Instituto Nacional de Antropología e Historia

Ardelean C.F., Becerra-Valdivia L., Pedersen M.W., Schwenninger J., Oviatt C.G., Macías-Quintero J.I., Arroyo-Cabrales J., Sikora M., Ocampo-Díaz Y.Z., Rubio-Cisneros I.I., Watling J.G., de Medeiros V.B., De Oliveira P.E., Barba-Pingarón L., Ortiz-Butrón A., et. al.

The initial colonization of the Americas remains a highly debated topic1, and the exact timing of the first arrivals is unknown. The earliest archaeological record of Mexico—which holds a key geographical position in the Americas—is poorly known and understudied. Historically, the region has remained on the periphery of research focused on the first American populations2. However, recent investigations provide reliable evidence of a human presence in the northwest region of Mexico3,4, the Chiapas Highlands5, Central Mexico6 and the Caribbean coast7–9 during the Late Pleistocene and Early Holocene epochs. Here we present results of recent excavations at Chiquihuite Cave—a high-altitude site in central-northern Mexico—that corroborate previous findings in the Americas10–17of cultural evidence that dates to the Last Glacial Maximum (26,500–19,000 years ago)18, and which push back dates for human dispersal to the region possibly as early as 33,000–31,000 years ago. The site yielded about 1,900 stone artefacts within a 3-m-deep stratified sequence, revealing a previously unknown lithic industry that underwent only minor changes over millennia. More than 50 radiocarbon and luminescence dates provide chronological control, and genetic, palaeoenvironmental and chemical data document the changing environments in which the occupants lived. Our results provide new evidence for the antiquity of humans in the Americas, illustrate the cultural diversity of the earliest dispersal groups (which predate those of the Clovis culture) and open new directions of research. Chiquihuite Cave (Zacatecas, Mexico) provides evidence of human presence in the Americas between about 33,000–31,000 and 14,000–12,000 years ago, and expands the cultural variability known from sites of this date.

Alpaslan-Roodenberg S., Anthony D., Babiker H., Bánffy E., Booth T., Capone P., Deshpande-Mukherjee A., Eisenmann S., Fehren-Schmitz L., Frachetti M., Fujita R., Frieman C.J., Fu Q., Gibbon V., Haak W., et. al.

We are a group of archaeologists, anthropologists, curators and geneticists representing diverse global communities and 31 countries. All of us met in a virtual workshop dedicated to ethics in ancient DNA research held in November 2020. There was widespread agreement that globally applicable ethical guidelines are needed, but that recent recommendations grounded in discussion about research on human remains from North America are not always generalizable worldwide. Here we propose the following globally applicable guidelines, taking into consideration diverse contexts. These hold that: (1) researchers must ensure that all regulations were followed in the places where they work and from which the human remains derived; (2) researchers must prepare a detailed plan prior to beginning any study; (3) researchers must minimize damage to human remains; (4) researchers must ensure that data are made available following publication to allow critical re-examination of scientific findings; and (5) researchers must engage with other stakeholders from the beginning of a study and ensure respect and sensitivity to stakeholder perspectives. We commit to adhering to these guidelines and expect they will promote a high ethical standard in DNA research on human remains going forward. In this Perspective, a group representing a range of stakeholders makes the case for a set of five proposed globally applicable ethical guidelines for ancient human DNA research.

Pedersen M.W., De Sanctis B., Saremi N.F., Sikora M., Puckett E.E., Gu Z., Moon K.L., Kapp J.D., Vinner L., Vardanyan Z., Ardelean C.F., Arroyo-Cabrales J., Cahill J.A., Heintzman P.D., Zazula G., et. al.

