THE GUANGALA AND MANTEÑO-HUANCAVILCA SHELL ORNAMENT
PRODUCTION METHODS
Sydney Cargill, Isha Chavva, Shannon Duffy, Julia Flores, Jennifer Mao, Gabrielle Shvartsman,
Cindy Weng, Sharmitha Yerneni
Advisor: Dr. Maria Masucci
Assistant: Kaushaly Patel
ABSTRACT
In the ancient civilizations of Latin America, Spondylus shells were utilized to create valuable
ornaments. Despite the knowledge of the usage of the ornaments, the means of production are
unknown. The goal of this research was to not only determine the methods used to reduce and
refine the shells (i.e. knapping, sawing, and grinding), but also to compare the ornaments from
the Guangala cultural period to those from the Manteño-Huancavilca cultural period. The
Guangala and Manteño-Huancavilca cultural periods occurred in southern Ecuador from 200
B.C. to 800 A.D and 800 A.D. to 1532, respectively. Both civilizations crafted miniscule beads
that ranged in value based on the color of the shell they were formed from. From analysis of the
archaeological samples, it was concluded that back-and-forth grinding played a large role in
refining the Guangala and the Manteño-Huancavilca beads. When comparing the Guangala and
Manteño-Huancavilca beads, the observations supported the hypothesis that the ManteñoHuancavilca beads would exhibit a more refined structure advances in techniques, especially
polishing processes. The major unknown factor of the ornaments was the reduction process. It
was concluded that knapping and sawing were used in conjunction while grinding, due to the
extensive time required, was used in the refinement process.
INTRODUCTION
Originating deep within the seas of the Pacific Ocean, the thorny oyster, Spondylus sp. is
renowned as a symbol of power, wealth, and fertility among cultures of ancient Latin America.
These societies fashioned intricate beads and ornaments from the shell, placing them in tombs of
the wealthiest and most powerful. Ironically, the means of production of Spondylus shell
ornaments, the very embodiment of creation, lies in obscurity. Archaeologists have studied the
consumption of these marine shells and their distribution through ancient hierarchies, but have
neglected to concentrate on the production of the valuable artifacts. Evidence for extensive
working of these shells proliferated during the Guangala and Manteño-Huancavilca (M-H)
cultural periods of ancient Ecuador, from 200 B.C. to 800 A.D and 800 A.D. to 1532,
respectively. Workshops large and small provided shell beads and ornaments which were traded
throughout the empires and societies of neighboring regions. Based on differences in form and
texture of tool markings on archaeological samples, it is evident that during the Guangala and MH periods, the methods craftspeople used to shape shell ornaments varied. These differences may
reflect the differences in market demands as well as social, political or economic differences
between the two societies. As archaeologists know very little about the organization of these
societies or their relationship with neighboring societies, the production methods and their
variations in time may hold useful clues to reconstruct these complex systems.
[6-1]
Reconstruction of shell working methods remains an underdeveloped field of study in
archaeology. Societies of South America left behind a wealth of shell beads, ornaments, and
jewelry, including the shell beads and ornaments discovered in a Chimú tomb, which may have
come from Ecuadorian M-H workshops (Figure 1). However, research conducted on their
production methods is sparse. In the published academic literature, there is little mention of how
the shell jewelry was produced. Most current literature focuses on drilling and shaping of beads,
rather than the shell reduction process, moving from describing the fresh shell to the drilling of
holes in beads (2). This project looks to bridge the gap in Latin American archaeology and the
understanding of Spondylus bead production by exploring the craftsmanship of the beads and
artifacts excavated from south Ecuadorian workshops in further detail. One major goal of the
project is to investigate and determine the efficiency of various shell-crafting techniques in order
to ascertain the likelihood that the Guangala and M-H craftspeople employed these methods.
Only when the production methods are discerned can the organization of the production and thus
the societies themselves begin to be reconstructed and appreciated, which is the ultimate
potential contribution of this study.
Figure 1. Spondylus shell and other ornaments found in a Chimú tomb. Photograph from
Matthew Helmer for National Geographic (1).
BACKGROUND
Ecuador, home of the Guangala and M-H, is a microcosm of all the environments that
exist in South America. The area has long been considered a “backwater,” and even the Incas
only conquered the southern half of the country and left the coastal lowland natives alone.
However, the region’s natural resources have made it an important contributor to the growth of
other great civilizations (3). The southern part of Ecuador is a challenging environment for
agriculture, but can be productive with a mixed economy supplemented by production and trade
for export of a range of materials and artifacts (Figure 2). Balsa wood, for example, which is
extremely light and floats on water, grows in Ecuador and was used by the coastal Guangala and
M-H to create seacraft that allowed them to transport and exchange Spondylus beads and
ornaments and other materials and products all along the Pacific coast from Western Mexico to
Chile (3). These facts make it evident that trade was an essential component of the economy of
[6-2]
the Guangala and the M-H. It appears that these societies successfully adapted to their
challenging environment by creating the goods most valued by other neighboring societies.
Figure 2. Map of Ecuador adapted from Masucci, showing the two sites of interest: El Azúcar,
the location of the Guangala site, and south of El Azúcar in Chanduy, the location of the M-H
site (3).
