The myths and realities of Bayesian chronological modeling revealed

We review the history of Bayesian chronological modeling in archaeology and demonstrate that there has been a surge over the past several years in American archaeological applications. Most of these applications have been performed by archaeologists who are self-taught in this method because formal training opportunities in Bayesian chronological modeling are infrequently provided. We define and address misconceptions about Bayesian chronological modeling that we have encountered in conversations with colleagues and in anonymous reviews, some of which have been expressed in the published literature. Objectivity and scientific rigor is inherent in the Bayesian chronological modeling process. Each stage of this process is described in detail, and we present examples of this process in practice. Our concluding discussion focuses on the potential that Bayesian chronological modeling has for enhancing understandings of important topics

The Mississippian fin de siècle in the middle Cumberland region of Tennessee

Bayesian chronological modeling is used to investigate the chronology for a large-scale human depopulation event during the Mississippian period (AD 1000–1600) known as the Vacant Quarter phenomenon. The Middle Cumberland region (MCR) of Tennessee is within the Vacant Quarter area, and six villages from the final phase of Mississippian activity in the MCR have been subjected to radiocarbon dating. Complete radiocarbon datasets from these sites are presented within an interpretative Bayesian statistical framework. The results provide a unique history of each settlement and demonstrate that Mississippian occupations at each site likely terminated in the mid- to late fifteenth and possibly early sixteenth centuries AD, which is 50 to 100 years later than the most recent estimate for the timing of the Vacant Quarter. Mississippian abandonment in the MCR was relatively quick, likely occurring over less than a century. The exact reasons for abandonment are not entirely clear but appear to be linked to climate change. A radiocarbon simulation experiment indicates that future robust radiocarbon dating with well-selected samples could greatly improve the chronological precision for this late Mississippian activity. More broadly, this example demonstrates that model building with radiocarbon simulations can be used to address regional-scale chronological issues within the American Southeast and beyond

Timing of precolumbian militarization in the U.S. Midwest and Southeast

Bayesian chronological modeling is used to investigate the chronology of bastioned palisades during the precolumbian period in the Midwestern and Southeastern United States. Nine precolumbian settlements in the Midwest and Southeast with bastioned palisades have been subject to scientific dating (Angel Mounds, Annis Village, Aztalan, Cahokia Mounds, Etowah, Kincaid Mounds, Jonathan Creek, Moundville, and Southwind). Complete radiocarbon datasets from these sites are presented within an interpretative Bayesian statistical framework. The results provide a glimpse into the history of Mississippi period (A.D. 1000–1700) fortifications with bastions and indicate that the analyzed fortifications were built and maintained predominantly in A.D. 1200–1400. This finding suggests a greater institutionalized role for defense and warfare in post-A.D. 1200 Mississippian societies. Additionally, modeling results further indicate that the investigated Mississippian centers continued to maintain fortifications for generations after their construction

Research in progress: Assessing marine radiocarbon reservoir effect variation in greater Utqiaġvik, Alaska

No abstract available

Contemplating the history and future of radiocarbon dating in the American Southeast

We consider the history, present, and future of radiocarbon dating in the American Southeast. We point out some of the past and present flaws related to archaeological research and dating. Our approach to this review is rooted in the perspective that each radiocarbon date collectively adds to our knowledge of the region and not just a particular site. Based on our observations, we suggest some “good” practices with respect to certain aspects of radiocarbon dating. Our concluding discussion considers Bayesian chronological analysis and the growing contribution of chronological modeling to the Southeast

Warfare, Demography & Anthropogenic Transformation at Angel Mounds State Historic Site

poster abstractRecent investigations by the Department of Anthropology (IU School of Liberal Arts) and the Glenn A. Black Laboratory of Archaeology (IU-Bloomington) at Angel Mounds have greatly enhanced our understanding of this Mississippian period (AD 1050-1450) village located on the Ohio River in southwestern Indiana. During this timeframe, the Ohio Valley and adjoining regions witnessed an evolution in social complexity with the emergence of small-scale polities, population aggregation in fortified towns, and associated earthwork construction. Angel Mounds was established, grew in prominence, and was eventually abandoned. However, until recently, absolute ages from the site were sparse and the chronology of the town’s settlement, growth and abandonment was poorly understood. Similarly, chronological models for earthwork and fortification construction were non-existent. Our research has revealed that Angel Mounds began as a ceremonial center between AD 1100 and 1300 with few occupants. The residential population at Angel Mounds grew precipitously after AD 1300. By AD 1400, we estimate that as many as 1,000 people lived at Angel Mounds. Concurrently, a series of fortifications were erected at the site to protect the inhabitants from neighboring polities. Meanwhile, earthworks on site were “capped” and abandoned soon thereafter, which may reflect the sociopolitical disintegration of Angel Mounds. Depending on the type of agricultural production and environmental change with the onset of the Little Ice Age, these patterns have important implications for settlement longevities, the historical ecology of land-use, and population estimates in the Eastern Woodlands of North America by AD 1500. With support from the Nation Science Foundation, the next three years of investigations at Angel Mounds will continue to focus on population dynamics, earthwork construction and use, anthropogenic transformation of the landscape, and environmental change during the Medieval Warm and Little Ice Age

Chronology of a Fortified Mississippian Village in the Central Illinois River Valley

Geophysical survey and excavations from 2010–2016 at Lawrenz Gun Club (11CS4), a late pre-Columbian village located in the central Illinois River valley in Illinois, identified 10 mounds, a central plaza, and dozens of structures enclosed within a stout 10 hectare bastioned palisade. Nineteen radiocarbon (14C) measurements were taken from single entities of wood charcoal, short-lived plants, and animal bones. A site chronology has been constructed using a Bayesian approach that considers the stratigraphic contexts and feature formation processes. The village was host to hundreds of years of continuous human activity during the Mississippi Period. Mississippian activity at the site is estimated to have begun in cal AD 990–1165 (95% probability), ended in cal AD 1295–1450 (95% probability), and lasted 150–420 yr (95% probability) in the primary Bayesian model with similar results obtained in two alternative models. The palisade is estimated to have been constructed in cal AD 1150–1230 (95% probability) and was continuously repaired and rebuilt for 15–125 yr (95% probability), probably for 40–85 yr (68% probability). Comparison to other studies demonstrates that the bastioned palisade at Lawrenz was one of the earliest constructed in the midcontinental United States

Genetic variant effects on gene expression in human pancreatic islets and their implications for T2D

Most signals detected by genome-wide association studies map to non-coding sequence and their tissue-specific effects influence transcriptional regulation. However, key tissues and cell-types required for functional inference are absent from large-scale resources. Here we explore the relationship between genetic variants influencing predisposition to type 2 diabetes (T2D) and related glycemic traits, and human pancreatic islet transcription using data from 420 donors. We find: (a) 7741 cis-eQTLs in islets with a replication rate across 44 GTEx tissues between 40% and 73%; (b) marked overlap between islet cis-eQTL signals and active regulatory sequences in islets, with reduced eQTL effect size observed in the stretch enhancers most strongly implicated in GWAS signal location; (c) enrichment of islet cis-eQTL signals with T2D risk variants identified in genome-wide association studies; and (d) colocalization between 47 islet cis-eQTLs and variants influencing T2D or glycemic traits, including DGKB and TCF7L2. Our findings illustrate the advantages of performing functional and regulatory studies in disease relevant tissues.Peer reviewe