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Post by Admin on Jul 27, 2023 0:59:48 GMT
Who lived at Machu Picchu at its height? A new study, published in Science Advances, used ancient DNA to find out for the first time where workers buried more than 500 years ago came from within the lost Inca Empire. Researchers, including Jason Nesbitt, associate professor of archaeology at Tulane University School of Liberal Arts, performed genetic testing on individuals buried at Machu Picchu in order to learn more about the people who lived and worked there. Machu Picchu is a UNESCO World Heritage Site located in the Cusco region of Peru. It is one of the most well-known archaeological sites in the world and attracts hundreds of thousands of visitors every year. It was once part of a royal estate of the Inca Empire. Like other royal estates, Machu Picchu was home not only to royalty and other elite members of Inca society, but also to attendants and workers, many of whom lived in the estate year-round. These residents did not necessarily come from the local area, though it is only in this study that researchers have been able to confirm, with DNA evidence, the diversity of their backgrounds. "It's telling us, not about elites and royalty, but lower status people," Nesbitt said. "These were burials of the retainer population." This DNA analysis works in much the same way that modern genetic ancestry kits work. The researchers compared the DNA of 34 individuals buried at Machu Picchu to that of individuals from other places around the Inca Empire as well as some modern genomes from South America to see how closely related they might be. The results of the DNA analysis showed that the individuals had come from throughout the Inca Empire, some as far away as Amazonia. Few of them had shared DNA with each other, showing that they had been brought to Machu Picchu as individuals rather than as part of a family or community group. "Now, of course, genetics doesn't translate into ethnicity or anything like that," said Nesbitt of the results, "but that shows that they have distinct origins within different parts of the Inca Empire." "The study does really reinforce a lot of other types of research that have been done at Machu Picchu and other Inca sites," Nesbitt said. The DNA analysis supports historical documentation and archaeological studies of the artifacts found associated with the burials. This study is part of a larger movement in archaeology to combine traditional archaeological techniques with new technologies and scientific analyses. This combination of fields leads to a more complete understanding of the discoveries made. More information: Lucy Salazar et al, Insights into the Genetic Histories and Lifeways of Machu Picchu's Occupants, Science Advances (2023). DOI: 10.1126/sciadv.adg3377. www.science.org/doi/10.1126/sciadv.adg3377Journal information: Science Advances Insights into the genetic histories and lifeways of Machu Picchu’s occupants Abstract Machu Picchu originally functioned as a palace within the estate of the Inca emperor Pachacuti between ~1420 and 1532 CE. Before this study, little was known about the people who lived and died there, where they came from or how they were related to the inhabitants of the Inca capital of Cusco. We generated genome-wide data for 34 individuals buried at Machu Picchu who are believed to have been retainers or attendants assigned to serve the Inca royal family, as well as 34 individuals from Cusco for comparative purposes. When the ancient DNA results are contextualized using historical and archaeological data, we conclude that the retainer population at Machu Picchu was highly heterogeneous with individuals exhibiting genetic ancestries associated with groups from throughout the Inca Empire and Amazonia. The results suggest a diverse retainer community at Machu Picchu in which people of different genetic backgrounds lived, reproduced, and were interred together. www.science.org/doi/10.1126/sciadv.adg3377
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Post by Admin on Aug 5, 2023 18:11:50 GMT
Insights into the genetic histories and lifeways of Machu Picchu’s occupants Abstract Machu Picchu originally functioned as a palace within the estate of the Inca emperor Pachacuti between ~1420 and 1532 CE. Before this study, little was known about the people who lived and died there, where they came from or how they were related to the inhabitants of the Inca capital of Cusco. We generated genome-wide data for 34 individuals buried at Machu Picchu who are believed to have been retainers or attendants assigned to serve the Inca royal family, as well as 34 individuals from Cusco for comparative purposes. When the ancient DNA results are contextualized using historical and archaeological data, we conclude that the retainer population at Machu Picchu was highly