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. Author manuscript; available in PMC: 2020 Oct 8.
Published in final edited form as: Nature. 2020 Apr 8;581(7807):190–193. doi: 10.1038/s41586-020-2162-7

Early Holocene crop cultivation and landscape modification in SW Amazonia

U Lombardo 1,*, J Iriarte 2, L Hilbert 3, J Ruiz-Pérez 4, JM Capriles 5,6, H Veit 1
PMCID: PMC7250647  EMSID: EMS85793  PMID: 32404996

Abstract

The beginning of plant cultivation is one of the most important cultural transitions in human history1–4. Based on molecular markers showing the genetic similarities between domesticated plants and wild relatives, south-western Amazonia has been proposed as one of the early centres of plant domestication4–6. However, the nature of the early human occupation and the history of plant cultivation in south-western Amazonia are still little understood. Here, we document the cultivation of Cucurbita at ca. 10,250 cal yr BP, Manihot at ca. 10,350 cal yr BP and Zea mays at ca. 6,850 cal yr BP in the Llanos de Moxos. We show that, starting ca. 10,850 cal yr BP, pre-Columbians created an anthropic landscape made of approximately 4,700 artificial forest islands within a treeless seasonally flooded savannah. Our results confirm the Llanos de Moxos as a hotspot for early plant cultivation and demonstrate that ever since their arrival, humans have caused a profound alteration of Amazonian landscapes, with lasting repercussions for habitat heterogeneity and species conservation.

Recent genetic and archaeological evidence suggests the existence of at least four independent centres of early Holocene domestication, two in the Old World and two in the New World (Mesoamerica and northern South America)1. However, the closest wild ancestors of several globally important domesticated cultigens occur in south-western (SW) Amazonia. These include the wild ancestors of manioc (Manihot esculenta) M. e. subsp. flabellifolia7; squash (Cucurbita maxima spp. maxima) C. m. spp. andreana8; peach palm (Bactris gasipaes)9; jack bean (Canavalia plagiosperma) C. piperi4 and chili peppers’ (Capsicum baccatum var. pendulum) C. baccatum var. baccatum10. This suggests that SW Amazonia could be the fifth global early Holocene centre of domestication. However, with the exception of Calathea sp. phytoliths, possibly representing lerén (C. alluoia), recently documented in the upper Madeira11, archaeological evidence has not been found for early plant cultivation in SW Amazonia. Our research fills this gap with new data from 61 early and mid-Holocene archaeological sites that we refer to as forest islands (FIs)12–14 because they now occur as patches of forest surrounded by savannah.

Mapping of forest islands

Using remote sensing data, we mapped 6643 FIs in the Llanos de Moxos (LM). The average size of FIs is 0.5 ha (min: 0.05 ha; max: 16 ha; SD 0.65 ha). We surveyed 82 of these, which represents ca. 1.2% of all sites. We took column sediment samples in all of them and carried out archaeological excavations in four. Out of the total 82 sites sampled, 83 including Monte Castelo in Brazil14, we classified 64 sites as anthropic, based on the presence of deep dark sediments rich in organic matter, charcoal, and burned earth frequently associated with shell and bone fragments (Fig. 1). The FIs surveyed are between ~0.5 m and 3 m high. The proportion of anthropic vs. natural sites suggests the existence of at least 4700 anthropic FIs in the LM (Fig. ED1). This is probably far less than the original amount built in the early and mid-Holocene, as during the transition to the late Holocene, most of the rivers in the SW part of the LM became very active and many of the pre-existing soils and potential archaeological sites were covered by alluvial deposits, sometimes up to 5 m thick15. This explains the modern distribution of FIs and why 48% of the 6643 FIs we mapped are concentrated in a relatively small area in the north-western LM (Fig. ED1), where the landscape did not change notably during this period. Anthropic FIs are mostly located in interfluvial settings covered by seasonally flooded savannahs, and they account for an estimated 24 km2 of forested area and 1,000 km of forest/savannah ecotone.

Figure 1.

