An essay on energetics: the construction of the Aztec chinampa system.

An essay on energetics: the construction of the Aztec chinampa system. Introduction All civilisations are dependent upon their ability to grow oraccess large amounts of food through exchange, trade, taxation and/ortribute. The archaeological and historical records demonstrate thathydraulic management in some form was an essential component ofgenerating this supply (Wittfogel 1957). One form of hydraulicmanagement involved the building of agricultural fields in low-lyingswampy areas, which were otherwise unproductive and, therefore, outsidethe agricultural economy. This orchestrated dredging of muddy soil toform highly productive agricultural fields was practised by the Mexica,or Aztecs, of central Mexico during their imperial rule (AD 1428-1519).The fields, termed chinampas, have long been regarded as one of the mostproductive forms of agriculture in pre-Hispanic Mesoamerica. The mostextensive region of reclamation was the swampy environs of theChalco-Xochimilco lakebed which constituted the southern portion of LakeTexcoco This article is about the lake. For the pre-Columbian city-state, see Texcoco (Aztec site). For the modern municipality and city, see Texcoco, M��xico.Lake Texcoco was a lake in Mexico. (Figure 1), in close proximity to the Aztec capital ofTenochtitlan. Once this area fell under Aztec control through a seriesof sweeping military conquests, the orchestrated construction ofchinampa fields was initiated. As a result of this reclamation project,a once agriculturally underused area was converted into the mosteconomically productive region within the Basin of Mexico (Sanders etal. 1979; Parsons 1991). [FIGURE 1 OMITTED] There are several goals for the present research. The first is toquantify, through the methodology of architectural energetics en��er��get��ics?n. (used with a sing. verb)1. The study of the flow and transformation of energy.2. The flow and transformation of energy within a particular system. , theinitial cost of construction of the Aztec chinampa system in thesouthern lake district. Although architectural energetics has been mostfrequently applied to Mayan architecture (Abrams 1994), it may beapplied to intensive agricultural systems, which we deem horizontalmonuments. The quantification is designed to better inform our estimatesof the scale of initial construction. Sanders (1976: 131) noted that'large areas along the lakeshore consisted of swampy land thatcould have been cultivated only with a considerable outlay of labour onthe part of the individual farmer'. Parsons et al. (1982: 377)noted that 'the labour intensity of chinampa cultivation has neverbeen adequately quantified, but it was certainly very demanding. Just asanalyses have quantified both the labour expended in growing maize onchinampa fields (Sanders et al. 1979) and the productivity from suchfields (Parsons 1976a), the current research generates baselineestimates of the scale of initial construction of the chinampa system.By doing so, we advance architectural energetic analyses by placing thequantified costs in the context of historical process, an applicationrarely done in archaeology (but see DeLaine 1997). For comparative perspective, we then consider the quantifiedestimate of labour expended in chinampa construction relative to thatexpended in cloth production Historically, cloth production in England, Wales, and much of Europe was often historically organised under the domestic system, prior to (and also in the early stages of) the introduction of the factory system. . Specifically, we examine the annual labourdevoted to cloth production for tribute given by the Aztec village ofCihuatecpan in the Teotihuacan Valley. A major observation is that theannual allocation of labour in chinampa construction was in fact verydemanding on households and that inferences regarding state impositionare well founded. We find, however, that cloth production was almostequally demanding in terms of time. Our overall conclusion is thatincorporation of smaller polities into a unified Aztec state leddirectly to an increased level of household labour expenditure thataffected all commoners, regardless of the product required wholly or inpart by the state. Environmental background to chinampa construction The Chalco-Xochimilco drainage basin drainage basin:see catchment area. (Figure 1) is a uniqueenvironment in the highlands of Mexico. Here, adequate rainfall andprime soil conditions provide much agricultural potential (Sanders 1957:30). Before the construction of large hydraulic control mechanisms, theBasin of Mexico contained an immense lake system. Lake Xaltocan and LakeZumpango were to the north, Lake Chalco Lake Chalco was an endorheic lake formerly located in the Valley of Mexico and was important for human development in central Mexico. The lake was named after the city of Chalco on its eastern shore. and Lake