Evidence of eared doves consumption and the potential toxic exposure during the Regional Development period in Quito-Ecuador

Abstract

Throughout history, food has played a fundamental role in the development of societies. An understanding of the diets of different cultures and their impact on health can provide valuable insights into their lifestyle. The identification of the animal remains found within two vessels is reported and, in addition, an assessment of whether the diet and soil composition of the period may be associated with toxic elements was carried out. The animal bones retrieved from the settlement, which dated from 25 to 203 cal AD, were identified as belonging to Zenaida cf. auriculata, commonly known as eared dove. Ancient starch was discovered in the sediments inside the vessels. These sediments, along with the pre-Hispanic soil collected in the study zone, showed moderate pollution, suggesting potential environmental contamination. For the first time, evidence that eared doves were part of the diet of the ancient inhabitants of Quito is presented, as shown by the occurrence of their bones within food processing utensils. Furthermore, the study highlights the possibility of environmental contamination due to volcanic eruptions that occurred during the Regional Development period from 500 BC to AD 500. These results can contribute to a better understanding of the living conditions of the early inhabitants of Quito and similar regions.

Introduction

The study of tombs has been a crucial aspect of the understanding of pre-Hispanic cultures in the Andean region, offering significant insights into various socio-political, religious, and economic processes of the era¹. Moreover, animal bones recovered from these tombs can be used to achieve a deeper understanding of dietary practices. Additionally, the trousseau has enabled the identification of available food resources and social stratification, revealing the disparities in foodstuffs among individuals of different social classes². In this context, the Tablada de Luríen cemetery, situated on the central coast area of Lima (Peru), has been a subject of interest for archaeologists due to its rich historical and cultural significance. Dating back to the period 200 BC-AD 200, the site has yielded a plethora of interesting findings, including a collection of animal bones belonging to species such as deer “taruca” (Hippocamelus antisensis), alpaca (Vicugna pacos), llama, pelican (Pelecanus sp.), and Andean condor (Vultur gryphus), which were discovered near human remains. It is important to note that not all of these animals were necessarily consumed as part of the daily diet of the people who inhabited the area, as not all the bones displayed lesions, nor were they found within vessels which suggests that they may have been intended as funerary offerings³.

The eared dove (Zenaida auriculata) belongs to the order Columbiformes and coexists with other species of pigeons and doves. This species is found in the Caribbean area and many regions of South America. It exhibits a synanthropic behavior and tends to live close to humans. Eared doves prefer semi-arid climates and are used as a food source in some areas of the region. However, they may also be involved in the transmission of zoonotic diseases^4,5. In particular, Ecuador is renowned for its exceptional biodiversity. The International Ornithological Committee reported that the country boasts a list of 1722 bird species, of which 1673 have been confirmed, and 49 remain undocumented as of the year 2022⁶. In 2015, a Christmas Bird Count was conducted in the urban and peri-urban areas of Quito, Ecuador. The count encompassed parks, reservoirs, streams, natural areas, and routes in proximity to the city, notably Puembo, Tababela, and Pululahua. The study revealed that the Zenaida auriculata was the most frequently observed bird species in the city. Subsequently, in 2017, a bird diversity sampling was performed on the campus of a university situated in the center-north of Quito. The study found that the eared dove, Zenaida auriculata, was the most prevalent bird species on that campus. These studies highlight the ecological significance of the Zenaida auriculata in Quito’s avifauna^7,8.

Quito, the capital city of Ecuador, boasts a rich pre-Hispanic history marked by the migration of people and the establishment of settlements. This history spans from 11,000 BC to AD 1534 and is divided into several distinct periods: Preceramic (11,000–1500 BC), Formative (1500—500 BC), Regional Development (500 BC–AD 500), Integration (AD 500–1500), and Inca period (AD 1500—1534)^9,10. The Regional Development period is particularly noteworthy because four volcanoes near the city (“Pichincha, Pululahua, Atacazo, and Cotopaxi”) erupted during this time. These eruptions led to the loss of crops, water, flora, and fauna, and caused the city to be uninhabited for almost a thousand years. As a result, people moved to live in nearby valleys, primarily in “Jardín del Este”, which is now the parish of “Cumbayá”^9,11,12. The contemporary urban center of Quito has been exposed to environmental conditions caused by volcanic eruptions that caused an excess of volcanic ash in the environment and, perhaps, toxic metals to contaminate the soil. The consensus was that the current territory of Quito was entirely uninhabited during the period of Regional Development. However, a recent discovery of a settlement in Llano Chico, a parish in the urban perimeter of the city, has opened up new hypotheses that some of the ancient settlers stayed in certain areas and were possibly exposed to toxic elements derived from volcanic ash¹³.

The Llano Chico excavation revealed an atypical discovery of bones contained within two vessels, as opposed to their usual location on the tomb floor in archaeological contexts. The primary research objectives were twofold: firstly, to establish the animal species to which the bones belonged, having been found within two vessels dated to the Regional Development period in tombs located in the Llano Chico sector of Quito. Secondly, in consideration of the environmental conditions of Llano Chico and the potential influence of volcanic activity, the occurrence of toxic elements in soil and sediments recovered from cooking vessels was determined and evaluated. The analysis aimed to determine whether the food prepared in the vessels may have been compromised by environmental pollution. The initial phase involved an examination of the sediment to detect evidence of food processing through the identification of ancient starch, followed by the analysis of toxic elements. This exploration opened the discussion on the potential toxicity in the environment and food to which the population who lived in Quito during that period may have been exposed.

Results

Faunal remains retrieved from two pre-Hispanic vessels in Llano Chico, Quito, Ecuador, were subjected to identification to ascertain their potential use as a food source. Furthermore, an analysis of toxic elements was conducted at various points within the context of the bone recovery, in light of the likelihood of food contamination by volcanic eruptions across the city’s history.