heterogeneous with individuals exhibiting genetic ancestries associated with groups from throughout the Inca Empire and Amazonia. The results suggest a diverse retainer community at Machu Picchu in which people of different genetic backgrounds lived, reproduced, and were interred together. INTRODUCTION Machu Picchu is arguably the best-known archaeological site in the Western Hemisphere, and, before the 2020 pandemic, it attracted over a million travelers from throughout the world. In recent decades, its image has been used as an icon of the Peruvian nation and a symbol of the historic accomplishments of Latin America’s indigenous peoples (1). Despite its fame, little was known of Machu Picchu’s function and the daily life of its inhabitants until recently. These lacunae were due to the absence of references to Machu Picchu in 16th and 17th century Spanish accounts and the failure of modern investigators to decipher the knotted string records (quipus) that the Incas used to record their history (2, 3). However, over the past two decades, scholars have begun to understand the site as a result of archaeological fieldwork and the application of new scientific techniques to laboratory research. The latter has yielded important results related to the diet and health of Machu Picchu’s ancient population and insights into the daily activities carried out there (4). There is a now a consensus among archaeologists and historians that Machu Picchu was part of a royal estate belonging to the lineage (or panaca) of the emperor Pachacuti (2, 3, 5), the ruler credited with establishing the Inca Empire (or Tahuantinsuyu) (6). The monumental architecture at the core of Machu Picchu is actually the remains of a country palace located within the royal estate of Pachacuti (2, 7, 8). Royal estates were lands claimed by an Inca emperor for his noble lineage that was maintained in perpetuity for the ostensible purpose of caring for and making offerings to the ruler and, after his death, the ruler’s (9). Often, these royal estates were established to commemorate conquests, and Machu Picchu may have been built to celebrate Pachacuti’s conquest of the lower Urubamba Valley (7). The emperor and members of his lineage only resided seasonally in the elaborate palaces built within these country estates, but a retinue of retainers was left behind to maintain the facilities there. The Urubamba Valley was a favored location for royal estates and Machu Picchu, Pisac, Ollantaytambo, and over a dozen others have been identified in the drainage (2, 10). Some royal estates such as Cheqoq lacked palaces but fulfilled economic roles for the panacas such as maize cultivation, pottery production, and salt mining (5, 9). The royal lineages were served by individuals known as yanacona who were ethnically non-Inca and were permanently resettled to attend to the daily needs of the Inca, his , and his guests. The yanacona were believed to be privileged compared to the general population, and this was expressed in their proximity to royalty and material benefits, such as luxury goods (9, 11, 12). They were taken from conquered lands by the emperor or presented as gifts by other panacas, even after the death of the founder of the royal estate (13, 14). The yanacona, who were male, appear to have received wives from the class of females known as aclla, “chosen women” who were severed from their ethnic group and educated in special facilities (15–17). Machu Picchu would have been occupied by several hundred permanent retainers (yanacona and former aclla) throughout the year and, at peak season, a still larger population of attendants, members of the Inca royalty, and their guests. Judging from the intact architecture, it is unlikely that more than 750 people ever resided in Machu Picchu at one time (4). While the Inca elite individuals who visited the palace were buried in the capital of Cusco, the yanacona and former aclla were usually interred in cemetery areas outside the palace walls. Isotopic (12, 18, 19), osteological (20), and artifact studies (21) indicate that there was substantial diversity in this attendant population but these studies have had limited success in answering questions about where the residents came from, how they were related to each other, and how their regional and ethnic background affected the way in which they lived and were buried. This article presents an ancient DNA (aDNA) analysis of a large sample of individuals buried around the palace at Machu Picchu to begin answering these questions. In addition, we provide aDNA results for individuals excavated in the Inca capital of Cusco and nearby sites coeval with Machu Picchu for comparative purposes. These samples highlight the remarkable genomic composition of the Machu Picchu yanacona population and the considerable genomic variability of the Cusco inhabitants.