Xochimilco Lake Xochimilco is an ancient endorheic lake located in the Valley of Mexico, part of a series of lakes, which included the brackish Lake Texcoco, Lake Zumpango, and Lake Xaltocan and the fresh water Lake Chalco. to thesouth, while Lake Texcoco dominated the central region. Those lakes inthe southern Basin were not separated by any natural landmass land��mass?n.A large unbroken area of land.landmassNouna large continuous area of landlandmass? and arecommonly referenced as a single body of water (Lake Chalco-Xochimilco).With depths ranging from 0.8 to 3.0m (0.8-1.2m in the majority of thelake), and an estimated surface area of 150[km.sup.2] (Sanders 1957:40), this dual lake system was segregated during seasonal dry periods bysmall ponds and swampy terrain (Sanders 1979: 86). The notion that theselakes were open bodies of water is incorrect, as they were covered witha thick coating of aquatic vegetation from the genera Scirpus and Typha(Crossley 1999: 10). Anton Kovar's (1970) studies of the Basin of Mexico'sphysical environment prior to human occupation have revealedhydrological hy��drol��o��gy?n.The scientific study of the properties, distribution, and effects of water on the earth's surface, in the soil and underlying rocks, and in the atmosphere. patterns that are paramount to our research. LakeChalco-Xochimilco drained into Lake Texcoco owing to owing toprep.Because of; on account of: I couldn't attend, owing to illness.owing toprep → debido a, por causa dethe latter'slower elevation. Lake Chalco-Xochimilco's 3m heightened elevationpermitted the preservation of its fresh water contents and resulted(with drainage from other sources) in the salinity of Lake Texcoco(Kovar 1970:15). In addition to differential elevation, a perpetual flowfrom springs provided continual renewal of flesh water (Coe 1964: 93).This 'sweet water' contained extremely low levels of sedimentas it was filtered by igneous rock igneous rock:see rock. igneous rockAny of various crystalline or glassy, noncrystalline rocks formed by the cooling and solidification of molten earth material (magma). before entering the lakebed; however,the springs (primarily located on the southern side of Lake Xochimilco)saturated the ground and kept the water table high (Coe 1964: 93). LakeChalco was predominantly fed by the Tlalmanalco and Amecameca rivers inthe eastern region of the Basin, which carried coarse sediments with lowdissolved loads (Crossley 1999: 13). While the deep alluvial plain Noun 1. alluvial plain - a flat resulting from repeated deposits of alluvial material by running wateralluvial flatflat - a level tract of land; "the salt flats of Utah" surrounding the lakeshore contained significant agricultural potentialand supported a wide range of wildlife, its marsh-like characteristicsdeterred settlement and cultivation. Armillas (1971: 659) attributed the lakebed's relief andvolume of standing water as prime natural controllers of chinampaexpansion and drainage works. His studies revealed.... the shallowdish-shape of the Chalco-Xochimilco basin as well as the gradual bankthat retained its freshwater contents. At 2240m above sea level, thisbank is the critical boundary above which the alluvial plain would havebeen filled with standing water. However, below 2238m, the majority ofwater would have been drawn to deeper reliefs, exposing a vast swampyexpanse conducive to chinampa construction (Armillas 1971: 659). Rainfall throughout the Basin is seasonal, with the wet seasonspanning from May to October, and the majority of precipitation fallingduring June through August (Sanders 1957: 42). Annual precipitation onthe floor of the Basin averages 800mm, with temperature highs recordedin May and lows in January (Crossley 1999: 16). Frost may occur betweenOctober and March, exposing the crop complexes of the region to asignificant risk of failure (Crossley 1999: 16). Further, Crossley (1999) noted that significant temperatureincreases were facilitated by the standing water in canals. Creatingchannels of warmer air, the morphology of raised fields and associatedcanals can raise air temperatures as much as 6.3[degrees]C above that ofdry fields (Crossley 1999: 280). These pockets of air hovering over thewater-filled canals have a significant effect on temperature, byreducing if not eliminating frost damage and crop destruction. Benefitsof such a system are amplified when the chinampa fields are tree-lined.Once mature and fully leaved, the trees create a canopy, blocking windand trapping warm air, adding further to field protection (Crossley1999: 288). Temperature amelioration a��me��lio��ra��tion?n.1. The act or an instance of ameliorating.2. The state of being ameliorated; improvement.Noun 1. , however, decreases as the distancefrom the canal edge to the chinampa field increases (Crossley 1999:293). In effect, productivity of chinampa fields increased with thephysical expansion of the chinampa