underlying causes may reveal fundamental
principles of ecology—are extinctions synchronous across species, are
they abrupt or gradual, why do some taxa survive in refugia while the
majority are lost, and can a single new species disrupt ecosystems
in equilibrium for hundreds of millennia?
Previous studies of the late Quaternary extinctions in South America
have found evidence for both human-driven (11) and climate-driven
(12) megafauna loss, as well as synergistic impacts of these two fac-
tors (3,13). However, direct evidence of human predation on extinct
megafauna in South America is rare (8), despite thousands of years
of apparent overlap in some regions (9) and evidence that some taxa
could even have survived into the Holocene (10,14,15).
We use the Argentinian archeological site, Campo Laborde, to
demonstrate that humans hunted and butchered a giant ground
sloth, that advanced radiocarbon dating techniques do not sup-
port Holocene survival of megafauna in the area, and that these new
dates cast doubts on other published Holocene ages for Pleistocene
fauna in the Pampas.
The essential data for assessing the interactions of fauna, climate,
and humans are accurate chronologies for extinctions, climate changes,
and the timing and rates of human dispersals. These data must de-
rive from well-dated archeological sites having indisputable associ-
ation with remains of extinct taxa (1618). While most New World
archeological sites with unquestionable extinct megafauna have Late
Pleistocene dates [~14,500 to 13,000 cal years before the present (BP)],
some sites in the South America Pampas (Fig.1A) have been dated to
the Early and Middle Holocene (10,1923), thereby causing archeolo-
gists and paleontologists to question the impact of humans on Late
Pleistocene extinctions (3,7,15). Besides Campo Laborde, archeolog-
ical sites that supported Holocene survivals of megafauna include La
Moderna (19), Arroyo Seco 2 (18,24), and Paso Otero 4 (22), as well as
paleontological localities that yielded Early Holocene dates on extinct
megamamals such as Arroyo Tapalqué (10) and Río Cuarto (25).
Of these sites, La Moderna has provided the greatest number of
Early and Middle Holocene dates. It is an open-air site located on
the banks of the Azul Creek (Fig.1A), where a close stratigraphic
association between lithic artifacts (expedient tools of crystalline
quartz and some curated tools of orthoquartzite and chert) and ex-
tinct faunal remains [Doedicurus clavicaudatus (Glyptodontidae)]
was confirmed (19). La Moderna is interpreted as a procurement site,
where, during a single event, a D. clavicaudatus was butchered at the
edge of an ancient swamp (19). The chronology of this event has
always been problematic and controversial. For these reasons, mul-
tiple samples have been run on D. clavicaudatus bone collagen and
organic sediment samples. The first dating result was a standard age
processed by Beta Analytic and yielded an age considered to be too
young: 6550 ± 160 14C years BP (Beta-7824). A second bone sample
yielded an accelerator mass spectrometry (AMS) age of 12,350 ±
370 14C years BP (TO-1507) through the IsoTrace Lab. Two addi-
tional dates from the same bone from the same laboratory with a
more appropriate pretreatment yielded ages of 7010 ± 100 14C years
BP (TO-1507-1) and 7510 ± 370 14C years BP (TO-1507-1). Last,
radiocarbon dating a third bone fragment gave a result close to these
ages [7460 ± 80 14C years BP (TO-2610)]. Two organic samples were
taken from lithostratigraphic unit (a), which contained the archeo-
logical deposit produced ages of 8356 ± 65 14C years BP (DRI-3012)
and 7448 ± 109 14C years BP [DRI-3012 (19,26)]. As a consequence,
1INCUAPA-CONICET, Facultad de Ciencias Sociales (UNICEN) and Facultad de Ciencias
Naturales y Museo (UNLP), Olavarría, Buenos Aires B7400JWI, Argentina. 2INCUAPA-
CONICET, Facultad de Ciencias Sociales (UNICEN), Olavarría, Buenos Aires B7400JWI,
Argentina. 3Stafford Research LLC., Lafayette, CO 80026-1845, USA. 4La Brea Tar Pits
and Museum, Los Angeles, CA 90036, USA.
*Corresponding author. Email: gpolitis@fcnym.unlp.edu.ar
Copyright © 2019
The Authors, some
rights reserved;
exclusive licensee
American Association
for the Advancement
of Science. No claim to
original U.S. Government
Works. Distributed
under a Creative
Commons Attribution
NonCommercial
License 4.0 (CC BY-NC).
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this series of dates suggested that the age of La Moderna was be-
tween 7000 and 7500 14C years BP. The 6550 ± 160 14C years BP date
was considered too young, while the 12,350 ± 370 14C years BP age was
discarded as too old; both dates were considered as outliers (26).
The other site with Holocene dates on extinct fauna is Arroyo
Seco 2. The site presents abundant evidence related to the study of
the Pleistocene megafauna (7,18,24). This multicomponent, open-air
locality lies between a low ridge of loess and a small stream, Arroyo
Seco Creek (Fig.1A). The Arroyo Seco 2 site has an early component
containing a lithic assemblage composed of unifacial, marginally re-
touched tools associated with bone remains of nine extinct taxa:
Equus neogeus, Hippidion sp., Toxodon platensis, Megatherium
americanum, Eutatus seguini, Glossotherium robustum, Macrauchenia
sp., Glyptodon sp., and Camelidae cf. Hemiauchenia (18). Three ex-
tinct species found in the early component show evidence of human
exploitation: E. neogeus, Hippidion sp., and M. americanum. The lower
component of Arroyo Seco 2 is interpreted to be the result of several,
low-resolution, human occupations at the end of the Pleistocene.
In the late 1980s and early 1990s, three radiocarbon ages from bone
collagen of E. (Amerhippus) neogeus and M. americanum yielded
Early Holocene ages: 8890 ± 90 14C years BP (TO-1504), 8470 ±
240 14C years BP (LP-53), and 7320 ± 50 14C years BP [TO-1506 (7)].
