Early agriculture in the Americas (Chapter 20) - The Cambridge ...

Summary
Seasonal environments, especially forests and forest fringes, were key habitats for domestication in the Americas. Based on available data, plant domestication in the Americas was characterized by multiple, independent domestications of species in useful genera in North, Central, and South America. This chapter considers this pattern for pseudocereals, legumes, chiles, squashes, tobacco, cotton and a number of fruit trees. Plants needed for nutritionally balanced meals were domesticated multiple times in diverse settings. The early history of plant domestication begins in lower Central America and northwestern South America and is known in large part from microfossil evidence. Agriculture led to landscape transformations in the Americas, the scale of which varied across time and place. Fire was an important, early management tool. Other practices that changed landscapes include management of water and soil. Native agriculturalists in the Americas also practise crop rotation, sequential planting and fallowing.
Crops of the Americas and the geography of domestication
At the time of European contact in the fifteenth century ce, millions of people throughout the Americas lived in agriculturally based societies. Some practices and foods were millennia old; others coalesced late in prehistory. Domestication and agriculture did not arise everywhere, however, nor did all societies take an agricultural route. Distributions of wild ancestors, genetic studies of American crops, and archaeology give us snapshots of the geography of plant domestication (Figure 20.1) and of the diversity of crops grown (Table 20.1).
Figure 20.1 Likely areas of origin for selected crops of the Americas.
Today our understanding of the ancestry and areas of origin of a few crops is quite good, while for others little has changed since the 1970s, when one of the first comprehensive overviews, Crops and Man, was written by Jack Harlan.Footnote 1 Economically important crops are more likely to have been studied by agronomists and plant geneticists. For example, decades of debate and study of the only widespread American grain, maize, and its related wild species leave little doubt that wild Zea mays subsp. parviglumis, Balsas teosinte, gave rise to maize in a single domestication.Footnote 2 Balsas teosinte grows today in the deciduous tropical forests of southern and western Mexico, making this region the likely area of origin. How early Native farmers achieved the dramatic transformation of teosinte to maize is still being studied, but it was likely a process of a few thousand years that combined conscious and unconscious selection targeting seed dispersal, seed size, photoperiod, and starch production. Of the lowland root and tuber crops (arrowroot, cocoyam, llerén, manioc, sweet potato, yam), only productive and undemanding manioc is well studied. The primary stable crop for millions of people worldwide, mostly the poor of tropical countries, manioc was domesticated from Manihot esculenta subsp. flabellifolia on the southern border of the Amazon basin.Footnote 3 For many other crops, from fruit trees to roots and tubers to pseudocereals, we know only the broad geographic range of their likely area of origin. Seasonal environments, especially forests and forest fringes, were key habitats for domestication in the Americas.Footnote 4
More basic research, especially collection of wild related species and traditional crop varieties, is needed to understand the ancestry of many crops, and the pace of extinction, habitat loss, and loss of indigenous knowledge is accelerating. Based on available data, plant domestication in the Americas was characterized by multiple, independent domestications of species in useful genera in North, Central, and South America.Footnote 5 We see this pattern for pseudocereals, legumes, chiles, squashes, tobacco, cotton, and a number of fruit trees. Plants needed for nutritionally balanced meals were domesticated multiple times in diverse settings. For example, where land can be farmed in the Americas, there is a domesticated legume or pulse to thrive there, from peanuts, adapted to moist lowland environments, to the cold-tolerant lupine and the versatile common bean.
Tracing the domestication of root and tuber foods is especially challenging, since only manioc and potato are well studied. Each of those crops emerged in a single region/centre. Whether this pattern characterizes root and tuber domestication in general is unknown; archaeological data hint at multiple domestications (or the very early spread) of some root and tuber crops. Better understanding of the geography of plant domestication could provide valuable insights into the nature of early social networks in the Americas.
The early history of domestication
The early history of plant domestication begins in lower Central America and northwestern South America (Map 20.1), and is known in large part from microfossil evidence (phytoliths, starch grains, pollen). Human occupation of the neotropics began in the late Pleistocene, and by 10,900–9400 bce people occupied diverse environments and in some cases modified them by fire.Footnote 6 Burning of forests and small-scale land clearance is dated to 11050 bce* at Lake La Yeguada in Panama, for example. Arrowroot was the earliest domesticate there, dating to 7800 bce* at the Cueva de los Vampiros site and 5800 bce* at Aguadulce. By 5800 bce* maize and gourd were introduced to Panama and llerén and squash were present, and manioc was introduced shortly thereafter.
Map 20.1 Earlly agricultural sites and regions in the Americas.