Summary Analysis of ancient environmental DNA (eDNA) has revolutionized our ability to describe biological communities in space and time,1–3 by allowing for parallel sequencing of DNA from all trophic levels.4–8 However, because environmental samples contain sparse and fragmented data from multiple individuals, and often contain closely related species,9 the field of ancient eDNA has so far been limited to organellar genomes in its contribution to population and phylogenetic studies.5,6,10,11 This is in contrast to data from fossils12,13 where full-genome studies are routine, despite these being rare and their destruction for sequencing undesirable.14–16 Here, we report the retrieval of three low-coverage (0.03×) environmental genomes from American black bear (Ursus americanus) and a 0.04× environmental genome of the extinct giant short-faced bear (Arctodus simus) from cave sediment samples from northern Mexico dated to 16–14 thousand calibrated years before present (cal kyr BP), which we contextualize with a new high-coverage (26×) and two lower-coverage giant short-faced bear genomes obtained from fossils recovered from Yukon Territory, Canada, which date to ∼22–50 cal kyr BP. We show that the Late Pleistocene black bear population in Mexico is ancestrally related to the present-day Eastern American black bear population, and that the extinct giant short-faced bears present in Mexico were deeply divergent from the earlier Beringian population. Our findings demonstrate the ability to separately analyze genomic-scale DNA sequences of closely related species co-preserved in environmental samples, which brings the use of ancient eDNA into the era of population genomics and phylogenetics.

Preciado A., Santos J.C., Silva C., Ramírez-Gaytán A., Falcon J.M.

• A Summary of typical seismic performance and failure modes of massive URM buildings. • A Summary of typical seismic behavior and failure mechanisms of URM bell-towers. • Overview of the September 19, 2017 (M w = 7.1) Puebla-Morelos EQ and seismic risk. • Observed damage description in URM buildings in Puebla, Morelos and Mexico City. • Practical applications of seismic rehabilitation/retrofitting of damaged Churches. Unreinforced masonry is one of the main construction materials used in the edification of most historical buildings around the world. This is due to its availability in nature, low-cost benefits and durability. Churches and bell towers were built to mainly withstand vertical loading induced by self-weight, disregarding the lateral performance mainly by the limitations of masonry. These massive structures present poor seismic performance due to the low tensile strength of masonry, lack of structural integrity, elevated seismic forces and heterogeneity. The last plays an important role in the in-plane and out-of-plane behavior/failure by anisotropy. This paper is aimed at presenting post-earthquake investigations in damaged Churches and bell towers by the September 19, 2017 (M w = 7.1) Puebla-Morelos Earthquake which damaged thousands of historical buildings. These buildings presented partial and total collapses in façades, domes, vaults, arches and bell towers. The structural vulnerability, combination of materials, large openings and reduced vertical loading at top parts of belfries induced a rapid propagation of heavy damage which ended in brittle collapses. The widespread damage was induced by the missing compatibility of deformations and integrity among structural elements/materials and previous damages. These post-earthquake observations are aimed at identifying the behavior/failure of these buildings to propose practical intervention measures. The most suitable retrofitting materials/strategies were identified as practical applications for walls, bell towers, domes, vaulted covers and timber roofs/slabs to increase the displacement/strength capability by inducing more ductile failure with increased EQ energy dissipation through the enhanced hysteretic behavior.

Inomata T., Fernandez-Diaz J.C., Triadan D., García Mollinedo M., Pinzón F., García Hernández M., Flores A., Sharpe A., Beach T., Hodgins G.W., Durón Díaz J.J., Guerra Luna A., Guerrero Chávez L., Hernández Jiménez M.D., Moreno Díaz M.

City plans symbolizing cosmologies have long been recognized as a defining element of Mesoamerican civilizations. The origins of formal spatial configurations are thus the key to understanding early civilizations in the region. Assessment of this issue, however, has been hindered by the lack of systematic studies of site plans over broad areas. Here, we report the identification of 478 formal rectangular and square complexes, probably dating from 1,050 to 400 bc, through a lidar (laser imaging, detection and ranging) survey across the Olmec region and the western Maya lowlands. Our analysis of lidar data also revealed that the earlier Olmec centre of San Lorenzo had a central rectangular space, which possibly provided the spatial template for later sites. This format was probably formalized and spread after the decline of San Lorenzo through intensive interaction across various regions. These observations highlight the legacy of San Lorenzo and the critical role of inter-regional interaction. Using lidar over an area of 85,000 km2, Inomata et al. identified 478 early ceremonial complexes in southern Mexico. These discoveries offer new information for understanding the origins of Mayan civilization and its relation with the Olmecs.