However, 15 AMS ages on megafauna bones, from different taxa,
from Arroyo Seco 2 run at different radiocarbon laboratories yielded
ages between 12,240 ± 110 14C years BP and 10,500 ± 90 14C years
BP (18). Among these, three new results were particularly substantial
as they were obtained on the same M. americanum bone sample pre-
viously dated to 7320 ± 50 14C years BP. These new results negate the
Holocene age of the sample and place it at the end of the Pleistocene:
12,200 ± 170 14C years BP (CAMS-58182), 12,155 ± 70 14C years BP
(OxA-10387), and 11,770 ± 120 14C years BP (AA- 62514). Therefore,
the 7320 ± 50 14C years BP and 8470 ± 240 14C years BP measure-
ments should both be rejected. The age of 8890 ± 90 14C years BP
from E. neogeus was also not replicated. Four ages, from separate
bone samples of Equus, gave Late Pleistocene ages [between 11,320 ±
110 14C years BP (AA-39365) and 11,000 ± 100 14C years BP (OxA-
4590)]. As a consequence, the new group of radiocarbon dates from
Arroyo Seco 2 does not appear to support a Holocene fauna survival
at the site as previously proposed (7), with the exception of medium-
sized E. seguini [dated in 7388 ± 74 14C years BP (AA-90117)] (18).
The third site with a purported Holocene age is Paso Otero 4
(Fig.1A). There are no direct dates on extinct faunal bones despite
several failed attempts. The only dates for Paso Otero 4 are Early
Holocene 14C dates on humates [between 8913 ± 49 14C years BP
(AA-87938) and 7729 ± 48 14C years BP (AA-85157)] from the lower
unit 2 containing E. seguini bones (22). Other 14C Holocene dates
from extinct fauna in the Pampas (Fig.1A) include two dates on
Scelidotherium leptocephalum, one of 7615 ± 85 14C years BP (GrA-
48388) from Arroyo Tapalqué (10) and another of 7550 ± 60 14C
years BP (LP-1407) from Río Cuarto (25). Last, an age of 9890 ± 50 14C
years BP (GrA-49321) was reported for Macrauchenia patachonica
from Centinela del Mar (10).
The Campo Laborde site can provide high-quality data for dis-
cussing the human impact on the Pleistocene fauna and the timing of
the megamammal extinctions in the Pampas and in South America
due to its good stratigraphic resolution and high-accuracy radiocar-
bon dates. The site is located in the upper basin of Tapalqué Creek,
~15 km north-northeast of Olavarría city (Pampas region of Argentina;
Fig.1, A and B). In 2000, the landowner discovered in situ a com-
plete femur and vertebrae fragments from a giant ground sloth,
M. americanum. The original test pits were started here, and the site
was expanded with subsequent excavations during two field pro-
grams. The first was between 2001 and 2003, when an area of 29 m2
was excavated (20,21). The second field session was in 2016 and 2017,
when a new area of 21 m2 was excavated. This report presents and
integrates the findings of the 2016–2017 field seasons and includes
the new radiocarbon dates made with more advanced and accu-
rate methods for radiocarbon dating bone.
Fig. 1. Location of Campo Laborde site in South America. (A) Map of the Pampas grassland of Argentina (province of Buenos Aires), showing main sites men-
tioned in the text . References: 1, Campo Laborde site ; 2, La Moderna site; 3, Arroyo Seco 2 site; 4, Paso Otero 4 and 5 sites; 5, Arroyo Tapalqué; 6, Centinela del Mar; red
circles, archeological sites; blue circles, paleontological sites. (B) Aerial view of excavation area, picture courtesy of C. F. Dubois. [Photo credit: Dr. Cristian Favier Dubois.
INCUAPA-CONICET, Facultad de Ciencias Sociales (UNICEN)].
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RESULTS
The 2001–2003 excavations uncovered a great amount of giant ground
sloth bones associated with lithics and only two glyptodont bones
(Fig.2 and fig. S1) in swamp sediments between 1.00 and 1.30 m
below ground level (BGL). Approximately 70% of the lithic artifacts
were found among the megamammal bone concentration, while the
remaining percentage was recovered around the concentration but
in sectors very close to the bones (fig. S2). We made the statistical test
correlation between the frequency of spatial distribution of lithics
and bones. As a result, we find a positive and significant correlation
(Spearman’s rho = 0.454, P = 0.00072) supporting an intimate spa-
tial association between bones and cultural remains. Lithic material
included a lanceolate bifacial projectile point stem, a broken side
scraper, one orthoquartzite flake, and 128 orthoquartzite, silicified
dolomite, and chert microflakes ranging from 2 to 9 mm long (27).
The artifact interpreted as the base of a broken lanceolate bifacial
projectile point (FCS.CLA.33) has a convex bottom, a transverse
distal fracture (Fig.3A), and edges with no intentional abrasion (28).
Use-wear analysis indicates that both edges have postdepositional
alterations (e.g., soil sheen), and for this reason, they do not show
diagnostic characters associated with the tool’s use. One face of this
point has laminar pressure-flaked scars along the base, and the op-
posite face has a single, small, basal thinning flake. The latter has
modifications in the fracture of the quartz crystals, and micropo-
lishing in the first stages of formation associated with striations and
small pits suggests that this projectile point was hafted (Fig.3B). The
orthoquartzite side scraper fragment (FCS.CLA.183) is made from
a large flake without cortex. It has two working edges with unifacial
and marginal retouches (Fig.3C). This tool is completely modified
by sedimentary abrasion and soil sheen that render any polishing
unrecognizable (28).
Excluding micromammals, 282 faunal bones were recovered. One
individual each of three extinct megafauna taxa was identified: a giant
ground sloth (M. americanum) and two glyptodonts (Neosclerocalyptus
sp. and Doedicurus sp.). Giant ground sloth fossils were, by far, the
most abundant [79 elements, number of identified specimens (NISP) =
108], and all the anatomical elements of the body were present, includ-
ing 102 dermal bones assigned to M. americanum (table S1). One
Neosclerocalyptus sp. humerus and one partial Doedicurus sp. femur
were also recovered (table S1). Modern species are represented by a
few remains of Patagonian hare (Dolichotis patagonum), vizcacha
(Lagostomus maximus), dwarf armadillo (Zaedyus pichiy), peccary
(Tayassu sp.), fox (Lycalopex sp.), bird (Rheidae), and artiodactyls
(Camelidae) (table S2). A significant number of smaller vertebrates
were also recovered: Reithrodon auritus, Ctenomys sp., Akodon cf.
Akodon azarae, and Galea leucoblephara (20,29). With the exception
Fig. 2. Plan map of the Campo Laborde excavation site. Distribution of complete and fragmentary bones and lithic tools. Shaded drawings (black) indicate lithic materials
(FCS.CLA.33, FCS.CLA.183, FCS.CLA.1989, and FCS.CLA.1990). Red and green dashed lines show lithic refits. Sample dated in this paper (FCS.CLA.154). A-B black line indi-
cates geologic cross section (see Fig. 4 and fig. S5).
