Bone Tool Types and Microwear Patterns

chapter
11
Bone Tool Types and Microwear Patterns:
Some Examples from the Pampa Region, South America
Natacha Buc
Instituto Nacional de Antropología y Pensamiento Latinoamericano - CONICET, Argentina
Daniel Loponte
Instituto Nacional de Antropología y Pensamiento Latinoamericano, Argentina
“A” soil horizon with an average thickness of 50 cm.
Underneath was an archaeologically sterile “C”
horizon that represents a fluvial deposition period (cf.
Parker and Marcolini 1992).
Introduction
Archaeological sites located in the lower Paraná’s
wetlands (South America, Argentina, Pampa region)
and occupied by Late Holocene hunter-gatherers
contain large quantities of specialized bone tools
made with antler, mammal and fish bones. The aim of
this paper is to categorize the morphological types
and their microwear traces. Bone tools were
observed with binocular, metallurgical and
environmental scanning electron microscopes (ESEM)
in order to explore different morphological
modifications on bone and antler surfaces due to
manufacture and use. Properties of micro traces such
as polishes and striations were recorded by taking
into account their orientation, aggregation and
distribution. Archaeological bone tools were
compared with an experimental sample of tools
previously made out of lamb bones, deer antler and
fish bones (Buc 2003).
The Environment
The Pampa region is a great grass plain located in the
East-Central portion of Argentina, between the 31°
and 39° south. It is bounded by the Atlantic Ocean to
the east and the Sierras Centrales to the west. The
Pampa includes most of Uruguay and the southern
territory of the Río Grande do Sul State in Brazil
(Cabrera and Willink 1973). The Lower Paraná River is
located in the middle of this large plain, sectioning the
Pampa in two parts (fig. 1). The environment of this
area (cf. Burkart et al. 2000) is characterized by a
flood plain along the Paraná River and several islands,
which constitute a delta. Fluvial banks are the highest
elevation of the area, regularly left by the periodic
flooding. These levees are found along streams, as well
as in lagoon and marsh margins, and typically are
colonized by grasses and many species of shrubs and
trees. Fluvial banks are the primary locations where
archaeological sites are found.
Figure 1: Map of the Pampa Region and the Lower Parana wetlands.
Archaeological Background
Archaeological sites located in the Lower Paranà’s
wetlands were characterized as multi-purpose sites.
Most of them were occupied by complex huntergatherers during the Late Holocene (tab. 1). Economy
was mainly based on fluvial resources (mostly fishes
from the Siluriforme and Characiforme orders), on
rodents (coypu and cavy) and ungulates (marsh and
Pampa deer). Zooarchaeological studies suggest the
existence of size selection and delay consumption of
fishes. On the other hand, analyses of ungulate
skeletal representation show elements of high and
low utility. Isotopic analyses carried out on human
bones recovered from burials suggest that wild plant
food (C3 photosynthetic pathway) constitutes around
30% of the diet. Moreover, ethnographic records
Every archaeological deposit was contained within an
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BONES AS TOOLS: CURRENT METHODS AND INTERPRETATIONS IN WORKED BONE STUDIES
coefficient (Neiff 1999). Hence, environment shows
high sedimentation rates, low aeolian and fluvial
erosion as well as high and localized soil formation.
Artifacts on the surface are rapidly captured by
point out to the existence of storage, delay
consumption and active territorial defense of the
primary catchments areas during the XVIth century
(Loponte et al. 2002).
Table 1: Archaeological pampean sites with bone tool examples discussed in the text
Site
Las Vizcacheras
Las Vizcacheras
Garín
Anahí
Ao. Guazunambí
La Bellaca sitio 1
La Bellaca sitio 2
Latitude
34° 16' 81"
34° 16' 81"
34° 22' 38"
34° 16' 95"
34° 23' 33''
34° 23' 07"
34° 22' 79"
Longitude
58° 48' 11"
58° 48' 11"
58° 42' 30"
58° 48' 47"
58° 09' 34''
58° 40' 14"
58° 39' 53"
14C
BP (conventional)
1090±40
1070±60
1060±60
1020±70
940±60
1110±70
680±80
Lab No
Beta 148-237
LP-1401
LP240
Beta 147-108
Beta 147-109
LP-1288
LP-1263
Sample dated
Guanaco
Seed palm
Marsh deer
Coypu
Mammal bone
Coypu
Mammal bone
grasses, thus initiating the burial process. Therefore,
bone assemblages have low weathering profiles
presenting predominantly 1-2 stages (Acosta 1997,
Loponte and Acosta 2002). Even though bones are
mineralized to some extent by contact with salts and
manganese oxides, the action of diagenetic
processes was low. Not only does the C/N ratio
obtained from human bones falls between 2.9 and
3.6, but bones also tend to preserve high collagen
content (Acosta and Loponte 2002). Correlations
between bone mineral density and %MAU for
ungulate and fish bones were null (Acosta et al. 2002,
Loponte and Acosta 2002). The low frequency of
carnivore and rodent marks in faunal collections
suggest that destruction and/or modification by these
agents was not significant (Acosta 1997, 2004).