Archaeological context

During the 2022 excavation, conducted by the Metropolitan Institute of Quito (IMP), a settlement was uncovered in the “La Dolorosa” neighborhood, located in the parish of Llano Chico, Quito’s northwestern region. The excavation area spanned 82 m of the southern section of streets: 2 de Agosto, Feliciano Checa, Manuela Cañizares, Manuela Sáenz, and 92 m south of Rosa Vélez Street. Magnetic prospecting was conducted to identify areas of archaeological interest. As a result of the concentration of evidence at the intersection of Manuela Cañizares and Manuela Sáenz Streets, two excavation cuts were made at this location. In the first cut, a total of eight features were recorded. The present investigation focuses on the materials found in features 4 and 7, both corresponding to human graves which contained goods and funerary offerings including vessels and fauna bones associated with it. Figure 1 illustrates the grave locations where the bones were found inside the vessels and the general stratigraphic column in the parish of Llano Chico. Stratigraphical indicators like the presence of volcanic ash attributed to Pichincha Volcano, in association with one carbon-14 datation obtained from a dental piece, recovered at feature 7 were used to locate the studied contexts in the Regional Development period¹³.

Fig. 1.

Location of features 4 and 7 where vessels containing faunal remains were discovered in Llano Chico-Quito and the stratigraphic column. Stratigraphy description: D1: modern soil; D1A: soil – cultural occupation deposit; D2: ash from Guagua Pichincha volcano; D3: mud flow; D4A: compact pyroclastic flow; D4: culturally sterile deposit (Note: The map was created using ArcMap 10.3 (https://www.esri.com) by Andres Mosquera, based on data from the excavation of the Llano Chico settlement¹³).

As graves correspond to single closed events in the archaeological process of site formations, the strata identification during the excavation and study of the funerary contexts (excavation of the pit, deposition of the burial and grave goods and filling of the grave) allowed the identification of the D1a and D2 deposits of the site as the ones with human occupation relevant to this research. The occurrence in both strata of components of Guagua Pichincha ash from an eruption dated 1915 B.P., identified by the granulometric analysis, allowed the confirmation of the datation reported earlier in literature^13,14. With this information, the deposition processes developed as follows: The excavation of the grave pits started at D1A deposit, removing also the D2 stratum; after the offerings and the deceased remains were deposited, the pits were filled back with D2. Table 1 shows the result of the carbon-14 datation obtained from the sample from feature 7 (estimated age of 1930 ± 20 BP, with a calibrated date range of 25 cal AD to 203 cal AD), and ash of Pichincha Volcano (PICH 86). The analysis of PICH 86 was carried out at the Center for Applied Isotope Studies of the University of Georgia, USA; and the calibration of the datation obtained by Robin et al.¹⁴ (plot and calibration dates are available in Supplementary Figs. 1 and 2).

Table 1.

Absolute dating of archaeological context and soil related to volcanic ash.

Feature	Sample ID	Material	14C yr BP	±	Calibrated range (2 sigma) 95.4% confidence level yr BP
Feature 7	CO-1C-04	Enamel	1930	20	1925–1747
PICH 86	PICH 86	Ash	1915	50	19801715

Feature 7 was dated from a tooth from the burial recorded in the archaeological context at Llano Chico. Data for sample PICH86 were taken from Robin et al. (2008:11)¹⁴ and calibrated again in the framework of the present investigation. (Calibrated at 2 sigma with the OxCal 4.4 program, using IntCal20 calibration curve; Reimer et al.¹⁵). Plot and calibration dates are available in Supplementary Figs. 1 and 2.

Particular attention is drawn to the funerary offerings discovered in unit 1, within the graves identified as features 4 and 7, situated approximately 4 m apart. The finds in Feature 4 indicated a secondary burial, with two vessels and disarticulated bone remains being discovered (Fig. 2a). Among these remains, a globular vessel (Fig. 2a-1) stands out due to the presence of faunal bones. On the other hand, Feature 7 yielded bone remains, ceramic fragments, and three tripod vessels, which corresponded to a primary burial (Fig. 2b). In addition to these, a tripod vessel (vessel 2) with faunal bones (Fig. 2b-1) was also located. Notably, out of the entire excavation and the subsequent findings, only the vessels discovered in Features 4 and 7 were found to contain bones.

Fig. 2.

Vessels containing faunal bone remains were unearthed at the archaeological site of Llano Chico (25 cal. AD – 203 cal. AD). (a): Vessels and bone remnants observed within a secondary burial context. (a-1): Globular vessel containing faunal remains. (b): Vessels and bone remnants associated with a primary burial setting. (b-1): Tripod vessel containing faunal remains.

Analysis of faunal remains

Diagnostic material discovered in Vessel 1

The bone samples collected for diagnosis comprised the proximal portion of the humerus, a proximal fragment of the femur, a proximal fragment of the coracoid, a proximal fragment of the radius, and the ulna fragment, as depicted in Fig. 3. A comparative analysis was conducted to determine the taxonomic classification of sample 1, which was found to belong to Class: birds, Order: Columbiformes, Family: Columbidae, Genus: Zenaida, Species: Zenaida cf auriculata, commonly known as eared doves (in Spanish, “tórtola”) and was derived from a single individual.

Fig. 3.

Diagnostic materials for taxonomic identification of faunal remains recovered from vessel 1. (a): Faunal remains discovered within vessel one. (b): coracoid bones (c): proximal femur segment (d): proximal humerus segment e: Proximal radius segment f: articular ulna fragment. The archaeological material displayed in images b, c, and f is situated on the left side, while that in images d and e is located on the right. Bone material derived from a contemporary Zenaida auriculata individual is observed on the right side in images b, c, and f, whereas in images d and e, the same material is situated on the left side.