Plant domestication began before 8500 bce in southwest coastal Ecuador. Squash phytoliths were recovered from terminal Pleistocene and early Holocene strata at Vegas sites.Footnote 7 Phytoliths recovered from the earliest levels are from wild squash, with domesticated-size squash phytoliths directly dated to 9840–8555 bce.Footnote 8 Other Vegas crops included gourd and llerén, and maize was introduced just before 5800 bce*. Maize continued to be grown at Real Alto and Loma Alta, two Valdivia tradition farming villages (4500–2250 bce), along with cotton, jack bean, achira, manioc, chile pepper, llerén, and arrowroot.Footnote 9 Agriculture in coastal Ecuador remained broad-based for many millennia, incorporating wild/managed tree fruits as well as annual crops.Footnote 10
Domesticated arrowroot dates back to 9250–8500 bce* at the San Isidro site in the Colombian Andes, where starch was identified on a pounding tool.Footnote 11Palms and avocado were also present, but whether domesticated or wild/managed is unknown. Pollen records documented maize in association with forest clearance and disturbance beginning at 7250 bce* in one core, and in several sequences from 5500 bce* and after. Palm and domesticated squash, llerén, and gourd were directly dated to 8250–6500 bce* at the Peña Roja site in eastern Colombia.
At sites in the Nanchoc valley of northern Peru, initial direct dates on domesticates with primitive morphologies, including manioc and peanut, were modern, but new direct dates document squash at 8283 bce, peanut at 6538 bce, and cotton at 4113 bce, and confirm early occurrence of manioc.Footnote 12 Starch from bean and pacae seeds, squash flesh, and peanut was recovered from dental calculus of teeth dating from 7163–5744 bce.Footnote 13 Domestication may be equally ancient in the central Peruvian sierra, but dating ambiguities exist for important sites. Oca, chile pepper, lucuma, and common and lima beans were recovered from Guitarrero Cave in strata dated 9250–8500 bce*, but beans were directly dated as much younger.Footnote 14 Several root crops were recovered from Tres Ventanas Cave in equally ancient strata, but one was directly dated to 5800 bce*. Domestication of a diverse array of local Andean tubers, pulses, and quinoa was likely underway before 5800 bce*.Footnote 15
The best-known data on early domestication in Mesoamerica come from two caves, Coxcatlán and Guilá Naquitz, each located in the semi-arid highlands of central Mexico. The excellent preservation of crop remains in these dry sites, and in the case of Coxcatlán, its historically early excavation and thorough publication, have long influenced perceptions of the history of plant domestication. Maize, squash, and bottle gourd first appear at Coxcatlán during the Coxcatlán phase, 5800–4400 bce*; by the end of the phase, tree fruits were present whose dispersal and maintenance depended on humans.Footnote 16 Another squash, common bean, tepary bean, and chile pepper appeared over the next 2,000 years. The supposed antiquity of domesticates in the Coxcatlán sequence has largely not stood up to direct dating of crop remains, however. Coxcatlán-phase maize was directly dated to 3600 bce, common beans 300 bce, and tepary beans 440 bce.Footnote 17 Only bottle gourd was as ancient as expected from site stratigraphy. Guilá Naquitz Cave also documents early domesticated squash, maize, chile pepper, and bottle gourd.Footnote 18 Squash (Cucurbita pepo) was directly dated to 8000–6000 bce and maize to 4250 bce.Footnote 19
Recent research at Xihuatoxtla shelter in the central Balsas River valley, southwest Mexico, has now documented early maize in the dry tropical forest setting of its wild ancestor.Footnote 20 Maize phytoliths were recovered from site sediments, and maize starch and phytoliths from grinding stones, dating to 6700 bce. Domesticated squash was also present. From the Balsas region maize spread first through the lowlands; it is documented, for example, at 5100–5000 bce in a sediment core on the Gulf Coast, and maize pollen and/or phytoliths document the crop in southern Pacific coastal Mexico, Pacific coastal Guatemala, northern Belize, and Honduras by 3500 bce.Footnote 21 Maize was carried south through the tropical lowlands prior to this time, however, as it is documented earlier in Panama, Colombia, and Ecuador.
Early domestication in the Americas took place in the context of changing climatic conditions, namely increasing warmth and moisture.Footnote 22 The earliest crop records in the northern tropics fall within the northern thermal maximum (8500–3400 bce), a period wetter than present, some prior to a reversal to colder, drier conditions (6300–5800 bce: maize, arrowroot), others at the end or shortly after that reversal (squash, llerén, manioc). Domestication was earlier in the southern tropics, with arrowroot, llerén, squash, and gourd present before the southern thermal maximum (8000–5500 bce). The list of domesticates in the southern tropics expands greatly during the thermal maximum and the millennia during which ENSO (El Niño – Southern Oscillation) was weak (6800–3800 bce: maize, peanut, cotton, Phaseolus, jackbean, achira, manioc, chile, potato). Domesticates were moved during this warm interval: for example, maize from west Mexico into Central and South America, and manioc from the southern edge of the Amazon to Peru (with peanut), Ecuador, and Panama. Too little is known of the areas of origin of many crops to trace early movements; many early finds are starch or phytolith residues from artefacts, and artefacts of comparable ages have not been studied from possible areas of origin.
