By the time of the Spanish Conquest, nearly all available sources of fresh water in central Mexico had been tapped for irrigation. Although archaeological remains of canals and dams are scarce, Spanish administrative documents mention the use of irrigation throughout sixteenth-century central Mexico. In many areas, small-scale irrigation systems were the norm. Dams diverted water from springs or small rivers into simple ditch canals that brought the water to nearby fields. In a variation called flood-water irrigation, small dams diverted the frequent rainy-season flash floods onto nearby fields.
In some areas the Aztecs built larger and more technologically advanced irrigation systems. For example, a major segment of the Cuauhtitlan River in the northwest Valley of Mexico was diverted and channeled to provide water to a large area of fields. The river channel itself was deepened, widened, and straightened, and the results are impressive even today (figure 3.5) A series of canals were built leading off the river to the fields. In the eastern part of the valley, a complex irrigation network was built in the area of Mount Texcotzinco. Springs were tapped to feed canals, some of which were up to 10 km in length. The longest canals were built of stone and the channels were lined with plaster. Aqueducts carried the canals over ravines and other low points.
Figure 3.5 Aztec embankment built to contain the new channel of the Cuauhtitlan River in the Valley of Mexico (photograph by William E. Doolittle; reproduced with permission)
Aqueducts were also used to bring water to the city of Tenochtitlan. The swampy island had a limited supply of drinking water, so an aqueduct was built to carry fresh water over the lake from springs at Chapultepec on the mainland. These elaborate hydraulic works were some of the most impressive accomplishments of Aztec technology. This hydrological knowledge was also applied to a third form of intensive agriculture, the chinampas.
Farming the Swamps
Raised fields, or chinampas, were an ancient Mesoamerican technology for turning swamps into highly productive fields.17 Large straight ditches were dug to drain away excess water. Between the ditches, long narrow artificial islands were built up to form planting surfaces (figure 3.6). Mud and muck from the lake bottom were piled up, along with vegetation and other organic matter, and the fields were held together with wooden stakes driven into the lake bottom. Trees were also planted to help stabilize the fields. The resulting plots were very productive. The muck and organic matter served as fertilizers, and the roots of the maize and other crops drew on abundant ground-water from the naturally high water table. The fields were piled high enough to prevent the roots becoming waterlogged, and fertility was maintained by periodically adding more vegetation and rich muck scraped from the canals. Farmers used flat-bottomed canoes to travel on the canals between the fields and bring in their harvest.
Figure 3.6 Modern chinampa fields in Xochimilco, ca. 1905. The farmer is in a traditional chinampa canoe (image from an old postcard)
Plants were germinated in seedbeds built on floating reed rafts, and these were pulled by canoe to individual chinampa plots for replanting. These floating seedbeds have given rise to the modern term “floating gardens,” used mistakenly to refer to the chinampa fields themselves. Their high fertility and their location in the frost-free southern Valley of Mexico allowed three or four crops to be grown annually on the chinampas. This made them the most intensive and productive of all Mesoamerican agricultural practices.
The Aztecs built chinampas throughout Lakes Chalco and Xochimilco, the two lakes that formed the southern arm of the Valley of Mexico lake system. Archaeological surveys that were carried out in this area before the recent urban expansion of Mexico City located many square kilometers of long narrow ridges arranged in an overall grid pattern indicative of Aztec chinampa cultivation. According to Early Colonial documents, chinampas also were built on the outskirts of Tenochtitlan. The system survives today in a few areas of the southern lakebed, particularly in the modern towns of Xochimilco and Mixquic. Aztec chinampa farmers probably looked quite similar to the 1910 Xochimilco farmer shown in figure 3.6. The chinampas historically have provided vegetables for the Mexico City market, but recent environmental degradation, caused by pollution, urban expansion and a lowered water table, is having a negative affect on their economic viability. The chinampa towns have developed into tourist attractions, and for a fee one can still travel through the old canals on boats. Although raised field agriculture was practiced throughout Mesoamerica and South America in pre-Hispanic times, the fields were abandoned before or soon after Spanish conquest in all areas except for the southern Valley of Mexico. These modern chinampas provide crucial insights on this important and widespread ancient technique of intensive agriculture.