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of the giant ground sloth and the Patagonian hare (see cultural modifi-
cation below), all other modern and small vertebrates species are inter-
preted as the result of incremental accumulation of fossil bones (“bone
rain”) that occur at the site due to natural deaths (eto-ecological processes)
and owl activity (29) that postdate human- Megatherium interaction. In
relation to the rest of the other megamammal species (Neosclerocalyptus
sp. and Doedicurus sp.), it is difficult to interpret their incorporation
into the deposit as a result of human activity since they are only rep-
resented by a single bone each (absence of any evidence of a human
selective pattern) and they do not show any trace of human action on
bones (cut marks, impact points, anthropic fractures, or burning).
In contrast, in addition to the close stratigraphic, vertical and
horizontal association with lithics (Fig.2 and fig. S2), other evidence
supports the butchering and processing of M. americanum and
D. patagonum. Evidence of butchering included stone tool modifi-
cations on an M. americanum rib (FCS.CLA.9) and a D. patagonum
tibia (FCS.CLA.227), as well as flakes and helical fractured bones
of megafauna taxa caused by human agency (fig. S3A). We made all
diagnoses and identifications on the original specimens under a Leica
Stereo Zoom S6D Trinocular stereoscopic microscope with magni-
fications ranging from 6.3 to 40× under adjustable incident light and
with a digital Leica DMC 4500 camera.
Cut marks on the right rib of M. americanum are located on the
interior surface. They represent four areas of marks with a transverse
orientation to the rib axis (Fig.4). This element shows unambiguous
stone tool cut marks that are perpendicular to the cortical surface,
straight V-shaped in cross section, and with internal microstriations,
two of them showing multiple parallel marks (Fig.4). We infer that
these marks are associated with defleshing the animal. Cut marks
on a D. patagonum tibia are located on the posterior surface of this
Fig. 3. Lithic tools found at Campo Laborde site. (A) Lanceolate bifacial projectile point stem (FCS.CLA.33). (B) Striations and small pits related with hafted micropolishing
(×200 magnification). (C) Distal half of a broken side scraper (FCS.CLA.183). (D) Proximal half of a broken side scraper (FCS.CLA.1990). (E) Biface (FCS.CLA.1989). [Photo
credit: Pablo Messineo. INCUAPA-CONICET, Facultad de Ciencias Sociales (UNICEN)].
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element and have a length of ~1 cm, with an oblique/transverse ori-
entation, generally parallel to the axial axis of the bone (fig. S4).
These cut marks were interpreted as a result of activities related to
the skinning the animal (29).
In addition, two bone tools were made from megamammal ribs.
One of them corresponds to the right distal end of M. americanum
rib (FCS.CLA.47), which is a fracture-based utilitarian bone tool and
has a rounded and polished fracture edge (fig. S3B). We solely placed
these traces on the end section of the fracture edge (fig.S3C), whereas
adjoining segments of the fracture edge and the rest of the rib do
not present any type of bone modifications (i.e., abraded, smoothed,
and polished). The second bone tool is a fragment of a rib (FCS.
CLA.184) from an unidentified megafaunal species (same size of
Megatherium) that has, at least, five negative flaking scars along the
external compact bone produced during the manufacture of the tool
(fig. S3D). One bone flake (FCS.CLA.26) was refitted onto one of
these negative scars (fig. S3E). The bone tool and flake were separated
by ~0.75 m horizontally (Fig.2). The distal end edge of this bone is
rounded and polished with parallel striations and microflaking on
the external cortical surface (fig.S3F). This is probably related to its
use. The rest of the bone does not show these types of modifications.
In the use-wear analysis, the wear polish was interpreted as the result
of contact between the bone tool and a hard material. It is important
to remark that no other bones in the collection show evidence of
abrasion or polishing, not even in a lower degree (as happens occa-
sionally in swamp environments). These observations support the
human manufacture of the two bone tools (28).
Geologic studies identified stratigraphic units typical of the Late
Pleistocene-Holocene Pampas (Fig.5 and fig. S5). In the lower sec-
tion of the profile (~1.30 to 1.35 m BGL), lacustrine sediments cor-
responding to the Luján Formation (30) are present. Most of the
archeological deposit (i.e., bones and lithics) was located from ap-
proximately 0.95 to 1.30 m BGL in stratum 1. This paleoswamp
unit rested unconformably on Guerrero Member sediments and
consisted of alternating layers of silty clays and sandy muds whose
deposition was punctuated by pedogenesis (Fig.5 and fig. S5). We
excavated small numbers of microflakes (n = 25) and small bone
fragments in an overlying paleosoil, 3Ab3, between 0.85 to 0.95 m
BGL (fig. S6). These two units are located in a transition between the
Río Salado and Guerrero Members (20,30). Above the archeological
deposits are two additional buried soils; the stratigraphic sequence is
capped by the modern soil (A). We recovered no archeological evi-
dence from sediments above 0.85 cm BGL (Fig.5 and fig. S5). The
lithics are directly associated with the sloth’s stratigraphic position
and occur from 0.85 to 1.35 cm BGL, mainly in stratum 1 (figs. S5
and S6). The scarce materials found in the Guerrero Member and in
the paleosoil 3Ab3 are due to the vertical migration of microflakes and
small nonidentifiable bones from the stratum 1 (3ACb3 and 3AC3;
see refitting among lithic materials).
The chronology of Campo Laborde has been difficult to establish
due to extreme degradation and loss of bone organic matter and the
bones’ severe humate contamination. Initially, only 7 of 12 bones
had detectable collagen (table S3). M. americanum fossils containing
collagen yielded ages ranging from 6740 ± 480 14C years BP (AA-
71667) to 9730 ± 290 14C years BP (AA-71665). We obtained two soil
organic matter samples from the northern profile of the site. One
of the samples came from paleosoil 3Ab3 and gave a date of 7960 ±
100 14C years BP (LP-1983). The second sample was taken from
stratum 1, the paleoswamp where there was the highest proportion
of bones and stone materials and provided an age of 8090 ± 190 14C
years BP (LP-2003). These results should be taken with caution be-
cause dates obtained from soil organic matter must be considered
Fig. 4. Cut marks on M. americanum rib (FCS.CLA.9). [Photo credit: Pablo Messineo. INCUAPA-CONICET, Facultad de Ciencias Sociales (UNICEN)].
