Preceramic Adoption of Peanut, Squash, and Cotton in Northern Peru

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Science  29 Jun 2007:
Vol. 316, Issue 5833, pp. 1890-1893
DOI: 10.1126/science.1141395


The early development of agriculture in the New World has been assumed to involve early farming in settlements in the Andes, but the record has been sparse. Peanut (Arachis sp.), squash (Cucurbita moschata), and cotton (Gossypium barbadense) macrofossils were excavated from archaeological sites on the western slopes of the northern Peruvian Andes. Direct radiocarbon dating indicated that these plants grew between 9240 and 5500 14C years before the present. These and other plants were recovered from multiple locations in a tropical dry forest valley, including household clusters, permanent architectural structures, garden plots, irrigation canals, hoes, and storage structures. These data provide evidence for early use of peanut and squash in the human diet and of cotton for industrial purposes and indicate that horticultural economies in parts of the Andes took root by about 10,000 years ago.

Research on the origins and dispersal of agriculture around the world has concentrated on the environments and periods in which plants were first domesticated from indigenous wild species. Less concern has been given to the adoption of cultivars and their uneven use and development, the movement of populations practicing cultivation into areas where it was previously unknown, and the wider cultural contexts within which these processes occurred. In the Andes, potatoes, corn, squash, beans, manioc, cotton, and chili peppers have long been considered the primary “founder crops” by at least 5000 14C years before the present (yr B.P.) (1, 2). Here we report evidence for radiocarbon-dated human cultivation of squash (9240 and 7660 yr B.P.), peanut (7840 yr B.P.), quinoa (8000 and 7500 yr B.P.), and cotton (5490 yr B.P.) in the form of macrobotanical remains recovered from sealed house floors and hearths in buried preceramic sites in a tropical dry forest of the Ñanchoc Valley, a tributary of the Zaña Valley located at 500 m above sea level, on the lower western slopes of the Andes in northern Peru (Fig. 1). Evidence of other crops (manioc, unidentified tubers, and fruits), circular and later rectangular houses, storage units, stone hoes, ground stone bowls and pallets, furrowed garden plots, small-scale irrigation canals, and earthen mounds dating to the same period have been found nearby (39).

Fig. 1.

Location map of study area in north Peru.

Before the adoption of crops and the development of new farming technologies, hunters and gatherers lived in semi-sedentary, dispersed encampments between 10,800 and 9000 yr B.P. (9). From 9000 to 7000 yr B.P., people formed more tightly bound and organized communities, living 200 to 400 m apart near springs and along the banks of small streams on wide alluvial fans 1 to 3 km from the valley floor where they gardened, continued gathering and hunting, and engaged in down-the-line exchange of ideas and products with horticulturalists living in distant coastal, highland, and tropical forest areas.

We recovered macrobotanical specimens from late Paiján (10,000 to 9000 yr B.P.), Las Pircas (9000 to 7000 yr B.P.), and Tierra Blanca (7000 to 4500 yr B.P.) houses, including squash (Cucurbita moschata), a morphologically wild peanut (Arachis sp.), cotton (Gossypium barbadense), a quinoa-like chenopod (Chenopodium sp. cf. quinua), manioc (Manihot sp.), an edible malphigiaceous fruit (Bunchosia sp.), and unidentified tubers and fruits (Figs. 2, 3, 4, 5) (6) (see SOM Text, section 1, and table S1 for the number of remains recovered in sites). Accelerator mass spectrometry (AMS) radiocarbon dates processed nearly two decades ago for charred and uncharred squash, peanut, cotton, and coca remains recovered from houses ranged widely from 11,650 14C yr B.P. to 200 years into the future (6). Despite the wide variation in dates, the plant remains were thought to represent early crop cultivation in the Andes, because they were embedded in buried house floors and hearths beneath grinding stones and in excavated stone-lined storage units, and were directly associated with 14C dates ranging between 7800 and 5800 yr B.P. on wood charcoal from sealed hearths (Table 1). Most of these remains display morphological traits that do not correspond to those of any modern varieties, and most of these plants are not native to the lower western Andean slopes of northern Peru. New AMS dates on macrobotanical squash, peanut, and cotton remains are now available from the same previously dated house floors and hearths and from new buried floor contexts. Dates are 9240 ± 50 yr B.P. [Beta 179512: 10,403 to 10,163 calibrated (Cal) yr B.P.] and 7660 ± 40 yr B.P. (Beta 219589: 8535 to 8342 Cal yr B.P.) on squash seeds from sites CA-09-77 and CA-09-27, respectively; 7840 ± 40 (Beta 219588: 8640 to 8435 Cal yr B.P.) on a peanut hull from site CA-09-77; and 5490 ± 40 yr B.P. (Beta 183279: 6278 to 5948 Cal yr B.P.) on cotton fibers from CA-09-71. These new dates conform to the standard radiocarbon dates derived from wood charcoal in hearths and floors and directly associated with the same plant species that previously produced erratic dates (see SOM Text, section 2, and table S2). In addition to the new dates, research carried out by botanical and other experts over the past two decades on the characteristics and distributions of modern wild and domesticated species of Cucurbita, Arachis, Gossypium, and Chenopodium allows the inter-pretation of these remains to be more precise.