system. Formation processes of chinampa construction There are many examples of raised fields in both the New and OldWorld archaeological records (Scarborough 2003). Although some arerelatively small in scale, such as the raised fields built by theLowland Maya (Scarborough 2003: 159), the Aztec chinampa system is oneof the larger scales of construction. Given the character of the naturalswampland (above) the water flow could not itself be used to assist inthe excavation of channels, which the Aztec would have needed to dig byhand. The creation of the watered fields was therefore, by allobservations, entirely artificial. The southern lake chinampa system built by the Aztecs utilisedenormous numbers of intricate drainage canals, or zanjas, as well as thechinampa fields themselves. Both of these features were constructedusing only simple wooden tools and human strength. Based on Spanishethnohistorical documents (Armillas 1971; Sanders 1976; Parsons 1991),Mexican ethnography (Gomez-Pompa et al. 1982), and field archaeology(Armillas 1971; Nichols & Frederick 1993), we know the stages ofconstruction: (1) an area was demarcated, generally aligned withexisting fields or influenced by landforms; (2) labourers excavated soilcreating canals and tossing that soil into rectangular masses of earthwhich formed the chinampa field; (3) vegetation from the canals andlakewater were added periodically to the field, even duringconstruction, and (4) trees were planted in the corners of thenewly-constructed field to serve as anchors. Clearly, the dominantlabour cost is the excavation of soil from the eventual canalssurrounding the fields. The canals were first extended from islands and mainlandpeninsulas, proceeding from shallow areas to those of greater depth,thus facilitating water drainage Wa´ter drain´age1. The draining off of water. (Sanders 1976: 134). Displaced earthwas situated along the canal, forming fields between 2.52-3.36m wide(Armillas 1971: 653; Table 1). Of relevance in our analysis is thatthese fields, when described by Spanish chroniclers, were noted to be'strips' or 'very narrow strips' of land (Armillas1971: 653). Sanders (1965: 44) referred to the fields as 'long,narrow rectangles'. The fields and drainage canals, when alignedand cross-sectioned, formed small islands, typically long and narrowranging in lengths between 6.0 and 9.0m (Wilken 1969: 223; Armillas1971: 653). The average distance between parallel canal medians was anestimated 4.8m, with canal widths ranging from 1.44-2.28m (Armillas1971: 659). The depth of the canals varied. Sanders (1965: 44) noted that theheight of each field was only 'a few inches above the lakesurface'. In the Xoltocan region of Lake Texcoco, the depth ofcanals varied from between 1.0 and 1.2m (Nichols & Frederick 1993:139). In order to create new chinampas, ditches were simply extended todeeper depressions and/or other drainage canals (Wilken 1969: 223). According to according toprep.1. As stated or indicated by; on the authority of: according to historians.2. In keeping with: according to instructions.3. Armillas (1971), a total of 120[km.sup.2], or 12000ha,of swampland was reclaimed in the Chalco-Xochimilco lakebed region.Armillas reduced this number by 25 per cent to account for canals anddispersed unused sections such as islands, resulting in a figure of 9000agriculturally viable hectares (Armillas 1971: 660). This figure hasbeen used in most subsequent analyses of productivity (Parsons 1976a;Sanders et al. 1979), although 120[km.sup.2] has also been used (Denevan& Turner 1982). However, Crossley (1999: 73) suggested that thephotogrammetric analysis of the Chalco-Xochimilco region performed byArmillas may have led to an exaggerated estimation of chinampaagricultural land, and Frederick (1999) noted that the Aztec chinampaswere much narrower in form and lacked the tree-lined borderscharacteristic of more recent raised-field agricultural constructionsand restorations (see also Coe 1964: 90). Since the real extent of thechinampa system is crucial to our analysis, we revisited the issue ofscale. Taking the total size of reclaimed swampland at 120[km.sup.2], wemeasured and subtracted from this total the area of islands within thelake (12[km.sup.2]), leaving 108[km.sup.2] as lake area for potentialconversion to intensive agriculture. We then measured the area (notvolume) of fields and canals employed as chinampas (Parsons 1976a: 241;Figure 12.4), which generated a field:canal ratio of roughly 3:2, i.e.60 per cent of the surface area was fields. A 1:1 ratio is observed fromthe physical measurement of the chinampa remnants (Parsons et al. 1982:227, Table 42). Here Parsons et al. indicate that both the field and thecanal are lm deep, and that the field width of 2m is matched by thecanal width of 2m. Finally, logic dictates that the canals must have hadsufficient width to provide clearance for labourers in canoes scoopingout vegetation