Diagnostic material discovered in Vessel 2

Figure 4 displays diagnostic material obtained from vessel number two, which comprised a proximal fragment of the humerus, a fragment of the scapula, and two distal fragments of coracoid bones (left and right). Taxonomic determination of the bones was made following a thorough analysis, which enabled the identification of the class, order, family, genus, species, and common name of the bird from which the bones originated. The order was identified as Columbiformes, family Columbidae, genus Zenaida, the species as Zenaida cf. auriculata, and the common name as eared doves. The material was obtained from a single individual.

Fig. 4.

Diagnostic materials for taxonomic identification of faunal remains recovered from vessel 2. (a): Faunal remains discovered within vessel one (b): proximal humero segment (c): proximal scapular fragment (d): distal coracoid portions. In Images b and c, the archaeological material is displayed on the left side, while the bone material of an individual of Zenaida auriculata on the right side. In Image d, the archaeological material (left and right fragments) is positioned at the bottom.

The identification of Zenaida cf. auriculata was determined through anatomical comparison of bones recovered from the site with specimens from the Department of Biology at the Faculty of Sciences of the Escuela Politécnica Nacional (EPN). Additionally, the bones were cross-referenced with the species descriptions of Z. auriculata and Z. meloda outlined in Tellkamp (2019) study¹⁶. The bones discovered in the vessels correspond to the description of the bones of Z. auriculata, however, there are differences in the characteristics of the Z. meloda bones.

Recovery of ancient starch

The analysis revealed the presence of ancient starch in two vessels containing faunal remains. Comparative analysis of the starch samples with ancient and contemporary sources enabled the identification of starch granules from maize (cf. Zea mays), manioc/cassava (cf. Manihot), potato (Solanum spp.), sweet potato (Ipomoea spp.), and a cluster of multiple starch granules within vessels associated with cooking activities. This seems to confirm the use of the vessels for the preparation and/or manipulation of food. In Fig. 5a and a1, the images depict a potential cassava starch granule under normal and polarized light. These images suggest that the granule may have undergone initial milling and subsequent rapid or no cooking at high temperatures¹⁷. Figure 5b and b1 exhibit an altered starch granule, displaying characteristics consistent with potato starch. The granule exhibits gelatinization properties indicative of cooking in a high-temperature, humid environment, and an alteration of its extinction cross is observable ^18,19.

Fig. 5.

The first column contains ancient starch granules retrieved from vessels with animal bones at Llano Chico. (a) possibly manioc/cassava starch. (b) starch granule possibly from a tuber. Each granule is shown in bright light, and to its right, the same granule is shown under polarized light. The second column displays the toxic elements that suggest contamination according to the Enrichment Factor (EF) and the Pollution Load Index (PLI). (a) toxic elements identified within pre-Hispanic soils. (b) toxic elements identified in vessel sediments. (c) toxic elements identified in contemporary soil. Red PLI: moderate pollution. Green PLI: non-polluted.

Potentially toxic elements

Table 2 presents the values obtained for potentially toxic elements in Pre-Hispanic soil from Llano Chico, soil sample within vessel 1, soil sample within vessel 2 (group 2), food-related sediments in the vessels (food-related sediment) samples and soot (group 1), and the control group of current soil in Llano Chico. The enrichment factor (EF) of each element and the general pollution load index (PLI) were used to identify possible contamination in soil and food. According to their EF values, the elements found in the vessels (group 1) that could pose a risk to pre-Hispanic food, in descending order, were Se > Zn > Cu > V > Co > Ni > Cr. For the pre-Hispanic soil in Llano Chico (group 2), the elements that could be considered soil contaminants were Se > Co > V, Zn > Ni > Cu > Cr. Se was the element that showed the highest pollution potential to food in all samples, including the control group. Zn showed moderately polluted results for both groups of pre-Hispanic samples, while Co and V showed moderate pollution for group 2, and Cu for group 1. The elements that showed slight pollution were Co, Cr, Ni, and V for group 1, and Cu, Cr, and Ni for group 2. The control group of contemporary soil in Llano Chico had lower contamination values in general compared to the samples from the Regional Development period and showed slight pollution for the following elements: Co > V > Zn > Ni.

Table 2.

Concentration of potentially toxic elements (mg/kg) identified in the Llano Chico settlement: associations with volcanic eruptions and implications for health risks. TME: Trace metal element. Group 1: sediment within vessel 1, sediment within vessel 2, soot within vessel 2. Group 2: Pre-Hispanic soil from Llano Chico, soil sample within vessel 1, soil sample within vessel 2. Control: Current soil control. *The inclusion of the term “Yes” denotes the discovery of elevated concentrations of metal within soil, water, food sources, or animal populations, with its occurrence intricately linked to volcanic eruptions. The values in parentheses within the initial column denote the maximum permissible limit of the respective element in the soil as stipulated by Ecuadorian regulatory standards. NP: non-polluted.