Farming in Town
Much of the land devoted to terracing, irrigation, and raised field cultivation was located either away from settlements or adjacent to them. The Aztecs also practiced the intensive cultivation of gardens within their villages, towns, and cities. In most settlements, each family had a substantial garden plot adjacent to the house, which was used to grow some maize, fruits, herbs, medicines, and other useful plants. These houselot gardens, called calmil, were intensively cultivated in that they were fertilized with domestic refuse, weeded and carefully tended by family members. Susan T. Evans's archaeological study of the village of Cihuatecpan suggests that much of its surface area was taken up with calmil cultivation that used maguey semi-terraces on the gently sloping terrain. This intensive garden cultivation may be one reason for the dispersed nature of most Aztec settlements, from villages to cities.18
Household Enterprise or State Control?
Was the state involved in the management of Aztec intensive agriculture? This is an important question in the study of ancient civilizations, for some scholars have suggested that intensive agricultural methods such as irrigation could only be managed by centralized bureaucratic states, whereas others have argued that independent households could take care of their own intensive agriculture without interference from the state.
Aztec terrace agriculture was similar to terrace systems in many parts of the world today where construction, maintenance, and cultivation is carried out on the household level.19 The labor of individual families or cooperative groups of a few families was sufficient to build terraces, and most farming was probably done on a small scale by the individual owners of the terraces. The intensive cultivation of terraces and the need for continual maintenance on the walls made it advantageous for farmers to live close to their plots. This contributed to the great dispersion of rural settlement across the landscape during the Late Aztec period. Houselot calmil gardens were also organized on a household basis.
Unlike rainfall agriculture or terracing, which are organized on the household level in most societies, irrigation systems normally require cooperative labor for their construction and maintenance and some form of central authority for their management. Irrigation networks must be planned carefully from the start. Considerable labor goes into digging canals and building dams. Canals silt up frequently, and clearing them out is a regular and time-consuming task that goes beyond the labor supply and organizational capability of individual households. A common political authority is usually needed to establish water rights and schedules and to settle the numerous disputes that inevitably arise in the operation of any irrigation system. This authority does not have to be the state, however, since in many modern systems the body regulating irrigation is a lower-level local organization.20
In Aztec central Mexico, irrigation was most heavily used in the area of the modern state of Morelos. The size and shape of the major Late Aztec states in this area suggest a link between irrigation and state organization.21 A series of north–south river valleys were extensively irrigated, and the major states, such as Cuauhnahuac, Yautepec, and Huaxtepec, were each confined to individual valleys. Each state could control its own irrigation system without having to rely upon the goodwill of upstream competitors for water. The capital cities of each of these
domains were located near the northern or upstream edges of their territory. Irrigation was important to the people of Morelos, and the size and layout of city-states reflected this importance.
The organizational requirements of raised field cultivation were intermediate between those of terracing and irrigation. The initial construction of a system of raised fields required planning and a considerable investment of labor, but once they were built, chinampas were easily farmed and maintained by households. Some archaeologists see the hand of the state in the regular gridlike arrangement of chinampas in Lakes Chalco and Xochimilco, but documentary sources on the chinampas at the edge of Tenochtitlan describe small plots of several fields farmed by individual households who lived among their fields.22
In sum, some of the intensive agricultural methods used by the Aztecs required organization and control by a central authority, perhaps local lords or city-state bureaucrats, but other methods were almost certainly organized and operated entirely at the scale of the individual farm household.