and soil from the canals. Taken as a whole, we concludethat a ratio of 3:2, or a 60 per cent reclamation, is a reasonableworking estimate in the present analysis. These measurements andobservations suggest that, of the 108[km.sup.2] available formodification, 60 per cent were fields and 40 per cent were canals,yielding an area of earth moved of 65[km.sup.2] which, given a depth oflm, translates into a volume of 65 000 000 [m.sup.3]. Our re-examination of the chinampa system reduced the estimatedfield area from 90[km.sup.2] to 65[km.sup.2]. Although this potentiallyreduces the estimated maize productivity of the system (depending uponestimates of yields), it simultaneously increases the lacustrine la��cus��trine?adj.1. Of or relating to lakes.2. Living or growing in or along the edges of lakes.[French or Italian lacustre (from Latin lacus, lake) + resources procured from the canals. Canals were not simply smallerversions of the lake, but actually were more productivemicroenvironments. The canal as a biotic biotic/bi��ot��ic/ (bi-ot��ik)1. pertaining to life or living matter.2. pertaining to the biota.bi��ot��icadj.1. Relating to life or living organisms. environment was rich in a widevariety of fish and amphibians (Berres 2000). In addition, the abundanthydrophilic hydrophilic/hy��dro��phil��ic/ (-fil��ik) readily absorbing moisture; hygroscopic; having strongly polar groups that readily interact with water. hy��dro��phil��icadj. vegetation on the water surface was utilised in constructionof the chinampas themselves. Tule tu��le?n.1. Any of several bulrushes of the genus Scirpus, growing in marshy lowlands of the southwest United States.2. tu��les Northern California Marshy or swampy land. , water hyacinth water hyacinth:see pickerelweed. water hyacinthAny of about five species of aquatic plants that make up the genus Eichhornia of the pickerelweed family (Pontederiaceae). They are native mainly to the New World tropics. and tepalacate wereadded to the lake mud to create somewhat of a compost heap Noun 1. compost heap - a heap of manure and vegetation and other organic residues that are decaying to become compostcompost pilecumulation, heap, pile, agglomerate, cumulus, mound - a collection of objects laid on top of each other , whichenhanced soil fertility (Sanders 1957: 86). Energy expended in construction Energy analyses have provided the field of archaeology with theability to compare quantitatively labour intensities of agricultural,architectural, and other constructed complexes (Abrams 1994: 38). Inaddition to this primary contribution, energetics has surpassedtraditional volumetric volumetric/vol��u��met��ric/ (vol?u-met��rik) pertaining to or accompanied by measurement in volumes. vol��u��met��ricadj.Of or relating to measurement by volume. studies by refining labour costs. For example,equal proportions of material do not equate with equal labourinvestments; independent factors such as transportation and location ofraw materials play a significant role in total labour costs. The valueof this approach is that it 'provides a means of explicitlydefining subjective assessments of scale and quality ... thus makingpossible an array of analyses otherwise unavailable' (Abrams 1994:38; also Abrams 1998; Abrams & Bolland 1999). The equations and figures used to quantify the construction costsof the chinampa system are extrapolated from Erasmus' (1965) earthexcavation and transportation analyses at Las Bocas Las Bocas is a minor archaeological site in the Mexican state of Puebla, whose name has become, often erroneously, attached to a wide-ranging style of Olmec-style figurines and pottery. on the YucatanPeninsula. Based on replicative experiments, it was concluded that afive-hour person day (p-d) of earth excavation using a wooden diggingstick dig��ging stickn. AnthropologyA rudimentary digging implement consisting of a pointed stick, sometimes with an attached stone or crossbar, used to loosen and till the soil and to extract plant foods. would 'conservatively' produce 2.6[m.sup.3] of earth(Erasmus 1965: 285). The five-hour work period was used as a'day' since effective work rates dropped significantly afterthat time span; 'person' is used since we do not presume thesex of the labourer. Cost analyses of transportation are unnecessary asexcavated soil was neither imported nor carried from any distance beyondits source. Since our analytic focus is on the initial construction ofthe chinampas, we intentionally avoid the question of farming andmaintenance costs of farming the fields and maintaining the fields(Parsons 1976a; Sanders et al. 1979; Wilken 1969). Analysis 1: assessing total cost The first energetic exercise was aimed at generating a total costof the chinampa system. With a volume of 65 000 000[m.sup.3] of earthdug and a rate of digging at 2.6[m.sup.3] per p-d, the total cost ofbuilding the chinampa system is estimated at 25 000 000p-d. This numberis best