Los Hornos Activity
Los Hornos: A Case Study in Chronology (Effland and MCC 2004)
HOHOKAM
The Hohokam are people who lived in the Sonoran Desert in prehistoric
times. It is believed they are the ancestors to the Tohono O'odham and
Pima. The Hohokam were desert farmers who lived in villages scattered
across the desert. They were masters of irrigation, digging extensive
canal systems (estimated at extending more than 800 miles in the Salt
and Gila River Valleys) that carried water from the rivers to their
fields. Early on, they lived in pithouses; later, in adobe structures
placed in compounds. They had ball courts, where it is believed games
may have been played, much like their Mesoamerican cousins to the south.
They were expert craftsmen, creating beautiful shell ornaments, clay
figurines, and red-on-buff painted pottery. They excelled in the production
of shell ornaments such as beads, rings, bracelets, and pendants. They
often etched designs into the shells using an acid solution made from
fermented saguaro juice.
Sustained occupation and the founding of small but permanent rancheria-like
settlements in the Salt-Gila Basin areas by the Hohokam began in what
is commonly known as the Pioneer period. Sites dating to the earliest
period within the Pioneer phase (A.D. 1-750) are often characterized
by small villages or hamlets located primarily near rivers, with a mixed
subsistence of agriculture and hunting and gathering. This early period
is characterized by small pithouse hamlets, grooved and decorated pottery,
and floodplain agriculture. By the middle of the Pioneer period, villages
consisted of loose clusters of pithouses, with some larger sites containing
plazas. The end of the Pioneer period, the Snaketown phase, was a time
of regional expansion and rapid culture change.
Settlements increased in size, and irrigation systems grew in complexity.
It is probable that expansion of irrigation agriculture was a strong
factor in reducing residential mobility and increasing the size of the
villages. The stability of field locations and the labor costs associated
with canal construction and maintenance possibly stimulated more cooperation
and economic ties among family groups.
The Colonial period (A.D. 750-900) is characterized as one of continued
expansion by the Hohokam. In the Gila Butte phase, villages become larger,
with a more formalized settlement structure including a central plaza,
patterns of mounds, complex irrigation systems, and ceremonial features
known as ball courts. Demographic growth and the success of the Hohokam
culture apparently were supported by the development of complex irrigation
systems and a regional economy linked to northern Mexico. Public architecture
included oval-shaped ball courts, caliche-capped mounds, and large communal
plazas. More than 200 ball courts have been found in Arizona, most of
which are oval-shaped, with a wide range in size. It is believed a ritual
contest, similar to that played in Mesoamerica, was played within the
ball court. There appears to have been a general expansion of Hohokam
cultural and economic influence throughout central and southern Arizona
during the ninth and tenth centuries.
One of the most prominent features of Hohokam culture is a vast network
of hand-dug irrigation canals. The main canals fed thousands of smaller
ditches that brought water to an estimated 25,000 acres of cultivated
fields. The Hohokam established villages at regular intervals along
the main canals to create a complex, interlocking social and economic
system that provided them with great success for many years. They grew
a variety of plants, including beans, corn, squash, agave, and cotton.
In addition to their agricultural activities, they harvested more than
200 species of wild plants with nutritious seeds and fruits and hunted
birds and mammals.
In the Sedentary period (A.D. 900-1150), the small rancheria settlement
system that typified the occupation of the early Hohokam was slowly
replaced by larger villages. These villages were supported by a mixed
economy based on floodplain farming, irrigation agriculture, and the
exploitation of wild food sources in the bajadas. Another important
component of the local economy was the transport, manufacture, and trading
of marine shell and marine shell jewelry. Also during this period, reservoirs
and wells were constructed to provide the communities with dependable
water supplies. The presence of several ball courts and relatively high
frequencies of red-on-buff pottery at these communities suggest they
were integrated into the main Hohokam socioeconomic system.
The Classic period (A.D. 1150-1450) is characterized by change throughout
central Arizona. During this period, many long-established Salt-Gila
Basin communities, including those at Gila Butte and Snaketown, were
abandoned, relegated to positions of insignificance, or shifted locations.
There appears to be a trend toward greater aggregation of the population
into larger settlements. In the Salt-Gila Basin, irrigation systems
reached their greatest extent and level of complexity. Platform mounds
were constructed at important settlements throughout the Salt-Gila Basin.
By the Soho phase, the Pueblo Grande, Mesa Grande, and Casa Grande communities
appear to have grown far greater in size than other nearby settlements.