García-Ortiz H., Barajas-Olmos F., Contreras-Cubas C., Cid-Soto M.Á., Córdova E.J., Centeno-Cruz F., Mendoza-Caamal E., Cicerón-Arellano I., Flores-Huacuja M., Baca P., Bolnick D.A., Snow M., Flores-Martínez S.E., Ortiz-Lopez R., Reynolds A.W., et. al.

The genetic makeup of Indigenous populations inhabiting Mexico has been strongly influenced by geography and demographic history. Here, we perform a genome-wide analysis of 716 newly genotyped individuals from 60 of the 68 recognized ethnic groups in Mexico. We show that the genetic structure of these populations is strongly influenced by geography, and our demographic reconstructions suggest a decline in the population size of all tested populations in the last 15–30 generations. We find evidence that Aridoamerican and Mesoamerican populations diverged roughly 4–9.9 ka, around the time when sedentary farming started in Mesoamerica. Comparisons with ancient genomes indicate that the Upward Sun River 1 (USR1) individual is an outgroup to Mexican/South American Indigenous populations, whereas Anzick-1 was more closely related to Mesoamerican/South American populations than to those from Aridoamerica, showing an even more complex history of divergence than recognized so far. Indigenous populations, including in those in Mexico are underrepresented in genetic studies. Here, the authors perform a population genetics study of indigenous peoples in Mexico to explore demographic histories of the region in the context of geography and cultural influences.

Preciado A., Peña F., Colmenero Fonseca F., Silva C.

• Observed damages during post-earthquake investigations on Colonial Churches. • Damage identification and failure propagation on different masonry elements. • Schematic representation of cracks/failure patterns in several structural elements. • Crack propagation in arches, vaults, domes, bell towers, belfries and façades. • Valuable insights to propose suitable rehabilitation and retrofitting works. This paper aims to describe the observed damage and crack propagation in patrimonial masonry buildings of Puebla and Morelos, Mexico due to both September 7 (M w = 8.2) and 19 (M w = 7.1) 2017 earthquakes. Historical masonry buildings are earthquake prone structures due to the missing structural integrity by the low tensile strength of masonry, heavy inertial forces, large openings and structural elements with different in-plane and out-of-plane behavior, especially when detached from the rest of the building. The two large seismic events damaged 2340 architectural heritage buildings, mainly in the States of Puebla, Morelos and Mexico. The observed damages during post-earthquake investigations ranged from moderate to heavy, with partial and total collapses, mainly in vaulted systems and bell towers. The presented damage identification and failure propagation description allowed to generate practical schematic representations of crack patterns in several structural elements such as domes, vaulted covers, façades, bell towers and so on, providing valuable information that can be useful to propose suitable rehabilitation and retrofitting works. The 2017 earthquakes also generated uncountable damages in different cultural assets including retables, painted murals and bells, being of great cultural and historical value. The main causes of the observed damages in masonry structures are also due to the lack of maintenance, previous structural modifications and inadequate interventions. Continuous and correct maintenance of structures is indispensable to reduce the possible damages due to earthquakes. Thus, a detailed structural assessment of the buildings is always necessary to carry out an adequate intervention according to the criteria of restoration.

Guzmán-Solís A.A., Villa-Islas V., Bravo-López M.J., Sandoval-Velasco M., Wesp J.K., Gómez-Valdés J.A., Moreno-Cabrera M.D., Meraz A., Solís-Pichardo G., Schaaf P., TenOever B.R., Blanco-Melo D., Ávila Arcos M.C.