Fig. 2.

Close-up of a fragment of a peanut hull (Arachis sp.) recovered from a buried house floor at site CA-09-77.

Fig. 3.

Close-up of two dark brown squash seed (C. moschata) fragments recovered from a buried house floor at CA-09-27.

Fig. 4.

Close-up of carbonized quinoa seed (Chenopodium quinoa) recovered from a buried house floor in CA-09-77.

Fig. 5.

Close-up of cotton boll recovered from a buried house floor at CA-09-71.

Table 1.

Radiocarbon dates from selected preceramic sites in the Ñanchoc Valley. New AMS dates on archaeological macrobotanical remains are in bold.

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The peanut was long thought to be among the later cultivated plants of the Andes, and one that is particularly suited to the lowland tropical forests and savannahs where it was prized as a high-protein complement to starchy manioc-based diets (1, 2). The peanut's center of origin is believed to be in an area east of the Andes comprising southeastern Bolivia, north-western Argentina, northern Paraguay, and the western Mato Grosso region of Brazil (1012). It has not been found in other middle preceramic archaeological contexts of southwestern Ecuador, Colombia, or the Amazon basin. The Las Pircas and Tierra Blanca peanuts are elliptically shaped, fibrous remains of fruits (6) that appear to correspond morphologically to a wild species, a situation that could be expected during the early stages of domestication. The sites at which they were recovered are far removed from the known range of wild Arachis.

Early and middle preceramic squash phytoliths have been recovered from the Las Vegas Phase in southwestern Ecuador (10,000 to 7000 yr B.P.) and the Colombian Amazon (9300 to 8000 yr B.P.) (1, 2, 13). In both cases, phytolith size indicates the presence of domesticated species. The newly dated squash seeds from the late Paiján and Las Pircas sites have similar dates and are the earliest macrofossil remains of Cucurbita recovered from an archaeological context. These small seeds (6 to 7 mm long, 2.5 to 4 mm wide) have a uniform dark brown color, prominent raised seed margins, and an elliptical shape. Seeds of this size, shape, and color have been found in fruits of modern traditional landraces of C. moschata from lowland northern Colombia (14). No other species of Cucurbita resemble these traits (15). The color alone is unique to this species in a genus composed of about 14 species, including 5 domesticates. There is no evidence to suggest that postdepositional processes discolored lighter-colored seeds that are typical of other squash species and cultivars of C. moschata. Despite their small size for a domesticated squash, the archaeological seeds were mature, because the brown seed coat does not develop until near the end of maturation. The wild ancestor of this major domesticated squash has not yet been found, but lowland northern South America, especially Colombia, has been proposed as its area of origin on the basis of molecular data and occurrence of modern, primitive-looking landraces (1317). Fruits of C. moschata with dark brown seeds are also most prevalent today in this region. It thus appears that the peanut specimens and the Ñanchoc squash specimens represent early cultigens dispersed at an early date to northwestern Peru from their respective areas of origin.

Wild populations of Gossypium barbadense are found on the coastal plains of southwestern Ecuador and northwestern Peru (1), where their domestication likely occurred (18). Archaeological cotton has been found in the Valdivia strata of the Real Alto site in Ecuador (19) and in the late preceramic sites of the Ancon-Chillon area of central coastal Peru. Between 4500 and 3500 yr B.P., this plant anchored what has been called the Cotton Preceramic Phase of Peru. Cotton was initially used for fishing nets, and probably for hunting nets, storage bags, and clothing (20). Cotton is absent from the earlier Las Pircas Phase in the Ñanchoc Valley, but complete cotton bolls were recovered from house floors of the later Tierra Blanca Phase. During this same period, gourds (Lagenaria) were probably used for industrial containers and for the consumption of their seeds (21).

