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Early and middle holocene hunter-gatherer occupations in western Amazonia: the hidden shell middens.

Lombardo U, Szabo K, Capriles JM, May JH, Amelung W, Hutterer R, Lehndorff E, Plotzki A, Veit H - PLoS ONE (2013)

Bottom Line: Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region.Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites.The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged.

View Article: PubMed Central - PubMed

Affiliation: Institute of Geography, University of Bern, Bern, Switzerland.

ABSTRACT
We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged.

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Photographs of the 3 meter cores extracted from the SM1, SM2 and SM3 sites.The thickness of the anthropogenic sediments is 2.5, 1.7 and 2.5 meters respectively. In SM2 the first 50 cm are made of sediments that have been deposited on top of the archaeological site in modern times.
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pone-0072746-g002: Photographs of the 3 meter cores extracted from the SM1, SM2 and SM3 sites.The thickness of the anthropogenic sediments is 2.5, 1.7 and 2.5 meters respectively. In SM2 the first 50 cm are made of sediments that have been deposited on top of the archaeological site in modern times.

Mentions: The study looks at three sites (SM1, SM2 and SM3 in Fig. 1b). For SM2 and SM3 only two minimally invasive cores were extracted with a Wacker vibracorer in order to recover material for radiocarbon dating and gain an overall idea of their stratigraphy (Fig. 2). In the case of SM1 (Isla del Tesoro) an exploratory 1×1 meter pit was excavated to a depth of 1.7 meters, where the appearance of the water table halted further excavation. About 500 gr. of material was sampled at ten centimetre intervals and stored in plastic bags. The stratigraphy and the relationship between SM1, a buried paleosol abutting it and the surrounding sediments have been established based on a transect of sediment cores extracted across the midden-savannah boundary. The chronology of the formation and abandonment of SM1 is based on 28 radiocarbon ages (Table 1). Radiocarbon ages have been measured at Poznan Radiocarbon Laboratory and were calibrated using Calib 6.0 [41] and the ShCal04 calibration curve [42]. Despite the variable condition of the shell fragments, paired dates from shell fragments and charcoal throughout the sequence are in close agreement, and show that problems with unpredictable reservoir effects in the radiocarbon dating of freshwater shell [43], [44] do not significantly affect our chronology. 30 µm ( = 0.03 mm) thin sections with cover slips have been prepared following standard procedures by Geoprep at the Department of Earth Sciences, University of Basel. Samples have been impregnated with epoxy and then cut vertically in order to maintain consistency with the original stratigraphic position. Soil organic carbon (Corg) has been measured with a C/N analyser after removal of carbonates with HCl 10%. The total amount of carbonates has been measured by loss on ignition as W950°–W550° after 2 hours at 550°C and 2 hours at 950°C. The respective contribution of aragonite and calcite to the total amount of carbonates has been measured by powder x-ray diffraction (XRD) using a Philips PW 1800. Steroid composition has been analysed by gas-chromatography and mass spectrometry (GC-MS) (Figure S1, Table S1 and S2) after accelerated solvent extraction with DCM:MeOH 9∶1 (v/v), derivatization with BSTFA and pyridine (see Text S1 for further details on the methods). The content of black carbon (BC) has been estimated after converting condensed aromatic moieties to benzene-polycarboxylic acids as specific BC markers [45], [46] (Table 2; see Text S1 for further details on the methods). Multi-element analysis has been performed by x-ray fluorescence (XRF) (Table 3). For each sample, 4 g of dried and milled (vibration disk mill) sample material was mixed with 0.9 g of wax (Licowax C Micropowder PM) and then pressed to a pellet at 10–15 tons. Elemental composition was determined with the Phillips 2400 x-ray fluorescence spectrometer. The semi-quantitative measurements were carried out with the UniQuant program. Producing quantitative datasets for the faunal remains proved difficult due to the uneven nature of preservation. Cemented blocks of fragmented shell ruled out any form of quantification involving counting and also distorted weights. Likewise, carbonate concretions on many of the bones rendered quantification by weight spurious. In acknowledgement of these limitations, Table S3 presents a partially quantitative and partially qualitative description of the faunal assemblage.


Early and middle holocene hunter-gatherer occupations in western Amazonia: the hidden shell middens.

