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Shifting to Sedentism: Salvaging Evidence of the Earliest Inhabitants of Quito

Eric Dyrdahl, Pontificia Universidad Católica del Ecuador, Project Grant 2018–2019

Relatively little is known about the populations that occupied various parts of South America in the range of time between the Paleoindian and Formative periods. The northern Ecuadorian sierra, and in particular what is now modern Quito, is one such example. Evidence of Paleoindian occupation in the Quito Valley, dating to roughly 10000 cal BC, has been found at the site of El Inga, located on the slopes of the dormant Ilaló Volcano (Salazar 1980, Bell 2000, Nami and Stanford 2016, Ugalde 2019:22). Until recently, this was followed by a more than 8000-year archaeological silence in the regional chronology, with the earliest evidence of occupation at the Formative type site of Cotocollao dating to roughly 1500 cal BC (Villalba 1988:244–45, Ugalde 2019:23).

The evidence from Cotocollao creates the impression that sedentary agricultural villages with well-developed ceramic assemblages abruptly appeared in Quito with no clear precedents (Ugalde 2019:24–25). Considering our knowledge of the development of these patterns elsewhere in the world, it is likely that the shift to a sedentary agricultural lifestyle was more gradual and we simply have not yet discovered the antecedents to the Formative in much of Ecuador (Bruhns 2003:127). On the plateau that constitutes much of modern Quito, isolated finds at sites like Rumipamba indicate that pre-Formative populations were present in the region. Unfortunately, relatively little attention has been paid to these limited pieces of evidence available only in unpublished reports.

Fig. 1. Map of excavations at Rancho Bajo (illustration: Carlos Montalvo)

Rancho Bajo, located in the northern extreme of urban Quito, provides an important opportunity to document the preceramic populations that occupied Quito prior to Formative Cotocollao groups. The site was discovered in 2011 when a private landowner uncovered a Pre-Columbian cemetery while digging in his patio (Figure 1) (Ugalde 2019:15). In the two research campaigns realized prior to the fieldwork discussed in this report, a portion of the cemetery was excavated (27 individuals), as well as a nearby area dedicated to the production of lithic tools. Both of these activity areas are associated with a burnt paleosol that covers at least a 250 m2 area (Ugalde 2019:16). No ceramic artifacts were found in the excavation of these contexts.

Both the site’s stratigraphy and radiocarbon dates indicate that this preceramic population occupied the area prior to Formative groups. The burnt paleosol is located in Deposit 8, directly below Deposit 7, which contains Cotocollao ceramics. Radiocarbon dates suggest that the occupation that utilized the contexts associated with the paleosol ran from 1600–1450 cal BC, immediately prior to or slightly superimposed with the proposed beginning of the Cotocollao occupation (Villalba 1988:244–45, Ugalde 2019:23).   

The fact that Rancho Bajo is located at the margins of Quito´s urban sector makes it especially susceptible to destruction. A third field season at Rancho Bajo began in 2018 under the direction of Carlos Montalvo, María Fernanda Ugalde, and Eric Dyrdahl. The original proposal called for 64 m2 of excavations until reaching sterile soil on a parcel of land located 25 m to the south-southwest of the Pre-Columbian cemetery. All of the archaeological evidence on this terrain was destined to be destroyed as part of the construction of a tower for the Quito Cables project. The grant provided by Dumbarton Oaks allowed us to expand our excavations to 80 m2 while also dating six additional radiocarbon samples. As part of the project, we also took advantage of ongoing construction of sporting fields on land located 80 m to the northwest of the first discoveries at Rancho Bajo. In this area, we excavated 8 m2 until reaching sterile soil and another 45 m2 to various depths.

Fig. 2. Aerial photograph of 32 m2 block of excavations with paleosol exposed in majority of area (photograph: Carlos Montalvo)

The additional 16 m2 excavated on the first parcel of land were placed alongside another 16 m2 block of excavations located as close as possible to the discoveries from previous field seasons. This was done with the goal of exposing a contiguous 32 m2 swath of the burnt paleosol in order to better understand its characteristics and analyze the distribution of any associated artifacts (Figure 2). Unfortunately, a small water channel that likely was utilized during later prehispanic times cut through a portion of the relevant stratigraphy in the original 16 m2 block.