The history of plant domestication begins in temperate North America between 3200 and 1785 bce, when native squash, chenopod, marshelder, and sunflower were domesticated in the Eastern Woodlands, and maygrass, erect knotweed, little barley, and giant ragweed were grown and moved outside their native ranges.Footnote 23 Variation exists in the relative importance of native crops and wild plants, with American Bottom populations (Mississippi floodplain near St Louis) producing the largest quantities of native crops over the longest time period. Acorn use was often higher in regions with less reliance on native crops.Footnote 24 Maize was incorporated into indigenous crop husbandry in the Eastern Woodlands around 300 bce.Footnote 25 For the better part of a millennium maize was one food in a broad diet, until its transformation into a staple crop between 800 and 1200 ce. Directly dated maize macro-remains and cooking residues place the crop in the Midwest and Northeast at about the same time.Footnote 26
Maize was introduced from Mexico into the Southwest by 1600 bce or somewhat earlier, just prior to the late Archaic or early Agricultural period (1500 bce to 0–500 ce), and by the end of the period had transformed foodways based on native plants.Footnote 27 With the widespread adoption of maize came substantial habitations with storage features. Maize, beans (common and tepary), and pepo squash form the core of Southwestern agriculture, with cotton and bottle gourd also introduced early, and other beans and squashes later arrivals. Wild native annuals, commonly used during the early middle Archaic (prior to 1500 bce), remained a component of diet through the Pueblo IV/Classic period.Footnote 28
In the Great Plains, during the Archaic (3500–500 bce) plant foods included native annuals, fleshy fruits, nuts, roots, and grasses.Footnote 29 The earliest directly dated domesticates are squash (2218–2142 bce), marshelder (628–609 bce), and maize (813–878 ce), which was likely introduced earlier. Woodland populations (500 bce to 800–900 ce) were more sedentary, ceramics were introduced, and cultivated plants were increasingly used. The maize-based Plains Village tradition (900–1600 ce) developed out of this foundation. Maize was also a widespread component of diet from 700–1600 ce in the eastern Canadian prairies and adjacent boreal forests.Footnote 30
Early food-producing societies
What was life like in early mid-Holocene food-producing societies of the Americas? Several examples illustrate the range of variation that existed and also commonalities, such as reduction in mobility and emergence of villages. At Real Alto, Ecuador, one of the earliest American agricultural villages, inferences can be drawn concerning social organization, ritual activities, and emerging political complexity. Other examples of early food-producing societies will be drawn from Mesoamerica and the desert borderlands of the southwest United States and northwest Mexico.
There are many ethnographically documented combinations of domesticated, managed, and wild plants used by non-agricultural societies, i.e. those that do not depend on domesticates for a substantial part of their diet.Footnote 31 The length of time between the appearance of domesticates and agriculture is variable, with cases of a long period of low-level food production, such as in Eastern North America (4,000-year separation between domestication of native crops and dependence on maize). But it can be difficult to gauge the contribution of domesticated plants to past diet.Footnote 32Presence of domesticates is not the same as dependence on domesticates; different kinds of food may become incorporated into the archaeological record in different ways (e.g. foods with robust inedible parts survive as charred macro-remains, tubers as starch or phytolith residues on tools). There is a tendency to assume that roots and tubers, squashes, legumes, and tree fruits were not staples in early food-producing systems, and to equate agriculture with maize as a staple crop.Footnote 33 But many root and tuber crops are equal to or exceed maize in caloric production, and when such resources are available, agriculture may follow quickly after domestication.
In southwest coastal Ecuador, domesticated plants are first documented during the early mid-Holocene Vegas tradition.Footnote 34 All Vegas sites but one are very small – dense scatters of lithic debris, likely associated with ephemeral structures. Site 80 is distinctively different: covering an area of over 2,000 m2, it served as a base camp for the seasonally mobile population, who buried their dead there.Footnote 35 Thus, prior to the appearance of villages in coastal Ecuador, a dispersed community began to link themselves to place via ancestors. One burial is distinctive: a female burial in a small structure, suggesting an early, central role for women in community and ceremonial life. Site locations – along seasonal streams – indicate that plant cultivation had already begun to shape the interactions of people and landscape.
Following a brief hiatus, life in southwest Ecuador was transformed during the Valdivia period (4400–1400 bce).Footnote 36 Valdivia is one of the earliest ceramic traditions of the Americas; the earliest Valdivia sites are among the first villages of the Americas; by the time of the middle Valdivia, the Real Alto site had grown to be a town, one of the earliest in the Americas.
Household and community structure at Real Alto provide insights into Valdivia society.Footnote 37 The earliest village was small (150 m across), and circular or U-shaped, with 12–15 houses. Houses were small (8.4 m2) single-family dwellings, giving a total population of 50–60 people. The village grew until by the end of the early Valdivia it had doubled in size, and was occupied by 150–250 people. The village plan continued to reflect a division of space into domestic (outer ring of houses) and public (interior plaza) domains; no structures for public ritual were present.