In Peru, contemporaneous with both the Guangala and M-H, many complex cultures,
such as the Moche and the Inca, thrived. These societies were characterized by sophisticated
social, political, and economic organizations as evidenced by the wealth of their leaders seen in
ornate tombs, filled with jewelry consisting of large quantities of tiny beads and ornaments made
from shells of Spondylus, or the Thorny Oyster. Spondylus shells were associated with fertility
because the shells came from the ocean, and were imbued with the symbolism of water, life, and
health. The Guangala also made many sculptures out of Spondylus depicting animals from their
environment, such as the parrot shown in Figure 3. Interestingly, Spondylus is only found off the
shores of the Pacific coast from California to southern Ecuador, possibly extending only to far
northern Peru (4). This means that inland peoples or those living to the south of Peru, would
have had to obtain Spondylus or Spondylus ornaments through trade. As the distance from the
source increases, the cost and therefore the value of the Spondylus shell fine goods
proportionally would likely have increased. The shells also contain a lip of color, usually red and
pink, though on occasion purple or even yellow, which was especially coveted. For these
reasons, shell ornaments and beads became prestige goods in the Peruvian cultures, meant to
convey status, wealth, and power.
The Guangala, a society identified by its characteristic ceramics, occupied southwest
coastal Ecuador beginning approximately 200 B.C. The Guangala were contemporary with the
Moche, a powerful and dominant society that lived along the central coast of Peru. These two
peoples were likely trading partners, as indicated by the Spondylus beads found in Moche tombs
[6-3]
as well as the importance of Spondylus dust in Moche rituals. Between 600 and 800 A.D. a large
number of Guangala left the region. It is possible that there was a drought or other natural
disaster or a conflict among the inhabitants, but there is no conclusive evidence. Interestingly,
the Moche collapsed at the same time, suggesting a possible economic crisis. From 700 A.D.
through 900 A.D., the M-H established themselves near the former location of the Guangala. It is
unclear if they are the same people returning to the area or a new people. Regardless, the M-H
were contemporaries of the Inca and Chimú, a powerful coastal society conquered by the Inca.
Many shell artifacts found at the Inca and Chimú sites were likely produced by the M-H in
Ecuador and intended for use by prominent individuals.
Figure 3. Example of the bird imagery
prevalent in Guangala sculptures.
Figure 4. Examples of archaeological and
modern shell, as well as Guangala and M-H
beads.
Archaeological findings suggest that by the time the M-H settled in Ecuador between 700
and 900 A.D., their shell crafting techniques had dramatically diverged from those used by the
earlier Guangala (Figure 4). The Guangala had household workshops located throughout their
interior villages, suggesting that shell bead and ornament manufacture was a side activity that
simply supplemented their income (5). By the M-H period, not only were there more and larger
workshops, but they were located near the coast, closer to the raw materials, suggesting a mass
production model and an increased importance of shell manufacture within the local economy.
The evidence of the change in the organization of the shell working from domestic
workshops to mass production specialty workshops supports a shift towards a more complex
society among the M-H. It is possible that a trade relationship with more complex societies, such
as the Inca, led to these changes; as the demand grew, so did the need for higher production
efficiency. The M-H were likely forced to change their production techniques in order to meet
demand. These changes in production techniques should be visible in the archeological material,
specifically the tool markings on samples. Providing information of production techniques would
be a significant contribution to the field, because this is an untapped area of study.
Because of the relatively small amount of literature that has been published on South
American shell working and particularly on reduction methods, comparative research was
conducted on bead production techniques in other civilizations to help in the reconstruction of
the Ecuadorian methods and suggest avenues for this investigation. The prehistoric inhabitants of
[6-4]
the Mississippi Valley also made shell beads and their processes have been reconstructed
through experimental replication studies, microwear analysis, and ethnographic observations.
Studies found that the Mississippian artisans used a technique called knapping, in which an
incision is made in the shell with a chert flake and an antler is inserted into the incision and
stricken with a wooden baton to flake off pieces of the shell in a controlled manner. To drill
holes in the beads, a microdrill was attached to a reed drill shaft and the shaft was rotated
between the artisan’s hands. The microdrill produced regular striations within the hole in the
bead. The beads were then polished on a flat grooved stone (6). Knapping, grinding, and drilling
techniques were also investigated in this study through experimental replication. Microwear
analysis was used similarly to analyze archaeological samples and compare tool markings on
experimental and archaeological samples.
Another area of comparative research was the bead production techniques of the Indus
River Valley civilization. Archaeologists have been able to study the evolution of drilling
techniques and bead styles over the last 1,400 years by observing artifacts and the remnants of
workshops (7). The researchers in this field believe that the changes in techniques were
stimulated by spiked market demand which therefore increased competition between workshops.
Additionally, demand for higher quality beads led to refined fabrication methods. Although these
beads were made of stone, not shell, they were also “quite small, between one and a half and
three mms in diameter and one to two mms long” (7). The small size presents similar problems
as those faced by the Guangala and M-H, including drilling holes and polishing the beads. The
archaeologists found that the craftsmen cut crude beads from the stone, drilled holes, and then
ground the beads down to size and polished them on grindstones. It was found that a
combination of abrasives and drilling techniques were employed. For harder materials, the drill
holes were started by first pecking and then drilling (7).
Although the Mississippian and Indus Valley societies provide similarities on the drilling
technology and the consumption and cultural significance of beads and shell jewelry there is still
little detail on the reduction process. Another society known for its extensive bead making, the
Egyptian civilization, even illustrates the drilling process in its tomb paintings. But, their shell
beads are from Ostrich egg shell, not thick Spondylus. Experimental work has been unsuccessful
in discovering how harder materials, like Carnelian stone, of a similar hardness to Spondylus,
were reduced, worked and drilled. Fine grit made from the hardest stone material known
(corundum) may have been used to enhance the cutting, knapping and drilling process (8).