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minimum soil ages and do not date the time of human occupation.
Since this group of ages roughly dated this component between
~9700 and 6750 14C years BP, Campo Laborde was interpreted as an
Early Holocene giant ground sloth procurement site along the border
of an ancient swamp, where megafauna were killed and butchered
(20,21). Although the possibility that the giant ground sloth was
scavenged by humans cannot be ruled out (31,32), we believe that
the sloth would have been hunted on the basis of the location of
the event (driving prey into a swamp is a frequent hunting strategy)
and the finding of a the broken bifacial projectile point that could
be interpreted as one of the hunting tools (27).
Excavations in 2016 and 2017 (Fig.2 and fig. S7A) yielded a taxo-
nomically indeterminate rib fragment, 2 M. americanum metapodi-
als (fig. S7B), 1 Lama guanicoe cervical vertebra (tables S1 and S2), 2
orthoquartzite tools (Fig.3,DandE, and fig. S7, C and D), and
58 microflakes and debitage made from orthoquartzite, chert, silicified
dolomite, and quartz. All the lithic materials and bone remains were
found in stratum 1, the paleoswamp, between 0.95 and 1.30 m BGL.
One of the tools is a knife manufactured on a biface (FCS.CLA.1989;
81.6 cm by 55.8 cm by 15.3 cm); one of the convex edges has been
retouched and has an angle of ~40° to 50°, which makes it suitable
for cutting activities (Fig.3E). The other tool is the proximal half of
a broken side scraper (FCS.CLA.1990) that refits with the other dis-
tal half (FCS.CLA.183) found ~3.5 m away in 2003 (Figs.2and3,
CandD). The edge of the distal-half side scraper was resharpened
after breaking (Fig.3C), indicating that the tool was broken during
use and that one-half was repaired and used again. In 2003, four
silicified dolomite microflakes that came from different grids and
levels also refitted (Fig.2). One of the refits was between proximal
(FCS.CLA.238) and distal (FCS.CLA.251) flakes that were separated
by ~2 m horizontally (Fig.2). The other refit connects proximal
(FCS.CLA.239) and medial (FCS.CLA.242) flakes separated by ~3 m
horizontally (Fig.2). In this last refitting, one fragment come from the
level 1.30 to 1.35 m BGL (in the limit between the Guerrero Member
and the paleoswamp) and the other piece come from the level 1.20
to 1.25 m BGL (stratum 1), supporting the conclusion that the lithic
material in Campo Laborde is associated with the paleoswamp and
the small quantity of microflakes in the Guerrero Member and in the
stratum 2 (paleosoil 3Ab3) correspond to vertically dislocated ma-
terials. This vertical migration of microflakes may be the result of
the depositional environment (lentic environment of alluvial plain
margin) and pedogenic processes that subsequently affect the de-
posit. Likewise, the presence of few burrows and a small grouping of
bones (Ctenomys sp.) in a limited sector of the site supports the ac-
tion of fossorial animals and could explain the migration of micro-
flakes downward and upward into the Guerrero Member and the
stratum 2.
2016–2017 AMS 14C DATING PROGRAM
Accurate and precise radiocarbon chronologies are the foundation
for studying Late Pleistocene megamammal extinction times and
rates and for assessing what degree of temporal overlap exists be-
tween extinct taxa and humans. Once initial stratigraphic association
is shown between megamammal fossils and human-manufactured
lithic or bone artifacts, and these associations are determined ta-
phonomically valid, the geologic age of these sites is determined by
directly dating bones of the extinct mammals and bone tools. Indi-
rect dating of physically associated macroflora, microfauna, molluscs,
nonextinct mammal taxa, or organic matter from enclosing sediments
or soils is not acceptable.
Excepting bones from tar seeps, fossil bones from Campo Laborde
and similar localities are the most difficult to radiocarbon date ac-
curately. Campo Laborde fossils have zero to low quantities of col-
lagen, the collagen is poorly preserved chemically and is difficult to
extract, and the protein (collagen) is heavily contaminated with sedi-
mentary and soil organic matter, usually occurring as humates (fulvic
acids, humic acids, and humins). The single most intransigent chem-
ical problem to overcome is the covalent bonding of humates to col-
lagen, which occurs through the Maillard reaction (33). Separating
Fig. 5. Stratigraphy of the Campo Laborde site. [Photo credit: Pablo Messineo. INCUAPA-CONICET, Facultad de Ciencias Sociales (UNICEN)].
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humates from collagen and isolating indigenous collagen and its
amino acids require chemical pretreatments not commonly used by
radiocarbon laboratories.
Humate contamination cannot be overcome by using standard
bone collagen preparation techniques (e.g., decalcification, alkali
leaching, gelatinization, or ultrafiltration). During burial, the Maillard
reaction covalently binds humic and fulvic acids to proteins (17,33),
resulting in very dark brown to light yellowish brown collagen (34).
Although alkali treatment extracts some humates, and gelatiniza-
tion removes other, nonbound humates, covalently bound humic
and fulvic acids can only be separated from collagen by breaking the
collagen-humate bounds by hydrolyzing the collagen in 6 M HCl
for 24 hours at 110°C (35). The resulting hydrolyzate contains free,
cationic amino acid hydrochlorides and weakly charged to uncharged
fulvic acids. The collagen’s amino acids are isolated for 14C dating
by passing the hydrolyzate through hydrophobic XAD-2 resin, which
binds to the fulvic acids and allows the amino acids to pass through
XAD-2 resin.
Low collagen content per se is not a hindrance to 14C dating fossil
bones or teeth. One concern is that larger masses of bone are needed
to compensate for low weight percentages of collagen (e.g., needing
5 g of bone instead of 0.1 g). A greater problem with low protein
content is the remaining collagen has undergone increasingly more
diagenesis, which decreases the protein’s stability during HCl decal-
cification and KOH treatment and decreases the collagen’s solubility
during gelatinization. The result is that less protein is recoverable,
and although the bone initially contained marginal amounts of col-
lagen, no collagen may ultimately be recoverable.