Figure 1

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Forest islands mapped in the LM. Numbers associated with middens are ages expressed in median cal yr BP from the deepest anthropic datable layer at each site (Table ED1). Insets a, b, d and e identify the four areas that were surveyed to estimate the total number of anthropic FIs in the LM (Fig. ED1). The square in inset c identifies the study area; the shaded area in inset c depicts Greater Amazonia.

Sixty-six AMS 14C dates from 31 archaeological sites (Table S1) bracket the human occupation of FIs throughout the Holocene between ca.10,850 and 2,300 cal yr BP. Except for three sites in the north-eastern LM dated at ca. 2,350, 2,350 and 4,100 cal yr BP, the remaining dated sites were established between the early and mid-Holocene.

Evidence of early plant cultivation

We analysed phytoliths from the radiocarbon-dated profiles of 30 FIs (Figs. 2, 3). The earliest evidence of Manihot is a heart-shaped phytolith16 documented at the Isla Manechi dated ca. 10,350 cal yr BP and in Isla del Tesoro dated ca. 8,250 cal yr BP (Fig. 1). Scalloped sphere phytoliths derived from the rind of Cucurbita sp. were identified in layers dated to ca. 10,250 cal yr BP in Isla Manechi and ca. 9,850 cal yr BP in Site 575. We have identified wavy-top rondel phytoliths, produced in the cob of maize17, dated ca. 6,850 cal yr BP (Site 570) and ca. 6,700 cal yr BP (Site 421). We detected the early presence of Marantaceae Calathea sp. rhizome phytoliths at ca. 8,275 cal yr BP (Isla del Tesoro), before ca. 7,800 cal yr BP (Site 433) and at ca. 7,400 cal yr BP (Site FIN 14). Other Marantaceae, Cyperaceae, Phenakospermum guianensis, and Heliconia phytoliths have been found in almost all the samples starting from ca. 10,400 cal yr BP (Fig. 2, S2). We identified Oryza seed phytoliths dated at ca. 6,250 cal yr BP (San Pablo); and phytoliths from the epidermis of Celtis seeds from contexts dated to ca. 9,600 cal yr BP (Site FIN8). Hat-shaped and globular echinate phytoliths diagnostic of subfamily Arecoideae17 of the palm family (Arecaceae) are present at ca. 9,975 cal yr BP (site 493). Peach palm (Bactris sp.), a member of this subfamily, is the only palm domesticated in South America, and its domestication likely took place in SW Amazonia6. Bactris produces these hat-shaped phytoliths, but does not produce diagnostic phytoliths at the species level18. Bactris and other arecoid genera growing today in the LM (Astrocaryum, Desmoncus, Geonoma and Socratea), are used for food, building materials and medicine in present Amazonia19. The size of squash phytoliths is well in the range of the domesticated species (table ED2), however, they do not show increase in size over time as would be expected under domestication pressure (Table. ED2)17.The presence of domesticated Cucurbita sp. beginning at ~10,250 cal yr BP in Isla Manechi is the oldest evidence of Cucurbita sp. in Amazonia and coincides with the domestication of several species of Cucurbita across Central 20 and South America21,22 at the very beginning of the Holocene. Further studies analysing larger sample sizes are needed to determine whether the domesticated squash cultivated in the early Holocene was adopted in the LM from other regions or was domesticated in situ. Maize cob phytoliths were documented at site 570 ca. 6,850 cal yr BP representing the oldest evidence, by a few centuries, of maize cultivation in the Amazon basin. As hypothesized by Kistler et al.23, early maize in this and other areas probably represented a partially domesticated variety that later diverged into two South American groups of fully domesticated maize varieties. This early evidence of maize phytoliths is consistent with a temporal gradient of maize dispersal that began in western Amazonia and reached the eastern Amazon by ~4,300 cal yr BP. The early use of Manihot in Isla Manechi in the LM began more than 10,000 years ago, which coincides with the time of estimated molecular divergence from the wild ancestor and with current biogeography of manioc’s closest wild ancestor7,24. It possibly spread later to northern Peru (8,500 cal yr BP), Colombia (7,000 cal yr BP) and Panama (7,600 cal yr BP)5suggesting the bi-directional exchange of cultivars between Amazonia and the Andes beginning since the early Holocene. Our study shows that, as in other regions of Amazonia and Central America, also in the LM the development or arrival of full-blown agricultural societies was a very late phenomenon9, as there is no evidence of land prepared for agriculture in the LM until raised fields and drainage canals were built around 1,500-1,000 years ago25.