understood in comparison with other architectural total costestimates. Using a methodology comparable to that used here, Webster& Kirker (1995) were able to generate labour estimates for theupper-end of Mayan architecture. It was determined that Temple 1 atTikal, Guatemala, required 90 000p-d and Temple 26 at Copan, Honduras,absorbed 124 000p-d (Webster & Kirker 1995: 372-4). Even withintricately carved exteriors and transportation costs considered, thesestructures hold no comparison to the 25 000 000p-d needed for theinitial construction of the Aztec chinampa agricultural complex. Thisfirst-line comparison reflects the enormous absolute scale of labourexpenditure in the initial construction of the chinampa system. In fact,if conceived by the Aztec state as a single, long-term building project,the southern lake chinampa system was one of the most costly labourundertakings in Mesoamerican history. Analysis 2: assessing individual chinampa construction A second energetic analysis involves the building of each chinampafield. Based on the figures in Table 1, each field was roughly 9m x 3m(27[m.sup.2]). With the actual fields covering an area of 65 000000[m.sup.2], the Aztecs prompted the construction of roughly 2.4million chinampa fields. If built over a 40-year period, then 60 000chinampa fields were built each year. Based on Erasmus' labourcost, each field required approximately 10p-d. This estimate iscorroborated by the cost of chinampa construction in Tabasco derivedfrom ethnographic observations (Gomez-Pompa et al. 1982). Those fieldswere 100[m.sup.2]; thus when extrapolated down to the size of the Aztecfield, we arrived at a cost per chinampa of about 10p-d. Analysis 3: assessing construction relative to population size For this analysis, a brief description of population trends andestimates for this lake region is necessary. Population in theChalco-Xochimilco region remained relatively low despite a minimalincrease through the Early Horizon (1500-1150 BC) and the FirstIntermediate Phase 1 (1150-650 BC). After reaching a peak estimatedpopulation of 29 100 in the First Intermediate Phase 2 (650-300 BC;Sanders et al. 1979: 197), this region endured a period of declineduring the Middle Horizon (AD 250-750), in large part as a result of theemergent Teotihuacano state in the north-eastern section of the Basin(Parsons 1991: 36). Nevertheless, after the seemingly rapid abandonment, theChalco-Xochimilco region underwent a slow and steady recovery (Parsons1991: 36). Xico, a small island in the eastern part of Lake Chalco,experienced considerable growth in the latter half of the eighth centuryas a result of the demographic shift following the fall of Teotihuacan(Parsons 1991: 30). In addition, settlements were established in the RioAmecameca delta. These two regions became home to the majority of thepopulation in the Chalco-Xochimilco area by AD 900. However, it was notuntil the Second Intermediate Phase 3, or Aztec I and II periods (AD1150-1350), that significant numbers of settlements appeared in thelakebed (Parsons 1976b: 97). Population density in the actual lakebedregion grew from 1.7 persons/[km.sup.2] during the Second IntermediatePhase 2 to 127.4 persons/[km.sup.2] during the Second Intermediate Phase3 (Sanders et al. 1979: 190). These settlements still remained situatedon or near islands and lakeshore portions with higher elevations(Parsons 1976a: 237). At these locales, small-scale chinampa agricultureundoubtedly was part of daily subsistence. Population increased evenfurther in the Late Horizon (AD 1350-1519), and it is during this periodthat the intensification of the chinampa system under study took place. During the Late Horizon, the standard estimates for population ofthe southern lakes centres totalled 26 500, divided as follows:Culhuacan (4000), Tlahuac (3000), Mixquic (2000), Xochimilco (15 000),Xico (2500) and Chalco (12 500) (Parsons 1976a: 243). The totalpopulation estimate for the entire southern lake region is 89 600(Sanders et al. 1979: 190). Of this, 26 per cent lived in uplandalluvial zones, presumably pre��sum��a��ble?adj.That can be presumed or taken for granted; reasonable as a supposition: presumable causes of the disaster. involved in alternative agriculture. Perhapshalf of the middle piedmont population (15 per cent) similarly wereinvolved in alternative economic practices. This leaves a population ofapproximately 59 000. Subtracting 10 per cent of that figure as beingmembers of social categories exempt from direct agricultural labouryields a working population of approximately 53 000 people. Regardlessof whether these were free commoners (macehualtin) or tenant workers(mayegues), this figure translates to about 10 000 households. In this analysis, we use 20-50 per cent of the total labour forceas viable options, assuming that if more than half the population wereinvolved in building new chinampas, there would be insufficient labourto farm