The platform mounds were surrounded by clusters of houses within adobe
compound walls; a good example can be seen at Pueblo Grande in Phoenix,
Arizona. Large villages consisted of clusters of smaller mounds, compounds,
plazas, cemeteries, and house clusters. Small villages may have contained
house clusters, compounds, and trash mounds. After A.D. 1300, contiguous
room structures became more common, and multi-storied great houses were
constructed at several sites, including Casa Grande.
The Classic period witnessed a series of major cultural changes that affected
most of central Arizona. These involved changes in settlement and site structure,
house form and construction methods, and nearly every aspect of material culture.
While most changes were gradual, by A.D. 1300 much of what was referred to as "Hohokam" during
the preclassic period had disappeared or was significantly altered. The late
Classic period is marked by a collapse and general abandonment of the extensive
Salt-Gila Basin settlement system.
INTRODUCTION TO CHRONOLOGY
Below is a brief summary for the dating methods you will use in this
exercise. Before we briefly reassess the methodology used to date Hohokam
remains, we should review what is basically known about Hohokam chronology
(The
Hohokam Cultural Sequence [Andrews and Bostwick 2000]).
Debates concerning the Hohokam chronology always start with and return
to Emil Haury's initial formation of the Hohokam phase sequence and
his subsequent reconfirmation of this sequence based on excavations
at the site of Snaketown, south of Phoenix. Haury defined a sequence
with four periods divided into nine phases. His sequence begins with
the Vahki phase around 300 B.C. and finishes with the end of the Civano
phase about A.D. 1450. Numerous variations of this sequence have been
advocated. Discussions of the Hohokam phase sequence primarily center
on differences and changes in ceramic types and chronometric dating.
Ceramic types created by Haury that mark each phase are relatively effective
in distinguishing individual phases; other items within the material
culture tend to be time sensitive as well. Changes in the distribution
of figurines, three-quarter grooved axes, and other artifact types can
be used to identify particular periods of time.
Challenges to this traditional period and phase sequence have left it
largely unchanged except in degree. There is evidence that phases tend
to overlap in time if measured across space. The calibration of the
Hohokam chronology has been a major source of challenge. Estimations
for the beginning of the sequence differ, as do starting points for
the Colonial, Sedentary, and Classic periods, and the end of the Classic
period.
There are differences in the sequence between the area around Phoenix
and that near Tucson. There is a general concurrence between the two
areas in the nature of material culture change, but there are obvious
differences.
Seriation
Seriation is a relative dating method. It involves arranging archaeological
materials into a presumed chronological sequence based on cultural and
stylistic change.
As long as items are gathered from the same cultural tradition, archaeologists
assume that stylistic change occurs relatively gradually over time. By tracing
similarities and differences in styles and by measuring the relative popularity
of these differing styles, one can reconstruct a sequence.
Hohokam ceramics have been grouped into types such as Estrella Red-on-gray,
Gila Butte Red-on-buff, Santa Cruz Red-on-buff, and Sacaton Red-on-buff.
These are distinctive in terms of the attributes that distinguish them
and can be ordered based on changing popularity. The assignment of a
feature in an archaeological site to a phase depends upon the archaeologist's
ability to associate the manufacture and discard of the ceramics in
the feature with the construction and use of that feature. Information
you will be provided is based on the assumption that final use (floor
contact) and initial filling with discard ceramics will provide a basis
for determining phase association. In certain cases, this is a highly
reliable measure. Feature 14, for example, had a nearly complete floor
assemblage when it burned and was abandoned. This leaves us a highly
reliable basis for determining its temporal placement. Other features
did not have intact floor assemblages. In these cases, we have to rely
on the trash found in the fill immediately above the floor. For this
reason, you will be provided information from the floor and the first
10 cm above the floor. This provided sufficient numbers of ceramics
to assist archaeologists in reconstructing temporal placement.
You will be provided information about both decorated and plainware ceramics
to use in a seriation. You will be provided raw counts and relative percentages.
Use the percentage data to perform the seriation.
Archaeomagnetic Dating
In the early to mid-1960s, a new technique for dating archaeological
material emerged. This technique, known as archaeomagnetism, was introduced
by Dr. Robert Dubois. As applied, archaeomagnetism relies on thermo-remnant
magnetism; that is, remnants of magnetic orientation in sediments that
were once heated sufficiently to alter their magnetic orientation toward
magnetic north. Clay, when heated, acquires a remnant magnetism with
a direction paralleling the earth's magnetic field. Once the clay cools,
the fired clay holds that magnetism until reheated. By knowing the date
(by some other dating method) of a feature and measuring the direction
of magnetism in clays from this feature, it is possible to determine
the ancient pole location (called the virtual geomagnetic pole or VGP)
of the earth's magnetic field at the time this clay was last fired.