Sherds and bones have no evidence of rolling.
Likewise, lithic flakes have low rates of postdepositional alteration (Sacur Silvestre 2004). Root
marks cover less than 5% of the surface of a great
number of mammal bone specimens, and even less
for fish bones. In a few cases, these root marks
represent a problem to microscopic analysis because
they modified or destroyed use features. Micro traces
are also seldom obscured by small and circular
“pittings” which could be consequence of soil acid
action. However, given these general results and
proxy data related with archaeological deposits, we
presume that bone assemblages are not significantly
modified by natural causes. Therefore, the integrity of
bone tools is acceptable for microwear analysis.
Regarding technological aspects, deposits have
abundant domestic plain pottery with charcoal
residues on the exterior surface (Perez and Cañardo
2004) and decorated sherds. Furthermore, deposits
contain specialized equipment for prey capture: lithic
projectile points, bola stones, bone hooks of
spearthrower and different types of projectile points
made in antler and bone. The diversity and
abundance of bone tool assemblages characterise
archaeological sites located in the Paraná’s wetlands
(Caggiano 1984; Lothrop 1932; Zeballos and Pico
1878). Bone industry is not well developed in the rest
of the Pampa where bone artifacts are few and have
little modification (Gonzalez de Bonaveri 2003;
Johnson et al. 2000; Mazanti and Valverde 2001).
Lack of local lithic quarries makes the analysis of
bone tools crucial; not only in the lower Paraná’s
wetlands, but also in similar zones as well (Perez
Jimeno 2004a, 2004b). However, the explanation
proposed for the development of bone technology as
determined by the absence of rocks is nowadays
partially questioned. On the basis of morphological
features and economic organization of local huntergatherers during the Late Holocene, the hypothesis of
partial complementary function between lithic and
bone materials in the area has recently been
proposed (Loponte and Sacur Silvestre 2002).
Current microscopic analysis on lithic natural flakes
shows patterns of work on hard materials such as
bone and antler (Sacur Silvestre 2004). Conversely,
bone tools would have achieved activities according
to their mechanical properties. Moreover, the
importance of fishing in the economy and the
utilization of large quantities of hide (obtained from
small rodents, mainly coypu), could be an explanation
for the development of specific bone tools (harpoons
and awls) as related to specific resources (Loponte
and Sacur Silvestre 2002).
A first microscopic approach to the faunal
assemblage showed that several bones without
modification have intense bright similar to those
recorded on archaeological tools (which may be due
to postdepositional processes). However, as Lyman
noted, these features are different in location and
aggregation to those recorded in bone tool
assemblages (Lyman 1994). This statement is useful
to the analysis if formal tools like the ones examined
here. However, it should be taken into account for the
analysis of less formal tools that could be remaining in
Taphonomy
The Paraná wetlands have a very low elasticity
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BONE TOOL TYPES AND MICROWEAR PATTERNS: SOME EXAMPLES FROM THE PAMPA REGION, SOUTH AMERICA – BUC AND LOPONTE
techniques used in the experimental program (Buc
2005). A binocular microscope working at
magnifications between 5X and 50X was used for
initial examination of tools to provide general
information about the extent and distribution of wear.
For higher magnifications, incident-light metallurgical
microscope with magnifications ranges of 50X, 100X
and 200X was used for most of the work. To explore
the patterns defined by optical techniques, we used
an environmental scanning electron microscope
(ESEM) at 100X-150X, rarely at higher magnifications.
To describe the microscopic patterns we mostly
follow the terminology defined by LeMoine (1991). In
the following sections, we summarize the results of
this analysis presenting the archaeological tool types
and the associated patterns of use-wear.
the faunal assemblage.