Figure 2.

Figure 2

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Diagram showing the percentage of most relevant phytolith groups from anthropic forest islands. Dots indicate presence ≤ 1% (for more details see Fig. ED2 and table ED1). *Non-domesticated, edible plants (used as food resources)26. Phytolith percentages are based on a minimum of 200 diagnostic phytoliths counted per slide.

Figure 3.

Figure 3

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Photomicrographs of phytolith morphotypes recovered from Isla del Tesoro, La Chacra and Isla Manechi: (a) wavy-top rondel from the cob of maize (Zea mays) (sampleIT190-200); (b) heart-shaped phytolith from the secretory cells of manioc (Manihot) (sample BANR17-UE1-57); (c) scalloped sphere from the rind of squash (Cucurbita sp.) (sample BANR17-UE1-31); (d) double-peaked glume from the seed of rice (Oryza sp.) (sample SM3-116s); (e) flat domed cylinder from the rhizome of Calathea sp. (sample IT30-40); (f) short trough body from the rhizome of Heliconia sp. (sample IT130-140); (g) stippled polygonal body from the seed of Cyperaceae (sample IT150-170); (h) nodular projections with a pointed apex phytolith from the seed of Marantaceae (sampleIT90-100) (i) stippled plate from the seed/fruit of hackberries (Celtis sp.) (sample SM3-69-74). Scale bars = 20μm.

The importance of starch-based foods

Paleoecological studies indicate that the LM was covered by cerrado-like savannah during the early and mid-Holocene15 indicating that plant cultivation in the Neotropics also started in shrub savannahs along with seasonal tropical forest environments4. It does not come as a surprise that phytoliths derived from plants producing underground storage organs constitute an important part of the total phytolith assemblages from the LM’s FIs including Manihot, Calathea and other Marantaceae, Heliconia, Cyperaceae and Phenakospermum. These plants, which are abundant in savannahs, produce carbohydrate-rich foods which, with the exception of some varieties of manioc27, are easy to process and cook. They are nowadays consumed by indigenous groups19 and probably provided a considerable part of the calories consumed by the first inhabitants of the LM. Large herbivores and fish available in the savannahs12,13 would have complemented a mixed economy. The fertile FIs were probably the home gardens where these crops were cultivated. Our data are in agreement with the hypothesis that plants producing underground storage organs were a fundamental part of the diet of human populations colonizing new territories28,29.

Implication for biodiversity

Our results show that inland savannahs were a key region for the early occupation of Neotropics and that they began to be transformed by the arrival of very early human settlers. FIs are entirely anthropic. However, their formation is not only an incidental effect of food-waste dumping, but it can also be seen as an active process of niche construction30. These accumulative middens also constitute fertility hotspots amid poor savannah soils, since: i) they became loci for the accumulation of nutrients that come from gathering activities in the surrounding savannah, and ii) they remained above the water level during the wet season12. It is only after 4,000 years BP, when the old and infertile soils of the south of the LM were covered with fertile alluvium deposited by the Río Grande, that agriculture in the savannahs was facilitated31. Overall, the construction of pre-Columbian FIs, which became key structures in the landscape32,33, increased forest patchiness (Fig. ED3, ED4a) and probably contributed to maintaining landscape-scale species richness in this Ramsar threatened biome. Nowadays, these anthropic FIs are preferential feeding and roosting sites for many species of birds, including the endemic and critically endangered blue-throated macaw (Ara glaucogularis)34. Taken together, our data show that the earliest inhabitants of the LM were not just tropical hunter-gatherers, but colonizers who had engaged in plant cultivation since the early Holocene, thus opening up the possibility that they already had a mixed economy when they arrived in the region. The thousands of keystone structures represented by FIs show that the human footprint on Amazonia is not just restricted to large-scale transformations by late Holocene farming groups9,35, but is rooted in the earliest human dispersal into this region and has lasting implications for habitat heterogeneity and biodiversity conservation.