Using the above information gathered about the techniques used by other civilizations as
well as our observations of the Guangala and M-H artifacts and shell working debris, several
hypotheses regarding the bead production process were formulated for this project. It was
hypothesized that shell reduction was accomplished through a combination of sawing and
knapping processes. It was also hypothesized that grinding techniques were added to the shell
reduction process during the M-H period due to the increased demand for finer beads and
ornaments. The practicality of these techniques was tested through experimental archaeology.
Drilling techniques were investigated by comparing Guangala beads, 4.62 and 6.60 mm
diameter, to a M-H bead, 5.68 mm diameter. Since the M-H existed centuries after the Guangala,
it was hypothesized that M-H beads would show evidence of finer drilling techniques and
improved drilling technologies.
[6-5]
SAMPLES
Archeological samples of shell working debris were recovered from both Guangala and
M-H sites. These materials can be used to compare the shell working techniques from the two
periods to determine whether there was a change in production techniques. The Guangala
samples were recovered from site 47 and the M-H were recovered from sites MV-C2-4o (TP2-2)
and MV-C2-4n (TP1-4). Images are labeled according to their context, which includes site
number as well as location within the site. Archaeological samples (labeled “A”) were also
carefully separated from experimental samples (labeled “E”).
Table 1: Shell Samples Used In Experimentation
Sample Type
Cultural
Period
Provenience
Analysis
Hypothesis
Tested
Whole Spondylus
Shells
Modern
Purchased
Stereoscope,
SEM
Grinding
Worked
Guangala, Archaeological Surface Samples
Spondylus Shells
M-H
G - El Azúcar Site 47
M-H - Chanduy Site MV-C2-4o
(TP2-2)
Stereoscope,
SEM
Knapping, Sawing,
Fracture Method,
Grinding
Guangala Archaeological Surface Samples
(n=2), MG - El Azúcar Site 47
H (n=1) M-H - Chanduy Site MV-C2-4n
(TP1-4)
Stereoscope,
SEM
Grinding, Drilling
Beads
METHODS
Prior to beginning the research, it was imperative to accurately document and record each
archeological sample, particularly since we utilized archaeological materials in some of the
experimental research. Once an archaeological sample has been changed, its original state could
not be recovered. Documentation utilized an iPad, a Bodelin Proscope Micro Mobile iPhone
magnifier, and iPhone camera on a Leica Zoom 2000 zoom stereoscope. These devices have
been found to very accurately capture color and texture.
Scanning electron microscopy (SEM) was a vital tool in this investigation because it
allowed detailed images of sample surfaces at a resolution impossible to obtain with a
stereoscope. SEM utilizes a focused beam of high-energy electrons to scan the surface of an
object. The interaction of the electron beam with the sample surface produces signals that are
then interpreted by a computer to give information about the external morphology of a sample. In
this study, the data regarding external morphology was collected to get a more detailed look at
tool markings on both archaeological and experimental samples. Since the SEM image depends
on the interaction between the electron beam and the sample surface a conductive coating must
be applied. Samples are first coated with a layer of metal by a sputter coater. The SEM used in
[6-6]
this research was the Topcon ABT-32 Scanning Electron Microscope. Table 1 summarizes the
samples used in specific methods in this current work.
Sawing
As small lines and markings were observed on a wide range of fragmented shell pieces
from the archaeological sites, it was hypothesized that sawing may have been used in
combination with knapping. To test this hypothesis, archaeological samples were examined for
tool markings suggestive of sawing and photographs were taken of these markings. A sample of
worked Spondylus collected from the surface of the archaeological site was chosen to be used as
an experimental sample. A replica drill bit on a chert blade secured with twine, fresh lemon
juice, and sand were used to make an incision in the shell. The lemon and sand were used based
on suggestions in the comparative literature of the use of grit and acids to aid in the reduction
process (8). A biface was inserted into the incision and was used to saw the sample. This
technique was unsuccessful, so samples were stored overnight with a half of a lemon fastened,
pulp-side-down on the incision. The experimental attempts at sawing were very slow, so heat
treating was investigated. Heat treating of lithic materials in order to alter their physical
properties and increase their brittleness and knapping properties is well known throughout
human history. Therefore, it was hypothesized that such a technique could improve the knapping
properties of the hard Spondylus shell. A fragment of Spondylus shell was first measured for
hardness using the Moh’s Hardness Scale. Shells were submerged in boiling water for five
minutes, followed by five minutes of cooling. Shell hardness was recorded after heating and
cooling periods also using the Moh’s Hardness Scale.
Knapping
A further technique investigated was the way in which the shell craftsmen were able to
remove the rough, spiky outer coating of the shell to expose the colored and white portions of the
shell needed for shell bead production. One hypothesis was that the craftsmen used a knapping
technique. This method is also referred to as the “punch technique” in which a sharp tool was
used to remove flakes from a hard material (9). In order to evaluate whether this technique was
utilized, archaeological samples were examined for tool markings suggestive of knapping and
photographs were taken of these markings. Dental impression material was used to take
impressions of these markings as well. A surface Spondylus sample was chosen to be used as an
experimental sample. A replica drill bit on a chert blade secured with twine, as well as fresh
lemon juice, and sand were used to make an incision in the shell. A biface was inserted into the
incision and was stricken with a replica work deer antler tine to flake off the exterior of the shell.