Rural Settlement
Settlement Patterns
Most of the several million Aztecs in central Mexico were peasants – rural cultivators who farmed land controlled by lords. Rural settlements took a variety of forms, depending upon the local environmental setting, the type of agriculture practiced, and the nature of local social organization. When the Aztlan migrants first arrived in central Mexico, their new settlements were small and scattered widely across the landscape. Only a few large cities – such as Tenayuca (see chapter 2) – existed in the Valley of Mexico during the Early Aztec period. As the population grew, small groups moved into the swampy backwaters of Lakes Chalco and Xochimilco and constructed the earliest chinampas. Then, during Late Aztec times, large numbers of people moved onto the lakeshore plain and built irrigation systems, and into the foothills, where they constructed terraces. These farming systems had a major impact on the nature of rural settlement patterns.
Archaeological surveys indicate that much Late Aztec settlement was dispersed. The remains of individual houses and house groups are widely scattered across the landscape, particularly in areas where terrace agriculture was practiced. The Late Aztec settlement of the Buenavista hills, an alluvial fan in western Morelos, is typical. This ancient geological formation of long, gently sloping ridges extends out for several miles from the Ajusco mountain range to the north. Late Aztec house foundations, which are visible on the ground surface, are scattered along the ridge tops. The sloping sides of the ridges are covered with the remnants of stone terrace walls, and check-dams are present in the ravines between the ridges. As one moves along the narrow ridge tops, the density of houses increases periodically, clustering around small groups of mounds, which were probably elite residences and/or small temple-pyramids. Between the mound groups, house density drops off but never to the point where there are large empty areas.23
Not all Aztec farmers lived in these dispersed settlements. Nucleated villages and towns were also common, particularly in the chinampa zone of the southern Valley of Mexico and in the irrigated valleys of Morelos. In these settlements, houses were packed more closely together, and the communities had clearer boundaries. Towns and some larger villages contained distinctive buildings that had administrative and religious functions. These buildings might include the residence of a village headman or a lord, a temple, or other special structures. Large villages, towns, or areas of dispersed settlement often corresponded to a calpolli, a social and territorial unit that helped regulate land tenure and tax payment (see chapter 6).
Excavations at Cuexcomate and Capilco
Archaeological fieldwork at the rural sites of Cuexcomate and Capilco in western Morelos provides a case study that illustrates some of the topics covered in this chapter. My wife, Cynthia Heath-Smith, and I directed mapping and excavations at these sites in 1985 and 1986 in a project designed to gather information on social and economic conditions among Aztec peasants.24 Although ethnohistoric sources provide rich data on the lives of Aztec nobles and urban-dwellers (see chapter 6), little was known about the Aztec peasantry. We selected these sites for study because they were not deeply buried, and the foundations of individual houses were visible on the ground surface. Archaeologists have found that the best information on social and economic organization comes from the excavation of houses, and conditions at Cuexcomate and Capilco made them ideal sites. We could begin to excavate houses immediately, without wasting a lot of time and effort looking for buried structures. The sites are located in a rural area today and, at the time of fieldwork, were little disturbed by modern settlement or activities.
Capilco is a small site with 21 house foundations, and Cuexcomate is a larger site with over 150 houses and other structures, including temples, storehouses, and ritual dumps (see figure 3.7). One of our first tasks was to estimate the populations of these sites. Since we were unable to excavate all 164 houses at the two sites, we used the technique of random sampling to select a sample of houses at each site. At Capilco, 8 of the 21 houses (38 percent) were selected in a simple random sample, while at Cuexcomate 21 out of 143 houses (15 percent) were chosen in a stratified random sample.25
Figure 3.7 Maps of Cuexcomate and Capilco, rural Aztec sites in Morelos. The black squares are houses (drawing by Michael E. Smith)
For each house in the two samples, two test pits were dug: one in the structure to date its construction, and one in a nearby midden (trash deposit) to recover information on domestic artifacts and living conditions. Through a combination of dating methods, we determined the periods of occupation of each house. We used a detailed sequence of temporal phases based upon the types of pottery present. The latter part of the Early Aztec period is represented at these sites in the Temazcalli phase (AD 1200–1300), and the Early Cuauhnahuac (AD 1300–1440) and Late Cuauhnahuac (AD 1440–1550) phases correspond to the Late Aztec A and B periods (figure 2.1).