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Post by Admin on Aug 6, 2023 19:00:48 GMT
Machu Picchu’s occupants Machu Picchu is located in southern Peru on the eastern slopes of the Andes (Fig. 1A) at 2430 m above sea level on a ridge overlooking the Urubamba River. The Urubamba/Vilcanota drainage was a favored location for country palaces by many Inca rulers because of its rich lands, good climate, and proximity to the capital. Located 75 km from Cusco, Machu Picchu would have been especially attractive during the dry season (May to October). The ruler, his family, and his guests would have appreciated Machu Picchu’s tropical climate and vegetation and the absence of nightly frosts that occur in Cusco during the winter months. According to historic accounts, the Inca royalty carried out a range of activities at royal estates including feasting, singing, and dancing in the plazas and hunting in the forested lands surrounding the palaces of royal estates (13, 14, 22), The Spanish chronicles also describe numerous religious ceremonies practiced by the Inca priests that were linked to celestial events, sacred geography, and agricultural fertility. It is likely that the emperor and/or his representatives would also have participated in these ceremonies when he visited Machu Picchu (4, 23, 24). Fig. 1. Maps of the provenience of the sites, groups, and individuals analyzed in this study. (A) Map of South America showing the geographic distribution of genetic ancestry groups described (33, 34), the location of published reference genomes from modern-day (circles) and ancient (triangles) individuals that constitute these groups and of the archaeological sites from which individuals in this study derived (squares, also see inset). (B) Map showing the location of burial caves at Machu Picchu and highlighting the caves sampled in this study [adapted from figure 2 of (25)]. A recent radiocarbon study of the osteological collection from the site based on 26 human bone and tooth samples concluded that Machu Picchu had been occupied from circa 1420 to 1532 CE (25). Subsequently, the same AMS measurements were analyzed using a Bayesian single phase model, and the probabilities produced suggest an occupation from 1400 to 1435 CE to 1470 to 1520 CE (95.4%) (see Supplementary Text; table S1, B and C; and fig. S1). Excavations by the Yale Peruvian Scientific Expedition in 1912 documented 107 burials containing the remains of a minimum of 174 individuals (20, 26). These simple interments sometimes included multiple individuals and were in shallow chambers with protective coarse stone walls beneath large boulders or underneath natural overhangs. Many burials lacked grave goods or contained only a small number of pots or other artifacts. A large number of the ceramics were in provincial Inca or non-Inca styles from the Peruvian north coast, the Peruvian central coast, the circum-Titicaca area, and Chachapoyas. In contrast, exotic ceramics are rare or absent from nonburial contexts at the site (8, 21, 27). The dead also showed evidence of different types of cranial modification, including forms associated with Lake Titicaca and the coast rather than Cusco or Urubamba (20). The nature of the skeletons and the burial goods found with them led investigators to posit that the burial caves held the remains of retainers and attendants who served the elite at Machu Picchu (4, 12, 17, 19). Most burials at Machu Picchu were found along the periphery of the site (Fig. 1B), grouping in four clusters referred to as cemeteries 1 to 4 (26, 28). Additional research on burial ceramics (21, 27), skeletal morphology and cranial modification (20), stable carbon (C) and nitrogen (N) isotopes (18, 19), and lead (Pb), strontium (Sr), and oxygen (O) isotopes (12, 17) demonstrated a high degree of diversity among the Machu Picchu burial population, consistent with the interpretation that the buried individuals were yanacona and former aclla. However, cultural identifiers such as burial contents may have been acquired on site rather than being indicators of an individual’s homeland. Isotopic methods on their own are limited for determining the ancestral regions from where these individuals might have originated. For example, high degrees of Sr-isotopic variability and the absence of regional and pan-regional isoscapes limit inferences (29). After