In the middle Valdivia, Real Alto grew into a town, 400 m across and U-shaped or rectangular. Average house size increased to 102 m2 extended-family dwellings, and population grew to 1,800. Community structure also changed, with the construction of two ceremonial mounds (Fiesta and Charnal House mounds) facing each other across the central plaza. The mounds divided the plaza into two segments, creating several levels of potential segmentation/opposition within the community. While there is no direct evidence of who participated in and who led ceremonies, most researchers argue that ritual life at Real Alto included shamanism.Footnote 38 Shamanic practices of tropical forest agriculturalists include rituals focused on life-cycle issues of women (puberty, pregnancy), curing, and divination. Shamans also keep a community’s ceremonial calendar, and provide leadership in both the domestic and sacred realms.
Over time at Real Alto, distinctive rituals became formalized within structures built on platform mounds, two to four social groups existed in the town, and family structure changed to extended families, with house clusters suggesting increased emphasis on descent group.Footnote 39 Two sizes of extended-family house existed, indicating differences in relative social standing of households, but there was no evidence of differential access to resources. Neither were there differences in grave goods, but some individuals were treated differently after death.Footnote 40 Most individuals were buried next to or in wall trenches of domestic structures. The Charnal House mound had a concentration of burials in a very different context: an adult female was buried in a tomb under the threshold, with nearby male and juvenile burials within the structure. The inference is burial of a woman in the apical role for a corporate kin group. The Fiesta mound also represented a distinctive context: large pits within a series of paired structures contained evidence of feasting activities, such as broken drinking vessels and exotic sea food. The inference is social competition through feasting: ritual to attract and retain group members.
The transformation of Real Alto from village to town during the middle Valdivia period represented significant changes in social relationships, and ritual feasting, led perhaps by shamans, helped create and maintain the new social order. While there are hints of differences in social standing, access to more labour (acquired by attracting followers through feasting), rather than prestige goods, seems to be the key element of status differences: labour to put more fields into production, to water long-growing root crops during the dry season, or to grow an extra maize crop in an albarrada (water catchment feature).
The first farmers of western Mexico were small groups of cultivators who likely shifted settlements seasonally.Footnote 41Xihautoxtla shelter, where early maize was identified, was repeatedly visited by small groups who stayed for several weeks or more. They used unmodified river cobbles and stone slabs as grinding tools, and manufactured chipped stone tools. Two contemporary sites in the region lack grinding stones, suggesting that different sets of activities were carried out there. Palaeoenvironmental data from nearby lakes indicate that lacustrine environments were used by Archaic period inhabitants of the region, including, perhaps, for cultivating plants on the lake edge. Population mobility appears to decline over time with the emergence of food production in Mexico. In the highland Tehuacan valley, for example, researchers argue on the basis of site locations, numbers, and sizes that semi-sedentary camps (i.e. occupied for two or three seasons) appear in the Riego phase (7500–6000 bce*) and small sedentary sites by the Abejas phase (4500–2750 bce*).Footnote 42 By 2000 bce, sedentary villages appear widely in Mesoamerica, marking the beginning of the Formative period (2000 bce to 250 ce), which represents the time when agriculture, village life, and ceramic production came together.Footnote 43
The late Archaic through early Formative was a period of change in Mesoamerica, from sparse populations of low-level food producers to settled agriculturalists and growing populations.Footnote 44 The southwest Pacific coasts of Mexico and Guatemala provide contrasting views of life during this transition. Large shell mounds, dating to 5500–1800 bce, are highly visible Archaic sites in coastal Mexico. These sites have been interpreted as seasonal occupations of foragers who harvested estuarine resources, and perhaps used some domesticated plants. Pollen, phytolith, and charcoal data from environmental cores adjacent to sites now document that sustained slash-and-burn farming, incorporating maize, took place between 2700 and 1800 bce.Footnote 45 Farming settlements were likely located inland, away from saline and seasonally inundated soils, and now buried beneath stream alluvium. The inference is that populations of farmer-foragers with reduced mobility lived in base camps near the best agricultural land, with seasonal settlements near rich estuarine resources.
This rich coastal environment extends into Pacific coastal Guatemala, where there is a 6,000-year palaeoenvironmental record of human occupation.Footnote 46 Evidence for anthropogenic fire survives from the late Archaic, and microfossil evidence indicates that maize, squash, and cotton were cultivated and arboreal species managed by non-sedentary peoples before the appearance of the first permanent villages. The lack of late Archaic sites indicates that populations were more mobile than those of coastal Mexico; the overall scarcity of crop remains suggests a low level of food production, with fire used to encourage useful wild plants and to attract animals.
Recent research in the desert borderlands of northwest Mexico and the southwest United States indicates that Archaic populations who grew domesticated plants were less mobile than previously thought.Footnote 47 Early farming systems were very diverse in this region, incorporating flood, water-table, run-off, irrigated, dry, and rain-fed farming systems, with nearly all early systems focused on alluvial lands with naturally replenished soils.Footnote 48 In southeast Arizona, for example, maize, bean, cotton, and amaranth were grown before evidence of canals, terraces, and larger and more permanent settlements appears.Footnote 49 Eventually there is large labour investment in canals and terraces, suggesting reduced mobility and increased territoriality.
