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Early Agriculture in the Southwest



            This article is an overview of the pre-ceramic cultures which inhabited the Southwestern region of what is today known as the United States.  I will focus specifically on the time period ranging from about 1200 B.C. to around 200 A.D. and the degrees to which agriculture was introduced in various areas of the Southwest during this time.  Due to the nature of variability among climates and topography, as well as general preservation issues of organic artifacts in this region, the timetable associated with the development of agriculture is somewhat discontinuous and difficult to determine.  There have been a handful of researchers interested in this topic and I will include the studies of such archaeologists as Emil Haury, Bruce Huckell, R.G. Matson, Barbara Roth, and W.H. Wills just to name a few.  Each of these archaeologists has made significant contributions to scholarly knowledge of the beginnings of agriculture and each has developed their own thoughts and hypotheses on what actually occurred among the cultures of these ancient people.

Time Table

            In the past few years, our knowledge regarding specific times that are important to the introduction of agriculture has increased greatly.  There are two phases associated with agricultural history in the southwest known as the San Pedro Phase (1200 B.C.-800 B.C.) and the Cienaga Phase (800 B.C.-200 A.D.).  The earliest maize remains have been discovered at a Middle Archaic site, Sweetwater Locus, and date back to a time between 1400 B.C. and 1600 B.C.  Although these remains were found to belong to the Middle Archaic Period (also known as the Early Agricultural Period) (Huckell 1995), the San Pedro Phase has proved to be a more popular source of study since maize has been recovered from all sites occupied during this time (Roth and Wellman 2001).  The San Pedro Phase is defined by the San Pedro point, which is a shallow side-notched assemblage.  The sites from this phase consist of small, oval pit houses (Huckell 1995).  The Cienaga Phase sites are characterized by larger and more formal structures, a diverse variety of artifacts and numerous storage pits.  The formality of these sites is reason to believe the groups which inhabited them led a more sedentary life than in previous years (Roth and Wellman 2001).


Theories and Models

            Several archaeologists have proposed models which try to explain the processes surrounding agriculture's movement across the Southwest.  The first theory is based on findings by Emil Haury's excavations and formulations from 1962.  This model postulates that crop plants and the technology needed to cultivate these plants was introduced into a region of an already existing hunter/gatherer population.  In 1981, Haury's initial model was updated by Ford which suggested that the spread of agricultural plants such as maize, squash, bottle gourd, and beans first reached into the higher altitudes of the Southwest.  These were not initially used as their main source of fuel, but as a supplement to their hunting and gathering lifestyle.  It was a way of gathering food in an area that could be predicted from year to year.  In 1985, Minnis termed this model as "casual agriculture" and thought that it could be introduced to a population without creating any dramatic changes in their lifestyle, as long as agriculture didn't completely replace the hunting and gathering form of acquiring subsistence.  Minnis also developed theories on why a hunter/gatherer population would adopt agriculture as their main source of subsistence.  His main suggestion was that it may have been necessary for survival, as in the case of increased population density, or possibly could have created a chance for opportunity since it has the ability to increase economic security.  Other researchers have suggested that these groups adopted agriculture as a response to growing population during the late pre-ceramic period and where natural resources were low. 

            The second model postulates that immigration and the spread of pre-existing agricultural populations into the Southwest, displaced hunter/gatherer populations.  These types of models are based more on archaeological evidence than the first group of theories.  Due to droughts in the lowlands during this period, immigrant groups were forced into the highlands which fostered the growth of agricultural settlements.  When the climate in the lowlands returned to normal, these agricultural populations were then free to move about the entire region. 

            The final model is one that includes ideas from both models, and that agriculture may have been introduced in different areas depending on the area and time period being addressed.  R.G. Matson has created a "maize evolutionary model" (Fig. 1.1) based on the history of changes in maize.  His idea is that changes in the actual genetic makeup of the maize itself, allowed for better adaptation to colder and dryer environments.  As the maize evolved, it was able to spread across a greater region and had improved viability.