Previous 14C dating of extinct fauna from Campo Laborde (table S3)
yielded Holocene ages ranging from 6740 ± 480 (AA-71667) to 9730 ±
290 14C years BP (AA-71665). We obtained these ages using three dif-
ferent chemical fractions: (i) acid-base-acid purified collagen (alkali-
extracted decalcified collagen), (ii) gelatin, and (iii) ultrafiltered
(> 30 kDa) gelatin (table S3 and Materials and Methods).
In 2016–2017, only 1 of 10 bones processed from Campo Laborde
contained collagen. The one successful specimen was an M. americanum
Metacarpal V (FCS.CLA.154; Fig.2) that was first dated in 2007 as
9730 ± 290 14C years BP (AA-71665; table S3) and was redated.
AMS 14C measurements for this paper used XAD-2 resin purification
to date total amino acids from hydrolyzed collagen and fulvic acids
separated from the collagen hydrolyzate (Table1, table S4, and
Materials and Methods). XAD purification followed Stafford etal.
(35) and Stafford (34) and comprised decalcification in HCl, extrac-
tion with KOH, gelatinization and filtering through 0.45-m mem-
branes, 6 M HCl hydrolysis, and passing the hydrolyzate through
XAD-2 resin. Fulvic acids bound to the XAD resin were eluted by
washing the resin with 0.05 M HCl to remove excess acid, eluting the
fulvic acids with 0.05 M NaOH, drying the liquid under vacuum, and
finally, acidifying the fulvic acids solution with 1 M HCl. AMS 14C
measurements on XAD hydrolyzates produced three radiocarbon ages
(RC years ± 1 SD) for the Metacarpal V: 10,570 ± 170 14C years BP
(CAMS-171851), 10,655 ± 35 14C years BP (CAMS-171852), and
10,690 ± 380 14C years BP (CAMS-171861; Table1). AMS 14C mea-
surements (fraction modern or Fm) on fulvic acids solution rep-
resent an integration of all ages of fulvic acids that accumulated in the
bone since its deposition. While the average Fm value for the three
XAD dates was 0.2660 ± 0.0078, the fulvic acids had a higher (more
modern) averaged Fm = 0.3238 ± 0.0099. Calculated “ages” for the
fulvic acids are given to demonstrate that fulvic acids contain more
14C than the collagen and cause more recent (Holocene) ages when
non- XAD chemistry is used to date the bones (Table1 and table S4).
We conclude that humates remaining in collagen caused the pre-
vious Campo Laborde bones to date younger than their actual age
and that only XAD purification chemistry is acceptable. While well-
preserved collagen with no-to-negligible humates can sometimes be
dated accurately using either ultrafiltered or 0.45-m filtered gela-
tin (34,36), both filtration methods and lesser purity fractions as
decalcified collagen and alkali-extracted collagen will produce erro-
neous 14C dates.
A geologic profile 20 m upstream from Campo Laborde was
studied (37), with paleosoil 3Ab3 being reinterpreted as a black mat
(highly organic marsh deposit). The study produced a date of 5680 ±
40 14C years BP (Beta-254925) on organic material from the black
mat and a date of 8550 ± 50 14C years BP (Beta-254924) from a bio-
genic cavity fill below the paleoswamp (where we recovered most of
the archeological evidence). This cavity fill was interpreted as an
“intrusion of younger organic matter from overlying early Holocene
marshes” (37). In addition to the 14C dates, an Optically Stimulated
Luminescence age of 12,120 ± 2120 years BP (X-3565) was mea-
sured for the paleoswamp. Last, Succinea sp. shells were dated
as 10,620 ± 60 14C years BP (Beta-254926) and 10,420 ± 60 14C years
BP [Beta-254928 (35)]. On the basis of these results, Toledo and
Schewenninger (37) concluded that the bone samples from several
Pampean archeological sites (e.g., La Moderna and Paso Otero 5)
had been contaminated by younger organic matter and that Campo
Laborde “…appear(s) to have a terminal Pleistocene age (12-14 ka CAL
BP? and not a basal Holocene age as previously proposed, …)”.
DISCUSSION
The interpretation of Campo Laborde as a kill (or procurement)
and butchering site makes it difficult to discuss the broader subsis-
tence pattern during Late Pleistocene times in the Pampas (23,38)
because this type of site can bias the interpretations about the sub-
sistence strategies as a whole. However, on the basis of the evidence
from other sites, the role of megafauna appears to have greater im-
portance in the Pampas during this period in comparison with other
regions of South America (38). The presence of the orthoquartzite
stem allows a comparison with the other projectile points from the
Pampas. The main projectile point type in the region is the Fishtail
point, which has been dated between ~11,800 and 10,000 14C years
BP (3942), although the only site in the region with a clear associ-
ation between this point type and extinct megamammals is Paso
Otero 5 (43), which dates between 10,440 ± 100 14C years BP and
9560 ± 50 14C years BP. While Fishtail points are the most abundant
in the Pampas, other Late Pleistocene projectile types have been re-
corded in the region (44) and in the Southern Cone (45). Among
them, Tigre points in the Pampas of Uruguay show a wide stem with
a convex base and have been dated between ~10,420 and 9730 14C
years BP (44). However, no Tigre points have been found in the
Pampas of Argentina. In any case, the stem found in Campo Laborde
(with a similar concave base but different in dimensions and tech-
nological features) suggests that, around 10,650 14C years BP, at least
two projectile point models were used to hunt Pleistocene megama-
mmals in the Pampas of Argentina. Moreover, the bifacial knife of
Campo Laborde also confirms the use of this technology in the
Pampas at the end of the Pleistocene and shows similarities with
other comparable artifacts (42,44).
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The Pampas region has consistently produced younger last appear-
ance dates for extinct megafauna than other regions of South America
(9), leading some researchers to propose that it served as a refugium
during the Late Pleistocene (7,15). Pampas region sites with published
Early Holocene radiocarbon dates on extinct megafauna include
Arroyo Seco 2 (7,10), La Moderna (7,19), Paso Otero 4 (22), Arroyo
Tapalqué (10), Centinela del Mar (10), and Río Cuarto (25). Many of
these Holocene dates have been rejected by authors due to diagenetic
concerns or failure to replicate dates or are otherwise suspect because
the material dated is considered less reliable than bone collagen (e.g.,
tooth enamel bioapatite carbonate). Notably, none of these dates
used amino acid–based methods, except some of the Arroyo Seco 2
dates (18), and therefore, this study raises the possibility that the
Holocene 14C ages may be due to contamination by fulvic acids and
other exogenous compounds that cannot be completely removed by
traditional radiocarbon preparation methods. This contamination
may be a particular problem in the Pampas, as compared with other
parts of South America, because the open-air, fluvial, and lacustrine
deposits typical of the region both produce low collagen yields
through leaching and offer ample opportunity for plant- and animal-
based humates to penetrate bones and bind with collagen.