One carbonized specimen of a large-seeded chenopod (1.9 mm diameter) was recovered from the house floor of CA-09-27 and placed by direct association with dated hearths between about 7500 and 8000 yr B.P. Its size and quadrilateral cross-section closely resemble those of quinoa (Chenopodium quinua), but ridges on the specimen are a minor morphological difference from herbarium specimens. Thirty similar specimens, both carbonized and desiccated, were recovered from several later Tierra Blanca sites. Large-seeded chenopods like quinoa are thought to have been domesticated in the Lake Junin and Lake Titicaca regions of southern Peru and the Bolivian highlands by 4000 yr B.P. (22). The highland origins and ecology of quinoa contrast with the lower elevation, tropical dry forest association, and northern location of the Ñanchoc sites. Quinoa has several characteristics that make it an unusual cultigen. The seed bitterness, a saponin coating, must be removed by washing before preparation for consumption, but the bitterness is an advantage in storage, because rodents and insects do not infest the seeds. Seed fragility also is a crucial attribute of quinoa. Seeds do not usually remain viable for more than 1 year, and quinoa must be planted every year, or it may be lost to a region. Even a small of amount of quinoa in an archaeological site thus may represent a long period of local cultivation.

There is no evidence to indicate that the Ñanchoc Valley was a domestication center for any of these major economic plants. Thus, the adoption of peanut, squash, cotton, quinoa, and other crops suggests that these plants must have been cultivated elsewhere earlier than 9200 yr B.P. for squash (1, 2), 8000 yr B.P. for peanut, 5500 yr B.P. for cotton, and about 7500 yr B.P. for quinoa, after which groups of down-the-line local traders or mobile horticulturalists brought them into the valley. Between ∼9200 and 5500 yr B.P., the Ñanchoc communities passed from advanced Paiján foragers with a broad-spectrum economy, to Las Pircas horticulturalists primarily dependent upon seasonal rainfall to grow a few crops, to Tierra Blanca incipient agriculturalists managing irrigated water and growing a wide variety of crops. Associated with these changes are demographic, architectural, and technological developments indicative of more complex social groupings.

The new dates confirm the internal logic of the archaeology of the Las Pircas and Tierra Blanca phases, with their nucleated household patterns and relocation closer to the valley floor. The adoption and cultivation of both food and industrial crops between 9000 and 5500 yr B.P. were aspects of wider cultural processes that included sedentism, artificial water management systems, mound-building, appearance of exotic artifacts, and probably ritually sanctioned crop production, the latter suggested by the presence of rock crystals and other exotics in mounds, buried garden plots, and canals (7, 8). These processes in Ñanchoc [and other areas of the Andes (23)] also served as catalysts for rapid social changes that eventually contributed to the development of intensified agriculture, institutionalized political power, and towns in both the Andean highlands and on the coast between 5500 and 4000 yr B.P. (24). The Ñanchoc data indicate that agriculture played a more important and earlier role in the development of Andean civilization than previously understood, especially within suitable, low-elevation mountain environments.

The distribution of structures, canals, and furrowed fields in the study area indicates that early agriculture was associated with management decisions made to socially aggregate people in the context of regulated crop production beyond the individual household level to emerge as creative agricultural communities. Our data show that public ritual and probably ceremonialism were manifested to an unprecedented degree between 7000 and 6000 yr B.P. in the form of small mounds associated with lime production probably for coca leaf consumption (4, 7), which also led to increased social cohesion among local households. The mounds at site CA-09-04 were intermittently modified and used for two millennia, suggesting that public ritual coevolved with agriculture and wider community developments (7).

The data amplify existing evidence and arguments on the development of domesticated plant production. The squash remains constitute more evidence from another region that squashes and gourds were among the earliest cultivars in the Americas (13, 25) and that a number of different squash species were undergoing manipulation and incipient domestication at about the same time during the early Holocene in Meso-america and the northern half of South America. The evidence also points to an early development of horticulture in more southerly regions of tropical South America, where the peanut is thought to have its origin. There is evidence for similarly early domestication of manioc to the north of the Ñanchoc Valley in Colombia and Panama (26, 27). Our data also show that horticulture and cultural complexity developed in the Americas nearly as early as it did in many parts of the Old World. Early to middle Holocene populations exploiting suitable environments in both the Old World and New World combined different suites of resources and technologies to affiliate into larger, more advanced communities that differentiated themselves from others between 12,000 and 9000 yr B.P. (1, 2, 28, 29).

Supporting Online Material

SOM Text

Tables S1 and S2


References and Notes

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