            Although we can't prove that one model fits the development of agriculture better than another, we can see that the spread of agriculture was a complex process (Matson 1991).


Economic Impact and Food Production

            Archaeologists often interpret agricultural origins by measuring the amount of surplus production.  Some archaeologists believe that agriculture during the Late Archaic was practiced in a casual manner.  If we take into consideration a few theories, this casual farming doesn't seem to be a plausible explanation.  If obtaining a food surplus was one goal of agriculture, this would require a large pool of labor and a large seed crop since "overplanting would need to take place to compensate for loss from climatic factors, predation, disease, and differential seed viability (Wills and Huckell 1989)."  This adoption of a new food source would increase the predictability of subsistence which would possibly lead to the intensification and further organization of foraging activities.  Also important to agricultural economies is the idea that the production of a surplus yield requires a certain amount of labor investment and since plants are not mobile, becoming an agricultural community requires a certain amount of sedentism.  Of course there are other factors which would result in increased sedentism, so in order to better understand agricultural intensification we will compare three different regional sites.  The first is located in the Eastern Tucson Basin, which include sites in the Santa Cruz, Cienega, San Pedro, and Sulphur Spring Valleys that all have thick deposits of cultural remains (Wills and Huckell 1989).

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            The Cienaga Creek Basin (Fig. 1.2), adjacent to the Santa Cruz and San Pedro valleys, has a climate that is wetter and cooler compared to the rest of the region.  Precipitation is bi-seasonal with late summer and winter rainy seasons with spring and fall droughts.  The Cienaga Basin is surrounded by mountain ranges with diverse biotic communities including riparian, semi-desert grassland, oak woodland, and pine forests.  This area is also characterized by a rich and varied group of fauna including both small and larger mammals.  These environmental characteristics I have mentioned make the Cienaga Basin a very productive subsistence environment for humans.  But to what extent did the late pre-ceramic inhabitants utilize this rich environment for agriculture?  Although we cannot determine the answer to this question by assessing only a percentage of agricultural remains found in the diet, we can assess the macrobotanical and bioarcheological evidence.

             Macrobotanical evidence includes artifacts and natural remains such as architecture and food remains.  Archaeologists at the Donaldson and Los Ojitos sites have uncovered remains including fragments of maize cobs, some kernels, maize pollen, and domestic beans at Los Ojitos (Wills and Huckell 1989).  Evidence of maize remains with a high ubiquity value, at almost 100%, has been found at both of these sites.    Even though we must take into consideration the possibility of excellent preservation, due to rapid burial and the physical makeup of the corn cob itself, this abundance of evidence has revealed that maize agriculture was an important part of life in southeastern Arizona.   We also find evidence of bell shaped storage pits which could have held massive amounts of corn ears.  Huckell calculated that the average storage bin could have held almost 9,200 ears of maize, which would provide 364 person-days of food (Huckell 1995)!

            In addition to these remains, we have also excavated agricultural sites which are located on terraces at the Milagro site on Tanque Verde Creek.  The results of a wood charcoal assay have dated to 2800±90 B.P. and maize remains from the same site at 2780±90 B.P., are some of the earliest evidence of agricultural remains in this area (Wills and Huckell 1989). 

            Bioarchaeological evidence includes interpretations made by assessing human remains that have been discovered.  One method of interpretation includes analyzing human tissue for evidence of maize in the diet.  This is a complicated and involved technique where collagen is extracted from the bones to determine the isotopic composition of the carbon since the genetic makeup of maize yields certain distinct test results.  Dental attrition has also been used in determining maize consumption among the people of the southwest since agriculturalists tend to have angled wear patterns on their teeth.  This approach has been used to evaluate dental remains in the Los Ojitos and Matty Canyon areas.