TME	Group 1			Group 2			Control	Associated with volcanic eruptions* Observations/Health hazard
As	6.59	3.59	2.86	5.68	4.38	6.09	2.28	Yes: Ref: 20–22	This metal was detected to be below the regulatory thresholds established for soil in Ecuador
Mean		4.35			5.38
EF (12)		0.36 (NP)			0.45 (NP)		0.19 (NP)
Cd	0.16	0.11	0.18	0.10	0.15	0.28	0.11	Yes: Ref: 23–25	This metal was detected to be below the regulatory thresholds established for soil in Ecuador
Mean		0.15			0.18
EF (0.5)		0.31 (NP)			0.35 (NP)		0.22 (NP)
Co	17.52	16.38	15.49	15.76	26.16	39.58	14.74	Yes: Ref: 26–28	Vomiting, nausea, diarrhea, hemorrhaging, hypotension, cardiac ailments, thyroid dysfunction, alopecia, skeletal abnormalities, and the suppression of certain enzyme functions29
Mean		16.46			27.17
EF (10)		1.65 (SP)			2.72 (MP)		1.47 (SP)
Cu	111.14	17.70	36.26	22.40	15.21	54.18	12.66	Yes: Ref: 30–32	Gastrointestinal manifestations including nausea, abdominal pain, and diarrhea, as well as liver-related disorders such as infantile cirrhosis in infants and children. Its potential as a tumor promoter, pathogenic processes underlying liver disorders and neurodegenerative alterations33
Mean		55.03			30.60
EF (25)		2.20 (MP)			1.22 (SP)		0.51 (NP)
Cr	79.20	43.53	48.97	44.64	70.21	77.49	42.09	Yes: Ref: 32,34,35	Depending on its oxidation state, exposure to this substance may elicit various adverse effects, including nasal irritation and ulceration, hypersensitivity reactions leading to dermatitis, acute bronchitis, emphysema, liver and kidney diseases, lung and skin cancer, internal bleeding, diminished immune function, suppression of cellular enzymes, and DNA damage36
Mean		57.23			64.11
EF (54)		1.06 (SP)			1.19 (SP)		0.78 (NP)
Ni	38.54	19.11	25.71	19.64	26.72	38.64	20.65	Yes: Ref: 23,32,34	Contact dermatitis, headaches, gastrointestinal and respiratory symptoms, pulmonary fibrosis, renal and cardiovascular ailments, as well as lung and nasal cancers, have been documented as consequences of exposure. Moreover, evidence suggests that it induces mitochondrial dysfunction and prompts epigenetic modifications37
Mean		27.79			28.33
EF (19)		1.46 (SP)			1.49 (SP)		1.09 (SP)
Pb	10.53	6.90	4.92	33.68	7.31	7.22	5.95	Yes: Ref: 23,26,32	This metal was detected to be below the regulatory thresholds established for soil in Ecuador
Mean		7.45			16.07
EF (19)		0.39 (NP)			0.85 (NP)		0.31 (NP)
Se	5.05	4.20	4.17	6.94	9.48	3.77	3.55	Yes: Ref: 38–40	Induces complications through food intoxication such as diarrhea, nausea, and vomiting. Potentially posing a risk factor in the development of type 2 diabetes mellitus and likely in non-alcoholic fatty liver disease41,42
Mean		4.47			6.73
EF (1)		4.47 (HP)			6.73 (HP)		3.55 (HP)
V	159.97	115.62	121.70	134.27	181.66	192.97	102.13	Yes: Ref: 26,43,44	Vanadium absorption via dietary intake is generally minimal. However, inhalation of vanadium oxides can result in rhinitis and transient irritations of the respiratory tract. Additionally, pulmonary dysfunctions such as bronchitis, pneumonia, and asthma may occur. Animal studies have indicated that excessive vanadium ingestion can induce severe outcomes including paralysis, convulsions, and fatality45
Mean		132.43			169.64
EF (76)		1.74 (SP)			2.23 (MP)		1.34 (SP)
Zn	90.21	88.41	297.35	79.61	122.57	181.91	74.54	Yes: Ref: 23,34,46	Muscle fatigue, chest pain, cough, respiratory distress, fever, acute gastrointestinal illness, vomiting, cramps, diarrhea, and epigastric pain are among the reported symptoms. Furthermore, it has been implicated in the etiology and progression of prostate cancer47
Mean		158.65			128.03
EF (60)		2.64 (MP)			2.13 (MP)		1.24 (SP)
PLI		1.18 (MP)			1.38 (MP)		0.74 (NP)	Pre-Hispanic sediment and soil: MP Current soil: NP

The Pollution Load Index (PLI) results for Group 1 and Group 2 were 1.18 and 1.38, respectively, indicating that the soil in the studied area is moderately polluted. However, the soil in Llano Chico area scored 0.74, which suggests that it is not considered to be polluted. It is noteworthy that the elements analyzed in this study can be attributed to volcanic eruptions, as suggested in reports previously published. Table 2 presents information on the occurrence of potentially toxic elements due to volcanic eruptions, Supplementary Table 1 shows the concentration of all the metals measured by ICP-MS.

Figure 5 presents a photo of the excavation of vessel two in cut 1, unit 1, feature 4, revealing tripod vessels, human skeletal remains, the soil from the period under investigation, and the current soil layers. In addition, the potential contamination hazard related to relevant elements is depicted taking into account the EF values. The data is presented in three sections, with section A including data for the pre-Hispanic soil, section B including data for the vessels and sediments, and section C including data for the current soil. The findings reveal that samples of sections A and B exhibit a PLI colored in red, which means moderate pollution at the site, while the PLI of the current soil sample is colored in green, indicating no contamination issue. The results provide a comprehensive insight into the contamination hazards affecting the area during the historical period which is referred to in this study and can influence future research works in the field.