reviewing all of the available evidence, Inca specialist D’Altroy (2) concluded that the people of the estate complex at Machu Picchu were largely from areas to the south of Cusco, but he hesitated to be more specific. This study was undertaken to further elucidate the origins of the individuals buried at Machu Picchu and/or of their ancestors, as well as to shed light on their genetic histories and potential multigenerational relationships (see “Ethics statement” in Supplementary Text). For this purpose, we generated genome-wide aDNA data from 34 individuals deriving from all four cemeteries at Machu Picchu (Fig. 1B and table S1) excavated in 1912. Samples were selected to optimize comparisons with data generated by the aforementioned previous studies investigating cranial modification types and isotopes. We further generated genome-wide data for 36 individuals from the Urubamba Valley, sites in neighborhoods of modern-day urban Cusco, and Kanamarka in the southern Cusco region (Fig. 1A and table S1). We extracted DNA from teeth and enriched for a targeted set of ~1.2 million single-nucleotide polymorphisms (SNPs). The DNA data for each individual exhibit low nuclear and mitochondrial (mtDNA) contamination rates and damage rates characteristic of aDNA (table S1 and Supplementary Text). We analyzed these data jointly with published ancient and modern genomes available from South America (see Supplementary Text). In addition, we generated radiocarbon dates for 15 individuals buried at the sites in the Urubamba Valley and Cusco (table S1 and fig. S1) and for 26 individuals buried at Machu Picchu (25), all of whom were included in the genetic analysis.
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Post by Admin on Aug 9, 2023 18:24:46 GMT
RESULTS AND DISCUSSION Ancestry and genetic population structure in the Urubamba Valley and Cusco preceding the Imperial Inca period Studies of pre-Hispanic and modern-day genomic diversity indicate that the regional genetic substructure in the Central Andes and adjacent geographic regions has persisted for at least 2000 years (30–34). This allows for the identification of genomic ancestries that are associated with larger geographic regions during that time span [e.g., NorthPeruCoast, SouthPeruHighland, and TiticacaBasin following the nomenclature by Nakatsuka et al. (34)] (Fig. 1A). While 16th century documents indicate ethnic diversity in the Inca city of Cusco and among the remaining yanacona at Yucay, a royal estate in Urubamba belonging to Huayna Capac (35, 36), before this study, this claim could not be evaluated because only limited genome-wide aDNA had been reported for individuals from the Urubamba Valley and Cusco. Radiocarbon dates obtained from the individuals in our sample buried at Ollantaytambo, Urubamba Valley (~1040 to 1380 CE) and San Sebastian, Cusco (~1300 to 1400 CE) indicate that these burials pre-date the Inca imperial expansion and the construction of Machu Picchu (table S1B, fig. S1A, and Supplementary Text). These individuals come from the groups inhabiting the Cusco area before the reign of Pachacuti, and, while limited in numbers, they are one possible source of information permitting us to investigate genetic changes that may have occurred because of subsequent Inca policy and occupation (table S1, fig. S1, and Supplementary Text). We combined the individuals for each site into groups named Ollantaytambo_LIP and San Sebastian_LIP, respectively, after confirming intragroup genetic homogeneity using f4 tests (table S3 and Supplementary Text). Statistical tests of the type f4 (Mbuti, X; Ollantaytambo_LIP, San Sebastian_LIP) indicate that the individuals from Ollantaytambo share significantly more alleles with ancient individuals from the ancestry group SouthPeruHighland described by Nakatsuka et al. (34) (Fig. 1) than the individuals from San Sebastian (table S2 and Supplementary Text). Furthermore, qpWave modeling (see Supplementary Text) reveals that Ollantaytambo_LIP and SouthPeruHighland are consistent with one source of ancestry (P > 0.01 for rank 0; table S2). San Sebastian, however, is best modeled (P = 0.2058) as a two-way mixture between 80 ± 8% ancient PeruSouthHighland ancestry and 20 ± 8% ancestry associated with ancient Titicaca Basin groups using qpADM (table S2 and Supplementary Text) (34). This is expected as the Cusco Valley and