Methods

Mapping of FIs

FIs were mapped by visual scanning of high-resolution satellite imagery of Esri ArcGIS basemaps (Fig. ED5). When the identification of FIs was not straightforward due to cloud cover or poor resolution, TanDemX and SRTM digital elevation models were used as complementary resources. Patches of forest were classified as FIs when they had a round shape and were completely or partially surrounded by savannah (n = 4,341); or they had an irregular shape but were relatively small (<400 m in diameter) and completely surrounded by savannah (n = 2,304). For each FI, the following attributes were recorded: diameter; shape (perfectly round, almost round, elongated or irregular); location (along paleochannel, along modern river, seasonally flooded savannah, border between seasonally flooded savannah and upland, along a drainage stream, upland surrounded by bushes); presence of other earthworks within ~500 meters; and whether or not FIs were established over fluvial deposits or uplands. The latter attribute is partly redundant with “Location” but sometimes fluvial deposits are not connected to paleochannels (as in the case of old crevasse splays or old meander belts where paleochannels have been infilled) or the FIs are located along a paleochannel with completely eroded levees and the FIs have clearly been built after the erosion of the levees.

Selection of survey areas

Four survey areas were selected in different regions of the LM to ground-truth FIs and evaluate their natural or anthropic origin. The four areas (Fig. 1) were selected based on differences in soil, landcover, hydrology, and accessibility by car. These four areas cover all the different eco-regions identified in the LM36,37. These areas belonged to organizations (area a -see inset in Fig. 1- in the Barba Azul Nature Reserve) or ranchers (b, c, and d) who granted us permission to conduct surveys. In total, we surveyed 21 FIs in area a, 22 in b, 13 in d, and 17 in e. Nine other FIs were surveyed outside of these four areas.

Criteria for identification of anthropic FIs

Several anthropic FIs in the LM have been excavated 12–14. These excavations have revealed thick strata of sediments rich in organic matter, charcoal, burnt earth, and fragmented animal bones and shells; they also have revealed human burials. The clear difference between the sediments found in the anthropic FIs and the soil types found in the LM38–41 makes the field identification of FIs relatively straightforward. In the present work, the FIs surveyed have been classified as anthropic when thick layers of organic-rich sediments contained at least two archaeological materials such as charcoal, burnt earth, animal bones, and shells.

Sampling of FIs

Sampling of undisturbed material was performed at regular intervals in the four sites where archaeological excavations were conducted: Isla del Tesoro (SM1), La Chacra (SM3), San Pablo (SM4), and Isla Manechi (Fig. ED6). The rest of the sites were sampled using an auger soil sampler. The stratigraphy of the recovered cores was described in the field and sampling was carried out only where stratigraphic changes were detected in the field (Fig. ED7). The deepest sample with evidence of charcoal was always sampled. After extraction, cores were inspected to avoid contamination and check that the soil section sampled show no evidence of soil mixing (i.e. root penetration and invertebrate burrowing were absent). The excess of material has been cut off with a knife and only the inner, uncontaminated part of the extracted samples has been stored in plastic bags. Samples have been air-dried in Bolivia before being shipped. Charcoal fragments for 14C have been collected in situ, enveloped in aluminium foil and stored in plastic bags.

Phytolith processing and identification

Phytoliths were extracted from sediments following Lombardo et al.42. Phytoliths were identified and counted using a Zeiss Axioscope 40 light microscope at 500× magnification. Phytolith identifications were made using published material for the Neotropics17,43–46 and by direct comparison with the phytolith reference collection of the Archaeobotany and Palaeoecology Laboratory in the Department of Archaeology of the University of Exeter. A minimum of 200 diagnostic phytoliths were counted per slide. A full scan of the slides was performed to detect the presence of squash, manioc and maize. Phytolith assemblages in SW Amazonia have been studied in modern soils46 and 29 paleosols from the early and late Holocene15 in different natural environments and land covers. In none of these natural contexts have phytoliths of Manihot or Curcubita been found, strongly suggesting that phytoliths of these two genera found in FIs are the direct result of human activity and not of the chance occurrence of wild relatives on these FIs

