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Abstract:

The Llanos de Moxos in the Bolivian Amazon, the second largest South American wetland, hosts many endemic species and a rich archaeological record that spans the entire Holocene. Despite its ecological and archaeological importance, very little is known about its Holocene environmental history. A growing body of evidence suggests that neotectonics played an important role in shaping its modern landscape and controlling past flooding dynamics, but the chronology and vertical displacements of past tectonic events are still largely unknown. Here, we present new data from a core taken at Lake Oceano, a large ria lake in the northern part of the Llanos de Moxos. To identify changes in the lithology and environment, we performed a battery of analyses, such as XRF scanning, mineralogy, granulometry, C/N and C and N stable isotopes, and also built an age-depth model using eighteen radiocarbon dates obtained from accelerator mass spectrometry (AMS) determinations. Based on the sedimentology and chemical analyses, we identified three major disturbances in the lake sedimentation that we interpret as positive tectonic events (i.e., tectonic uplifts). The first identified event occurred at approximately 13,400 cal yr BP and led to the formation of the lake by blocking the river course. A second uplift event took place around 10,000 cal yr BP, accompanied by a significant change in the geochemistry of the lake sediments. Furthermore, we have verified a third event at 6000 cal yr BP, previously recognized as responsible for the onset of Lake Rogaguado (aprox. 100 km NE of Lake Oceano), one of the largest lakes in South America. Overall, we show that ria lakes can provide key sedimentary archives to reconstruct the past timing and intensity of tectonic events. We discuss the interplay between tectonics and climate, highlighting the connection between tectonics and the region's flood history, with crucial implications for the interpretation of both archaeological and palaeoecological records throughout the Holocene.

Abstract:

The Casarabe culture (500–1400 ce), spreading over roughly 4,500 km² of the monumental mounds region of the Llanos de Moxos, Bolivia, is one of the clearest examples of urbanism in pre-Columbian (pre-1492 ce) Amazonia. It exhibits a four-tier hierarchical settlement pattern, with hundreds of monumental mounds interconnected by canals and causeways. Despite archaeological evidence indicating that maize was cultivated by this society, it is unknown whether it was the staple crop and which type of agricultural farming system was used to support this urban-scale society. Here, we address this issue by integration of remote sensing, field survey and microbotanical analyses, which shows that the Casarabe culture invested heavily in landscape engineering, constructing a complex system of drainage canals (to drain excess water during the rainy season) and newly documented savannah farm ponds (to retain water in the dry season). Phytolith analyses of 178 samples from 18 soil profiles in drained fields, farm ponds and forested settings record the singular and ubiquitous presence of maize (Zea mays) in pre-Columbian fields and farm ponds, and an absence of evidence for agricultural practices in the forest. Collectively, our findings show how the Casarabe culture managed the savannah landscape for intensive year-round maize monoculture that probably sustained its relatively large population. Our results have implications for how we conceive agricultural systems in Amazonia, and show an example of a Neolithic-like, grain-based agrarian economy in the Amazon.

Abstract:

A 350 14C yr discrepancy was found between dates on postcranial remains and mandibular teeth on what was thought to be the same individual from the Early Neolithic cemetery of Shamanka II, Lake Baikal. Stable nitrogen isotope results suggested a major shift in diet between childhood (when the teeth formed) and adulthood (represented by the postcrania), which could have resulted in different 14C ages through a freshwater reservoir effect. Subsequent additional dating on the mandible and postcranial elements, however, indicated that the mandible actually belonged to a different individual. More subtle reservoir effects can be seen on the sequentially forming teeth and mandible. The practice by prehistoric hunter-gatherers of Lake Baikal of re-opening graves and removing cranial elements has long been known, but this is the first evidence for the inclusion of a mandible from a separate individual, though whether it was intentional or incidental is uncertain. As well as providing new insights into mid-Holocene mortuary practices in the region, our findings raise a cautionary note for the examination of disturbed graves.

Abstract:

As in the rest of Europe, the population of medieval England grew steeply, especially between the tenth and thirteenth centuries. This volume investigates how medieval farmers managed to produce sufficiently large harvests to sustain this growth—which in turn fuelled a major expansion of towns and markets—and the impact of this ‘cerealisation’ on the landscape. It presents new evidence recovered from hundreds of archaeological excavations for the development of the medieval farming regimes that shaped the English landscape in ways still visible today. Medieval farming is a contentious topic, not least because of the different approaches taken by historians, archaeologists, and geographers. No consensus has been reached about the cultivation regimes that underpinned the remarkable increase in cereal production seen in this period. A large-scale analysis of the excavated remains of medieval crops, weeds, livestock, and pollen has generated new evidence using a range of science-based methods. The results reveal the conditions in which medieval crops were grown and the way in which land use changed between the late Roman period and the Black Death. The authors relate the results to archaeological and written evidence for farms and farming, bringing an ecological perspective to the debate about the so-called medieval agricultural revolution. The ‘cerealisation’ of England emerges as a regionally variegated process lasting several centuries, whose overall impact can nevertheless be described as ‘revolutionary’.