Report

Starch Fossils and the Domestication and Dispersal of Chili Peppers (Capsicum spp. L.) in the Americas

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Science  16 Feb 2007:
Vol. 315, Issue 5814, pp. 986-988
DOI: 10.1126/science.1136914

Abstract

Chili peppers (Capsicum spp.) are widely cultivated food plants that arose in the Americas and are now incorporated into cuisines worldwide. Here, we report a genus-specific starch morphotype that provides a means to identify chili peppers from archaeological contexts and trace both their domestication and dispersal. These starch microfossils have been found at seven sites dating from 6000 years before present to European contact and ranging from the Bahamas to southern Peru. The starch grain assemblages demonstrate that maize and chilies occurred together as an ancient and widespread Neotropical plant food complex that predates pottery in some regions.

Chili peppers, members of the genus Capsicum, have been cultivated extensively, initially in the Americas and, after Columbus, around the globe (1, 2). The lack of a comprehensive archaeobotanical record has hampered accurate reconstructions of the origins, domestications, and dispersals of these plants. Macroremains of the fruits are confined to rare sites in arid environments, and reports of seeds and pollen are even less common (Table 1). We found that a widespread, but previously unidentified archaeological starch morphotype is derived from chili pepper fruits and is commonly preserved on artifacts. We documented this microfossil from seven archaeological sites ranging from the Bahamas archipelago to Andean South America (Fig. 1) beginning 6000 years ago (Table 2).

Fig. 1.

Archaeological sites mentioned in the text. Red sites yielded starch grains of chili pepper. Blue sites yielded all other classes of remains of chili pepper.

Table 1.

Published reports of archaeological Capsicum from well-dated sites with clearly defined stratigraphy.

SpeciesPlant partRegionSite(s)Date(s) (yr B.P.)Source
C. annuum Fruits Mexico Tehuacan Valley 500-6000 (View inline)
C. annuum Seeds and peduncles El Salvador Ceren 1400 (View inline)
C. baccatum Fruits Peru Huaca Prieta, Punta Grande 4000 (View inline)
C. chinense Fruits Peru Huaca Prieta, Punta Grande 4000 (View inline)
C. chinense Fruits Peru Casma Valley Ca. 2500-3500 (View inline)
Capsicum sp. Seeds Haiti En Bas Saline 600 (View inline)
Capsicum sp. Pollen Venezuela La Tigra 450-1000 (View inline)
Table 2.

Summary of Neotropical archaeological starches of Capsicum. F, flaked tool; G, groundstone tool; C, ceramic sherd; S, sediment sample.

Sample#Size (μm)SourceDate in yr B.P. (Ref.)
Los Mangos, Venezuela (Arauquinoid, Valloid)
Lev 1, 1 1 15 G ∼500-1000 (View inline)
Lev 2, 1 1 17 F ∼500-1000 (View inline)
Lev 3, 1 1 15 F ∼500-1000 (View inline)
Lev 3, 2 1 22 F ∼500-1000 (View inline)
Lev 5, 2 2 19, 20 F ∼500-1000 (View inline)
Lev 7, 1 2 20, 20 F ∼500-1000 (View inline)
Three Dog, Bahamas (Lucayan)
Z87-89 1 19 F 969-1265 CalView inline (View inline)
Z1032-1035 1 21 F 969-1265 CalView inline (View inline)
Waynuna, Peru (Preceramic)
Tool 10 2 18,24 F 3564-3837 CalView inline (View inline)
Tool 11 6 14-34 G 3564-3837 CalView inline (View inline)
Tool 29 2 24,25 G 3564-3837 CalView inline (View inline)
Tool 30 6 19-28 G 3564-3837 CalView inline (View inline)
Cat 36 1 18 S 3689-3969 CalView inline (View inline)
Zapotal, Panama (Early Ceramic)
C2N8F4 4 20-28 G 3560-4850 CalView inline (View inline)
C7N2 1 25 G 3560-4850 CalView inline (View inline)
C32N7 1 32.5 G 3560-4850 CalView inline (View inline)
Real Alto, Ecuador (Valdivia 3)
Structure 1 1 20 G 4400-4800 CalView inline (View inline)
Structure 1 3 24-26 G 4400-4800 CalView inline (View inline)
Structure 10 3 18-24 G 4400-4800 CalView inline (View inline)
Structure 10 1 24 G 4400-4800 CalView inline (View inline)
Aguadulce, Panama (Late Preceramic)
350 3 24-28 G 5600 Cal (View inline)
Loma Alta, Ecuador (Early Formative)
SS275 5 22-26 G 5050-6250 CalView inline (View inline)
SS275-2 6 16-24 G 5050-6250 CalView inline (View inline)
SS292 2 19, 20 G 4550-6050 CalView inline (View inline)
Sample 13 2 24, 28 C 4830-5280 CalView inline (View inline)
Sample 7 1 27 C 4080-4410 CalView inline (View inline)
Level 12 2 24, 28 S 4990-5310 CalView inline (View inline)
Sample 11 1 18 C 4250-4860 CalView inline (View inline)
Sample 10 1 22 C 4990-5310 CalView inline (View inline)
Level 14 2 24, 24 S 4990-5310 CalView inline (View inline)
Sample 9 1 28 C 4990-5310 CalView inline (View inline)
  • View inline* Standard and AMS radiocarbon dates from associated charcoal, 2σ calibrated result.