Radiocarbon dates

The deepest recoverable sample of charcoal from 32 sites was dated in order to establish the minimum age of site foundation. For the four sites that were excavated, 35 samples from different depths were dated in order to establish periods of occupation and abandonment. The complete dataset and code used to calibrate all of radiocarbon dates are available respectively in Table ED1 and Supplementary Information. Radiocarbon dates from the studied sites were calibrated using SHCAL1347. For Isla del Tesoro, Isla Manechi and La Chacra, where stratigraphically ordered ages were available, we run a series of Bayesian age-depth models using the P_Sequence command in OxCal 4.348 with default settings. Each model was stratigraphically constrained by the youngest age in the profile and the deepest section reached in each site (Fig. ED8). Ages of undated samples were estimated using the command Date within the model.

Extended Data

Fig. ED1.

Fig. ED1

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Estimated number of anthropic FIs. The number was estimated by extending the proportion of anthropic FIs in the surveyed areas (in green) to the portion of the LM with similar physical geography and land cover (polygons). Background image represents the density of FIs, calculated using the Kernel Density tool in Esri ArcGIS.

Fig. ED2.

Fig. ED2

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Detailed percentage phytolith diagram for all the samples analyzed from anthropogenic FIs. *Non-domesticated, edible plants. Phytolith percentages are based on a minimum of 200 diagnostic phytoliths that were counted per slide

Fig. ED3.

Fig. ED3

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Map of all the FIs and platform fields in a north-western subset of the LM. Platform fields are mostly built along paleochannels. Rivers Omi and Yruyañez flow inside old channels of the Beni River. FIs are mostly located in interfluvial areas. The region contains a total of 2428 patches of forest, 955 of which are FIs. Once all the patches of forest within a 2-km buffer of a river, paleoriver and lake are removed, FIs account for 60% of the remaining 1191 patches.

Fig. ED4.

Fig. ED4

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Characteristics of FIs. a) Photo of the anthropic landscape dotted with forest islands in the Barba Azul Nature Reserve; b) Histogram showing the distribution of the diameter of FIs. The left side of the distribution is truncated at 25 m because smaller FIs have not been mapped; c) Photo taken at Site 579, natural FI. Samples are taken every 10 cm, from top left to down right. Material is silt with no organic matter; d) Photo taken at Site 425, anthropogenic FI. Depth of the sample 140 cm; e) Photo taken at Site 430, anthropogenic FI. Depth of the sample 160 cm. Samples in d) and e) are representative of the whole profile in site 425 and 430 respectively (see also Fig. ED7). We performed one core for each FI we visited.

Fig. ED5.

Fig. ED5

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Examples of surveyed FIs as seen in high-resolution satellite imagery of Esri ArcGIS basemap. a-f: FIs classified as anthropic (a, Sm4; b, Isla Manechi; c, Site 575; d, SM3; e, FIN 12; f, Isla del Tesoro); g-i: FIs classified as natural (g, FIN2; h, FIN11; I, Sire 529). Source: ESRI, DigitalGlobe, GeoEye, Earthstar Georaphics,CNES/Airbus DS.

Fig. ED6.

Fig. ED6

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Stratigraphic profile and sampling sites at Isla Manechi. Charcoal fragments for AMS 14C dating were collected during the excavation and yellow triangles indicate their depth. Yellow squares indicate the sampling locations of sediments analyzed for phytoliths, which have been sampled after the excavation from the vertical profile. The dashed line indicates the transition from the ceramic phase to the pre-ceramic one. This transition is characterized by a sharp increase in the compactness of sediments and amount of burnt earths. Values in parenthesis are median calibrated radiocarbon ages BP. A chronological gap of almost 4500 years exists between the two phases (Table ED1). All of these differences make it possible to exclude any contamination of phytoliths coming from the ceramic to the pre-ceramic contexts. For a description of archaeological excavations at Isla del Tesoro (SM1), La Chacra (SM3), and San Pablo (SM4) see Capriles et al.13

Fig. ED7.