the existing ones. Similarly, more than 100 days devoted to thisnew construction would leave little time to work the existing chinampas,especially in a farming system that requires double cropping of fields.Using these time and population parameters and 25 million p-d as thetotal cost of construction, several viable options for specific labourinvolvement are generated (Table 2). This set of scenarios demonstrates that the chinampa system couldhave been built by the resident population of the southern lake region.Hypothetically, if two members of each household of five worked for 30days on new field construction, the entire agricultural system couldhave been completed in 39 years. Reconfigured, if two members of eachhousehold worked on new chinampas for 30 days per year (or 60p-d), andeach chinampa required 10p-d of labour, then each household could addsix fields annually. If each of the 10 000 households did the same, then60 000 fields were added each year, with all 2.4 million built in a 40year period. Analysis 4: the regional and historical context of chinampaconstruction This exercise in energetics may be refined by a closer examinationof the history and chronology of chinampa construction. Armillas (1971:657) suggested that the institutionalised drainage of swamps andconstruction of chinampas in the lakebed of Chalco-Xochimilco wasentirely a Late Horizon endeavour, placing the peak of chinampaexpansion during the Aztec III, Aztec IV, and Early Colonial phases (AD1400-1600; contra Coe 1964: 96). Parsons' work (1976b) supportsArmillas' findings, indicating little occupation in the lakebedprior to Aztec III times (AD 1400). Although scholars agree thatearlier, small-scale chinampas in the southern lakes were built, thereis a general consensus that expansive construction occurred in thefifteenth century (Sanders 1976: 136; Townsend 1992: 167). Most specifically, Parsons (1976a) theorised that the conquest ofthe southern lakes occurred in two distinct phases. First, olderindigenous communities reclaimed marginal areas of the lakes forsmall-scale chinampa agriculture. Ethnohistoric documents state thatconquest of the southern lakes by the Aztecs occurred in c. AD 1383, butthe extent of such control is uncertain (Hassig 1988: 132, 306).Secondly, the Aztec state organised or inspired a highly planned,large-scale project between AD 1426-1467. It is this 41-year-long phase,during the reign of the first two Aztec rulers, Itzcoatl (AD 1426-1440)and Motechuzoma Ilhjicamina (AD 1440-1467), which may bracket the mainlabour expenditures in chinampa construction (Calnek in Parsons 1976a:236). Itzcoatl is credited with ordering the religious hierarchy andinstituting regulations such as the taxation system whereby food, goodsand labour were extracted from the population (Vaillant 1966: 112).After absorbing smaller, independent groups in the southern Basin suchas the Xochimilcas, he planned and executed this enormous reclamationproject. Succeeding Itzcoatl after his death in AD 1440, MotechuzomaIlhjicamina oversaw the completion of the system (Vaillant 1966: 113). This chronological framework is reinforced by the ethnohistoricresearch on Aztec conquests. Hassig (1988: 128, 141) stated that,despite various wars against Chalco beginning in AD 1375, no decisiveconquest of the southern lake population occurred until the reign ofItzcoatl (AD 1427-1440). The first centre attacked by the Aztec militarywas Xochimilco, engaging in a battle of conquest that lasted elevendays, which resulted in an Aztec victory (Hassig 1988: 150). This wasfollowed by surrender without combat by Mizquic. Soon after, Cuitlahuacwas attacked, reportedly with an armada of 1000 canoes (Hassig 1988:150). From these historic accounts, one gets the impression that themajority of lake communities were deemed primary targets of Aztecexpansion in a strategy designed to control the economically valuedsouthern lakes as quickly as possible (Townsend 1992: 166). It alsoestablishes the initiation of large-scale chinampa construction at AD1427, based on the logic that '1000 canoes' could not possiblyhave navigated the lake to attack Cuitlahuac had the chinampas alreadybeen built. The one obstacle to the Aztecs' total and rapid hegemony ofthe lake region was the resistance of Chalco. Despite repeated attacks,it was not until the early 1460s that Chalco was militarily defeated bythe Aztecs (Hassig 1988: 171). Once conquered, however, Chalco wastreated with great severity by the Aztecs, its leaders being killed andreplaced by Aztecs from Tenochtitlan. Thus, the initial construction began with the conquest of thosecentres closest to Tenochtitlan in c. AD 1427. Construction would havelasted for 41 years, but not necessarily in equal amounts each year. Thefinal phase of construction might have involved those built by thecitizens of Chalco, the last centre to be conquered. Based on theterritorial divisions of the southern lake