Materials and Methods
The program designed for microscopic examination
of archaeological tools follows the pattern of use-wear
analyses initially developed by Semenov (1964) and
continued by other authors. Following methodological
approaches from lithic technology (Keeley 1980;
Vaughan 1985), several microwear studies were
conducted to identify or test the function of
archaeological bone tools. Essentially, authors with
different theoretical models and particular problems
base their research programs on actualistic
information (taphonomical, ethnographical and/or
experimental) and archaeological examination of tools
at different magnifications (Bouchud 1977; Campana
1989; d´Errico and Blackwell 2003; d´Errico and Villa
1997; Greenfield 1999; Griffitts 1997; LeMoine 1991;
Nami and Scheinsohn 1997; Newcomer 1974, Olsen
1979, Runnings et al. 1989; Scheinsohn 1997;
Shipman 1989; Stordeur and Anderson-Gerfaud
1985). Their main conclusion is that different materials
leave identifiable traces on bone and antler.
Considering patterns of features (instead of individual
traces) and distinguishing natural from cultural marks,
function of archaeological bone tools can be
assigned. Therefore, based on the patterns of marks
that resulted from a previous experimental program
(Buc 2005), we expect to identify the materials
worked with the archaeological tools and the general
activities implied.
Results of Archaeological Analysis: Use-Wear of Bone
and Antler Tools
Awls
Awls are defined by a pointed tip made on any bone
splinter (Camps Fabrer 1967: 280). Nevertheless, this
analysis is exclusively focused on those awls that
retain either the proximal or the distal epiphysis. This
kind of tool is well known in different parts of the
world, including the Pampa region (Ameghino 1880;
Caggiano 1984; Lothrop 1932; Mazzanti and
Valverde 2001). Different authors have suggested two
main uses for these artifacts: as manipulators in the
making of basketry (Campana 1989; Olsen 1979) or
as perforators in the working of hide (Campana 1989;
LeMoine 1991). Awls under study are all made out of
metapodials of adult Ozotoceros bezoarticus (Pampa
deer) and juvenile Blastocerus dichotomus (marsh
deer) (fig. 2).
In this essay we examine a small sample of
archaeological bone artifacts from sites located in
Paraná’s wetlands, dated between 680 and 1100
radiocarbon years BP. Accordingly, the aim is to
explore the function of bone and antler tools in this
particular context. The overall assemblage is
composed of 150 bone and antler formal tools, which
are distributed mainly in six morphological groups
analyzed here. Details of the manufacturing
procedures of the bone tools can be found in Acosta
(2000) and Buc (2005). Categories such as beads of
canine teeth, perforated antlers, fractured artifacts
and other undetermined tools are not included in the
present study. Instead, this first analysis is
concentrated only in those well defined morphological
types. Some tool groups analyzed, such as hooks,
spearthrowers or harpoons usually do not have
disputed functions. Conversely, other categories have
less clear functions, for example bipoints, pin-like
objects, awls and smoothers.
Figure 2: Archaeological awls.
The manufacture of these awls implies a careful
design. Striations found microscopically along their
shafts suggest that they were made by grinding bone
with a coarse grained stone (fig. 3 and 4).
Microscopic examination of archaeological pieces
went through three levels of analysis, following the
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BONES AS TOOLS: CURRENT METHODS AND INTERPRETATIONS IN WORKED BONE STUDIES
visible here.
Figure 3: Archaeological awl: the tip shows manufacture features left
by grinding bone with a coarse-grained stone on its lateral.
Metallographic Microscope, 50x.
Figure 5: Archaeological awl: the tip shows short smooth transversal
striations and invasive polish. Metallographic microscope, 50x.
Figure 4: Archaeological awl: the tip shows manufacture features left
by grinding bone with a coarse-grained stone on its blade. SEM, 65x.
Figure 6: Archaeological awl: the tip shows short and smooth
transversal striations. SEM, 65x.
