Paleosol sequences along the lowest terraces of the Usumacinta River in southern Mexico were used to reconstruct Holocene environmental changes and examine human–environmental interactions. Study sections were correlated through paleosol morphology, radiocarbon dating, and artifact seriation of Formative, Classic, and Postclassic ceramics. The oldest paleosols have gleyic features. Although they contain hard carbonate concretions dating to 5450–5380 cal. yr B.P., these Gleysols formed in the Late Pleistocene to Early Holocene. Carbonates were deposited later. The uppermost paleosols lack gleyic features, the oldest of which contains vertic features, dating to 2000–2700 cal. yr B.P., and contains abundant Formative period ceramics. The upper two paleosols are morphologically less developed and are strongly affected by human activities; radiocarbon ages and ceramic assemblages indicate that they belong to the Maya Classic and Postclassic periods. Stable carbon isotope values from the decalcified organic matter vary among paleosols of different ages and sites. δ13C values are highest (−16 to −20‰) in the Formative period paleosol. Although it is possible that maize cultivation could contribute to the isotopic signatures, we believe that the δ13C values indicate the dominance of drought‐resistant C4 and CAM vegetation due to their association with vertic soils. The Classic period paleosol has a slightly lower isotopic value (−20 to −22‰), while the Postclassic paleosol shows the lowest values (−22 to −23‰), suggesting reforestation of the floodplain. These results indicate that the Early Holocene paleosols formed in a humid climate similar to that of today, which transitions toward dryer conditions around 5500 cal. yr B.P. In the Late Holocene (approximately 3000 B.P.) an increase in seasonality occurs. This condition favored the formation of Vertisols, suitable for agriculture.
This investigation leads us to conclude that the administration of corticosteroid is associated with a higher amount of apoptosis at the insertion site of the rotator cuff (rupture edge).
Archaeologists have begun to understand that many of the challenges facing our technologically sophisticated, resource dependent, urban systems were also destabilizing factors in ancient complex societies. The focus of IHOPE‐Maya is to identify how humans living in the tropical Maya Lowlands in present‐day Central America responded to and impacted their environments over the past three millennia, and to relate knowledge of those processes to modern and future coupled human–environment systems. To better frame variability in ancient lowland Maya development and decline, the area that they once occupied may be subdivided into a series of geographical regions in which the collected archaeological data can be correlated with environmental differences. Although beginning as small agricultural communities occupying a variety of ecological niches in the humid tropics of Mesoamerica, the ancient Maya became an increasingly complex set of societies involved in intensive and extensive resource exploitation. Their development process was not linear, but also involved periods of rapid growth that were punctuated by contractions. Thus, the long‐term development and disintegration of Maya geopolitical institutions presents an excellent vantage from which to study resilience, vulnerability, and the consequences of decision‐making in ancient complex societies.
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