region in c. AD 1500 (Hodge1994: Figure 2.5), the area of the lake controlled by each major centrewas calculated, allowing us to estimate the number of chinampa fieldsbuilt by each centre (Table 3). This indicates that approximately 92 per cent of the lake wasoverseen by centres which were very rapidly under Aztec control, withthese fields built in less than a 41-year period. Cuitlahuac alone wasresponsible for building 47 per cent of the chinampas. Chalco's 8per cent of the chinampa system perhaps was built rapidly after itsconquest, terminating construction at 41 years. Thus the vast majorityof the chinampa system could have been built, as an order of magnitude A change in quantity or volume as measured by the decimal point. For example, from tens to hundreds is one order of magnitude. Tens to thousands is two orders of magnitude; tens to millions is three orders of magnitude, etc. estimate, by 40 per cent of the lake population during two months eachyear for nearly twenty years TWENTY YEARS. The lapse of twenty years raises a presumption of certain facts, and after such a time, the party against whom the presumption has been raised, will be required to prove a negative to establish his rights. 2. , with the final component of the intensivesystem added years later. Discussion Most scholars who have considered the scale of construction of thesouthern lake chinampa system describe it as very demanding in terms ofits labour requirements, an observation corroborated and refined by ourresearch. From archaeological studies and ethnohistoric records, we findthat the intensification occurred with Aztec military control of theregion followed by an increased labour burden on all lakeshorecommunities. Those macehualtin building and working these new fieldswere possibly supplemented by mayeques and slaves of the noble class,the elite requiring the agricultural produce for personal consumption ormarket exchange (Parsons 1991: 38; Smith 1996: 79). However, ouranalysis indicates that although external labour may have been desiredit was not necessary, and that local households, by adjusting the amountof labour directed towards building new fields, could have created theintensive southern lake agricultural system with no new hierarchicalorganisation. The pressure for doing so, however, undoubtedly came fromthe administrators of the Aztec state. Questions still remain as to the more specific status of labourersand the relationship between the owners and labourers of the fields(Brumfiel 1991; Smith 1996; Berdan et al. 2003), questions which are notdirectly answerable based on the various quantifications. However, toprovide perspective on the scale of macehualtin labour contribution inchinampas, the comparable labour demand for cloth is considered. Thiscomparative case of labour obligation, well documented in thearchaeological record The archaeological record is a term used in archaeology to denote all archaeological evidence, including the physical remains of past human activities which archaeologists seek out and record in an attempt to analyze and reconstruct the past. , comes from the community of Cihuatecpan, in theTeotihuacan Valley (Evans 1988; 1990; 1991). Cihuatecpan was a piedmontfarming community absorbed into the economic sphere of the Aztecs. Onceobliged to an expanded hierarchy of external lords, the citizens of thiscommunity of about 1000 people began growing large quantities of maguey maguey:see amaryllis. to be processed into a variety of products (Evans 1990). One of theseproducts, constituting tribute to the state, was maguey mantles. According to the Matriculos de Tributos (Codex Mendoza The Codex Mendoza is an Aztec codex, created about twenty years after the Spanish conquest of Mexico with the intent that it be seen by Charles V, the Holy Roman Emperor and King of Spain. ),Cihuatecpan was obliged to provide 800 woven mantles each year astribute (Evans 1990: 128). With approximately 200 households, eachhousehold was required to produce on average four mantles as theircontribution to the state. This same pattern of increased labour demandfor cloth with Aztec control is archaeologically evidenced in Morelos.Once under Aztec hegemony, spindle whorl whorln.1. A form that coils or spirals; a curl or swirl.2. A turn of the cochlea or of the ethmoidal crest.3. An area of hair growing in a radial manner.4. frequencies increased by 53 percent as cloth in the form of tribute increased (Brumfiel 1996: 456). According to Hicks (1994: 93), between 26 and 27 days were requiredfor one person to weave 3.33 square yards of maguey fabric based onAztec technology. Here we equate this amount of fabric with one mantle.If each commoner household at Cihuatecpan produced four mantlesannually, then each household expended about 106p-d per yearmanufacturing mantles for the state, and the community as a wholeexpended about 21 200p-d annually. On a household and community basis, these