Manufacturing features are regularly obscured by later
use-wear marks, which are defined by rounded
blades and tips, and short smooth striations across
the shaft (fig. 5 and 6). Several authors have defined
these traces as characteristic of piercing hide (Griffits
1997; LeMoine 1991). Moreover, striations are similar
in orientation and aggregation to the ones recorded in
experimental awls made on metatarsal lamb bones
and used to pierce dry coypu hide for a duration of 45
minutes (fig. 7). Striations observed in experimental
awls used 45 minutes to pierce fresh coypu hide (Buc
2003) are scarce and more widespread (fig. 8). Since
both types could be indicative of different stages on a
continuum (LeMoine 1991), we can only conclude
that archaeological tools were used on a soft material
similar to hide and that an action involving piercing
movements was carried out. The exposure of osteons
was recorded by LeMoine (1991) as a characteristic
feature of working wet materials, but they were not
Figure 7: Traces left by piercing dry coypu hide: the tip of an
experimental awl shows short and smooth transversal striations, and
invasive polish. Metallographic microscope, 50x.
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BONE TOOL TYPES AND MICROWEAR PATTERNS: SOME EXAMPLES FROM THE PAMPA REGION, SOUTH AMERICA – BUC AND LOPONTE
Use-wear traces appear very different from
manufacture grooves. There are two main patterns of
use-wear. Some tools show light, smooth, and
transversally oriented striations confined to the tip,
similar to the use-wear pattern of awls but less
developed (fig. 10). Other pin-like tools show a
different use-wear pattern also confined to the tip. In
these cases, deep parallel and short striations are
mainly seen on the highest points of the bone surface
and rarely follow the microtopography of the bone (fig.
11 and 12). The latter pattern could be associated
with a soft material but slightly more abrasive and
rigid than hide, probably vegetal. In fact, experimental
tools used with local gramineous plants during 45
minutes show a similar pattern. Striations, though
similar to the ones recorded in hide processing, are
deeper and seldom follow the microtopography of the
bone (compare fig. 13 with fig. 12).
Figure 8: Traces left by piercing fresh coypu hide: the tip of an
experimental awl shows short and smooth transversal striations.
These features are scarcer and more widespread than on figure 7.
Metallographic microscope, 50x.
Pin-like Tools
Pin-like tools are tipped objects, as defined by
Campana (1989: 51), generally made from rays of
Siluriforme fishes (fig. 9). They are too fine to be
defined as awls and have no eye, so cannot be
included in the “needle” category (as defined by
Camps-Fabrer 1967). Most of the tools under study
have their articular ends broken and only their tips
have been often abraded while the rest of the tool
remains unmodified. Under microscopic examination,
coarse striations oblique and confined to the tip can
be seen. Thus, we can state that little energy and time
were involved in the manufacture of these artifacts.
Figure 10: Archaeological pin-like tool: the tip shows light smooth
transversal striations confined to the tip. Metallographic microscope,
50x.
Smoothers
This category defines a peculiar tool type made from
rays of siluriforme fishes (fig. 14). The original bone
elements are slightly modified but show a bright and
localized polish visible with the naked eye. There are
no references of similar tools in other areas of
Argentina, while identical tools are recorded in
Brazilian sites without artifactual descriptions (Schmitz
et al. 1993: fig. 41).
Under optical microscopic examination, these objects
show deep transversally oriented striations (fig. 15
and 16). These features are confined to an area
between 2 and 3cm below the tip and decrease in
number and intensity away from it. Use-wear marks
erase the natural fish bone grooves that remain intact
in the rest of the tool. In this last area, isolated
striations sometimes appear on the high points of the
bone micro-topography (fig. 17).
Figure 9: Archeological pin-like tools.
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BONES AS TOOLS: CURRENT METHODS AND INTERPRETATIONS IN WORKED BONE STUDIES
As Griffitts suggested (Griffitts 1997: 243), we verified
experimentally that different tempers produce different
wear patterns (compare fig. 18 and 19 with fig. 10).
Figure 11: Archaeological pin-like tool: the tip shows short
transversally oriented striations on highest points of the bone surface.
Invasive striations can be seen on the left corner of the picture.
Metallographic microscope, 50x.
Figure 14: Archaeological pottery smoothers.
Figure 12: Archaeological pin-like tool: the tip shows short, deep, and
transversally oriented striations on the blade. Metallographic
microscope, 50x.
Figure 15: Archeological pottery smoothers: the polished area shows
deep, transversally oriented striations obscuring the natural grooves of
the bone. Metallographic microscope, 50x.
Bipoints
Figure 13: Traces left by rubbing local gramineous plant: short, deep,
and transversally oriented striations. Metallographic microscope, 50x.