There were differences in the rates at which foraging populations in the desert borderlands were transformed into farming ones. For example, the population of the Cerro Juanaqueña site in Chihuahua, Mexico, made significant investments in agriculture by 1200 bce, while the nearby Jornada Mogollon region did not undergo this transition until 1000 ce.Footnote 50 Cerro Juanaqueña is the earliest known cerros de trincheras site (complex of hilltop terraces, rock rings, and stone walls). The terraces served as living surfaces, while farming took place in the floodplain of the Rio Casas, below the site. Maize was found in 60 per cent of features, suggesting it was a dietary staple; there were also large numbers of worn grinding stones, possible domesticated amaranth, and wild chenopod and other seeds. This suggests a population that was relatively sedentary: the Rio Casas floodplain offered a lower risk and higher return rate for maize agriculture than was possible in the Jornada Mogollon region, where more mobile populations relied on productive wild resources (especially shrubs and mesquite).
Agricultural practices and domestication of landscapes
Agriculture led to landscape transformations in the Americas, the scale of which varied across time and place. Fire was an important, early management tool. Other practices that changed landscapes include management of water (through irrigation, water catchment features, construction of raised and ditched fields) and soil (through terracing, formation of black earths, fallow regimes).
By the time of European contact, anthropogenic landscapes existed throughout the Americas. For example, the Gulf Coast and piedmont of Mesoamerica, where Cortés came inland, was a productive patchwork of cultivation interspersed with managed forests and scrublands.Footnote 51 Well-drained lands (hill slopes and constructed terraces) were cultivated in the rainy season, and in the dry season margins of wetlands were farmed as water receded or was drained away. Tree crops such as cacao were cultivated in special plots as well as being part of managed forests and house gardens. In the semi-arid basins of the central highlands, the upper slopes remained in forest, while rain-fed agriculture was practised on lower slopes, constructed terraces and floodwater and irrigation cultivation along watercourses and terraced basin floors, and wetland cultivation on poorly drained basin soils.
Landscapes were also significantly transformed in Southwest and Eastern North America, and intensive practices (i.e. those requiring high labour inputs) were used in both regions.Footnote 52 In the Southwest both stream floodplains and upland slopes were farmed. Irrigation systems that supplemented summer rainfall and sometimes permitted a second crop were found in many river valleys. Slopes were modified for agriculture by construction of terraces (to increase soil depth and water retention) and check dams (to slow and spread water run-off).
Historical accounts of farming in the Eastern Woodlands suggest that selective burning and clearance had created a productive mosaic of cultivated fields, successional growth, semi-permanent open areas, and open forests.Footnote 53 There are accounts of cropping for extended periods of time, with brief fallows and localized burns to control weeds (in-field burning).Footnote 54Fields varied in size, including very large fields, and systems that approached annual cropping. Raised fields, ridged fields, and hilled fields were known and house gardens were common, but slope modification has not been identified. The first farmers of the Eastern Woodlands appear to have targeted floodplain environments. In the lower Little Tennessee River valley, for example, human impact on bottomland forests, as shown by increases in disturbance-favoured species, increased after the appearance of squash and gourd.Footnote 55 Over time, lower terraces as well as active floodplains were farmed. Minimal forest clearance occurred in upland forests until nearly the time of Euro-American settlement.
Prior to European contact, farming throughout the Americas was carried out exclusively by hand tools and human labour; draught animals and the traction plough are post-contact. There were two broad classes of farming tool: digging or planting sticks and spade-like implements, with a blade in the same plane as the handle; and hoes or mattocks, with a blade set at an angle to the handle.Footnote 56 The wooden digging or planting stick was wedge-shaped and used to make planting holes or to turn the soil. The tip was fire-hardened or sometimes the tool was tipped with stone. In the Andes the foot-plough or chaqui-taclla brought the foot of the cultivator into use to turn heavy sod (Figure 20.2). Hoes or mattocks were used for cultivating around crops; blades were made of wood, stone, or bone scapulas. In Mesoamerica and western South America tools were sometimes tipped with copper or bronze. The steel machete is used today for clearing brush and felling trees; prehistorically, wooden and stone tools were used for cutting and clearing.Footnote 57Stone axes, made by hafting a shaped, sharpened stone to a wooden handle, smashed wood fibres, more rarely cutting through them. Cutting was supplemented by girdling and firing, with the largest trees often left standing. Clubs or ‘swords’ made of hard wood were used to remove undergrowth and for weeding. Other traditional approaches to weed control included mulching, shading out weeds with cover crops, and in-field burning.