figures are comparableto, if not higher than, those expended by communities involved inchinampa construction. The quantification of chinampas on a householdbasis suggested that between 60p-d and 120p-d would be the likely rangeof labour-time expended per year in additional agricultural activities.Although one could argue that dredging muck from the lake bottom wascalorifically more demanding than weaving or other craft activities, ouranalysis does not translate time-labour into its direct energyexpenditure. Nonetheless, while we conclude that the Aztec labourimposition on communities building chinampas was very demanding, weargue that Aztec demands on other communities for other products werecomparably demanding, at least in terms of time. Conclusions The chinampa system of the southern lakes district during the reignof the Aztecs was one of the most ambitious and costly reclamationprojects in Mesoamerica. Jeffrey Parsons (1991: 38) observed that thisagricultural system was the consequence of 'deliberate politicaldecisions made by state administrators who were strongly motivated bythe need to create and maintain a secure subsistence base for the urbanpopulations'. This echoes earlier opinion that theChalco-Xochimilco reclamation and maintenance project would not havebeen feasible until centralised political power was sufficient to forcea labour pool of commoners, tenants, and possibly slaves to work on sucha project (Sanders et al. 1979: 378). Our quantification of the initial construction of this system fullysupports these observations. We estimate that, by order of magnitude, 25million person-days were expended in the building of the chinampasystem. This was translated into an annual household labour equivalentof about two people working for one to two months over a period of 20 to40 years. Importantly, we also concluded that this scale of labour obligationto the state was required of many households, including those notdirectly involved in building raised fields. Quantification of clothproduction at the community of Cihuatecpan yielded comparable annuallabour requirements, suggesting that all commoner households weresubject to increased work regimes once placed under Aztec control. Acknowledgments The authors wish to thank Brad Jokisch, Ann Freter, Bill Boyd Bill Boyd is: Bill Boyd (gambler) gambler Bill Boyd (casino operator) CEO of Boyd Gaming Corporation Bill Boyd (baseball) - Major league baseball player. Bill 'Cowboy Rambler' Boyd andan anonymous reviewer for assisting with earlier drafts of thismanuscript. Peg Sattler at Ohio University's graphics departmentoversaw the creating of the figure. We assume responsibility for any andall errors contained within this manuscript. Received: 16 June 2005; Accepted: 14 October 2005; Revised: 7December 2005 References ABRAMS, E.M. 1994. How the Maya Built Their World: Energetics andAncient Architecture. Austin: University of Texas Press. --1998. Structures as Sites: The Construction Process and MayaArchitecture, in S. Houston (ed.) Function and Meaning in Classic MayaArchitecture: 123-40. Dumbarton Oaks Dumbarton Oaks is a 19th century Federal-style mansion with famous gardens in the Georgetown neighborhood of Washington, D.C. It currently houses the Dumbarton Oaks Research Library and Collection , Washington D.C. ABRAMS, E.M. & T. BOLLAND 1999. 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Abrams (2) (1) Department of Anthropology, Washington University of SaintLouis, Saint Louis, Missouri, USA (2) Department of Sociology/Anthropology, Ohio University, Athens,Ohio, USA (Email: Abrams@ohio.edu)Table 1. Numerical data and sources regarding pre-HispanicchinampasFigure Value SourceTotal area of swamp land 120[km.sup.2] Armillas 1971: 660 reclaimed in the Chalco-Xochimilco regionArea of chinampa fields 65[km.sup.2] Revised here from Armillas 1971: 660Average distance between 4.8m Armillas 1971: 659 canal mediansAverage canal widths 1.44-2.28m Armillas 1971: 653, 659Average canal depth 1.0m * Nichols & Frederick 1993: 139Average chinampa widths 2.52-3.36m Armillas 1971: 653Average chinampa lengths 6.0-9.0m Armillas 1971: 653Average chinampa height 1.0m ** Armillas 1971: 653 above waterRate of soil excavation 2.6[m.sup.3]/p-d Erasmus 1965: 285* Cited measurements were between 1.0 and 1.2m. 1.Om was usedfor simplification in area equations and estimations.** 1.0m is the most common measurement; however, seasonalityand water levels cause variation.Table 2. Chinampa construction demands (in years)relative to populationLabour force 30 days 60 days 100 days20 per cent 79 39 2430 per cent 52 26 1640 per cent 39 20 1250 per cent 31 16 9Table 3. Chinampa construction per centre Lake area Area in controlled chinampas ChinampasCentre ([km.sup.2]) * ([km.sup.2]) builtXochimilco 25.3 15.2 562 963Culhuacan 15.7 9.4 348 148Cuitlahuac 51.0 30.6 1 133 333Mixquic 7.5 4.5 166 667Chalco 8.5 5.1 188 889* With lake islands eliminated.