After knapping was unsuccessful, samples were stored overnight with a half of a lemon fastened,
pulp-side-down on the incision. Knapping was then successful the next day. The tool markings
on experimental samples were compared with those in corresponding locations on archeological
samples. A stereoscope was used to examine and record potential similar marks on the cortex,
the core of the shell, and on the middle layers. Additionally, dental impression material was
dispensed onto worked surfaces in order to create and compare impressions of the markings on
the experimental samples to corresponding areas of the archaeological samples.
Grinding
Archaeological samples were recovered from M-H workshops with ground surfaces.
These samples suggested that grinding may have been used in the reduction process, at least by
[6-7]
the M-H. To remove or possibly just smooth the outer coating of the shell during the reduction
process, it was hypothesized that craftsmen used grinding stones which are common at the sites
for processing corn and other food. To experimentally test this hypothesis, archaeological
samples were examined for tool markings suggestive of grinding and photographic records were
taken of these markings. The thickness of experimental samples was measured at their thickest
point. Experimental samples were ground on a sandstone grindstone. Two techniques were used:
a circular motion and a back-and-forth motion. This process was timed, and the final thickness of
experimental samples was measured to determine efficiency with regards to practicality as well.
Samples were polished using ground up topsoil from the excavation site mixed with water to
provide an abrasive, for intervals of thirty seconds, two minutes, and ten minutes. The markings
on experimental samples were compared to those on the archaeological samples using SEM.
Drilling
One objective of this research was to study the differences between the drilling
techniques of the Guangala and M-H civilizations. The drill markings in two Guangala
Spondylus beads were compared to those in two M-H Spondylus beads. To eliminate the
possibility of the supposed drill holes actually being predatory snail holes, only recognizable
beads were used. Shell debris from workshops often has multiple perforations but these may not
all be humanly made holes. Dental impression material was utilized to take impressions of the
drill holes of beads from both time periods. By injecting the impression material into the holes,
waiting for the impression to harden, and removing it with care, the intricate details of the hole’s
interior were able to be viewed with the naked eye. Impressions taken from samples from the
Guangala and M-H eras were compared. SEM was used to obtain more detailed pictures of the
impression surface and the inside of broken beads. Using SEM, the direction of grinding patterns
and smoothness of drill hole ridges were compared between the beads excavated from each
civilization.
Fracture Method
During one of the experiments, another method of reducing the shell to bead-size was
found. As opposed to the sawing and knapping method, it was hypothesized later in the project
that the Guangala and M-H would first fracture a shell with a heavy stone in order to create
fracture lines. These fracture lines would then provide weak points which could be sawed or
knapped using flakes of obsidian with sharp, thin edges. Obsidian would have been the sharpest
stone material the Ecuadorian peoples had access to. Once the cut was deep enough, the beadsized piece would chip off of the shell. In this experiment, the fracture method was practiced by
finding an experimental Guangala shell sample with a small fracture line. The line was sawed
through with a small shard of obsidian for about five minutes until the small piece chipped off.
The edges of the shell that had been sawed through were then compared, using the stereoscope,
to the edges of the shell that were already sawed through when the sample was found.
DATA
Sawing
Soaking the shells in lemon and utilizing the acid and grit technique was observed to
significantly expedite the sawing and cutting process. The experimental combination of lemon
juice, a substitute for a native acidic fruit, and grit formed a substance that could coat target areas
[6-8]
of sawing. Once this method was employed, the sawing efforts were much more efficient and
successful. Although the mixture did increase effectiveness, the timing was excruciatingly slow.
Unfortunately, after storing the sample over a weekend with a half of a lemon fastened, pulpside-down, to the incision, sawing on the harder core of the shell was not noticeably improved as
compared to the only grit and lemon mixture. The technique remained very time-consuming, yet
plausible when taking manpower and time available to the ancient Ecuadorian craftspeople into
consideration.
Since the sawing and knapping method by itself was inefficient, boiling was proposed as
an alternate method for softening the shell. The results of the boiling technique described in the
Methods section can be seen in Table II (Table II). From these findings, it can be observed that
the heat treatment did not have a noticeable effect on the hardness of the Spondylus shells based
on the Moh’s Hardness Scale. Regardless of the amount of time the shells were boiled for, the
hardness remained relatively constant at approximately 3 on the Moh’s Hardness Scale. This
matched the original hardness before any boiling took place.
Table 2: Hardness of Shell Throughout Heat Treatment
Hardness (Moh’s Hardness Scale)
Trial 1
Trial 2
Trial 3
After
Boiling 5
min.
After
Cooling 5
min.
After
Boiling 5
min.
After
Cooling 5
min.
After
Boiling 5
min.
After
Cooling 5
min.
2
3
3
3-4
3
3
The conclusion that sawing was an integral part of bead-making was supported by the
observations. When observed under the stereoscope, many archaeological samples showed
distinct linear markings that are suggestive of cutting with a sharp tool (Figures 5 and 6). These
markings matched the thin lines observed in experimental samples after the sawing method was
performed.
Figure 5. A worked Spondylus shell from an
archaeological site with evidence of sawing on
the bottom edge. Thin white cut lines suggest a
sharp tool was moved back and forth along the
surface in order to weaken it. The image was
taken under 45x under a stereoscope.
[6-9]
Figure 6. The experimental sample on
which sawing was performed. The thin
white cut lines are also very prevalent in
this image. The image is under 45x under a
stereoscope.