While examples of the ‘hard technologies’ of agriculture (i.e. permanent field features, discussed below) are well preserved in the Americas, ‘soft technologies’, the essential practices for manipulating the field environment, leave little to no archaeological evidence.Footnote 58 Adding organic fertilizer to soil (i.e. bird guano, fish, animal dung, mucking, composting) was likely a prehistoric practice, as was planting on anthropogenic soils (‘black earths’, former settlement sites). Fire was an important agricultural technology.Footnote 59Traditional farmers use fire in combination with forest clearing to create and maintain openings for sun-demanding crops; fire removes debris, kills pests, and returns nutrients to the soil via ash deposition. Cropping patterns are known from ethnographic accounts and some historical records.Footnote 60 The literature gives the impression that mixed cropping (polyculture) dominates traditional farming, but there are many variations, including companion planting (e.g. corn–beans–squash: each crop provides benefits to the others), agroforestry (combining annual and perennial crops with tree crops), zonation (different species in blocks or rings within fields), and planting that is nearly monocropping (fields dominated by one crop, with a few individuals of others). There are many examples of environmental zonation, where fields are dispersed across microhabitats, for example the verticality that characterizes traditional Andean agriculture, and planting the floodplains of major rivers, where crops are matched to microrelief, soil, and differential flooding. Native agriculturalists in the Americas also practise crop rotation (changing crops year to year in a field), sequential planting (one crop after another in a field), and fallowing (allowing land to rest, to restore fertility and combat weeds and pests).
Water management was essential to prehistoric agriculture in many parts of the Americas, and transformed landscapes. In desert coastal Peru, for example, early farmers cultivated self-watering alluvial lands along rivers and their outflows, and locations where short ditches or embankments could guide water.Footnote 61Intensification and expansion of agriculture depended on irrigation. Canal irrigation was practised in South America from southern coastal Ecuador to central Chile, in intermontane Andean valleys, the Altiplano of southern Peru/northern Bolivia, and some valleys along the Caribbean. In Peru, canal irrigation is documented in twenty-five to thirty coastal valleys, with the largest system and area irrigated on the north coast, dating to 1000 ce.Footnote 62 Small-ditch irrigation began by 4500–3400 cal bce in the Nanchoc valley.Footnote 63
Irrigation was also critical to agriculture in the Southwest United States.Footnote 64 Early farmers planted well-watered alluvial lands; rain-fed farming was practised only rarely in the region, in higher elevations with sufficient rainfall. Historical accounts indicate that stone and brush weirs and earthen berms were built to slow and divert water from streams, springs, and flood run-off. Rock terraces built on hillsides slow run-off, trap sediment, and create planting surfaces. Canal irrigation dates back to 1250–400 bce* in the southern and central parts of the Southwest. Irrigated farming likely required shifting field locations/fallow cycles to replenish nutrients and to avoid salinization. The roughly contemporaneous dates from the American Southwest and Mesoamerica (see below) suggest independent development of water management systems.
Development of water management technology began during the Formative in Mesoamerica.Footnote 65 Practices included use of floodwater and run-off, springs, and upland and valley-bottom perennial stream systems. Floodwater and run-off systems were the most common, dating to 1200 bce and later in numerous locations. Features include dams, canals, ditches, drains, artificial ponds and reservoirs, raised fields, terraced fields, and ridged fields. Much less common were spring-fed systems (770 bce), upland perennial stream systems (300 bce), and valley-bottom systems (1050 bce). A deep-water well dated to 7900 bce, possibly used for hand irrigation, has been identified at a site in the Tehuacan valley. Most of the familiar kinds of water control system were developed along with the emergence of villages throughout Mesoamerica between 1200 and 1000 bce. There is considerable variability in the scale of early systems, but horizontal, kin-based organization is inferred.
The development of agriculture in the Andean highlands was linked to the creation of productive agricultural lands through landscape modification. The basic forms were irrigation, terracing, and raised fields.Footnote 66 Irrigation supplemented rainfall, and was practised in many inter-Andean valleys, with extensive systems in larger basins with expanses of land. Irrigation canals are common in the Lake Titicaca basin, where canals associated with raised fields carried water away from the lake. Irrigated bench terraces at Huarpa near Ayacucho date from 200 bce to 600 ce.
Terraces, flat planting surfaces created on slopes, are mostly found in arid and semi-arid highlands in the Americas, and in the driest areas are associated with irrigation.Footnote 67 The most northerly zone of terracing stretches from southwestern Colorado through to the Sierra Madre of western Mexico. The distribution is quite dispersed, and consists of cross-channel terraces across narrow drainages. There are discontinuous zones of terracing in Mesoamerica, including the basins of central and southern Mexico and western Guatemala, with few terraces south of Guatemala until the Andes. Forms include cross-channel terraces, contour terraces, and valley-floor terraces. In higher elevations frost hazard is alleviated in part by terracing, since crops can be grown above frost-prone valley bottoms.
Terracing extended discontinuously in South America from Venezuela to Chile and northwest Argentina, with heavy concentrations of irrigated terraces in southern Peru, including around the Inca capital Cuzco and northern Bolivia.Footnote 68 Expanses of rain-fed terraces occur in the eastern Peruvian Andes and southern Ecuador. Sloping-field terraces, in which retaining walls running across a slope accumulated soil and controlled run-off, were the most common type. Bench or staircase terraces were long, narrow expanses of level, deep soil held by high stone retaining walls. Terraces altered field microclimates, optimizing production, reducing risk, and permitting cropping in unfavourable settings. Both unirrigated and irrigated terraces have been dated as early as 2400 bce in Peru, with large terracing systems dating to 600 ce and later.