Fig. ED7

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Stratigraphic descriptions of cored sites. Radiocarbon dates are included in ovals as median calibrated years before present.

Fig. ED8.

Fig. ED8

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Age-depth models of the modelled profiles. a) and b), Isla del Tesoro; c) Isla Manechi; d) and e) Isla La Chacra. The age-depth models have been produced using OxCal V4.3, code is available in Supplementary Information

Table ED1.

Radiocarbon ages of all the dated sites cited in the text including provenance and calibrations. Stratigraphically ordered dated depths have been modelled using a Bayesian age-depth model (OxCal 4.3’s P_Sequence). The modelled ages for samples BANR17-UE1-53 and BANR17-UE1-64 have been calculated using the Date command. Code is available in Supplementary Information.

Lab _ Code Site 14C BP 14C Age SD Unmodelled (BP) 95.4% Modelled (BP) 95.4% Median Material Depth (cm)
from to from to
D-AMS-1737 SM4, San Pablo 5476 35 6306 6124 6239 Bulk 58
Poz-46397 SM4, San Pablo 5190 80 6178 5664 5898 Charcoal 65
D-AMS-1741 SM4, San Pablo 5490 32 6306 6186 6245 Bulk 93
PSUAMS-4659 SM4, San Pablo 6665 25 7571 7441 7512 Charcoal 150
D-AMS-1739 SM4, San Pablo 6910 30 7787 7621 7696 Charcoal 150
Poz-46396 SM4, San Pablo 7700 90 8636 8218 8463 Charcoal 197
PSUAMS-1450 SM3, La Chacra 6030 30 6935 6736 6925 6734 6825 Charcoal 100
Poz-38862 SM3, La Chacra 5140 40 5930 5733 5933 5733 5825 Shell 107
PSUAMS-1563 SM3, La Chacra 6650 30 7566 7437 7568 7441 7506 Charcoal 121
PSUAMS-1564 SM3, La Chacra 7930 30 8972 8590 8951 8586 8672 Charcoal 155
Poz-38865 SM3, La Chacra 7860 50 8847 8435 8682 8426 8557 Shell 236
Poz-38866 SM3, La Chacra 7790 80 8760 8383 8748 8456 8590 Charcoal 240
Poz-38853 SM2, San Francisco 4950 40 5736 5585 5638 Shell 85
Poz-38850 SM2, San Francisco 4770 60 5588 5320 5465 Charcoal 155
Poz-38851 SM2, San Francisco 5380 40 6272 5994 6117 Shell 205
Poz-38852 SM2, San Francisco 5500 40 6393 6128 6253 Charcoal 205
Poz-34228 SM1, Isla del Tesoro 345 25 452 304 391 Bone 15
Poz-34229 SM1, Isla del Tesoro 3895 35 4411 4153 4414 4155 4292 Shell 35
Poz-34230 SM1, Isla del Tesoro 4945 35 5722 5586 5721 5585 5629 Shell 45
Poz-28854 SM1, Isla del Tesoro 3830 50 4405 3986 4172 Shell 48
Poz-28855 SM1, Isla del Tesoro 4415 35 5210 4849 4937 Charcoal 77
Poz-22902 SM1, Isla del Tesoro 5520 40 6395 6190 6280 Charcoal 115
Poz-34231 SM1, Isla del Tesoro 5520 40 6395 6190 6295 6190 6234 Shell 115
Poz-24633 SM1, Isla del Tesoro 5360 40 6266 5950 6096 Shell 115
D-AMS-1740 SM1, Isla del Tesoro 5502 30 6310 6190 6309 6207 6275 Charcoal 117
PSUAMS-4658 SM1, Isla del Tesoro 5565 20 6398 6281 6393 6278 6305 Charcoal 120