Discussion

Throughout history, in archeological research, animal bones were unearthed in diverse burial contexts. However, the discovery of bones within a cooking vessel at Llano Chico is still a remarkable finding since it deviates from the customary pattern of discovering bones solely within the burial⁴⁸. The finding at Llano Chico of animal bones inside a vessel intended for cooking food can be interpreted as a particular ritual practice in which food had to be involved, and certainly, this provides insight into the cultural practices of the people who lived in the area. To understand why bones were found inside the vessels, we suggest that eared doves may have been a common food for the people living in pre-Hispanic Quito. This could explain why the bird bones were present in both primary and secondary burials. To support this idea, we can refer to Pedro Cieza de León, who visited the Quito location in the sixteenth century. In 1553, he published "The Chronicle of Peru," which contains numerous details about the customs of the Andean people. Among the most noteworthy points in his writing, the author makes specific reference to the food consumption habits of the natives in Quito, noting their consumption of deer, rabbits, partridges, pigeons, and eared doves⁴⁹. This description holds significant relevance for our investigation as it provides firsthand observation of the people in Quito consuming eared doves. This implies that the tradition of consuming these birds, along with deer and rabbits, may have originated long ago. Consequently, we propose that our findings could be the earliest documented evidence of eared dove consumption in Quito. To provide additional information about bird consumption in Quito, we can refer to the research of Pennycook⁵⁰, which analyzed stable isotopes in the Tajamar settlement during the Formative period. The study indicates that there was bird consumption in the region, and specifically, bird bones were found in the faunal sample inventory of the site. Unfortunately, the research did not include a paleontological study to identify species. However, these conclusions allow us to know that birds were consumed in Quito before the Regional Development period, which may have continued to intensify over the years.

In the Stone Age of northern Europe, two burial sites, Middle Neolithic Ajvide (Gotland, Sweden) and Mesolithic and Neolithic Zvejnieki (Latvia), were discovered. These sites have yielded bones of various birds including ducks (Anatidae), jays (Garrulus glandarius), whooper swans (Cygnus cygnus), and guillemots (Uria aalge). These bones were not found in the context of feeding but were instead used for decorative purposes such as necklaces, ornaments, and whistles. Furthermore, the wings of the birds were found near the hands of the deceased, which could indicate that they were given as a tool to symbolize the person’s ability to fly⁵¹. This discovery allows for a symbolic interpretation of the context in which the bird bones were found. For instance, the discovery of eared doves in Llano Chico, located inside a vessel, may have represented their significance as a vital component of the population’s daily diet. This may explain why the deceased were provided with this food. The presence of bird bones in grave goods has been associated with art, economy, and as a source of food. In general, the presence of bird bones in burial sites reveals specific symbolic meanings within the community⁵². The use of birds in burials is a common practice across all cultures and has been a part of people’s lives for centuries. For instance, in Ipiutak, Alaska, it is believed that humans interacted with birds for at least 2000 years. In the grave of a shaman, archaeologists discovered a loon (diver) skull with ivory eyes. The interpretation of this burial practice is that the shaman’s spirit was that of a bird, even though he inhabited a human body. This burial ritual demonstrates how the people of that time understood death as a transformation, and they believed that different parts of birds would aid the deceased on their journey⁵³. Despite their mystical significance, birds have played a crucial role in the livelihood of ancient communities, serving as a primary source of sustenance. While they were hunted for their meat, eggs, and other nutritional benefits, they were also regarded as objects of veneration and artistic inspiration. It was demonstrated that their bones, feathers, and claws were often transformed into ornamental items that held symbolic value in the community, and their use was often linked to high social status⁵⁴. The eared doves found in Llano Chico exhibited no lesions indicative of their use beyond that of a food source. However, given the significant role that birds played in the daily diet of ancient people and their potential use in funerary rituals, it is plausible that their placement inside vessels was not solely for nourishment purposes. This assertion is supported by the historical use of bird bones in ceremonial practices and their association with various rituals depicted in ancient iconography^55,56. Archaeological reports in Ecuador have indicated the presence of a diverse range of bird species in burial contexts. However, there is a lack of analysis on the significance and importance of these species to the people of that time. The avian species belonging to the Zenaida genus present in Ecuador include galapagoensis (endemic to the Galapagos Islands), meloda (inhabiting the coastal region below sea level), and auriculata (found across all regions)⁵⁷. This observation is intrinsically linked to our identification of Z. auriculata, as this species shares its habitat in the Andes Mountains, an area where the other two species are absent.

A noteworthy investigation into the zooarchaeology of birds in Ecuador was conducted by Tellkamp¹⁶. The study provides a general review of the birds found in the burials of the people of Guangala at the El Azúcar archaeological site, which was excavated from 1986 to 1988. The bones found by the archaeologists were not inside vessels but were buried near the human bodies. While the passage of time had resulted in a significant number of bones being in poor condition, the study identified 686 individuals, an unusual amount of bird bones for these contexts. Icteridae with songbirds (Passeriformes) had the highest representation, followed by Columbidae with eared doves (Zenaida auriculata). In a related study, the same author investigated zooarchaeology at the La Chimba archaeological site near the Pichincha province in northern Ecuador (2640 to 1700 calibrated years BP). The study revealed the presence of several bird families, including Columbidae. Specifically, the research identified 11 individuals of the species Zenaida auriculata, while Zenaida meloda and galapagoensis were not observed⁵⁸. These findings suggest the exclusive presence of the Z. auriculata species in the Sierra region. The discovery of Z. auriculata within the vessels in Llano Chico corroborates the results of the study conducted at La Chimba. In addition, Stahl and Athens⁵⁹ also conducted research in La Chimba, where their zooarchaeological analysis revealed the presence of the Columbidae family. However, they did not specify the species, only noting that their common name is doves.