Bipoints or double-pointed implements (Campana
1989: 47) are narrow tools pointed on both ends with
sizes ranging from 11 cm long, a thickness of
approximately 0.7 cm and a maximum width of 1cm
(fig. 20). These objects are completely modified, so it
is usually not possible to identify the original bone
from which they were made. This tool type is not
common in other Argentinean contexts. However, a
very similar object was described as a piercing tool by
Most patterns are similar to the one recorded in
experimental tools used to smooth pottery for a
period of one hour (Buc 2003) and are comparable to
those described by Griffitts (1997). Although
archaeological tools show general patterns very
similar to the experimental assemblage, striations are
not identical because the first ones are narrower. This
difference may be related with temper type and size.
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BONE TOOL TYPES AND MICROWEAR PATTERNS: SOME EXAMPLES FROM THE PAMPA REGION, SOUTH AMERICA – BUC AND LOPONTE
(fig. 21). In some cases, extremities show different
use-wear patterns. For instance, one tool (LB2 52)
has slightly smooth manufacturing features and
transverse marks on its proximal end (fig. 22 and 23),
while the distal end shows a non-invasive polish and
intact manufacturing traces (fig. 24). This suggests
that different actions or materials would have affected
each distal end and that the midsection was not the
active area of the tool. Hence, the working hypothesis
is that only one of the tips was active and that the
midsection and the other tip were hafted. This is
supported by the fact that random striations and noninvasive polish correspond to patterns described by
other authors as wood use (Griffitts 1997; LeMoine
1991) and are features similar to the ones observed at
the base of the hooks of spearthrowers (see below
and compare fig. 21 with fig. 33). Otherwise, it is also
possible that the use of bipoints could have been
more generalized and that both tips could have been
used alternatively in different materials and tasks.
Mazzanti and Valverde (2001: 171-172), and identical
artifacts were documented in Brazilian huntergatherer sites without functional determinations
(Schmitz et al 1993: fig. 41). It is the most
controversial tool type regarding its precise use. While
some authors defined similar artifacts as hafted points
used as spears or arrow points (Campana 1989;
Newcomer 1974), others believe that they represent
fishhooks, fish gorges or elements of composite
toggling harpoons (Campana 1989; Lyman 1991).
Figure 16: Archeological pottery smoothers: the polished area shows
deep, transversally oriented striations obscuring the natural grooves of
the bone. SEM, 90x.
Figure 18: Traces left by polishing pottery: deep, transversally oriented
striations obscure the natural grooves of the bone. Metallographic
microscope, 50x.
Figure 17: Archeological pottery smoothers: away from the polished
area the tool shows deep, transversally oriented striations on the
highest points of the bone’s topography. Metallographic microscope,
50x.
In this particular case, we conducted the microscopic
analysis to test each of these functional hypotheses.
Therefore, ends and midsections were carefully
analyzed. The resulting use-wear pattern is also
controversial. In their midsection, most tools show
random striations or only glossy non-invasive polish
Figure 19: Traces left by polishing pottery: deep, transversally oriented
striations obscure the natural grooves of the bone. These features are
different to figure 19 due to differences in temper size.
Metallographic microscope, 50x.
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BONES AS TOOLS: CURRENT METHODS AND INTERPRETATIONS IN WORKED BONE STUDIES
(Stordeur 1980). The general form is parabolic,
pointed on one end and drilled on the other end to
accept a shaft (fig. 25). A thin rope would have
connected both shaft and point through an opening
drilled on the dorsal face. Results presented by
Lindström (1994) suggest that these tools have
relatively high costs of manufacture. Coarse
longitudinal striations seen in some pieces across the
shaft suggest that harpoons were made by grinding
deer antler, a suitable material for projectile points due
to its mechanical properties (Guthrie 1983).
Figure 20: Archeological bipoints.
Figure 23: Archeological bipoint (LB2 52), proximal end: its tip shows
short transversal marks. Metallographic microscope, 100x.
Figure 21: Archeological bipoint: its midsection shows glossy noninvasive polish. Metallographic microscope, 100x.
Figure 24: Archeological bipoint (LB2 52), distal end: its tip shows
intact manufacture features on its blade. Metallographic microscope,
100x.
Figure 22: Archeological bipoint (LB2 52), proximal end: its tip shows
slightly smooth manufacture features on its blade. Metallographic
microscope, 100x.
Harpoons
Harpoons are well defined ethnographically and
archaeologically, so their use is not often discussed.