When a large number of these ancient VGPs are dated through this method,
a composite curve of polar wandering (a VGP curve) can be reconstructed.
The VGP curve can be used then as a master record against which the
VGPs of samples of unknown age can be "dated." This implies
that by measuring the remnant magnetism from a clay hearth of a pithouse
from Los Hornos, we can obtain a reference point relative to this curve
and therefore chronometrically date the pithouse.
Measurement of the ancient magnetic field direction is made on pieces
of fired clay collected at archaeological sites in an oriented fashion.
Each of the pithouses that was excavated at Los Hornos had a clay-lined
hearth immediately inside the entry. These were the source for our archaeomagnetic
samples. Pieces of the baked clay were isolated by carefully sawing
into each hearth. A nonmagnetic, cube-shaped mold (aluminum) was placed
over the isolated column and filled with plaster. A record of magnetic
north and the vertical and horizontal placement of the sample was then
made and recorded on the sample recording sheet. Usually, eight to twelve
of these specimens were collected and submitted to Colorado State University
for processing. The ancient magnetic direction and age determination
for a given feature was calculated on the basis of the mean direction
of all specimens collected from the feature. The data were then summarized
and returned to Archaeological Consulting Services for interpretation
relative to other data from the site.
Radiocarbon Dating
The basis for radiocarbon dating is magnificently simple. Carbon 14
is continuously produced in the upper atmosphere by the action of cosmic
rays, which set free neutrons that transmute nitrogen in the air into
radioactive carbon. Incorporated in carbon dioxide, the radiocarbon
moves through the atmosphere and is absorbed by plants. Animals in turn
build radiocarbon into their tissues by eating the plants. As long as
they are alive, plants and animals go on ingesting radiocarbon. When
an organism dies, and ceases to take in fresh carbon, its built-in clock
begins to run down. The disintegrations of its carbon-14 atoms tick
away the seconds and the years: in 5,568 years (on the average) only
half of its original store of radiocarbon atoms is left, and in another
5,568 years only half of those, or one quarter of the original number.
Long before that time, of course, most plants and animals have decayed into
dust. but when the remains of an organism are fortuitously preserved, as a
house beam,
a bit of charcoal, or a seed, the age of the remains can be calculated. The
amount of radiocarbon the organism possessed when it was alive is known, and
so is the
rate of its radioactive disintegration. It is easy to compute the age of the
remains by counting the amount of radioactivity that still remains.
Since many of the features excavated at Los Hornos contained traces
of charcoal, there were ample materials to sample for radiocarbon dating.
Samples were carefully selected according to the type of material and
quantity available for processing. Priorities were given to materials
and plants such as arrow weed used in house construction. Second priorities
were given to house beams or support posts used in construction.
INTRODUCTION TO LOS HORNOS
In late 1987 and early 1988, Archaeological Consulting Services Ltd.,
a private archaeological company in Tempe, performed excavations at
the site of La Ciudad de los Hornos. The site of La Ciudad de los Hornos
is a very large and complex Hohokam village that covers nearly a square
mile. This site might have been occupied from as early as A.D. 450 to
as late as A.D. 1450. The Spanish word for oven is horno, and
the name of the site (Los Hornos) is derived from the large number of
communal ovens observed by Frank Cushing when the site was first recorded
nearly 100 years ago.
The purpose of this assignment is to give you a basis for understanding
how archaeologists build chronological sequences. Time is of vital interest
in order to study processual changes in behavior, perhaps the primary
goal of archaeological research. The first part of this exercise focuses
on data that you will use to order features (pithouses) using a seriation
method of dating. This is a relative dating procedure that can be useful
in reconstructing a basic sequence. A series of chronometric dates will
be provided. Both radiocarbon 14 and archaeomagnetic dates that were
derived from some of the features will be used to calibrate and adjust
the sequence you established using the seriation data. Once you have
completed the chronological evaluation, you can attempt to relate this
to other reconstructions of behavior from data taken from excavated
features, in this case directly from house floors.