This information allows us to interpret how eared doves were present throughout the country during the Regional period for Quito, which underscores the need to explore the relationship between these birds and the different cultures of Ecuador. Although present in pre-Hispanic times, there is no record of their importance and probable mysticism at that time. However, in Llano Chico, they were found inside vessels, indicating a potential significance that should alert archaeologists for their interpretation. Both specimens found in the vessels were identified as belonging to the species Zenaida cf auriculata. The Latin acronym “cf” (= confer) indicates that the two individuals belong to the same group⁶⁰, in this case, the group of doves (Birds, Columbiformes) of the genus Zenaida with an affinity to the species auriculata. Nevertheless, it is not possible to confirm with complete certainty that they are of this specific species since a complete and better-preserved skeleton would be required. Based on comparative analysis and archaeological evidence of the species in the area, it can be concluded that eared doves (in Spanish, tórtolas) were placed in the vessels 2000 years ago. The analysis of the data suggests that the presence of eared dove bones within vessels is indicative of the consumption of these birds. This conclusion is supported by a doctoral thesis that examined the bones found in tombs and refuse deposits at the Llano Chico site. The thesis determined that small and medium-sized birds were part of the site’s diet⁶¹, unfortunately, the study did not specify the family, genus, or species of the birds.

To address the issue of toxic elements, it becomes evident that there is a dearth of studies on palaeopollution that examine the presence of metals in archaeological soils, relics, utensils, and other such artifacts. This knowledge gap poses a significant impediment to the advancement of research in this field, as it limits our understanding of the potential health risks that ancient people may have been exposed to due to the presence of toxic elements⁶². As mentioned, the regional development period in Quito was characterized by several volcanic eruptions, which led to many inhabitants relocating to the valleys surrounding the city. One such example is the eruption of the Guagua Pichincha volcano, which occurred in 1915 BP during the Regional Development period. Another eruption is that of the Pululahua volcano, which occurred between the years 300 and 400 B.C. While evidence of the Pichincha volcano eruption was found in the settlement of Llano Chico, no such evidence of the Pululahua volcano eruption has been discovered in the form of pumice¹³. To determine whether the food could be contaminated during this time, an exploratory study on the possible presence of toxic elements in soils and sediments was carried out. The starch protocol was conducted to retrieve ancient starch, confirming the association of the vessel sediment with food. This marks for the first instance in which such a discovery has been used to establish a connection between toxic elements present in sediment and the diet of that period. Various starches from Andean region food sources were obtained for this study. The detailed results of these findings will be presented in a separate investigation. However, the recovered starches from this study allowed us to conclude that the analyzed sediment, containing toxic elements, was linked to the food preparations within the vessels.

Our findings indicate that the soil in the site and sediments (i.e., residues within the vessels) show a moderate level of pollution, compared to the current (unpolluted) soil (PLI). These results can be compared to the research conducted by Monge et al.⁶³ who analyzed heavy metals in archaeological caves in the Iberian Peninsula, including Gran Dolina, Gorham’s Cave, and El Pirulejo, covering the last million years of human evolution. Although the PLI was not calculated, they did analyze EF, finding levels of Cu, Zn, and Pb above recommended levels. In contrast, our findings in Llano Chico revealed high EF levels of Co, Cr, Ni, Se, and V, as well as Cu and Zn, but not Pb. This difference could be attributed to the fact that the Iberian Peninsula was mainly contaminated by fires and guano deposition, while volcanic eruptions could have been the main factor affecting the environmental quality in the region belonging to today’s Quito about 2000 years ago. It is important to point out that the determination of the content of toxic elements only in soil samples collected from archaeological sites could not be enough to assess potential cases of contaminated food consumption. There is a certain relationship between the content of toxic elements in soil and the content of these elements in vegetables and food products of animal origin produced in this place^64,65. Previous studies have primarily focused on analyzing soil samples and have not considered the organic residues found in vessels. This can limit the assessment of the exposition to food contaminants of ancient people. Nevertheless, Rouhani & Shahivand⁶⁶ conducted a study that analyzed soil samples from four settlements in Tappe Rivi, Iran. The findings revealed the possible contamination in the area and that long-term exposure to these metals could have affected the people who lived there. Results of their research indicated the highest value was 1.77 PLI, which is consistent with our findings and suggests moderate pollution. Thus, further examination of soil and organic residues in vessels is recommended to better assess the extent of contamination and long-term exposure risks.

A remarkable finding in this work is the occurrence, in high concentrations, of Se. This is a micronutrient fundamental for human health. Its excess in the diet, as well as its deficiency, can have detrimental effects such as hair and nail loss and damage; it has even been associated with other health problems such as cardiovascular disease⁶⁷. Moreover, the intake of Se even in its inorganic form, as may have been found in the archaeological site in Quito, can have deleterious effects, such as cardiopathy development, in doses as low as levels 16 µg/day⁶⁷. The main pathway of the potentially toxic elements that may have affected the population of Llano Chico is through their diet. When analyzing modern cultivars of Andean crops some specific aspects need to be taken into account to glimpse how moderate/high concentrations of toxic elements occurring in soils may have impacted the population. In the case of corn, there is no evidence of a preference to particularly accumulate any of the elements⁶⁸. Whereas in potatoes, another major Andean crop, there is evidence suggesting a tendency to accumulate Cd and Zn. Interestingly, the flesh of the tuber has lower concentrations than its peel⁶⁹. Thus, specific dietary costumes may have affected the level of exposure. Research on modern quinoa (Chenopodium quinoa) cultivars has shown differences between genetic lines or cultivars concerning heavy metal accumulation properties. However, the general trend in the case of Ni, Cr and Cd, is that the higher the soil content, the higher the element concentration in the seed and other plant tissues⁷⁰. Similar behavior could be expected for other elements of interest in this work. Still, even when there is some evidence we can gather from the research of modern cultivars, there is a significant gap in the knowledge of the effects and accumulation tendency of metals in Andean crops and its native and heirloom cultivars. Future studies on this topic can provide data useful not only to determine whether or not ancient people were exposed to contaminants through food but also to deal with current issues of food contamination.