CONCLUSIONS
The recent excavations and new 14C dates support Campo Laborde being
a kill and butchering site bordering a Late Pleistocene swamp. The
lithic artifacts found around and within the giant ground sloth bone
concentration suggest that hunters knapped directly around the car-
cass. The refitting of side scraper fragments and microflakes supports
the stratigraphic integrity of the deposit and that butchering activities
and resharpening of artifacts occurred at the site. Micro wear analysis
on the broken projectile point stem indicates that it was hafted.
The new 14C measurements solidly date the killing and exploita-
tion of the giant ground sloth to the Late Pleistocene. These new dates
do not support extinct megamammals surviving into the Holocene
at Campo Laborde and call into question Holocene survival of mega-
fauna at most, if not all, Pampas localities. Certainly, more radiocar-
bon analyses using amino acid–based methods are necessary in sites
such as La Moderna to test the supposedly Holocene age of the ex-
tinct megamammals in these sites.
Campo Laborde is the only confirmed giant ground sloth kill site
in the Americas. New dating also reduces the time span between the
arrival of humans and the extinction of the megamammals in the
Pampas of Argentina in ~2000 years. Both of these results support
previous proposals (3,7) on the contribution of human impact in the
extinction process of the South American megafauna. The Pampas
data are evidence that some extinct species (e.g., Megatherium, Equus,
and Doedicurus) were exploited by people, probably with a low level
of predation, over at least two millennia, before their extinction.
MATERIALS AND METHODS
Radiocarbon sample preparation
The following summaries describe what chemical pretreatments were
performed by each laboratory. The University of Arizona AMS
Lab processed dates labeled as AA−. Dates shown as CAMS− were
Table 1. AMS radiocarbon measurements for Campo Laborde M. americanum Metacarpal V (FCS.CLA.154) and humates separated during chemical
pretreatment. Accepted age is 10,655 ± 35 14C years BP (CAMS-171852) due to having the highest mass bone (3.058 g) and lowest SD. NA, not available; C.I.,
confidence interval.
AMS Lab no. Chemical fraction
dated
Bone
processed (g) Carbon dated (g) Fm ± SD
14C date ± 1 SD
RC years BP CAL BP (2) 95.4%
C.I. (46)
Original University of Arizona analysis
AA-71665 Gelatin 22 0.298 ± 0.011 9730 ± 290 10,250–11,982
CAMS bone dates
CAMS-171861
XAD KOH-
extracted
decalcified
collagen
1.025 40 0.2642 ± 0.0122 10,690 ± 380 11,304–13,207
CAMS-171873
Fulvic acids eluted
from CAMS-171861
XAD resin
165 0.3397 ± 0.0030 8670 ± 80 NA
CAMS-171851 XAD decalcified
collagen 1.137 90 0.2684 ± 0.0056 10,570 ± 170 11,924–12,732
CAMS-171875
Fulvic acids eluted
from CAMS-171851
XAD resin
30 0.2983 ± 0.0167 9720 ± 450 NA
CAMS-171852
XAD KOH-
extracted
decalcified
collagen
3.058 410 0.2654 ± 0.0010 10,655 ± 35 12,547–12,677
CAMS-171874
Fulvic acids eluted
from CAMS-171852
XAD resin
165 0.3335 ± 0.0021 8670 ± 80 NA
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chemically prepared and combusted by E.L.L. and were graphitized
and AMS 14C–dated at the LLNL Center for Accelerator Mass Spec-
trometry, California.
AA-55117, AA-55118, and AA-55119
Bone samples were demineralized in 0.25 M HCl, and the acid-
insoluble fraction was extracted with deionized (DI) water (pH 2) at
60°C. The hot water soluble fraction was dried and combusted to
yield CO2 for graphitization.
AA-71665 and AA-71667
Bone samples were demineralized in dilute HCl, leached with
NaOH, and acidified with dilute HCl using a continuous flow
Acid-Base-Acid (ABA) extraction system to yield the ABA-treated
bone fraction used for combustion and dating.
CAMS-155863
Approximately 200 mg of uncrushed, mechanically cleaned
M. americanum rib bone (FCS.CLA.9) was decalcified in 0.25 M HCl
at 4°C for 72 hours, replacing HCl daily, until the sample softened
(the sample never attained the fully soft, spongy texture characteris-
tic of demineralized collagen). The sample was then gelatinized in
0.1 M HCl at 58°C for 16 hours, after which the solution was filtered
through a Whatman quartz fiber filter with vacuum suction and
then ultrafiltered through 30-kDa Centriprep centrifugal filters that
had been prerinsed via centrifugation four times in Milli-Q purified
water. The ultrafiltered collagen was freeze-dried and combusted
at 850°C for 12 hours in quartz tubes containing copper oxide (CuO)
and silver (Ag). The resulting CO2 was purified and graphitized for
AMS 14C measurement.
CAMS-171851, CAMS-171852, and CAMS-171861
Approximately 1 g of bone for samples CAMS-171851 and CAMS-
171861 and 3 g for CAMS-171852 were removed from M. americanum
Metacarpal V (FCS.CLA.154) and were mechanically cleaned with a
Dremel tool. Bone fragments approximately 5 to 10 mm long were
decalcified at 4°C in 0.2 to 0.5 M HCl for up to 35 days. Decalcifica-
tion was considered complete when (i) CO2 effervescence had ceased,
(ii) the resulting collagen had a translucent appearance and spongy
texture, and (iii) no calcium phosphate density gradient was appar-
ent after the sample had been stationary for several hours in fresh
HCl. CAMS-171861 was subsequently alkali-extracted with 0.1 M
KOH for 2 days at 38°C.
