The plantation system and the roots of the southern rural mortality penalty in the northern Blackland Prairies of Texas.

In recent decades, public health researchers have observed that the health of rural people has declined relative to the health of urban people in the United States. This disparity in health and life expectancy across the rural/urban divide has been described as the Rural Mortality Penalty. However, public health researchers have also noted that health and life expectancies are not uniform across the rural United States, but vary according to race, sex, gender, and other factors. Rural health disparities also vary geospatially and are especially pronounced in the American South, leading to recent calls for greater attention to the structural factors that shape the health of rural Southerners. In this study, we take an anthropological and historically explicit approach to study the impacts of systemic violence on rural health. Specifically, we focus on farm labor within the plantation system as a context where geospatial, racial, and sexual differences in mortality, often studied in isolation, find a common historical source. Here we analyze vital records data from the post-emancipation period in the Blackland Prairies ecoregion of Texas, a period when emerging forms of plantation labor such as tenant farming, convict leasing, and migrant labor were being developed to maintain the plantation economy after the abolishment of chattel slavery. We find that the plantation system remains a strong predictor of differential mortalities in rural Texas, accounting for nearly all the variation that exists across the rural/urban divide and elucidating the complex interactions of race, sex, labor, and health in the rural South.

Evaluating population histories in Patagonia and Tierra del Fuego, Chile, using ancient mitochondrial and Y-chromosomal DNA.

OBJECTIVES: This study aims to characterize the genetic histories of ancient hunter-gatherer groups in Fuego-Patagonia (Chile) with distinct Marine, Terrestrial, and Mixed Economy subsistence strategies. Mitochondrial (mtDNA) and Y-chromosome data were generated to test three hypotheses. H0: All individuals were drawn from the same panmictic population; H1: Terrestrial groups first populated the region and gave rise to highly specialized Marine groups by ~7,500 cal BP; or H2: Marine and Terrestrial groups represent distinct ancestral lineages who migrated independently into the region. METHODS: Ancient DNA was extracted from the teeth of 50 Fuegian-Patagonian individuals dating from 6,895 cal BP to after European arrival, and analyzed alongside other individuals from previous studies. Individuals were assigned to Marine, Terrestrial, and Mixed Economy groups based on archeological context and stable isotope diet inferences, and mtDNA (HVR1/2) and Y-chromosome variation was analyzed. RESULTS: Endogenous aDNA was obtained from 49/50 (98%) individuals. Haplotype diversities, FST comparisons, and exact tests of population differentiation showed that Marine groups were significantly different from Terrestrial groups based on mtDNA (p < 0.05). No statistically significant differences were found between Terrestrial and Mixed Economy groups. Demographic simulations support models in which Marine groups diverged from the others by ~14,000 cal BP. Y-chromosome results showed similar patterns but were not statistically significant due to small sample sizes and allelic dropout. DISCUSSION: These results support the hypothesis that Marine and Terrestrial economic groups represent distinct ancestral lineages who diverged during the time populations were expanding in the Americas, and may represent independent migrations into Fuego-Patagonia.

Detection of Cytosine methylation in ancient DNA from five native american populations using bisulfite sequencing.

While cytosine methylation has been widely studied in extant populations, relatively few studies have analyzed methylation in ancient DNA. Most existing studies of epigenetic marks in ancient DNA have inferred patterns of methylation in highly degraded samples using post-mortem damage to cytosines as a proxy for cytosine methylation levels. However, this approach limits the inference of methylation compared with direct bisulfite sequencing, the current gold standard for analyzing cytosine methylation at single nucleotide resolution. In this study, we used direct bisulfite sequencing to assess cytosine methylation in ancient DNA from the skeletal remains of 30 Native Americans ranging in age from approximately 230 to 4500 years before present. Unmethylated cytosines were converted to uracils by treatment with sodium bisulfite, bisulfite products of a CpG-rich retrotransposon were pyrosequenced, and C-to-T ratios were quantified for a single CpG position. We found that cytosine methylation is readily recoverable from most samples, given adequate preservation of endogenous nuclear DNA. In addition, our results indicate that the precision of cytosine methylation estimates is inversely correlated with aDNA preservation, such that samples of low DNA concentration show higher variability in measures of percent methylation than samples of high DNA concentration. In particular, samples in this study with a DNA concentration above 0.015 ng/µL generated the most consistent measures of cytosine methylation. This study presents evidence of cytosine methylation in a large collection of ancient human remains, and indicates that it is possible to analyze epigenetic patterns in ancient populations using direct bisulfite sequencing approaches.