The Zhou Yuan site in China has recently yielded a significant archaeological find—a chariot pit containing a four-horse carriage believed to date back to the Shang or Zhou Dynasty. As part of the analysis of this find, soil contaminants were analyzed to determine whether the metals contained in soil could interact with those of the relic. The results of the analysis revealed that the archaeological soil had high concentrations of Cu and Pb, exceeding the recommended levels for China’s soil (local standard 21.4 mg/kg). This suggests that the population of the area may have been exposed to these pollutants⁶². A comparison with Llano Chico, where a similar level of Cu was found but not of Pb suggests that the type of metal contamination suffered by the soil may depend on both anthropogenic and natural factors^46,71. It has been observed that high concentrations of metals, such as Ni, Cr, Zn, and Cu, are found in soils due to volcanic eruptions⁷². These elements were found in concentrations above the acceptable limit for soil in the settlement of Quito. In contrast, there are no traces of Pb or Cd in the Llano Chico samples, which could be because Pb contamination in the Andes region began in the thirteenth century and increased significantly during the Spanish colonial period, along with Cd and Bi⁷³. Therefore, it can be inferred that the absence of high concentrations of these metals in the soil of Llano Chico and other settlements in the region is expected. Unfortunately, the analysis of metal concentrations in archaeological soils in Quito and Ecuador is limited, making it difficult to conduct cross-study comparisons. This presents an opportunity for future investigations, particularly in settlements near volcanic areas in Ecuador, to better understand the metal content of these soils. Heavy metals are prevalent in archaeological contexts, with human bones being one of the most investigated fields^74–76. Through such investigations, associations of exposure to heavy metals have been identified across various historical periods, indicating the potential health implications that different societies may have faced due to diverse natural or human-induced circumstances, such as organic matter combustion, tool and utensil manufacturing, among others⁷⁷. Therefore, it is crucial to conduct an initial analysis of toxic elements in organic matter related to food and soil to detect high concentrations before analyzing these elements in bones. This approach would enable the formulation of a stronger hypothesis regarding the probable contamination in the bodies of people and animals.

Conclusions

For the first time faunal bones were found inside two vessels in the Llano Chico settlement. These vessels date back to the years 25 cal AD to 203 cal AD. This finding is remarkable since offers another perspective on the research of ancient diets and cultural aspects of the first inhabitants of Quito. The discovery of a variety of artifacts in burial places is always an opportunity to recover a (hidden) piece of history.

The bones found at the Llano Chico archaeological site, within two vessels, were both identified as belonging to eared doves (Zenaida Auriculata). The discovery of these bird remains within food vessels suggests that eared doves were an important food source during that era. Additionally, it must be noted that the bird bones were found in burial contexts and, therefore, associated with mystical rituals. Further research is necessary to determine the significance of birds for the ancient inhabitants of Quito, including their use in ritual practices at Llano Chico.

During the Regional Development period (500 BC to AD 500), the city of Quito encountered several volcanic eruptions. Based on initial investigations, it was hypothesized that the inhabitants left the area. However, the discovery of the Llano Chico settlement suggests that some people remained in the city despite the volcanic eruptions. These individuals may have been exposed to contaminants. The analysis of toxic elements in the pre-Hispanic soil of the Llano Chico settlement and organic matter related to food (obtained from vessels) indicate an exposition to moderate pollution. The occurrence of Se (and other potentially toxic elements) in higher concentrations in archeological samples of Llano Chico than in current soil in this area is a remarkable finding that supports the theory of the worsening conditions of life due to volcanic eruption in that time.

Based on the findings of this study, it is crucial to conduct zooarchaeological research in areas of Ecuador where faunal bones are unearthed. Furthermore, sites showing evidence of volcanic eruptions necessitate analysis of toxic elements to facilitate studies on palaeopathologies within bones and to investigate potential correlations between diseases and environmental contamination. This approach will contribute to resolving numerous uncertainties in these areas, given that existing information predominantly resides within archaeological reports without expert evaluation.

This work allowed the identification of the dietary patterns and environmental conditions of the inhabitants of the historical period under investigation. Additionally, it provides a foundation for further research in Quito’s settlements, to obtain additional evidence and improve the understanding of the living conditions of ancient inhabitants in the region.

Material and methods

Sample processing

The soil-filled vessels were transported to the IMP laboratory for analysis of possible bone remains. A micro-excavation of each pot was conducted using dental instruments, resulting in the discovery of two vessels containing faunal remains. The remains were carefully sieved to remove excess soil and subsequently placed in sterile bags for transportation to the Department of Biology at the Faculty of Sciences of Escuela Politécnica Nacional (DB-EPN) for paleontological analysis. In order to investigate the presence of toxic elements in the settlement, soil samples were selected from the area where faunal bones were found. The selection of seven samples was based on the availability of the metal analysis that could be performed in the laboratory. Pre-Hispanic soil from the settlement and the soil found inside each vessel were used to obtain the samples, which were then transferred to sterile 5-mL Eppendorf tubes. Before collecting the samples, each vessel was subjected to deep cleaning with a brush to remove all non-adherent materials. Subsequently, sediment, likely associated with food, was isolated using a sterile scalpel and placed in plastic Eppendorf tubes of 2 mL. In vessel number 2, the presence of soot, a black by-product resulting from the combustion of the clay of the vessel, was observed, which was also scraped and stored. Finally, to serve as a control sample, actual soil from the place where the settlement was found was collected with a spatula for later analysis.

Analysis of faunal remains

The analysis involved the identification of two individuals, one was found in each of the vessels. The faunal material was subjected to a thorough cleaning process to ensure that the bones were free of irregularities. Subsequently, the bone fragments of each individual were compared, taking into account variables such as size, shape, main angles of inclination, presence or absence of foramina, and canals. An initial interpretation of the zoological group and other anatomical characteristics of the possible vertebrate group was made based on the anatomy of the bones. The bones were then compared with the osteological collections of vertebrates for paleontology and zoology, which are available to the DB-EPN. The study of the comparative anatomy of the different vertebrate species in the collections analyzed allows for taxonomic determination.