            One of the two San Pedro phase sites located in the Tucson Basin is the Milagro Site which yielded pithouses, storage pits, hearths, and basin pits dated to 2775-2930 B.P.  This site was most likely occupied year round based on the construction of the houses, large storage pits, and the presence of both spring and summer crops.

            The other site in this region is the Costello-King site, dated to about 2600-2800 B.P.  The most important discovery here are the irrigation canals, which may be the earliest canals in the southwest.  The only evidence that suggests an agricultural community is the plant processing tool assemblage and a few pollen remains of maize and cactus seeds (Roth and Wellman 2001).

            Studies completed on groups of the Tucson Basin have indicated that the there was a substantially different socioeconomic system than was present during the Middle Archaic Period.  Before the Late Archaic, there is no evidence of storage features or the co-association of structures.  Many burials found at these sites suggest that there was some idea of land ownership, which is often expected from an agricultural community (Wills and Huckell 1989).

Colorado Plateaus (Fig. 1.3)

            The earliest reported maize date in this region has been collected from Three Fir Shelter and dates to 1600 B.C.  Of course, we must take this one date for being a possible outlier.  We then find that the majority of radiocarbon dates put the earliest cultigens in the northern basin and plateau between 1000 and 800 B.C.  Most of the earlier remains have been found at campsites without architectural structures, although structures and storage do appear across this region between 200 B.C. and 200 A.D. and have been associated with maize.  Most of the cultigens in this area date at about 500 B.C.; a modest estimate considering the much earlier date found at Three Fir Shelter.  In addition to cultigens; storage pits, slab-lined cists, roasting features, and hearths, have all been discovered at this Basketmaker rockshelter (Wills and Huckell 1989).

            The Black Mesa area in general, has an extremely complex pattern of land-use.  Some evidence suggests rockshelters were in use by 500 B.C. and used as storage or for domestic activities.  On the opposite end, there is evidence of open-air habitation sites used for about 200 years starting in 1 A.D.

            Cedar Mesa, located in southeast Utah, also has good settlement data which is useful in the comparison of early agricultural land use.  The BM II culture at Cedar Mesa lasted approximately 200 years, starting in 200 A.D.  The site is located in a densely forested area with piñon-junipers.  The abundance of these natural resources may have led inhabitants to believe this was a suitable area for agriculture, leading them to settle there. 

            Jemez Cave was a rockshelter in the Jemez Mountains.  Originally excavated in 1934, it wasn't until the 1950's that archaeologists realized it contained early maize remains.  Even though this site was badly looted, it yielded evidence of maize cobs in deeper levels similar to those found at Bat Cave.  These were radiocarbon dated to 2440±250 B.P.  Sadly, we don't know much more about this site (Huckell 1990).

            From the sites I have just mentioned, it can be determined that the BM II groups in the Colorado Plateau invested in food storage as well as maintained a highly mobile lifestyle.  The strong similarity of BM II sites across large areas suggests that interaction among other populations was an integral part of life (Wills and Huckell 1989).

Mogollon Highlands

            The Mogollon Highlands are located in the higher elevations of west-central New Mexico and east-central Arizona.  For a long period of time, the highlands were thought to have acquired agriculture at a much earlier date than the rest of the Southwest.  Since the remains from Bat Cave, an important site for this region, have been reassessed, we now know that dates for other sites are equal to those found in the highlands.   Another important characteristic of the highlands seems somewhat contradictory in nature.  There is currently no evidence of any open-air pithouse sites until one or two millennia after the initiation of agriculture to this area.  The sites in this area are usually known as the "classics" and include Bat Cave, Tularosa Cave, and the Cienaga Creek site (Wills and Huckell 1989). 

             Bat Cave (Fig. 1.4), located in west central New Mexico, was first excavated in 1947 as part of the Peabody Museum project.  This site was chosen in hopes that pre-ceramic data could be collected.  This site consists of a large shelter and four smaller chambers, as well as remains of maize.  This maize, along with other cultigens, was originally dated using unreliable radiocarbon methods and was thought to have been part of the third or fourth millennia before Christ.  This date was later revised in 1967 by Mangelsdorf, Dick, and Camara-Hernandez who thought the maize existed no earlier than 2300 B.C. 