Lombardo U, Szabo K, Capriles JM, May JH, Amelung W, Hutterer R, Lehndorff E, Plotzki A, Veit H - PLoS ONE (2013)

Photographs of the 3 meter cores extracted from the SM1, SM2 and SM3 sites.The thickness of the anthropogenic sediments is 2.5, 1.7 and 2.5 meters respectively. In SM2 the first 50 cm are made of sediments that have been deposited on top of the archaeological site in modern times.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3755986&req=5

pone-0072746-g002: Photographs of the 3 meter cores extracted from the SM1, SM2 and SM3 sites.The thickness of the anthropogenic sediments is 2.5, 1.7 and 2.5 meters respectively. In SM2 the first 50 cm are made of sediments that have been deposited on top of the archaeological site in modern times.
Mentions: The study looks at three sites (SM1, SM2 and SM3 in Fig. 1b). For SM2 and SM3 only two minimally invasive cores were extracted with a Wacker vibracorer in order to recover material for radiocarbon dating and gain an overall idea of their stratigraphy (Fig. 2). In the case of SM1 (Isla del Tesoro) an exploratory 1×1 meter pit was excavated to a depth of 1.7 meters, where the appearance of the water table halted further excavation. About 500 gr. of material was sampled at ten centimetre intervals and stored in plastic bags. The stratigraphy and the relationship between SM1, a buried paleosol abutting it and the surrounding sediments have been established based on a transect of sediment cores extracted across the midden-savannah boundary. The chronology of the formation and abandonment of SM1 is based on 28 radiocarbon ages (Table 1). Radiocarbon ages have been measured at Poznan Radiocarbon Laboratory and were calibrated using Calib 6.0 [41] and the ShCal04 calibration curve [42]. Despite the variable condition of the shell fragments, paired dates from shell fragments and charcoal throughout the sequence are in close agreement, and show that problems with unpredictable reservoir effects in the radiocarbon dating of freshwater shell [43], [44] do not significantly affect our chronology. 30 µm ( = 0.03 mm) thin sections with cover slips have been prepared following standard procedures by Geoprep at the Department of Earth Sciences, University of Basel. Samples have been impregnated with epoxy and then cut vertically in order to maintain consistency with the original stratigraphic position. Soil organic carbon (Corg) has been measured with a C/N analyser after removal of carbonates with HCl 10%. The total amount of carbonates has been measured by loss on ignition as W950°–W550° after 2 hours at 550°C and 2 hours at 950°C. The respective contribution of aragonite and calcite to the total amount of carbonates has been measured by powder x-ray diffraction (XRD) using a Philips PW 1800. Steroid composition has been analysed by gas-chromatography and mass spectrometry (GC-MS) (Figure S1, Table S1 and S2) after accelerated solvent extraction with DCM:MeOH 9∶1 (v/v), derivatization with BSTFA and pyridine (see Text S1 for further details on the methods). The content of black carbon (BC) has been estimated after converting condensed aromatic moieties to benzene-polycarboxylic acids as specific BC markers [45], [46] (Table 2; see Text S1 for further details on the methods). Multi-element analysis has been performed by x-ray fluorescence (XRF) (Table 3). For each sample, 4 g of dried and milled (vibration disk mill) sample material was mixed with 0.9 g of wax (Licowax C Micropowder PM) and then pressed to a pellet at 10–15 tons. Elemental composition was determined with the Phillips 2400 x-ray fluorescence spectrometer. The semi-quantitative measurements were carried out with the UniQuant program. Producing quantitative datasets for the faunal remains proved difficult due to the uneven nature of preservation. Cemented blocks of fragmented shell ruled out any form of quantification involving counting and also distorted weights. Likewise, carbonate concretions on many of the bones rendered quantification by weight spurious. In acknowledgement of these limitations, Table S3 presents a partially quantitative and partially qualitative description of the faunal assemblage.

Bottom Line: Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region.Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites.The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged.

View Article: PubMed Central - PubMed

Affiliation: Institute of Geography, University of Bern, Bern, Switzerland.

ABSTRACT
We report on previously unknown early archaeological sites in the Bolivian lowlands, demonstrating for the first time early and middle Holocene human presence in western Amazonia. Multidisciplinary research in forest islands situated in seasonally-inundated savannahs has revealed stratified shell middens produced by human foragers as early as 10,000 years ago, making them the oldest archaeological sites in the region. The absence of stone resources and partial burial by recent alluvial sediments has meant that these kinds of deposits have, until now, remained unidentified. We conducted core sampling, archaeological excavations and an interdisciplinary study of the stratigraphy and recovered materials from three shell midden mounds. Based on multiple lines of evidence, including radiocarbon dating, sedimentary proxies (elements, steroids and black carbon), micromorphology and faunal analysis, we demonstrate the anthropogenic origin and antiquity of these sites. In a tropical and geomorphologically active landscape often considered challenging both for early human occupation and for the preservation of hunter-gatherer sites, the newly discovered shell middens provide evidence for early to middle Holocene occupation and illustrate the potential for identifying and interpreting early open-air archaeological sites in western Amazonia. The existence of early hunter-gatherer sites in the Bolivian lowlands sheds new light on the region's past and offers a new context within which the late Holocene "Earthmovers" of the Llanos de Moxos could have emerged.

Show MeSH
Related in: MedlinePlus