Possible occurrence of toxic elements

Recovery of ancient starch

In order to ascertain the potential relationship between the vessel sediments and food consumption, a starch identification analysis was carried out. Prior to this, our research group had developed and validated a method specifically tailored for laboratory conditions. Through this testing, it was determined that 0.25 g of material would reveal starch granules if the archaeological sample had undergone food processing⁷⁸. The recovery of starch from archaeological samples involves a specific procedure. Firstly, the area must be disinfected with acetic acid. Then, the archaeological material should be directly scraped to obtain the sample. Next, a sterile plastic tube should be used to combine at least 0.25 g of the sample with 1.25 ml of cesium chloride (specific gravity of 1.79 g/cm³). The mixture should be shaken for a duration of 10 min and subsequently centrifuged at 3000 rpm for 20 min. The resulting floating fraction, which may contain starch, is then transferred to a new sterile plastic tube and processed with distilled water through centrifugation at 9000 rpm for 8 min. The floating fraction is discarded, and further centrifugation with distilled water is performed at 5000 rpm for 5 min, repeated twice. The floating liquid is then discarded, and the final fraction of the tube is used and placed on a slide with a drop of glycerol for observation under a microscope. The quantities utilized can be adapted based on the available sample size. The protocol details have been documented in the publication by Ordoñez et al. (2024). The analysis was performed on two vessels containing faunal remains. dentification was performed using an Olympus BX53F optical microscope equipped with an Infinity 2 digital camera and polarized capability. Images were captured under bright-field view using a 40× lens and under polarized light using a 10× lens. The recovered granules were identified through a comparative analysis with the ancient and contemporary starch collection at the INPC laboratory, as well as with ancient starch granules documented in various publications. This comparison involved an examination of specific parameters recommended by Zarrillo⁷⁹, including shape, size, edge angle, hilum, fissures, facets, lamellae, and other characteristics of the extinction cross.

Determination of toxic elements

Soil samples were prepared and analyzed according to Soil Quality-Dissolution for the determination of total element content according to ISO 14,869–1:2001 with minor modifications from the investigations of Gorai & Mandal (2023) and Zulkafflee et al. (2020)^80,81. The soil samples were subjected to a drying process at room temperature followed by a grinding and sieving stage. To extract the elements, present in the sample, 0.5 g of each sample was treated with a mixture of 4.5 ml concentrated hydrochloric acid (HCl) and hydrofluoric acid (HF) and then passed through an argon plasma torch to ionize them. The trace elements present in the samples were analyzed using Inductively Coupled Plasma Mass Spectrometry (Perkin-Elmer, NexION 300, American), ICP-MS at the Research Institute for Humanity and Nature in Kyoto, Japan. Each element was identified using a standard solution and a blank sample (the analysis provides the result of the concentration of 21 elements—supplementary Table 1). The potentially toxic elements were analyzed on those that yielded positive results. According to the annex of soil quality criteria in the Environmental Quality of the Soil Resource and Remediation Criteria for Contaminated Soils in Ecuador (Agreement No 97/A, 2015) the potentially toxic elements to be analyzed are Arsenic (Ar), Cadmium (Cd), Cobalt (Co), Copper (Cu), Chromium (Cr), Nickel (Ni), Lead (Pb), Selenium (Se), Vanadium (V) and Zinc (Zn). These elements are also considered toxic by the environmental regulations of different countries or cities, which are based mainly on EPA regulations⁶³.

Pollution analysis

In order to assess the degree of contamination in the soil due to potentially toxic elements, the Enrichment Factor (EF) parameter was used. This parameter is also known as the Anthropic Factor or Contamination Index. The EF value is calculated by dividing the concentration of the element found in the soil by the maximum concentration that the soil should have according to Agreement No 97/A (2015). The contamination level is determined based on the following criteria: non-polluted (EF < 1), slightly polluted (1 ≤ EF < 2), moderately polluted (2 ≤ EF < 3), and highly polluted (EF > 3)^63,83. To determine the EF value, the analysis of samples were divided into two groups based on their provenance: food-related sediments (group 1), and pre-Hispanic soil with soot (group 2). An average value for each element was calculated for each group of samples, and the EF calculation was performed using these values. Additionally, the Pollution Load Index (PLI) was calculated to assess the degree of contamination in the soil of a specific site. Each individual EF value was multiplied to obtain the PLI and an n-th root was applied, where n is the number of metals evaluated. The resulting range of contamination is as follows: non-polluted (PLI ≤ 1), moderate pollution (1 < PLI ≤ 2), heavy pollution (2 < PLI ≤ 3), extremely heavy pollution (3 < PLI ≤ 4), and extremely heavy pollution (PLI > 4)^66,84.

Author contributions

Conceptualización, R.O-A., L.R-G., P.V-J. and J.R., methodology R.O-A., A.M., J.L.R–C., P.V-J., and J.L.R-P., formal analysis P.V-J., L.R-G., M.R-B., and C.M-P., writing—original draft R.O-A., A.M., J.L.R–C., writing—review and editing, P.V-J., L.R-G., M.R-B., C.M-P., and J.R., visualization, J.L.R-P., supervision, P.V-J., L.R-G., and J.R. All authors have read and agreed to the published version of the manuscript.

Data availability

All data generated or analysed during this study are included in this published article (and its Supplementary Information files).

Declarations

Competing interests

The authors declare no competing interests.

Supplementary Information

The online version contains supplementary material available at 10.1038/s41598-024-84388-y.