These excavations uncovered the same stratigraphic sequence noted elsewhere. Beneath the volcanic ash produced by the eruption of Pululahua around 467 cal BC (Zeidler 2016:80), a 20–30 cm deposit with Formative Period artifacts was discovered (Deposit 7). The burnt paleosol is located directly beneath the Formative deposit. In this area, only a small concentration of lithic material was found directly on the paleosol. The relative lack of cultural material associated with this surface suggests that it might have been cleaned with some regularity.

Fig. 3. Unifacial obsidian tool recovered from a stratigraphic context dating to 3341/3247–3100 cal BC. Artifact was not cleaned in order to include the piece in an ongoing study of microbotanical evidence (photograph: Eric Dyrdahl).

Where the support provided by Dumbarton Oaks made a significant impact was in the characterization of the archaeological evidence beneath this paleosol. When we excavated a portion (8 m2) of this excavation block until reaching sterile soil, we found small quantities of lithic artifacts, mainly obsidian, associated with a more formal technology than the obsidian assemblages from the paleosol and Formative deposit (Figure 3). A radiocarbon sample from a 5 cm layer with 20 obsidian artifacts was dated to 4445/4374–4324/4269 cal BC with 95.4% confidence (all dates from investigation calibrated with IntCal13 [Reimer et al. 2013]).

Similar results were obtained from the excavations on the other terrain. While the burnt paleosol was not documented in this area, we uncovered a stratigraphic sequence of roughly 3 m below the eruption of Pululahua. In the deposit associated with preceramic populations (Deposit 8), we found possible fragments of groundstone tools at depths more than a meter below the upper limit of Deposit 8. A portion of a carbonized seed from the earliest stratigraphic position with a likely tool fragment was dated to 2460–2290 cal BC with 95.4% confidence. The discovery of fractured groundstone tools and carbonized seeds in stratigraphic contexts dating to at least 800 years earlier than the beginning of the Formative represents a major step forward in our knowledge related to the transition to agriculture in the northern Ecuadorian highlands.

On a final and related note, the financial support from Dumbarton Oaks also enabled us to expand the number of radiocarbon dates for this second excavation. The suite of dates suggests that the stratigraphic sequence is intact. The earliest date is 4437/4370–4321/4266 cal BC, which is similar to the date from the other excavation. The congruency of these two dates suggests that Pre-Columbian occupation of this zone likely began at this time. Another important chronological discovery was the date for a carbonized seed whose δ13C value (-9.15) suggests it likely was a maize seed. This sample was dated to 3341/3247–3100 cal BC, a range that makes this sample the earliest macrobotanical evidence of maize agriculture in the northern Ecuadorian highlands. Athens and colleagues (2016) identified maize phytoliths in a core from Lake San Pablo that date to as early as 4650 cal BC, but no early macrobotanical evidence.

In conclusion, the support from Dumbarton Oaks helped document important information related to early agriculture and sedentism in Quito that otherwise would have been lost. The recovery of archaeological evidence stretching as far back as 4400 cal BC signifies a crucial discovery that should help promote the protection of cultural patrimony as well as the development of additional archaeological projects in the Rancho Bajo area.


References Cited

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Salazar, Ernesto. 1980. Talleres prehistóricos en los altos Andes del Ecuador. Cuenca: Departamento de Difusión de la Universidad de Cuenca.

Ugalde, María Fernanda. 2019. “Rancho Bajo: Primeras evidencias del Precerámico Terminal en Quito.” Arqueología Iberoamericana 42:14–27.

Villalba, Marcelo. 1988. Cotocollao: Una Aldea Formativa del Valle de Quito. Quito: Museo del Banco Central del Ecuador.

Zeidler, James A. 2016. “Modeling Cultural Responses to Volcanic Disaster in the Ancient Jama-Coaque Tradition, Coastal Ecuador: A Case Study in Cultural Collapse and Social Resilience.”  Quarternary International 394:79–97.