  • View inline Standard radiocarbon date from associated charcoal, 2σ calibrated result.

  • View inline Standard radiocarbon dates from associated shell, adjusted for 12C/13C ratio, 2σ calibrated results.

  • The five most economically notable species of chili pepper are C. annuum, C. baccatum, C. chinense, C. frutescens, and C. pubescens. Although it is generally agreed that the genus Capsicum originated in Bolivia (2), the centers of domestication and dispersal patterns of these species remain speculative. A combination of archaeological evidence, genetic analyses, and modern plant distributions have led researchers to suggest that C. annuum was initially domesticated in Mexico or northern Central America, C. frutescens in the Caribbean, C. baccatum in lowland Bolivia, C. chinense in northern lowland Amazonia, and C. pubescens in the mid-elevation southern Andes (2, 3).

    All five species of domesticated chili peppers produce large, flattened lenticular starch grains with a shallow central depression, not unlike a red blood cell in appearance (Fig. 2, A to C). When rotated into side view, a central linear figure—a clean line or split figure with sharp edges—runs parallel to the long axis of the grain. This figure can extend for the entire length of the grain or just a part of it (Fig. 2, E and F). Ranging from about 13 to 45 μm in length, the starches of domesticated peppers are easily distinguishable from smaller wild types in the microfossil record (Fig. 2D and table S1). Although the basic three-dimensional morphology is consistent among all species of Capsicum, micromorphological characters differ between species.

    Fig. 2.

    Modern and archaeological starch granules from Capsicum. (A) Starch granule from the fruit of modern Capsicum baccatum var. pendulum (aji mirasol) showing typical morphology. Note the rounded lenticular form and large, flat, central depression. (B) Archaeological Capsicum starch granule from Loma Alta. (C) Archaeological starch granule of Capsicum from Real Alto. (D) Starch granule from a modern specimen of Capsicum annuum var. minimum. This starch granule is typical of those from wild peppers. (E) Side view of a modern starch granule from Capsicum baccatum. Note the linear figure. (F) Side view of an archaeological starch granule of Capsicum from Zapotal.

    Three of the species—C. baccatum, C. frutescens, and C. pubescens—can be identified on the basis of diagnostic morphotypes that have unique features of the central depression. However, these features are rare even in modern starch grain assemblages. Otherwise, the morphologies of starch grain assemblages from C. annuum and C. frutescens are so similar that, in the absence of a diagnostic, it is not possible to assign grains to a single species. The morphology of starch from C. chinense is similar to but not identical to that of C. annuum or C. frutescens, and the morphologies of all three starches differ significantly from those of C. baccatum and C. pubescens which, in turn, differ from one another. Because similar types occur in all congeneric species of Capsicum, either a diagnostic or a large archaeobotanical assemblage is required for a secure species identification.

    The presence of a basic genus-diagnostic starch morphotype for Capsicum is predictable because of the lack of perfect barriers to intraspecific hybridization (4). C. annuum, C. chinense, and C. frutescens have been described as a species complex with a single ancestral gene pool (4). Therefore, it is not surprising that the starches of these three species are morphologically similar to one another. In contrast, C. baccatum and C. pubescens are distinct domesticated species in South America (4). Starches derived from other economically significant species in the Solanaceae including Lycianthes, the genus that recent phylogenetic studies indicate is the most closely related to Capsicum (5), differ from those of chili peppers (table S1 and fig. S1) (6). Thus, we have eliminated those plant species with the potential to confuse the source of the microfossils.

    We recovered securely identified genus-diagnostic Capsicum starch microfossils from seven sites throughout the Americas. The oldest positively identified starches were found at the contemporaneous sites of Loma Alta and Real Alto in southwestern Ecuador. Interpreted as a village-sized, permanent settlement, Loma Alta was occupied for more than a millennium beginning about 6100 years before present (yr B.P.) (7). We recovered chili pepper starches from sediment samples, milling stones, and food residues from ceramic sherds of cooking vessels, all of which were excavated from the lower levels of the site.