All decalcified collagen samples were rinsed in DI water and
placed in sealed tubes with 6 M HCl on a heating block at 110°C for
22 hours to hydrolyze the collagen. Heating in strong HCl hydro-
lyzes the protein’s peptide bonds to form free amino acids, releases
humates bound to the collagen through the Maillard reaction, and
causes other humate-related compounds to precipitate. The amino
acids are cationic in strong acid, while the hydroxyl and carboxyl
groups of the fulvic acids are fully protonated, making them neutral
molecules that strongly bind to the nonpolar XAD-2 resin. The hydro-
lyzates were passed through XAD-2 columns containing approxi-
mately 2 ml of Restek Ultra-Clean XAD-2 resin retained between
two 20-m Restek SPE frits; each column was fitted at the bottom
with a 0.45-m Restek SPE filter cartridge. The XAD-filtered hydro-
lyzates were evaporated in a vortex evaporator, and between 1 and
6 mg of hydrolyzed collagen, were combusted in sealed quartz tubes
containing copper oxide (CuO) and silver (Ag).
CAMS-171873, CAMS-171874, and CAMS-171875
Following the XAD-2 purification of the amino acid hydrolyzates
for samples CAMS-171851, CAMS-171852, and CAMS-171861,
the resin columns were washed with DI water (pH 8) to remove
excess HCl. Fulvic acids bound to the resin were eluted using a few
tens of microliters of 0.1 M KOH; the elute was acidified with HCl,
dried, and combusted in sealed quartz tubes containing copper
oxide (CuO) and silver (Ag). All CO2 resulting from the combus-
tions was graphitized, and targets were analyzed by accelerator
mass spectrometry.
SUPPLEMENTARY MATERIALS
Supplementary material for this article is available at http://advances.sciencemag.org/cgi/
content/full/5/3/eaau4546/DC1
Fig. S1. View of M. americanum bones (ribs and vertebrae) and lithic tool (red arrow) recovered
in 2003.
Fig. S2. Horizontal lithic distribution in Campo Laborde.
Fig. S3. Bone tools and flakes.
Fig. S4. Cut marks on D. patagonum tibia (FCS.CLA.227).
Fig. S5. Stratigraphic scheme of the Campo Laborde site.
Fig. S6. Vertical lithic distribution at Campo Laborde site.
Fig. S7. Bones and lithics exposed during new excavation.
Table S1. Stratigraphic and anatomical data for skeletal elements of giant ground sloth
(M. americanum) and glyptodonts (Neosclerocalyptus sp. and Doedicurus sp.) recovered from
Campo Laborde.
Table S2. Stratigraphic and anatomical data for skeletal elements (MNE) of modern fauna
recovered from Campo Laborde.
Table S3. Previous AMS 14C dates from Campo Laborde.
Table S4. AMS radiocarbon measurements for known-age samples and backgrounds.
References (47, 48)
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southern Cone. Quat. Int. 473, 161–172 (2018).
42. R. Suárez, G. Piñeiro, F. Barceló, Living on the river edge: The Tigre site (K-87) new data
and implications for the initial colonization of the Uruguay River basin. Quat. Int. 473,
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(Muséum National d’ Histoire Naturelle. Departement de Prehistoire, U.M.R, Paris, 2011),
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Southern hemisphere calibration, 0-50,000 years CAL BP. Radiocarbon 55, 1889–1903 (2013).
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Acknowledgments: We thank T. Guilderson from the Lawrence Livermore National
Laboratory (LLNL) for providing laboratory facilities, as well as advice and support, and
K. Harvati and the “Words, Bones, Genes, Tools” project because part of this paper was
written when two authors (G.G.P. and P.G.M.) were visiting scholars at the Institute for
Archaeological Science, Center for Human Evolution and Paleoenvironment, Eberhard Karls
Universität Tübingen (Germany). We also thank the undergraduate students from the
Universidad Nacional del Centro de la Provincia de Buenos Aires and from the Universidad
Nacional de La Plata who participated in the 2016 and 2017 field seasons. Funding: This
reserach was supported by the National Geographic Society (research grant 9773-15), the
Agencia Nacional de Promoción Científica y Técnica (ANPCYT, PICT 2015-2070), and the
Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET, PIP no. 0414) from
Argentina. Radiocarbon analyses were funded, in part, by NSF grant EAR-1148181 to
A. D. Barnosky. Author contributions: G.G.P. and P.G.M. led the investigation team for
Campo Laborde. P.G.M. analyzed the M. americanum bone collection and identified lithic refits.
T.W.S. and E.L.L. conducted the 14C dating. G.G.P., P.G.M., T.W.S., and E.L.L. wrote the paper.
Competing interests: The authors declare that they have no competing interests. Data and
materials availability: All data needed to evaluate the conclusions in the paper
are present in the paper and/or the Supplementary Materials. Additional data related to this
paper may be requested from the authors.
Submitted 12 June 2018
Accepted 28 January 2019
Published 6 March 2019
10.1126/sciadv.aau4546
Citation: G. G. Politis, P. G. Messineo, T. W. Stafford Jr, E. L. Lindsey, Campo Laborde: A La te
Pleistocene giant ground sloth kill and butchering site in the Pampas. Sci. Adv. 5, eaau4546
(2019).
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Campo Laborde: A Late Pleistocene giant ground sloth kill and butchering site in the Pampas
Gustavo G. Politis, Pablo G. Messineo, Thomas W. Stafford, Jr and Emily L. Lindsey
DOI: 10.1126/sciadv.aau4546
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... Cressman tried to assert that the human presence at Paisley Caves was contemporary with the remains of Pleistocene fauna such as camels, bison, and horses, particularly from the deposits in Cave 3 (Cressman, 1940). Critics, however, argued that Cressman's level of documentation of the stratigraphic and chronological context was not sufficient enough to adequately prove this association, and Cressman's theories of late Pleistocene human-animal associations at Paisley Caves were dismissed (Jenkins, 2007;Jenkins et al., 2016). Excavations ceased and the site was heavily vandalized and looted for decades afterwards by artifact collectors. ...
... Like other cave or rock shelter sites in the region, Paisley Caves was a seasonal hunting camp for native peoples residing in the northern Great Basin (Jenkins et al., 2016). Although pronghorn antelope and jack rabbit appear to be the most commonly hunted animals (Hockett et al., 2017), zooarchaeological evidence indicates the Paisley hunters also consumed mountain sheep, marmots, voles, sage hens, ducks, geese, swans, fish, and insects. ...