Poz-24634 SM1, Isla del Tesoro 5505 35 6388 6184 6262 Charcoal 120
Poz-34232 SM1, Isla del Tesoro 5460 40 6304 6021 6302 6205 6254 Shell 125
Poz-28856 SM1, Isla del Tesoro 4480 40 5284 4872 5047 Charcoal 140
Poz-28850 SM1, Isla del Tesoro 4495 35 5288 4886 5109 Shell 140
Poz-36136 SM1, Isla del Tesoro 5800 35 6657 6453 6660 6461 6563 Charcoal 160
D-AMS 032885 SM1, Isla del Tesoro 7271 40 8162 7966 8151 7956 8019 Bulk orqanic 205
D-AMS 032884 SM1, Isla del Tesoro 7447 37 8348 8065 8347 8174 8274 Bulk orqanic 225
Poz-34301 SM1, Isla del Tesoro 9270 60 10556 10248 10573 10259 10434 Bulk orqanic 235
Poz-36135 SM1, Isla del Tesoro 9420 50 10743 10433 10715 10416 10574 Charcoal 245
BE-4254.1.1 FIN8_182-187 8681 22 9671 9537 9582 Charcoal 185
BE-4253.1.1 FIN5_92-97 6963 25 7828 7680 7745 Shell 95
BE-4250.1.1 FIN3_95-100 8572 48 9560 9438 9514 Charcoal 97
BE-4257.1.1 FIN15_145-150 7997 25 8985 8649 8834 Shell 147
BE-4256.1.1 FIN14_85-90 6552 25 7486 7325 7429 Shell 87
BE-4255.1.1 FIN12_90-95 4092 24 4785 4424 4522 Shell 92
BE-8256.1.1 BANR17-UE1-5 3017 21 3236 3005 3319 3007 3144 Charcoal 25
BE-8257.1.1 BANR17-UE1-20 4324 22 4959 4743 4957 4728 4848 Charcoal 55
BE-8258.1.1 BANR17-UE1-31 4491 23 5285 4888 5288 4965 5172 Charcoal 85
BE-8259.1.1 BANR17-UE1-38 9138 24 10367 10195 10284 10196 10239 Charcoal 105
BANR17-UE1-53 10546 10231 10372 125
D-AMS 029221 BANR17-UE1-57 9346 41 10653 10298 10664 10380 10521 Charcoal 145
BANR17-UE1-64 13918 10307 10883 155
BE-7663.1.1 575_270-280 8849 50 10155 9632 9848 Charcoal 275
BE-7671.1.1 574_80-90 5516 62 6409 6025 6273 Charcoal 85
BE-7667.1.1 570_60-70 6046 48 6984 6695 6844 Charcoal 65
BE-7675.1.1 569_40-50 407 19 496 328 453 Charcoal 45
BE-7672,1.1 569_130-140 5759 53 6659 6399 6512 Charcoal 135
BE-7664.1.1 536_110-120 4994 37 5857 5595 5678 Charcoal 115
BE-7668.2.1 535_190-200 6069 51 7145 6730 6871 Charcoal 195
BE-7673.2.1 530_160-170 2397 20 2465 2327 2362 Charcoal 165
BE-7661.1.1 527_200-210 5337 281 6730 5472 6076 Charcoal 205
BE-7662.1.1 526_250-260 6217 40 7239 6945 7076 Charcoal 255
BE-7674.1.1 521_90-100 2346 89 2701 2094 2331 Charcoal 95
BE-7666.1.1 519_100 5647 22 6443 6308 6368 Charcoal 100
BE-6164.1.1 502 65 4365 110 5295 4583 4927 Charcoal 65
BE-6166.1.1 493 155 8920 49 10186 9766 10006 char/sed 155
BE-6153.1.1 490 95-100 3796 33 4237 3985 4115 Shell 97
BE-6167.1.1 434 270 7811 57 8696 8413 8543 char/sed 270
BE-6163.1.1 433 175 7058 50 7954 7718 7852 char/sed 175
BE-6168.1.1 430 235 6397 130 7552 6951 7269 chat/sed 235
BE-6158.1.1 429 220 8028 24 8999 8717 8870 char/sed 220
BE-6157.1.1 423 170 4365 21 4965 4840 4877 char/sed 170
BE-6159.1.1 421 170 5875 127 6953 6322 6646 char/sed 170
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Table ED2.