the Titicaca Basin had cultural and economic ties long before the Incas. Both Luis Lumbreras and Charles Stanish independently have observed that the pre-Hispanic societies of Cusco and the Lake Titicaca region maintained strong links for over two millennia before the appearance of the Inca Empire (37, 38), and, while their conclusions were based mainly on ceramic styles, they are consistent with studies of long-distance obsidian exchange in the southern highlands of Peru and northern Bolivia (39). Fig. 2. Genetic affinity of the individuals from Machu Picchu, the Urubamba Valley, and Cusco. PCA plot projecting previously published individuals (32–34, 41, 46, 75–82, 84–86) and the ancient individuals studied here onto principal components calculated from present-day Native American populations. The Machu Picchu individuals are depicted by black stars. Genomic insights into the burial population at Machu Picchu To explore the genetic diversity and affinities of the individuals from Machu Picchu and Cusco in the broader context of South and Central America, we performed a principal components analysis (PCA) using modern-day genomes from these regions as references and projecting the genomes obtained in this study and other published ancient genomes onto these axes (Fig. 2 and Supplementary Text). We find that the individuals from Machu Picchu cluster with individuals not only from throughout the Andean highlands but also from the North to South Peruvian coast. Furthermore, six individuals (MP3a, MP4b, MP4d, MP4e, MP4f, and MP61) group with modern individuals from the central and northwestern Peruvian Amazon, as well as the Ecuadorian and Colombian Amazon regions (Fig. 2). Individual profiles of shared genetic drift computed using f3 statistics (fig. S2 and Supplementary Text) reflect the diversity of genetic affinities observed in the PCA, with some individuals (e.g., MP3a, MP4b, MP4d, MP4e, MP4f, MP5a, MP61, and MP107b) sharing most genetic drift with either Northwestern or Southwestern Amazonian groups and some (MP9b, MP31a, MP63, and MP78) exhibiting distinct genetic attraction to modern-day Kichwa speakers from Ecuador and southern Colombia (33). Accordingly, most of the Machu Picchu individuals for which we obtained sufficient data (>100,000 SNPs, n = 30) share excess alleles with other regional coastal or highland Andean ancestry and adjacent tropical forest lowland ancestry groups (Fig. 1), when compared to the pre-Inca inhabitants of the Urubamba Valley (Ollantaytambo_LIP) or the preimperial inhabitants of the Inca capital Cusco (San Sebastian_LIP) using f4 statistics (Fig. 3, fig. S3, table S3, and Supplementary Text) to the limits of our statistical resolution.
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Post by Admin on Aug 11, 2023 19:48:07 GMT
Fig. 3. Genomic structure and diversity of the individuals from Machu Picchu. (A) f4 statistics of the type f4(Mbuti, X; Ollantaytambo/San Sebastian, MPindividual) using the HumOrg dataset (26). X represents either one of the Andean ancestry clusters or selected non-Central Andean groups from South and Central America (complete overview, see fig. S3 and table S3). (B) Conditional heterozygosity estimates (HE). Narrow and thicker black bars, ±1.96 and 3 SEs, respectively. We used qpWave and qpADM to test whether any of the Machu Picchu retainers can be modeled as sharing the same ancestral population with any of the groups representing the regional Andean ancestry clusters (34) and any non-Andean South American ancestry cluster (33, 40, 41) or as a two-way admixture of the two (Fig. 1 and Supplementary Text). To the limits of our statistical resolution, we discerned that 17 of 30 individuals can be linked to a single ancestral source shared with one of the mentioned regional ancestry groups (P > 0.05 for rank 0; Fig. 4 and table S4). Six of these individuals (20%), all biologically female, exhibit ancestry associated with modern-day groups from the Peruvian North and Central Western Amazon. Additional tests indicate that these individuals share more genetic drift with groups living along the eastern piedmont of the Central Peruvian Andes, such as the Matsigenka, Shipibo, Piros, and the Ashaninka, than with groups inhabiting the northwestern Peruvian Amazon (figs. S2 and S4, table S5, and Supplementary Text). The Ashaninka are one of the contemporary