            Tularosa Cave and Cordova Cave were excavated in 1950 by Paul Martin in order to gain better temporal knowledge of the Mogollon Culture.  Instead, they found maize ears, cobs, loose kernels, squash, bottle gourd, and beans.  At Tularosa Cave, Radiocarbon dates of 2223±200 B.P. and 2112±200 B.P. came in earlier than those found at Bat Cave.  The abundance of maize remains found at this site suggests that there was a significant dependence on these cultigens.  The abundance of stalks, leaves, and root fragments also suggests that the maize was probably grown closely to the habitation area.  Lawrence Kaplan reported similar plant remains from Cordova Cave in 1963.  Unfortunately, we don't have many direct dates on this site due to poorly followed archaeological excavation procedures. 

            The Cienaga Creek Site was also an important discovery for the study of pre-ceramic agriculture.  This site was excavated by Emil Haury in 1955 and is located south of Point of Pines in the mountains of east-central Arizona.  This open site revealed a record of human occupation in three major geological deposits.  Interestingly, Haury never reported any maize remains, but when a pollen sample was conducted it was positive for maize pollen.  The radiocarbon samples were then sent to two different laboratories, each which found dates differing by 1500 and 1800 years!  Haury seemed to favor the older dates, which placed the pollen at around 4000 B.P.  However, later down the road more reliable tests were conducted and placed the remains at around 3000 or 2000 B.P. which were in the range of the earlier date (Huckell 1990).

            Despite some questionable dating techniques, we do know that the presence of agriculture in the highlands was very intensive.  Unlike areas in the Sonoran Basin and Colorado Plateau, the earliest agriculture in the highlands was not associated with habitation structures.  We don't see much sedentary habitation until the early ceramic period which most likely means there was a long period characterized by mobile agriculturalists (Wills and Huckell 1989).


            As is presented in this article, we can see the uncertainties and discontinuities still present in the data for the spread of early agriculture in the Southwest.  Even some of the more well-documented sites are difficult to interpret.  The spread of agriculture most likely didn't follow a nice, even pattern of growth.  It was most likely a punctuated period of both growth and stagnation.  It is also known to vary between regions within the American Southwest.  For example, the people in the Colorado Plateau seem to have followed a more migratory lifestyle as compared to other regions.  What we can be sure of, despite conflicting opinions and poor data is that major changes took place during the Late Archaic which dramatically changed the economies and food production systems of the major cultures in the Southwest.  Hopefully there will be more accurate analysis and reconfiguration of studies done in the past as well as those which shall be done in the future.



Works Cited

1.  Huckell, Bruce Benjamin.  Late Preceramic Farmer-Foragers in Southeastern Arizona: A Cultural and Ecological Consideration of the Spread of Agriculture into the Arid Southwestern United States.  (UMI Dissertation Services: Michigan, 1990); pp. 132-137.

2.  Wills, W.H. and Bruce B. Huckell.  "Economic Implications of Changing Land-Use Patterns in the Late Archaic," (1989); pp. 34-52.

3.  Huckell, Bruce B.  Of Marshes and Maize:  Preceramic Agricultural Settlements in the Cienega Valley, Southeastern Arizona.  University of Arizona Anthropological Papers No. 59, (University of Arizona Press: Tucson, 1995); pp. 11-15.

4.  Roth, Barbara and Kevin Wellman.  "New Insights into the Early Agricultural Period in the Tucson Basin:  Excavations at the Valley Farms Site (AZ AA:12:736)," Kiva.  (Vol. 67, No. 1, 2001); pp. 60-79.

5.  Matson, R.G.  The Origins of Southwestern Agriculture.  (University of Arizona Press: Tucson, 1991); pp. 203-243.