Raised fields are artificially elevated earthworks that improve drainage and provide planting surfaces in wetlands.Footnote 69Such fields, called chinampas, were an important component of agriculture on the fringes of lakes in the Basin of Mexico, for example. Formed of lake mud, aquatic vegetation, and domestic refuse, chinampas did not float, but some seed beds were in the form of movable rafts. Chinampa fields were usually narrow, but could be quite long, and were often planted along the edges with trees.Footnote 70 Some 12,000 ha of chinampas helped feed the population of the Aztec capital. Earlier, buried chinampa systems have been documented by remote sensing in the northern Basin of Mexico. Raised-field systems occur elsewhere in highland Mexico, as well as in the lowlands of the Mexican Gulf Coast, northern Belize, and Guatemala. Swampy land can also be cultivated by digging ditches to drain away water, rather than building up soil.
The largest expanses of raised fields in the Andean highlands are in the Sabana de Bogotá (Colombia), northern Ecuador, and the Lake Titicaca basin.Footnote 71 In the Lake Titicaca region, from 600–1200 ce the Tiwanaku state supported dense populations in a region marginal for agriculture through raised-field technology and selection of nutritious local crops like potato, quinoa, and lupine.Footnote 72 Approximately 25,000 ha of raised fields were built on flat or gently sloping land. Fields functioned for thermal protection, provided higher fertility through mucking, and retained water in droughts and drained it in floods. Earlier, smaller field systems date to 1500–200 bce in the region.Footnote 73
In the South American lowlands, large expanses of raised fields are located in northern Colombia (earliest 800 bce), the coast of French Guiana (1000 ce), and the Guayas basin (southwest Ecuador).Footnote 74 In Ecuador, research at the Peñon del Rio complex discovered buried fields dating from 500 bce to 500 ce beneath larger, visible fields constructed after 500 ce. Maize phytoliths were identified from both early and late fields.Footnote 75 Raised fields supported intensive agriculture in this region of large-scale flooding and tidal influx.
Areas of the Amazon basin preserve evidence of intentional and non-intentional farming practices that transformed environments into productive, domesticated landscapes.Footnote 76 In addition to anthropogenic burning, already discussed, other elements of transformation included human settlements and their associated gardens; creation of mounds (domestic, ceremonial, burial), forest islands in savannas and wetlands, ring ditch sites, and raised fields; creation of black earths (resulting from domestic debris and large quantities of charcoal that may have been deliberately added); creation of paths, trails, and roads, including extensive systems of raised causeways; fisheries management; and agroforestry (culling non-economic species and replacing them with useful ones). Many of these practices were ancient and persistent in the Amazon.
American agriculture in worldwide perspective
New data, especially plant microfossils (phytoliths, starch grains, pollen), demonstrate that agriculture is as old in the American tropics as in the early Old World primary centres.Footnote 77 Plant domestication began in the early Holocene, and the longer-term environmental changes that accompanied the Pleistocene–Holocene transition can be considered the ultimate causal factors behind the development of food production. The identification of proximate causation in specific cases is much more conjectural, as cultural and environmental factors are difficult to disentangle, especially given the limitations of the archaeological record.
In the American tropics, early food producers were semi-sedentary to sedentary, occupying alluvial or wetland-edge habitats. Groups appear to have been organized at the level of family or hamlet, with no evidence for social complexity. Expansion of forests in the neotropics during the early Holocene changed plant distributions, closing formerly open woodlands and altering edge habitats favoured by many starch-rich root and tuber species. Among the human responses indicated by the record of early agriculture are creating and maintaining open habitats for favoured plants, altering mobility patterns as resources expanded or contracted, changing diet in response to changing availabilities of foods, and increasing densities of desirable plants and animals by cultivation/management. The record indicates that in the early Holocene there were frequent and dispersed plant domestications: some were advantageous and early domesticates spread, sometimes widely, through social interactions among foragers and horticulturalists. Cultivation was small-scale, in well-watered settings.
Increasingly productive crops fuelled population growth, which led to the spread of societies dependent on agriculture into new habitats, and creation of built environments for farming. This last is the most visible threshold of the process, having left its mark throughout the Americas on the landscape, in sediment cores, and in numbers of sites. Agriculture eventually spread into all suitable environments in the Americas, with landscape modification and crop improvements opening up or increasing the potential of previously unsuitable or geographically limited environments. With clear evidence that the roots of plant domestication lay in the early Holocene, the challenge now facing us is to expand the palaeoenvironmental and archaeological records of this process, and to better understand people–plant interrelationships during the late Glacial period.
20D.R.Piperno et al., ‘Starch grain and phytolith evidence for early ninth millennium bp maize from the central Balsas River valley, Mexico’, Proceedings of the National Academy of Sciences, 106 (2009), 5020–4.