tropical forest groups geographically closest to Machu Picchu, living in the lower Urubamba drainage and the lowlands of the Departments of Junín and Ucayali, north of Machu Picchu (Fig. 1). Fig. 4. Ancestry modeling for Machu Picchu individuals. Estimated ancestries for 30 individuals buried at Machu Picchu sorted by median date (table S1), considering qpWave and qpADM results. For admixed individuals, we only display only the model with the highest P value (including SE), but, in most cases competing models (P > 0.05) were observed (table S6). The light blue/middle blue candy stripes indicate that it was not possible to differentiate between PeruNorthCoast and PeruCentralCoast ancestry. Four individuals from Machu Picchu (three males and one female) exhibit ancestry associated with pre-Hispanic and modern-day individuals from the Peruvian Northern and Central Coast (table S4). One male individual shares the same ancestry with San Sebastian_LIP, representing the Cusco region, while only six individuals (four males and two females) exhibit ancestry associated with the ancestral inhabitants of the Urubamba Valley (Ollantaytambo_LIP) and the broader SouthPeruHighland ancestry group. This does not necessarily mean that these six individuals were locals because the regional ancestry cluster SouthPeruHighland includes individuals from Ayacucho and Huancavelica, with some individuals in this group found at archaeological sites up to 260 km west of Ollantaytambo in the upper reaches of the Nasca drainage (Fig. 1). We fitted two-way mixture models for the 13 remaining individuals (Fig. 4). In many cases, we observed multiple competing models, with several Andean sources fitting, while non-Andean sources were less problematic (table S6). The difficulty of determining distinct Andean sources when the number of SNPs is low is best explained by the low genetic differentiation among the Andean regional groups, most of whom share very recent ancestry (34, 40). Five male individuals were modeled as mixtures between two Andean sources, such as NorthHighland-SouthHighland or SouthHighland-TiticacaBasin (Fig. 3). For all other individuals, the models with the highest support (highest P value) suggest mixtures between an Andean and a non-Andean source (Fig. 4, table S6, and Supplementary Text). For two of the individuals, the models suggest a mixture of Central Andean ancestry (~63 to 70%) with a source from the Peruvian Amazon (~30 to 37%) that is closely related to the ancestry for the previously described six individuals of Amazonian ancestry. However, there are also two individuals for which the best fitting models (table S6) were a mixture of Andean ancestry (~30 to 40%) and ancestry associated with groups from the southeastern Amazon and Gran Chaco region of Bolivia, Brazil, Argentina, and Paraguay (~60 to 70%) such as the Chané, Guarani, Karitiana, and Xavante. We cannot exclude that the observed admixture reflects an unsampled regional ancestry, such as groups from the Eastern Slopes of the Bolivian Andes, rather than an admixture event in Inca times. Archaeological and ethnohistoric sources confirm interactions between the Inca and the ancestors of the Chané in the foothills of the Bolivian Andes, making both models plausible (42, 43). Four individuals (three females and one male) can be modeled as a mixture between a genomic source sharing ancestry with modern-day eastern Ecuadorian Kichwa speakers (33) and ancestry from the Peruvian North Coast (Fig. 4, table S6, and Supplementary Text). Additional tests indicated that these individuals are genetically homogenous (table S7); thus, we grouped them to increase our statistical power and found that a model considering a mixture of 46 ± 6% Ecuadorian-Kichwa–associated ancestry and 54 ± 6% NorthPeruCoast ancestry produces the highest P value (P = 0.41). However, alternative models considering other Andean sources (NorthHighland and CentralCoast) are supported as well (table S6). There are no published ancient or modern-day genomes from individuals living in the Ecuadorian highlands or along the Ecuadorian coast, which limits our ability to assess whether the observed admixture indicates a recent admixture event or whether it reflects the genetic ancestry of an unsampled group somewhere in Ecuador. Similar to the previous case, the intensive interactions between Ecuadorian