Archaeological harpoons recovered in the lower
Paranà wetlands are quite similar to the modern ones
still in use among aboriginal populations in the Chaco
area (Caggiano 1984). These tools resemble
morphologically those defined by Stordeur as type IA
for Paleoinuit inhabitants of the Igloulik region
Figure 25: Archaeological harpoons.
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BONE TOOL TYPES AND MICROWEAR PATTERNS: SOME EXAMPLES FROM THE PAMPA REGION, SOUTH AMERICA – BUC AND LOPONTE
1997; LeMoine 1991), but they are not exactly the
same. Microwear features are also quite analogous to
the microwear observed on the supposed hafted
areas of the bipoints (see fig. 22).
Such tools were examined microscopically in order to
support the traditional hypothesis of use as harpoons.
Although we supposed that soft tissue lubricated by
water can hardly leave readily identifiable traces
(LeMoine 1991), we presumed that the impact
against the bony structure of fishes might modify the
antler in some way. Although tool manufacture
features are obscured on almost every archaeological
harpoon, the micro traces found on the tips are
different from one tool to the other. For example,
while some tips have short transversal marks,
probably due to mechanical stress (fig. 26, compare
these marks with the ones recorded on the ends of
bipoints on fig. 23), others have a different pattern (fig.
27). Tools do not show invasive polish under
metallurgical microscope, while tips and blades
appear completely rounded under ESEM (fig. 28). The
results of the observations show highly variable
patterns, so the analyzed samples (archaeological
and experimental) must be increased. Transversal
light striations were recognized in the outer opening
of the pieces analyzed (fig. 29). These features are
similar to the ones associated with rubbing wet hide
(fig. 30) and plants (fig. 31). However, the
interpretation is provisory because we did not perform
an experimentation to identify these features in
particular. Whichever the material that has rubbed the
surface, it would have been in contact with water and,
as lubrication altered the formation of features (cf. Le
Moine 1991), it is not accurate to make analogies
without more comparative samples. Nevertheless,
these features may be the product of the thin cord
made with hide or plant fibers which was used to link
both parts of the harpoons. Therefore, these results
support the traditional hypothesis of use.
Figure 26: Archaeological harpoon: its tip shows short, transversal
marks. Metallographic microscope, 100x.
Figure 27: Archaeological harpoon: this tool show a different pattern
to the one recorded in figure 27. Metallographic microscope, 100x.
Hook of Spearthrowers
Spear Points
Spearthrowers (atlatl) made from wood are well
defined in the ethnographic literature.
Archaeologically, they are usually represented by their
hooks made from bone, antler or ivory (Catellain
1997). The hooks founded in our study area are made
from deer astragalae (fig. 32) and their manufacture
requires a significant amount of time and energy.
These artifacts are made with the compact osseous
tissue of big mammal bones (probably marsh deer)
(fig. 34). We have recovered only two specimens, one
of them being quite similar to the one illustrated by
Lothrop (1932: 179, fig. 70) and recovered from the
Sarandí site. Their thickness (2.5 mm) makes them
too fragile to be projectile points according to the
values presented by Guthrie (1983). Microwear
analysis on both points showed only coarse striations
resulting from manufacture. The absence of use
micro-wear traces and the intact preservation of the
manufacture features suggest a low rate of surface
bone modification, that pieces were not used, or
both. However, more artifacts like these are needed
to support any hypothesis about their precise
function.
As in the previous case, the use-wear analysis was
designed to support traditional hypotheses about
their use. Thus, the main areas explored were the
base, and the concave face of the hook, presumably
in contact with the projectile shaft. Both parts of the
composite tools would have been made of wood. The
microscopic analysis shows non-invasive, glossy
polish covering the highest points in both areas (fig.
33). These features are similar to those described by
other authors as resulting from work on wood (Griffitts
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manufacture, respectively). Likewise, the large
quantities of awls in the archaeological record could
be related with the high importance of coypu (a
source of small skins) in the economy as well
(Loponte and Acosta 2002). Moreover, current
information suggests a high correlation between tool
type and osseous element used as raw material,
pointing out a selection of bone materials due to
regional prey availability and mechanical properties of
the elements. Thus, tool design must be understood
as constrained by these technological choices and
technological costs (manufacture and procurement
costs, cf. Bamforh and Bleed 1997) should be
considered in the light of its efficiency.
Figure 28: Archaeological harpoon: its blades and tip appear
smoothed under SEM, 65x.
Figure 30: Traces left by rubbing wet coypu hide. Metallographic
microscope, 100x.