Knapping
Also referred to by some stone-tool specialists as the “punch technique,” knapping is one
of the most recognized methods of working large stones into smaller hand tools, blades, and
other artifacts. By forming an incision in the surface, inserting a thin blade into the groove and
applying pressure from an antler or some hard stone, ancient craftsmen were able to chip off
substantial pieces of rock from large samples. Many archaeologists hypothesized that shells
would respond to such a method in a similar fashion, presenting a possible solution to how the
Ecuadorians were able to shape the very hard Spondylus shells into pieces of manageable sizes
for bead and ornament-making. However, it was discovered that knapping was an unlikely
process as far as cutting the white inner core of the Spondylus shell. Spondylus shells do not
have the same molecular structures as rocks and stones, and therefore they lack the preexisting
fracture lines created by a stone’s natural structure. Over three hours of knapping efforts did not
result in any success in the knapping of the hard inner shell, and it was concluded that this was
not the most efficient method.
Although the inner core of the Spondylus shell did not respond as expected, knapping
proved highly effective and efficient in removing the cortex of the shell from the smooth inner
core. By applying pressure to the separation lines between the cortex and inner layer, the shell
fractured and separated along these lines, steadily removing sections of the cortex. This process
was expedited after the sample was stored over a weekend with a half of a lemon fastened, pulpside-down, on the cortex. The cortex was significantly softened and more workable than before.
Several pieces of the cortex were successfully separated from the inner shell, and the edges of
the pieces are similar to those found on the archaeological sample (Figures 7a-b).
Figure 7a. The underside of a piece
of removed cortex from an
experimental sample. The image is
at 10.5x under a stereoscope.
Figure 7b. The underside of a piece
of archaeological shell with the
cortex partially removed.
Essentially, knapping is a very plausible method for how the Guangala were able to
remove the cortex from the inner shell core, leaving a smooth, mostly undamaged white surface;
this technique is perfect for forming beads, but not for breaking off pieces of the harder inner
shell.
Grinding
Although the general purpose of this research was to compare the beads produced by the
Guangala and the M-H, one of the main objectives was to theorize the reduction method used by
both civilizations, a significant aspect of the production process that many archaeologists have
neglected to investigate. To provide a comprehensive approach to determining the likely method
[6-10]
used, several methods were experimentally tested in attempts to replicate the archaeological
samples. One of the techniques implemented was grinding, which was performed in two styles:
circular, and back-and-forth. The results of each style were analyzed using both the stereoscope
and the SEM and compared to archaeological samples from both the Guangala and M-H sites.
Examination using the SEM revealed that archaeological samples from both cultural
phases exhibited striations. When comparing the striations seen on the archaeological samples to
those produced by experimental circular grinding, it was found that the grinding patterns did not
match (Figure 8a-c). The striations seen in the Guangala and M-H beads were comparative to
parallel lines; however, circular grinding created a pattern with more randomness and
semicircular markings, in contrast to the archaeological samples. Thus, it can be concluded that
the Guangala and M-H were unlikely to have ground their beads using circular motions. One
possible explanation may be that the greater time the rotational motion required more time as
compared to a back-and-forth motion. Experimentally, it took one hour and twenty-eight minutes
to reduce the shell by 0.66 mm using circular motion while it took one hour and two minutes to
grind 1.09 mm using the back and forth motion. Since the back-and forth motion was more
efficient, there is a greater likelihood that this method was used by the Guangala and M-H Due
to the time-consuming nature of the grinding process, it may have been used more for the
refinement of shells and ornaments rather than for the reduction.
Figure 8a. The experimental shell that
has undergone circular grinding is
shown. The striations are curved and
scattered.
Figure 8b. The figure above shows the
intermediate stage of back-and-forth
grinding of the experimental shell.
Unlike in Figure 8a, the striations are
relatively straight and parallel.
Unlike circular grinding, grinding with a back-and-forth motion was met with success.
When replicated experimentally, the intermediate stage of the grinding process resulted in clearly
visible parallel striations; however, the SEM revealed the roughness of the surface (Figure 8b).
Once additional polishing was completed, the striations continued to be clearly seen, but the
shells were now smooth macroscopically and microscopically. Only miniscule rough patches
were seen using the SEM (Figure 8c). The first Guangala bead closely resembled the
experimental shell in the completed grinding and polishing stage with only a few patches that
looked similar to the experimental shell in the intermediate grinding stage. A second Guangala
bead was also examined under the SEM, which produced similar results. The second Guangala
bead’s parallel striations were almost identical in appearance to those created experimentally in
the completed stage of the refinement process (Figure 8d). When probing the M-H bead sample
under the SEM, parallel striations were also seen (Figure 8e). However, the striations in the M-H
bead were greater in depth than those seen in the Guangala beads.
[6-11]
Figure 8c. The completed
stage of the back-and-forth
grinding is shown. The
striations are almost uniform
and parallel.
Figure 8d. SEM images of a
chipped Guangala half-bead
display almost parallel
striations that mimic those of
the experiment sample
grinded with a back-and-forth
motion.
Figure 8e. A M-H bead is
seen to have back-and-forth
striations that are similar to
those created by
experimentally grinding backand-forth.