... Although pronghorn antelope and jack rabbit appear to be the most commonly hunted animals (Hockett et al., 2017), zooarchaeological evidence indicates the Paisley hunters also consumed mountain sheep, marmots, voles, sage hens, ducks, geese, swans, fish, and insects. Mule deer and elk were also seasonally available (Jenkins et al., 2016). Processed bone, hide, and hair in the Botanical Lens, an organic mat within Cave 2 consisting of sagebrush and other plant and animal remains spanning the Younger Dryas cooling period (11,600 -12,900 cal. ...
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The discovery of five individual specimens of the spinose ear tick, Otobius megnini (Dug è s), in late Pleistocene through middle Holocene deposits of the Paisley Caves site highlights an interesting aspect of prehistoric life not ordinarily visible through the analysis of traditional archaeological artifacts. A review of the literature provides ample evidence to postulate how the tick remains got into the cave deposits, and also implies the possibility of host-switching behavior in this tick and explores the manner by which ancient people dealt with ectoparasites. Furthermore, these remains mark the first record of the species in both archaeological and paleontological contexts.
... The diversity and density of tools from Levels 32, 33, and 34 suggest generally longer occupations at the site (Binford 1980;Shott 1986), possibly representing longer term residential occupations during which a variety of maintenance and production activities including plant and animal processing (e.g., McDonough et al. 2022), sewing and clothing manufacture (Lyman 2015;Osborn 2014), as well as stone-and bone-tool production and maintenance occurred. Younger Dryas-aged sites in the northern Great Basin such as Cougar Mountain Cave, Tule Lake Rockshelter, and Paisley Caves (Erlandson et al. 2014;Jenkins et al. 2016;Rosencrance et al. 2019), as well as sites in the southern Columbia Plateau like Lind Coulee and Marmes Rockshelter (Hicks 2004;Irwin and Moody 1978;Lyman 2015;Wilson 2008) exhibit similar patterns. These sites attest to the distinctive cold-adapted settlement-subsistence pattern of Pleistocene foragers in the Intermountain West and other regions across North America during the Younger Dryas (Lyman 2015;Osborn 2014). ...
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Stephen Bedwell excavated the Connley Caves in 1967 and 1968, uncovering dense Western Stemmed Tradition assemblages in the lowest deposits. Reporting a series of radiocarbon dates between 11,200 ± 200 14 C yr BP and 9150 ± 150 14 C yr BP, he suggested the earliest human occupation of Cave 4 dated to ∼11,000 14 C yr BP. Subsequent researchers have questioned the veracity of his claim and the reliability of his data. We revisit Bedwell's investigations to provide a detailed narrative of the excavations and more thoroughly report the Western Stemmed materials. We identify and date two Early Holocene and late Pleistocene cultural features and recharacterize the lithic assemblage. Our results suggest that Bedwell's oldest date is aberrant and current evidence for the earliest occupations spans the Younger Dryas. This study provides new information, resolves long-standing questions about Bedwell's assumptions and methodologies, and facilitates the incorporation of the collection into ongoing Western Stemmed research in the northern Great Basin.
... Faunal remains in the lowest cave layers include most of the fish remains studied here, as well as bones of extinct Pleistocene camel and horse (McHorse et al., 2016). Archaeological materials from the overlying strata record more extensive use of the caves during the period broadly equivalent to the YD (12.9e11.7 ka), based on the abundance of numerous artifacts, including Western Stemmed Tradition points, and faunal remains, including fish, surrounding hearth features (Hockett et al., 2017;Jenkins et al., 2016). The density of artifacts and coprolites declines precipitously in strata dating to the EH and MH, though a brief occupation is indicated by small hearth features and mammal bones dating to about 8.4 ka, in sediments just below the 7.63 ka Mazama ash (Egan et al., 2015). ...
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I explore human settlement patterns in the northwestern Great Basin during the terminal Pleistocene/early Holocene (TP/EH) (~16,000-8300 cal BP) using the ideal free distribution (IFD) model. I rank four basins using two suitability proxies: (1) a caloric resource abundance estimate; and (2) a resource return rate estimate. Both are based on common plants and animals found in the Great Basin. The settlement chronology for the region comes from time-sensitive Western Stemmed Tradition (WST) points. The results indicate that sagebrush steppe and upland environments were the environmental zones most influencing habitat suitability at the scale of prominent basins, even though most WST sites are found in wetland and riparian zones. These contrasting findings suggest that there may have been a division of labor among hunter-gatherers in the northwestern Great Basin as early as the Younger Dryas and into the early Holocene.
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The study of the peopling of the Americas has been transformed in the past decade by astonishing progress in paleogenomic research. Ancient genomes now show that Native American ancestors were formed in Siberia or the Amur region by admixture of ca. 15–30% Ancient North Eurasian genes with those of East Asians. The Anzick infant, buried with Clovis bifaces at 12,900 cal BP, belonged to a group that was ancestral to later Native Central and South Americans. Fishtail points, derived from Clovis, mark the arrival and rapid expansion of Clovis-descended Paleoindians across South America, also evident in the sharp increase of radiocarbon dates, continent-wide, at 13,000–12,500 cal BP. In both North and South America, extinction of most genera of megafauna was virtually simultaneous with Paleoindian expansion. Human hunting must have been involved, perhaps in concert with other indirect impacts. Contrary to the alternative bolide impact theory, there is no evidence of a dramatic human population decline after 12,800 cal BP. Ancient genomes show that divergent lithic traditions after 13,000 cal BP need not be attributed to a separate Pacific Rim migration stream. Several recent finds raise the possibility that pre-Clovis people might have reached the Americas before 20,000 cal BP, but these precursors must have either failed to thrive, or were ultimately replaced by proto-Clovis or Clovis people. Consilient paleogenomic and archaeological data indicate that initial colonization by Paleoindian ancestors of living Native Americans occurred after 14,500 cal BP.
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With over 24,000 copies in print, this bestselling book tells how the Paiutes survived in the harsh Nevada climate. Chronicling food-gathering methods, basket weaving, hunting, skinning, and working with rabbit skins, this book serves as an invaluable reference on early Paiute culture. Any inquiring person who has worked with the Native Americans of the West will testify to the difficulties of obtaining the information he seeks. They are an old and proud and reserved race, and acceptance of outsiders is not freely given. In her twenty years of painstaking work with the Northern Paiutes, Margaret Wheat earned that full measure of acceptance. She tells the story of the generation of Native Americans whose lives were changed forever by the arrival of pioneers and prospectors in 1849.