Figure 29: Archaeological harpoon: the outer opening of the piece
shows transversal, light striations. Metallographic microscope, 100x.
Discussion
The results of the microwear analysis partially support
previous hypotheses about the function of bone tools
based on morphological traits (Loponte and Sacur
Silvestre 2002). Microwear analysis performed on
lithic tools shows microwear resulting from cutting
activities, principally on hard materials such as bone
and antler (Sacur Silvestre 2004). Conversely, results
of microwear analysis on bone tools suggest that they
are linked to activities involving soft materials in
contact with the pointed parts of the tools instead of
their edges. Bone points and awls would have
replaced lithic projectile points and drills, but
harpoons, pin-like tools, pottery smoothers and
spearthrowers were not made out of bone material as
a response to the regional scarcity of lithic resources.
Harpoons and pottery smoothers are closely related
with the economic structure (fishing and pottery
Figure 31: Traces left by rubbing local gramineus. Metallographic
microscope, 100x.
Guthrie has stated that deer antler projectile points
are optimal because of their resistance (Guthrie 1983)
and this is consistent with the physical structure since
harpoons are made of antler. Similarly, astragalae
used to make the hooks of spearthrowers are tarsal
bones structurally similar to carpals, which are
suggested by Currey (1984) as bones mechanically
designed to resist static loads. Regarding awls, deer
metapodials are equivalent to guanaco metapodials,
which are good materials for actions involving high
impact strength (Scheinsohn y Ferreti 1995), similar to
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BONE TOOL TYPES AND MICROWEAR PATTERNS: SOME EXAMPLES FROM THE PAMPA REGION, SOUTH AMERICA – BUC AND LOPONTE
show different use-wear patterns. Some could be
associated with work on plant material, while others
show a use-wear pattern resulting from hide working.
The latter case is similar to the one presented by
LeMoine (1991) in her analysis of awls and needles
from Eskimo assemblages. Taking into account their
fragile tip, it is more likely that their work on hide
consists in widening holes or passing a cord through
holes previously made with awls (Bouchud 1977). In
addition, due to their slight modification and the
abundance of fish rays as raw materials, these tools
would have been used in different tasks, the previous
features being obscured by the last ones. In sum,
morphological groups and microwear patterns
suggest tool specialization. Even though the use-wear
patterns could not all be identified with a specific
worked material, it is clear that they are internally
homogeneous within a particular tool type.
those involved in hide piercing activities. Bipoints are
made from compact osseous tissue of large mammal
bones. Their thickness and biconvex profile make
them adequate to produce compact and resistant
spears. Consequently, despite their different
manufacture costs, all these tools can be defined in
terms of “curated technology” (Binford 1979).
Conversely, artifacts made out of fish rays, an
abundant resource in the area, show features
indicative of an “expeditive technology”. Not only are
pottery smoothers and pin-like objects slightly
manufactured, but it also may be that the latter do not
show recognizable use-wear patterns because they
were multipurpose expedient tools.
Figure 32: Archaeological hooks of spearthrower.
Figure 33: Archaeological hook of spearthrower: its concave face
shows non-invasive, glossy polish covering the highest points.
Metallographic microscope, 100x.
Figure 34: Archaeological projectile points.
Conclusion
Finally, awls, pottery smoothers, harpoons and hooks
of spearthrowers show distinct use-wear features that
can be related, with more or less accuracy, to their
specific inferred function. Although the precise
function of bipoints could not be assessed, the
hypothesis suggesting they may be spear points is
noteworthy considering the scarcity of lithic raw
materials in the area. Results presented by Guthrie
regarding bone point thickness support this idea
(Guthrie 1983). The thickness of the bipoints under
study is always less than 7 mm, while Guthrie stated
that optimal thickness to ensure penetration and
durability is approximately 1 cm. The results regarding
pin-like objects are also controversial because they
The archaeological record in the lower Paraná
wetlands occupied by late Holocene hunter-gatherers
has a significant bone tool specialization. Moreover,
this specialization is closely related to economic
organization. Microscopic analysis shows a
correlation between bone micro-wear and inferred
function in several tool types, specifically in curated or
formal artifacts. It is remarkable that most of them
belong to a tool-kit used to obtain prey (fish and
ungulates).
Actualistic and taphonomic research programs are
153
BONES AS TOOLS: CURRENT METHODS AND INTERPRETATIONS IN WORKED BONE STUDIES
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