The circumferences of the Guangala beads were much smoother than those of the M-H
beads. When looked under a stereoscope, the results seen were similar to those seen under the
SEM. It was shown that the circular method produced highly randomized white scratches in the
shell, while the back-and-forth method produced more regular, parallel white scratches (Figure
9). In Figure 10, a stratified pattern was visible on the back-and-forth method shell, but there was
a marked absence of white scratches (Figure 10). Similar to analysis under the SEM, shallow
grooves were also pinpointed in the M-H archaeological beads under the stereoscope (Figure 11).
Figure 9. Shell sample after
undergoing circular grinding.
Figure 10. Shell sample after
undergoing back-and-forth
grinding
Figure 11. Original
archaeological shell sample
After testing the hypothesis of an additional step through three phases of polishing, both
the circular ground shell and the back-and-forth ground shell were analyzed under the
stereoscope (see Figure 12 and 13). It was noted that although the white scratches were much
less apparent for both samples, they were still visible.
[6-12]
Figure 12. Shell sample with circular grinding
after polishing.
Figure 13. Shell sample with back-and-forth
grinding after polishing.
Drilling
Due to the very small size of the bead drill holes (less than 1 mm), the SEM was
necessary to view the details of the perforations. For the two Guangala beads observed, the inner
cavity of the drill hole was rough, although the outside rim of the drill hole was smooth (Figure
14). For the M-H bead, the interior cavity of the drill hole was much smoother than that of the
Guangala (Figure 15). It was evident on the beads from both cultures that the outside rims of the
drill holes were smooth.
Figure 14. The drill hole of a Guangala bead.
The rim of the drill hole is smooth but the
interior cavity is rough without the regular
striations seen in the M-H bead.
Figure 15. The drill hole of a M-H bead. The
rim of the drill hole is smooth with regularly
spaced striations in the interior cavity.
Fracture Method
The obsidian was able to saw through a preexisting fracture line and chip off the piece of
shell in less than five minutes with only about a one-mm-deep cut in the shell on the fracture
line. The shell specimen, the chipped-off piece, and the shard of obsidian used to saw the shell
can be seen in Figure 16 (Figure 16).
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Figure 16. The shell specimen
is located on the upper left,
the chipped piece on the
upper right, and the obsidian
shard used to saw the shell in
the bottom center.
Figure 17. The sawed and
chipped ridge that was created
during the experiment with a
shard of obsidian.
Figure 18. The original ridge
that was created by the
Guangala. When compared to
the experimental ridge created
in the lab, the two ridges were
observed to be extremely
similar, especially in regards
to the right-angled drop-off.
The edges of the shell and shell piece that were chipped off were compared with the
edges of the corresponding shells that were present during the time of recovery at the
archaeological site (Figure 17 and 18). Even though the original ridges in the shell were observed
to be extremely angular, it is hypothesized that if the chipped piece were to be held against the
ridge, there would be a small gap in the shape of a vertical “V” between the ridge and the piece
made by the thickening of the obsidian.
This can be observed in the holding of the experimental chipped piece against the shell
(Figure 19 and 20). These similarities were observed under a stereoscope. In conclusion, the
fracture method was supported through this experiment and is a likely method of reducing shells
used during the Guangala and the M-H time periods.
Figure 19. These are two different parts of the Figure 20. This is a photo that was taken to
gap between the chipped piece and the shell
include the whole chipped piece and how the
specimen. Even though in Figure 17 the shell gap looks as a whole from a distance.
ridge looked vertical, the chipped piece makes
the ridge look slightly sloped.
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DISCUSSION
Although the M-H existed centuries after the Guangala, the possible advent of mass
production is a plausible explanation for the lack of improved bead products. Originally, it was
hypothesized that the M-H shell samples would be much more refined than the Guangala
samples, and the reduction, refinement, and drilling methods would be much more efficient and
effective. However, upon replicating several methods and analyzing the resulting samples under
both the stereoscope and the SEM, it was apparent that the M-H samples were less refined. There
was certainly a change in the production methods of the Guangala and M-H methods, with more
focus on mass production and more advanced refinement techniques, and it is probable that the
M-H people developed the philosophy of quantity over quality due to the increased demand for
shell ornaments.
Sawing
The most plausible process that was explored in this experiment was sawing. It had been
noted that there were small incisions in shell samples that could have been the markings of stone
tools, and hand-held stone tools had been found at the sites. Researchers used stone tools similar
to those found at archaeological sites and attempted to saw the core of the shell using a backand-forth motion. Progress was extremely slow, however; it took over an hour to make only a
small incision in the shell. This raised the question of whether it was possible that the beadmakers had used an acidic substance to assist in wearing down the shell. When the researchers
attempted to utilize a grit and lemon juice mixture or just lemon juice, it did make the process
quicker, but it was still long and arduous. For a short time, boiling was suggested as a technique
to make the sawing process more doable. However, after several periods of boiling the shells, no
difference was noted in the toughness of the shell, making heat-treatment an unlikely method. It
would have taken a lot of time and manpower to accomplish reduction by sawing, and with
beads in such high demand, it is unlikely that the workers would have been able to produce beads
in the magnitude that excavated tombs suggests. These craftsmen would most likely have looked
for a quicker, simpler process, and the number of beads that have been found compared to the
number of workshops that have been found suggests that they did.