The use of random sampling to choose the 29 houses to excavate permits us to extrapolate characteristics of the houses in the samples to the total collection of houses at Capilco and Cuexcomate. For example, two of the eight houses (25 percent) tested at Capilco had occupation during the Early Aztec phase. We therefore inferred that 25 percent of the 21 houses at the site, or five houses, were occupied in Early Aztec times. The numbers of houses were then converted into population estimates using average family size figures from Early Colonial census documents from various towns in Morelos.26
Patterns of house occupation show a dramatic growth of population across the three phases (table 3.3). Although these results pertain only to the two sites, they suggest that the demographic explosion reported for the Valley of Mexico was also taking place in adjacent areas such as western Morelos. When we applied the demographic patterns from Capilco and Cuexcomate to nearby sites in western Morelos, it became obvious that by the Late Aztec B phase, the regional population far exceeded the carrying capacity of rainfall agriculture. This burgeoning population needed intensive agricultural methods to survive, and, in the hilly landscape of western Morelos, terraces and check-dams were the logical choices.
Table 3.3 Population and site areas of Cuexcomate and Capilco.
When we mapped these sites, we noticed check-dams at both sites. Although the remains of ancient check-dams and hillside terraces had been reported from various parts of central Mexico, no one had excavated these features to establish their age, construction methods, or use. At Capilco, we excavated two of the seven check-dams, and at Cuexcomate we dug three of the 36 check-dams that crossed a seasonal streambed just southwest of the occupation zone.
We were able to piece together the history of one extensively excavated check-dam at Cuexcomate by using a combination of methods, including stratigraphic analysis, pollen studies, soil chemistry, grain-size analysis, and radiocarbon dating.27 Its construction was begun sometime in the fifteenth century. A stone wall was built and the upstream side quickly filled up with sediments carried by flash floods. After a per
iod of active use, a flood breached the wall and carried away much of the accumulated deposit. The wall was repaired, and a long period of use followed, during which sediments gradually built up, and the wall was enlarged several times one row of stones at a time. A radiocarbon date of AD 1476 was obtained from a deposit early in this period of gradual expansion. Unfortunately our pollen results were equivocal and do not permit us to state which crops were grown on this or other check-dam fields. The dam was probably abandoned soon after the Spanish Conquest, when the occupants of Cuexcomate (those who did not succumb to disease) were forced to move to another community.
Although we had noted the remnants of a few stone terrace walls on hillsides around Cuexcomate and Capilco, they did not seem to cover a large area. The soils are very rocky, and today large and small stones are scattered all over the ground surface, in pastures and plowed fields alike. One of the student excavators first noticed that the sloping flanks of the ridge surrounding the settlement of Cuexcomate had many subtle stone alignments that could only be the bases of ancient terrace walls.28 The crew had been walking all over these features for months without noticing their existence. We mapped and excavated some of the stone alignments, but soil erosion on the hillsides has been severe since the site was abandoned, and preservation of the terraces is quite poor. The surviving terrace walls consist of rough lines of stones, only a single course high, often resting directly on bedrock.
The Rural Landscape
The peasants who farmed the hills, valleys, swamps, and villages of rural central Mexico were essential participants in the Aztec social order. Their efforts provided food and other products such as cotton to supply the tens of thousands of people who did not farm for a living. The nobility lived off the work of these peasants, as did craft specialists and other inhabitants of cities. Not all Aztec peasants were full-time farmers, however. Women produced textiles for trade and taxes, in addition to their other domestic tasks, and many men took up part-time crafts, producing goods like pottery, stone tools, paper, or rope.
The Aztecs Page 10