After the European colonization of the Americas, there was a dramatic population collapse of the Indigenous inhabitants caused in part by the introduction of new pathogens. Although there is much speculation on the etiology of the Colonial epidemics, direct evidence for the presence of specific viruses during the Colonial era is lacking. To uncover the diversity of viral pathogens during this period, we designed an enrichment assay targeting ancient DNA (aDNA) from viruses of clinical importance and applied it to DNA extracts from individuals found in a Colonial hospital and a Colonial chapel (16th–18th century) where records suggest that victims of epidemics were buried during important outbreaks in Mexico City. This allowed us to reconstruct three ancient human parvovirus B19 genomes and one ancient human hepatitis B virus genome from distinct individuals. The viral genomes are similar to African strains, consistent with the inferred morphological and genetic African ancestry of the hosts as well as with the isotopic analysis of the human remains, suggesting an origin on the African continent. This study provides direct molecular evidence of ancient viruses being transported to the Americas during the transatlantic slave trade and their subsequent introduction to New Spain. Altogether, our observations enrich the discussion about the etiology of infectious diseases during the Colonial period in Mexico.

Kowal E., Weyrich L.S., Argüelles J.M., Bader A.C., Colwell C., Cortez A.D., Davis J.L., Figueiro G., Fox K., Malhi R.S., Matisoo-Smith E., Nayak A., Nelson E.A., Nicholas G., Nieves-Colón M.A., et. al.

The ethics of the scientific study of Ancestors has long been debated by archaeologists, bioanthropologists, and, more recently, ancient DNA (aDNA) researchers. This article responds to the article “Ethics of DNA research on human remains: five globally applicable guidelines” published in 2021 in Nature by a large group of aDNA researchers and collaborators. We argue that these guidelines do not sufficiently consider the interests of community stakeholders, including descendant communities and communities with potential, but yet unestablished, ties to Ancestors. We focus on three main areas of concern with the guidelines. First is the false separation of “scientific” and “community” concerns and the consistent privileging of researcher perspectives over those of community members. Second, the commitment of the guidelines’ authors to open data ignores the principles and practice of Indigenous Data Sovereignty. Further, the authors argue that involving community members in decisions about publication and data sharing is unethical. We argue that excluding community perspectives on “ethical” grounds is convenient for researchers, but it is not, in fact, ethical. Third, we stress the risks of not consulting communities that have established or potential ties to Ancestors, using two recent examples from the literature. Ancient DNA researchers cannot focus on the lowest common denominator of research practice, the bare minimum that is legally necessary. Instead, they should be leading multidisciplinary efforts to create processes to ensure communities from all regions of the globe are identified and engaged in research that affects them. This will often present challenges, but we see these challenges as part of the research, rather than a distraction from the scientific endeavor. If a research team does not have the capacity to meaningfully engage communities, questions must be asked about the value and benefit of their research.

Kennett D.J., Masson M., Lope C.P., Serafin S., George R.J., Spencer T.C., Hoggarth J.A., Culleton B.J., Harper T.K., Prufer K.M., Milbrath S., Russell B.W., González E.U., McCool W.C., Aquino V.V., et. al.

The influence of climate change on civil conflict and societal instability in the premodern world is a subject of much debate, in part because of the limited temporal or disciplinary scope of case studies. We present a transdisciplinary case study that combines archeological, historical, and paleoclimate datasets to explore the dynamic, shifting relationships among climate change, civil conflict, and political collapse at Mayapan, the largest Postclassic Maya capital of the Yucatán Peninsula in the thirteenth and fourteenth centuries CE. Multiple data sources indicate that civil conflict increased significantly and generalized linear modeling correlates strife in the city with drought conditions between 1400 and 1450 cal. CE. We argue that prolonged drought escalated rival factional tensions, but subsequent adaptations reveal regional-scale resiliency, ensuring that Maya political and economic structures endured until European contact in the early sixteenth century CE. The influence of climate on premodern civil conflict and societal instability is debated. Here, the authors combine archeological, historical, and paleoclimatic datasets to show that drought between 1400-1450 cal. CE escalated civil conflict at Mayapan, the largest Postclassic Maya capital of the Yucatán Peninsula.