Knapping
Reduction of the cortex could also have been achieved through knapping. Using rocks
that were similar to those found at archaeological sites and animal bones, researchers attempted
to mimic the possible technique to produce the same markings as on the actual samples. Initially,
researchers utilized the process as a means of separating the core of the shell into smaller, easierto-work with pieces. This proved to be extremely difficult; the shell was so compact that it was
nearly impossible to break a piece off, let alone delicately enough to be able to make a bead out
of it. Additionally, the uniform nature of the beads that have been uncovered suggests that these
peoples used a more easily controlled method. Even when a small incision was made to expedite
the process, there was no difference observed – the core remained intact and seemingly
unbreakable. As a revered and valuable material, it is unlikely that these civilizations would have
used such a risky process. However, when the method was applied to the rough outer layer of
the shell, pieces did break off. This could be because the uneven outer surface is less dense than
the inner core and provides small fissures that can serve as breaking points for the Spondylus.
This possibility was further explored when lemon juice was applied to the shell: after several
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days of soaking in the juices, the outer layer was noticeably softer and pieces were able to break
off more easily. The newly-reduced shells bore similar markings to the archaeological samples.
Thus, the knapping process is a likely method for reduction, but not for work on the
actual core itself. It would have taken a lot of strength, patience, and effort to knap at the core,
not to mention the amount of time it would take. The process is a lot more difficult than previous
literature has established; it is not as easy to do on Spondylus shells as it is to do on rocks. This
could be due to the different chemical structures of rocks and shells, or perhaps the peoples were
able to find some way to make the process easier, such as lemon juice or a stronger rock. This
possibility was explored briefly in the study, but perhaps a chemical analysis can be done on the
remaining samples to see if any traces of acid remain or if this was a likely occurrence given the
time, location, and lifestyles of the Guangala and M-H people. It is most likely that the beadmakers used knapping to remove most of the outer cortex and then used grinding to make the
shell smoother and to remove the excess outer layers.
Grinding
Due to the extensive amount of time that was required to grind the Spondylus shell, it
was not likely that grinding was used as a method of reduction. Instead, it is probable that it was
used in conjunction with polishing as a refinement method. The analysis of the ground shells
showed apparent markings of white scratches from both methods, but each method produced a
very distinct pattern.
Contrary to the original hypothesis, the archaeological shell sample that was also
analyzed under the stereoscope did not exhibit a pattern that matched either of those produced by
the grinding methods used in the experiment. Because of the parallel and uniform nature of the
pattern, however, the conclusion that the back-and-forth method was likely used in the grinding
of the shells was drawn.
A possible cause for the lack of white scratches is an additional step of polishing after the
grinding. To ascertain whether an additional step was indeed present in the shell production
process, the experimental Spondylus samples were polished and then analyzed under the
stereoscope. According to literature, past civilizations used grooved stones and a sand-water
abrasive to perform the final smoothing (1). To replicate this process, surface soil from a M-H
excavation site was ground and mixed with water to create a gritty sand-water solution.
Since the white scratches were less visible but still present after the additional polishing
step, it is possible that the shells were polished for a greater period of time, but it is also possible
that the disappearance of the white scratches was facilitated by the passage of time and the
resulting wear and tear.
Although the cause of the disappearance of the white scratches is uncertain, distinctive
differences between the Guangala archaeological shell samples and the M-H archaeological shell
samples were noted. A sample each of Guangala and M-H archaeological shell was analyzed
under the SEM to clearly show the scratch patterns visible on the surface of the shell. Because
the Guangala sample exhibited more scratches similar to the ones visible on the experimental
samples while the M-H sample was much smoother, it is concluded that the Guangala and the M-
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H may have utilized the same grinding process, but differed in their polishing process. Due to the
smooth and unscratched appearance of the M-H sample, it is probable that they were able to
develop a more advanced method of polishing the shell. This correlates to the original hypothesis
that the M-H people, due to an increased demand for shell beads, discovered ways to make the
refinement process more efficient and effective.
Additionally, it is probable that the grinding method remained largely the same during
both the Guangala and M-H periods simply due to society’s resistance to change. After
becoming accustomed to a certain grinding technology, it was unlikely that the artisans would be
willing to rapidly adapt to a new method. Although the general grinding method did not exhibit
obvious signs of change between the two time periods, the results suggested that the polishing
process became more advanced, thus signifying an overall improvement in the refinement
technology.
Drilling
Due to the majority of previous studies, it was expected that Guangala shell beads would
be smaller and M-H shell beads larger. However, upon examining several specimens of
Guangala and M-H shell beads, it became apparent that the opposite was in fact true: the
recovered Guangala shell beads were larger than the M-H shell beads. This observation was
supported by Carter: “From the Middle Guangala to Late G/Early M-H periods, shell bead size
decreased and became increasingly focused upon ROP [red, orange, purple and pink] beads” (4).
The most plausible explanation for the discrepancy between the results obtained in this research
and the previously established studies lies in the size of the sifters used to recover these shell
bead samples. Most archaeologists use sifters with 1/4” holes to separate the shell beads from the
soil, but the samples used in this study were recovered using a sifter with 1/8” holes. Many of the
smaller shell beads may have slipped through the larger sifter holes, resulting in a dearth of
smaller shell beads and causing inaccurate results.
According to this research, the M-H shell beads were generally smaller; however, a more
distinctive difference observed was the patterns visible on the shell beads. Both the drill holes
and the surfaces of the Guangala shell beads were much smoother than those of the M-H shell
beads. The latter possessed rough and bumpy drill holes and surfaces, and these differences
could point to a crucial difference between the two time periods. A possible explanation for this
discovery is that the exterior appearance was seen by the consumers, requiring time for
refinement. However, the interior was only seen by the producer and could be haphazardly dealt
with, and so the M-H may have neglected to spend much time on that region of the bead for the
sake of mass production. Due to the greater demand for shell beads during the M-H period, it is
also possible that production of the shell beads shifted away from meticulous craftsmanship of
the Guangala towards mass production. The M-H people may have sacrificed quality for
quantity, choosing instead to use a rougher but quicker method of drilling the shell beads.