Length and thickness range and average size of scalloped-sphere phytoliths identified in this study. Based on Piperno et al. (2000), we consider scalloped spheres longer than 72 μm or thicker than 59 μm as coming from domestic varieties of Cucurbita sp.

Site Date cal. yr.
B.P.		 Length
(μm)		 Thickness
(μm)		 Domesticated Depth
Isla del Tesoro 7839-7020 80,361 59,804 Yes 170-180 cm
575 10155-9632 82,524 58,318 Yes 270-280 cm
72,804 65,178 Yes
72,775 54,214 Yes
519 6443-6380 77,884 55,212 Yes 100 cm
82,418 65,752 Yes
75,938 54,452 Yes
75,296 57,433 Yes
FIN-12 4785-4424 81.19 55,162 Yes 90-95 cm
80,653 60,988 Yes
61,005 45,635 No
77,871 67,843 Yes
La Chacra 6707-5826 83,697 59,724 Yes 80-84 cm
78,895 52,993 Yes
7350-6945 75,789 56,754 Yes 108-113 cm
8530-7965 63,119 41,238 No 140-145 cm
9212-8665 75,419 65,484 Yes 160-165 cm
Isla Manechi 3319-3007 74.28 52.33 Yes 25 cm
72.7 57.57 Yes
78.49 50.79 Yes
81.34 48.89 Yes
70.1 45.38 Yes
78.12 64.79 Yes
61.29 51 No
69.22 56.6 No
61.78 46.56 No
59.96 49.13 No
4957-4728 68.67 54.95 No 55 cm
57.22 40.23 No
70.53 49.5 No
63.21 49.51 No
70.59 44.29 No
81.74 66.85 Yes
72.76 58.61 Yes
5288-4965 74.27 57.12 Yes 85 cm
74.53 45.13 Yes
58.98 44.15 No
81.95 56.8 Yes
68.1 59.06 No
66.84 55.37 No
76.91 49.26 Yes
74.69 47.15 Yes
84.72 60.19 Yes
10284-10196 78,173 66,108 Yes 105 cm
84,996 67,836 Yes
72,601 54,422 Yes
64,201 50,158 No
84,858 64,479 Yes
68.44 57.37 No
81.82 60.62 Yes
86.81 63.17 Yes
10664-10380 60.46 51.16 No 145 cm
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Supplementary Material

Supplementary Information is available for this paper.

Supplementary Information

Acknowledgments

We acknowledge the support of the Bolivian Ministerio de Culturas y Turismo, the Gobierno Autónomo Departamental del Beni, and the owners of the properties where the study sites are located: J.P. Llapiz, F. Boheme, J. Rivero, O. Sikuajara, F. Velasco and T. Boorsma from the Barba Azul Natural Reserve. We thank L. Rodrigues, N. Zihlmann, G.P. Fernández and L.M. Ortega for participation during fieldwork, as well as E. Canal-Beeby, M. Madella, D. Mckey, J Carson, Mario González and Silvia Tin for their support at different stages of this work.

Funding

This work was supported by Swiss National Science Foundation grant nos. 200020-141277/1 and P300P2_158459/1; Marie Skłodowska-Curie Actions EU Project 703045; PAST project funded by the European Research Council (ERC), grant agreement No. ERC_Cog 616179; National Geographic Society grant HJ-074ER-17; TerraSAR-X/TanDEM-X mission, grant no. DEM_OTHER1040; AHRC-FAPESP MoU research grant HERCA, reference AH/S001662/1

Footnotes

Author contributions: U.L. designed the research. U.L., J.M.C., J. RP. and H.V. conducted the fieldwork. J.M.C. and J.RP conducted the archaeological excavations, U.L. conducted the GIS mapping and analyses. U.L., L.H., J.RP., and J.I. carried out the phytoliths analyses. U.L. and J.I. wrote the paper with the help of all authors.

Competing interests: The authors declare that they have no competing interests.

Data and materials availability: All data needed to evaluate the conclusions in the paper are included in the paper or in the Extended Data. Code used for 14C calibration in OxCal is available in Supplementary Information.

Reprints and permissions information is available at www.nature.com/reprints

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