Forty structures or fragments of structures (features known as pithouses
for Hohokam archaeology) were identified during the excavations. Twenty-six
(26) of these were excavated completely. Features were excavated using
arbitrary levels. Ceramics from the floor level and 10 cm above the
floor were collected and analyzed. These were typed according to traditional
ceramic types for the Hohokam culture; types such as Santa Cruz red-on-buff,
Gila Buttes red-on-buff, Sacaton red-on-buff were recorded. Ceramics
from three broad time periods were recognized: these periods were the
Pioneer, Colonial, and Sedentary. These would roughly place the features
in a range from A.D. 500 to 1150.
Hohokam pithouses were constructed as "houses in pits." Using
wood poles, arrow weed, and mud, walls were constructed around the periphery
of a shallow pit in which the actual floor of the pithouse was lined
with caliche. Caliche is a naturally occurring limestone deposit in
southern Arizona deserts. When wet, this deposit can be manipulated,
but when it hardens, it is like concrete. Many of the floors at Los
Hornos had caliche about 3 to 5 cm in thickness. Pithouses are of different
sizes and shapes.
ASSIGNMENT
You can now begin to prepare a report that focuses on reconstructing
the chronological sequence for the features from Los Hornos and then
relating this information to a reconstruction of the Hohokam who lived
in this small segment of the site. As you begin to reconstruct the behavior
of the people who built and lived in these pithouses, try to utilize
as much of the information as you can. Try to look at data relative
to house shape and size, for example, to see how these may have changed
over time. Were some houses used in particular ways—special purposes,
for example? How many people would you expect to have lived in houses
such as these? Did these people seem to trade and interact with other
peoples in southern Arizona? These are the types of questions archaeologists
would attempt to answer as they reconstruct the archaeological record
from this excavation.
You will be given information on 14 of these pithouses. The information
will vary because of the nature of the archaeological record for each.
You must recognize that there is a time depth to the archaeological
record. You job will be to work through the information and sort out
the temporal placement for these 14 pithouses. You will construct a
relative time sequence and then place a chronometric or absolute time
frame to this sequence. It will then be your responsibility to write
a short report with supporting tables, charts, etc., that (1) outlines
your assessment of temporal ordering, including data to support your
interpretations; and (2) briefly summarizes the patterns you found in
changing settlement at Los Hornos as a result of your temporal assessment.
Archaeologists use artifacts discarded in a location to infer the activities that went on there. We'd like you to report on a simple experiment that relates activities with the artifacts that are left behind. Your write-up should be typed (with a hand-drawn map), should be no more than a single page in length, and should do a reasonable job of completing all parts of the assignment. It is worth 10 points. We'll discuss the results in class.
1. Find a Location: Go to a public location, such as public park, a classroom, or an outside area on campus. Define a specific area of interest, no larger than about 25 feet by 25 feet (for example, 10 feet on either side of a picnic table, bench, newspaper stand, coffee bar, desk or whatever). The measurements don't have to be exact; you can pace it off or just estimate.
2. Location: In a sentence, identify the location (e.g., the picnic table in the Anthropology building courtyard).
3. Map: Draw a sketch map of your area. A sketch map can be in pencil and need not be drawn to scale or be of publishable quality, but it should be clear and should show the major features, such as tables, trash cans, planters, trees, grass, or sidewalks.
4. Artifact Inventory: Now look carefully all over the area you have laid out for discarded items on the ground or in formal disposal areas (like in a trash can). Your artifact inventory should consist of a list of artifact classes (five or so classes should be sufficient; e.g., snack wrappers, soda cans, or newspapers) quantified in relative terms (e.g., rare, moderate, or common). This should be presented in a simple table such as the one that follows. (It isn't part of the assignment, but you might think about whether different classes of material are found in different parts of your area. Are soda cans more often found in trash cans and candy wrappers on the ground?)
| Soda cans | rare |
| Snack wrappers | common |
| Unidentified paper | common |
5. Inferred Behavior: Describe in a paragraph what the trash that you have recorded implies about the behavior that occurs in this area and why you draw those conclusions. Include some relative statements about frequency (e.g., common eating of candy). Don't describe what you've seen go on here, but what you infer based only on the trash.
6. Observed Behavior: Finally, spend 10 minutes observing the area you have selected and describe in a short paragraph the behaviors you observe and their relative frequency, recognizing that your 10 minutes may not be representative of all of the activities that take place in this location.
7. Contrast: Briefly discuss the relationship between your inferred and observed behaviors and how you would account for any differences. Again, a paragraph will suffice.
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