23B.D.Smith and C.W.Cowan, ‘Domesticated crop plants and the evolution of food production economies in Eastern North America’, in P.E.Minnis (ed.), People and Plants in Ancient Eastern North America (Washington, DC: Smithsonian Books, 2003), 105–25.
24 C.M. Scarry, ‘Patterns of wild plant utilization in the prehistoric Eastern Woodlands’, in Minnis (ed.), People and Plants, 50–104.
27L.W.Huckell, ‘Ancient maize in the American Southwest: what does it look like and what can it tell us?’, in J.E.Staller et al. (eds.), Histories of Maize: Multidisciplinary Approaches to the Prehistory, Biogeography, Domestication, and Evolution of Maize (Amsterdam and London: Elsevier Academic Press, 2006), 97–107.
28 L.W. Huckell and M.S. Toll, ‘Wild plant use in the North American Southwest’, in Minnis (ed.), People and Plants, 37–114.
33J.Iriarte, ‘New perspectives on plant domestication and the development of agriculture in the New World’, in T.P.Denham et al. (eds.), Rethinking Agriculture: Archaeological and Ethnoarchaeological Perspectives (Walnut Creek, CA: Left Coast Press, 2007), 167–88.
35K.E.Stothert, ‘Expression of ideology in the formative period of Ecuador’, in J.S.Raymond and R.L.Burger (eds.), Archaeology of Formative Ecuador (Washington, DC: Dumbarton Oaks Research Library and Collection, 2003), 337–420.
41A.J.Ranere et al., ‘The cultural and chronological context of early Holocene maize and squash domestication in the central Balsas River valley, Mexico’, Proceedings of the National Academy of Sciences, 106 (2009), 5014–18.
44R.G.Lesure, ‘Early social transformations in the Soconusco’, in R.G.Lesure (ed.), Early Mesoamerican Social Transformations: Archaic and Formative Lifeways in the Soconusco Region (Berkeley: University of California Press, 2011), 1–24.
46 M. Blake and H. Neff, ‘Evidence for the diversity of late Archaic and early Formative plant use in the Soconusco region of Mexico and Guatemala’, in Lesure (ed.), Early Mesoamerican Social Transformations, 47–66.
47G.J.Fritz, ‘The transition to agriculture in the desert borderlands: an introduction’, in L.D.Webster et al. (eds.), Archaeology Without Borders: Contact, Commerce, and Change in the US Southwest and Northwestern Mexico (Boulder: University Press of Colorado, 2008), 25–33.
49J.B.Mabry, ‘Changing knowledge and ideas about the first farmers in southeastern Arizona’, in B.J.Vierra (ed.), The Late Archaic across the Borderlands: From Foraging to Farming (Austin: University of Texas Press, 2005), 41–83.
50 R.J. Hard and J.R. Roney, ‘The transition to farming on the Río Casas Grandes and in the southern Jornada Mogollon region’, in B.J. Vierra (ed.), Late Archaic across the Borderlands, 141–86.
51T.M.Whitmore and B.L.Turner II, ‘Landscapes of cultivation in Mesoamerica on the eve of the conquest’, Annals of the Association of American Geographers, 82 (1992), 402–25.
52W.E.Doolittle, ‘Agriculture in North America on the eve of contact: a reassessment’, Annals of the Association of American Geographers, 82 (1992), 386–401.
53W.M.Denevan, ‘The pristine myth: the landscape of the Americas in 1492’, Annals of the Association of American Geographers, 82 (1992), 369–85.
76 C.L. Erickson, ‘Amazonia: the historical ecology of a domesticated landscape’, in Silverman and Isbell (eds.), Handbook of South American Archaeology, 157–83.
77 Piperno and Pearsall, Origins of Agriculture; Pearsall and Stahl, ‘Origins and spread of early agriculture’.
References
Further reading
Bermejo, J.E.H. and León, J. (eds.). Neglected Crops: 1492 from a Different Perspective. Rome: Food and Agriculture Organization of the United Nations, 1994.
Blake, M. and Neff, H.. ‘Evidence for the diversity of late Archaic and early Formative plant use in the Soconusco region of Mexico and Guatemala.’ In Lesure, R.G. (ed.), Early Mesoamerican Social Transformations: Archaic and Formative Lifeways in the Soconusco Region. Berkeley: University of California Press, 2011. 47–66.
Hard, R.J. and Roney, J.R.. ‘The transition to farming on the Rio Casas Grandes and in the southern Jornada Mogollon region.’ In Vierra, B.J. (ed.), The Late Archaic across the Borderlands: From Foraging to Farming. Austin: University of Texas Press, 2005. 141–86.
Huckell, L.W. and Toll, M.S.. ‘Wild plant use in the North American Southwest.’ In Minnis, P.E. (ed.), People and Plants in Ancient Western North America. Washington, DC: Smithsonian Institution Press, 2004. 37–114.
Webster, L.D., McBrinn, M.E., and Carrera, E.G. (eds.). Archaeology Without Borders: Contact, Commerce, and Change in the US Southwest and Northwestern Mexico. Boulder: University Press of Colorado, 2008.
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