    Similar to Loma Alta, Real Alto was a village site at about 6100 yr B.P.; however, by about 4750 yr B.P., it had expanded into a regional ritual-ceremonial center (8, 9). The chili starches were extracted from milling stones from two house floors dating to the period of expansion. Microfossil evidence of maize, Canna edulis (achira), Maranta arundinacea (arrowroot), Calathea sp. (leren), manioc, cucurbits (squash), Canavalia sp. (jack bean), and the Arecaceae family (palms) has also been recovered from Real Alto (1012). A combination of evidence, including plant remains and site proximity to seasonally flooded bottomland, indicates that agriculture was important in the economies of both Ecuadorian sites. Ecuador is not considered to be the center of domestication for any of the five major economic species of chili peppers. Therefore, the presence of domesticated chilies within this early, complex, agricultural system indicates that these plants must have been domesticated elsewhere earlier than 6000 yr B.P. and brought into the region from either the north or the south.

    In central Panama, the Aguadulce Rock Shelter was occupied from about 13,000 to 3200 yr B.P. during both the Preceramic and Early Ceramic periods (13). The site has yielded evidence for the cultivation of other plants not native to southern Central America, including maize, manioc, and squashes dating from about 9000 to 5800 yr B.P. We identified chili pepper starch on a groundstone tool recovered from the top of the preceramic deposits; the tool and thus its associated starch residues have a stratigraphic date of about 5600 yr B.P. This artifact also yielded starch grains from maize and domesticated yam (13).

    The occupation of the coastal shell-midden site of Zapotal coincides with the Early Ceramic period of this region of Panama, beginning about 4800 yr B.P. (14). We recovered starches of chilies from groundstone tools, indicating that the peppers were processed and consumed alongside a number of other domesticates at the site, including maize, manioc, and yams (15). By this time, swidden cultivation of several domesticated species, including maize and manioc, was well established in the region, and farmers had significantly deforested the foothills near both Panamanian sites (16). Thus, the Panamanian record documents the use of domesticated chilies as components of the diet of swidden agriculturists in both Preceramic and Ceramic era groups.

    Farther south at 3600 m in the Peruvian Andes lies the site of Waynuna, a Late Preceramic house occupied beginning about 4000 yr B.P. At Waynuna, we found chili starches on processing tools in association with maize, arrowroot, and the remains of what is likely Solanum sp. (potato) (17). These data indicate that the residents of Waynuna were cultivating maize, tubers, and peppers and were processing them into food on site. Waynuna yielded the only starch assemblage that contained a species-diagnostic morphotype. These chili pepper starches appeared to be derived from C. pubescens, the species that includes varieties such as the rocoto pepper, a chili that is cultivated at mid-altitude in the Andes (2). When combined with macrofossil evidence (Table 1), the starch data indicate that the cultivation of three domesticated species of chili pepper was contemporaneous on the coast and in the highlands of Peru as early as 4000 yr B.P. in the Late Preceramic period. The presence of numerous other cultivars within the assemblages of each region indicates that sophisticated agriculture was practiced in both regions before the introduction of pottery.

    We also found starches of chili peppers at the Three Dog site located on San Salvador Island in the Bahamas. This site was occupied by a group of fisher-horticulturists about 1000 yr B.P. Representing the material remains of at least one household, the site consists of a midden, two activity areas, and a low-density (well-swept) area. Fifty-eight chert microliths, all typical of the morphology commonly described as manioc grater flakes (1820), have been recovered, as were ceramic griddle sherds. The microliths yielded the starchy remains of both maize and unidentified roots or tubers. We recovered chili starches from two flakes that also contained starches of maize.

    Lastly, we recovered microfossil evidence for chili pepper at Los Mangos del Parguaza in Venezuela, a large habitation site occupied about 500 to 1000 yr B.P. (21). Several large, deep stone metates were scattered over the surface of the site. Excavation of a midden deposit yielded ceramic griddle sherds and microlithic flakes that are often associated with manioc processing (22). As at the Three Dog site, the remains of manioc are conspicuously absent from an excavation that yielded artifacts usually associated with manioc processing (22). The same processing tools that contained starches of chili pepper also contained remains of maize. Root crops, including arrowroot, Myrosma sp. (guapo), and a member of the Zingiberaceae family (ginger) also left their starchy remains. When combined with the data from the Three Dog site, the chili pepper microfossils from Los Mangos del Parguaza support the notion that a sophisticated mixed subsistence economy of both root and seed crops occurred at these sites that were initially categorized as being occupied by manioc horticulturists (23).

    Neither microfossils typical of wild species nor transitional forms of Capsicum were recovered from any site. The presence of domesticated plants used as condiments rather than as staple foods during the Preceramic period indicates that sophisticated agriculture and complex cuisines arose early throughout the Americas and that the exploitation of maize, root crops, and chili peppers spread before the introduction of pottery. Evidence from both macrobotanical and microbotanical remains indicates that once chili peppers became incorporated into the diet, they persisted. Apart from the chili peppers, maize is present at every site we sampled. Maize and chilies occur together from the onset of this record until European contact and, thus, represent an ancient Neotropical plant food complex.

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    Materials and Methods

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    Fig. S1

    Tables S1 and S2

    References

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