populations and the Inca make such an alternative possible (2, 44, 45). On the basis of our results, Machu Picchu was substantially more genetically diverse—measured as conditional heterozygosity for nuclear DNA and nucleotide diversity for mtDNA—than contemporary rural villages in the Andes (Fig. 3 and fig. S5). Among the yanacona of Machu Picchu, we observe genetic ancestries that represent all regions comprising the Inca Empire, except Central Chile/Western Argentina, which represents the southern frontier. This observation is consistent with previous analyses of the Machu Picchu burials that indicated that many individuals exhibited nonlocal isotopic signatures (Sr and O) or cultural indicators (12, 20, 21) not associated with local cultural traditions (table S1). The rate of variation at polymorphic sites observed for Machu Picchu seems to remain consistently high throughout the site’s occupation (Fig. 2) (25). Individuals of nonregional (Ollantaytambo, Cusco) genetic ancestry and nonlocal strontium 87Sr/86Sr are found throughout the burial population across radiocarbon ages (e.g., MP63 and MP107; table S1). When combined with the genetic diversity estimates, this pattern suggests that the addition of yanacona and former aclla to the Machu Picchu community continued after the death of Pachacuti. This is consistent with historical evidence that yanacona were gifted to royal estates after the death of the founder (11, 14) because the mummies who founded their royal estates continued to be recognized as the owners of the estates and were expected to entertain mummies from other lineages and their guests. We observe a significant difference (P = 0.0157) when we compare the genetic ancestries of biologically male and female individuals, with most male individuals exhibiting ancestries associated with highland regions, while female individuals exhibit more diverse nonhighland ancestries (Fig. 4 and table S1). The genetic diversity observed at Machu Picchu also exceeds the diversity observed for the only genetically studied communities of mitimaes (i.e., ethnic groups forcibly resettled by the Inca state) from the Chincha Valley on the central Peruvian coast (46). This pattern is consistent with the conclusion that the burial population at Machu Picchu was composed of yanacona and former aclla (17) rather than mitimaes. The presence of individuals exhibiting ancestries associated with Amazonia (e.g., MP4b), Ecuador (e.g. MP9b), and the Peruvian North Coast (MP42b) in the earliest occupation phases of Machu Picchu (Fig. 4 and table S1) may suggest that the expansion of the Inca Empire occurred earlier or differently from models derived from historical sources. This observation is consistent with the increasing view among Inca specialists that the historicist chronology dominant since 1945 is untenable in light of recent archaeological evidence from Cusco and distant Inca provinces (2, 6, 42, 47, 48) (see Supplementary Text). The early presence of individuals exhibiting ancestry associated with, for example, Ashaninka and other Arawak speaking groups along the eastern Andean piedmont is exciting but expected. Archaeological, ethnohistorical, linguistic, and genetic sources indicate that the inhabitants of this region interacted with the adjacent highlands even before the Inca (33, 40, 49–51), and recent studies suggest a complementary relationship between the Inca and these groups, rather than one dominated by conflict and conquest (49). All individuals buried at Machu Picchu exhibiting this ancestry have been determined to be biologically female, suggesting that some might have been gifted as wives to favored individuals, a process recorded in historical sources (13, 16). The relationship between the Inca and populations of the former Kingdom of Chimor on the Peruvian North Coast and Ecuadorian groups such as the Cañaris were more bellicose, and the presence of some of the individuals at Machu Picchu with ancestries from these regions may be explained by their incorporation as yanacona who were craft specialists skilled in metal working. The identification of unfinished metal objects and production debris have allowed archaeologists to identify metal working as one of the activities present at Machu Picchu but apparently lacking at many other royal estates (8, 52).
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