Another notable deviation from previous studies that was observed in the research was
the coloring of the shell samples. It has been previously recorded that the M-H created more
white shell beads, but in this research it was noted that there were more colorful M-H shell beads
than white beads. It is possible that the coloring of the shell beads was related to the size; colored
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shell was more valuable than white shell, and even though the Guangala produced larger shell
beads, they were predominantly white and therefore less valuable.
A plethora of both external and internal factors may have contributed to the disparity
between the size, drilling, and coloring of the shell beads from the Guangala period as opposed
to the M-H period. Preference for smaller beads likely increased during the M-H period,
influenced by social inclinations as well as foreign demand.
Fracture Method
Towards the end of the experiment, researchers discovered another possible method for
reduction: fragmentation. A small piece of obsidian was again utilized because of its sharpness.
By placing the obsidian on a small fracture already present in the shell, it was possible to quickly
and efficiently break off a piece of the Spondylus. Even though this method could also produce
unpredictable and uneven fragments, a piece of shell could be taken off in under five minutes,
making it much more efficient than sawing or knapping alone. It is plausible that the beadmakers looked for small cracks already present and used those as the basis for reduction, but
more research will have to be done on the subject before conclusive results can be made.
FURTHER RESEARCH
The discrepancies between the findings in this study and those of other archeologists
highlight the need for further research. Archaeologists have always thought that the Guangala
crafted predominantly small beads while the M-H made more large beads and ornaments;
however, this research has found that the M-H people may also have created small, colorful
beads. This discovery could help archaeologists further untangle the mysterious relationships
between the Guangala and M-H time periods, as there is more evidence of overlap in
craftsmanship than previously believed. Discovering the lineage of similarities and differences
could shed some light on what caused the transition between the time periods. Perhaps
archaeologists could go back to excavated M-H sites and use a smaller sifter (⅛”) as in this study
to explore the possibility that these smaller shell fragments have been overlooked.
Additionally, the question of exactly how the peoples of the Guangala and M-H periods,
with their “primitive” knowledge and technology, were able to produce such small, detailed
works from the tough Spondylus shell. While this study explored several avenues for the means
of production, no conclusive results were found; many of the techniques proved to be viable
options, and not much other research has been done on production for comparison.
Archaeologists can look more closely into grinding, sawing, and knapping (the more probable
methods of reduction and refinement according to this experiment) and materials/techniques that
could have made the process easier, such as boiling the shell before reduction, grit, or acids from
fruits such as lemon and lime. Another interesting direction future studies could take is the
possibility of utilizing insects for drilling; the shells contained many holes prior to even being
worked on, so perhaps certain types of worms or other insects can produce juices strong enough
to bore into the hard outer layer of shell. There are certain types of parasitic snails who secrete an
acid to wear down the shell and then drill a hole through the rest to feed on the soft tissue of the
animals within. The people may have found these creatures buried in the shell and somehow
manipulated them into drilling. Regardless, this study demonstrated the need for further research,
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as shell bead production could hold a valuable piece for the puzzle of how the Spondylus divers,
shell craftsmen, and patrons fit together in these early societies.
CONCLUSION
Spondylus shell ornaments serve as a means of insight into the relationships between
ancient civilizations, societies, and peoples, particularly for Latin America. The organization of
the production of these ornaments is a key element of the economies and broader organization of
the ancient societies. Previously, there has been a dearth of research into the specific processes of
shell ornament production. Most of the literature has focused on the freshly harvested shell and
the final step of drilling, neglecting the finer details of reduction and refinement. This study
serves as one of the first explorations into possible Guangala and M-H methods for reduction and
refinement, including knapping, sawing, grinding, and polishing. Through various replications
and analyses, it was possible to take a step towards identifying the full production process of the
shell ornaments. Although the specifics of the process have not been determined, possible
methods have been eliminated and other possibilities have been hypothesized, bringing the
archaeological community closer to the discovery of the entire production process. While the
original hypothesis that knapping and sawing were the methods responsible for the reduction of
the Spondylus shells was proven unlikely due to the immense difficulty and inefficiency of the
method, it was discovered that using certain types of rock and cutting along natural fractures in
the shell was feasible. Likewise, the original hypothesis that grinding was another possible
method for reduction was readily rejected due to its inefficiency; however, it is now
hypothesized that grinding was used in conjunction with polishing for the refinement of the shell
ornaments. Overall, the results supported the overarching hypothesis that compared to the
Guangala period, the M-H period experienced more efficient and advanced production
techniques, especially evident from the difference in the drilling techniques of the two time
periods. Through the various conclusions drawn from each part of the production process, it was
possible to ascertain myriad aspects of the Guangala and M-H societies in relation to the
archaeological findings. Shell ornaments are not only archaeological artifacts; they provide a
deeper understanding of the relationships between ancient peoples and the change in societies
over time.
ACKNOWLEDGEMENTS
We would like to thank Dr. Maria Masucci, Dr. Adam Cassano, Dr. Steve Surace, Kaushaly
Patel, New Jersey Governor’s School in the Sciences, and Drew University.
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