Submarine groundwater discharge (SGD) is an important component of many coastal environments and ... more Submarine groundwater discharge (SGD) is an important component of many coastal environments and hydrologic processes, providing sources of nutrients to marine ecosystems, and potentially, an important source of fresh water for human populations. Here, we use a combination of unpiloted aerial systems (UAS) thermal infrared (TIR) imaging and salinity measurements to characterize SGD on the remote East Polynesian island of Rapa Nui (Easter Island, Chile). Previous research has shown that coastal freshwater seeps are abundant on Rapa Nui and strongly associated with the locations of ancient settlement sites. We currently lack, however, information on the differential magnitude or quality of these sources of fresh water. Our UAS-based TIR results from four locations on Rapa Nui suggest that locations of variably-sized SGD plumes are associated with many ancient settlement sites on the island and that these water sources are resilient to drought events. These findings support previous work indicating that ancient Rapa Nui communities responded to the inherent and climate-induced hydrological challenges of the island by focusing on these abundant and resilient freshwater sources. Our results highlight the efficacy of using UAS-based TIR for detecting relatively small SGD locations and provide key insights on the potential uses of these water sources for past and current Rapa Nui communities.
Examining how past human populations responded to environmental and climatic changes is a central... more Examining how past human populations responded to environmental and climatic changes is a central focus of the historical sciences. The use of summed probability distributions (SPD) of radiocarbon dates as a proxy for estimating relative population sizes provides a widely applicable method in this research area. Paleodemographic reconstructions and modeling with SPDs, however, are stymied by a lack of accepted methods for model fitting, tools for assessing the demographic impact of environmental or climatic variables, and a means for formal multi-model comparison. These deficiencies severely limit our ability to reliably resolve crucial questions of past human-environment interactions. We propose a solution using Approximate Bayesian Computation (ABC) to fit complex demographic models to observed SPDs. Using a case study from Rapa Nui (Easter Island), a location that has long been the focus of debate regarding the impact of environmental and climatic changes on its human population, we find that past populations were resilient to environmental and climatic challenges. Our findings support a growing body of evidence showing stable and sustainable communities on the island. The ABC framework offers a novel approach for exploring regions and time periods where questions of climate-induced demographic and cultural change remain unresolved.
ABSTRACTStructure from motion (SfM) mapping is a photogrammetric technique that offers a cost-eff... more ABSTRACTStructure from motion (SfM) mapping is a photogrammetric technique that offers a cost-effective means of creating three-dimensional (3-D) visual representations from overlapping digital photographs. The technique is now used more frequently to document the archaeological record. We demonstrate the utility of SfM by studying red scoria bodies known as pukao from Rapa Nui (Easter Island, Chile). We created 3-D images of 50 pukao that once adorned the massive statues (moai) of Rapa Nui and compare them to 13 additional pukao located in Puna Pau, the island's red scoria pukao quarry. Through SfM, we demonstrate that the majority of these bodies have petroglyphs and other surface features that are relevant to archaeological explanation and are currently at risk of continued degradation.
The archaeological record of Rapa Nui (Easter Island, Chile) is noteworthy for its massive statue... more The archaeological record of Rapa Nui (Easter Island, Chile) is noteworthy for its massive statues (moai) that were transported over long distances with relatively small numbers of people and minimal use of resources. Equally impressive are the colossal bodies of red scoria (pukao) placed on the heads of many of the moai. In this study, we use three-dimensional models of 50 pukao found across the island and 13 red scoria cylinders from Puna Pau, the island's pukao quarry, to study the process of pukao manufacture, transport, and placement atop statues. Our analysis identifies surface features that are explained by the process of construction and transport of these multi-ton objects. Based on shared physical features of pukao, evidence in the archaeological record, and the physics necessary for pukao movement, we propose a falsifiable hypothesis in which relatively small numbers of people rolled pukao up stone ramps to place pukao atop moai. We conclude that activities of pukao production and transport did not require oversight by a centralized political authority, nor do they support notions of a large population that collapsed with " ecological suicide " on Rapa Nui.
Three decades of archaeological excavations in Melanesia and Western Polynesia have led to a cons... more Three decades of archaeological excavations in Melanesia and Western Polynesia have led to a consensus among Oceanic prehistorians that the initial human colonization of the southwestern Pacific (east of the Solomons) was effected by populations of the Lapita Cultural Complex (Green, 1979; Kirch, 1982, 1984; Allen, 1984; Spriggs, 1984). Although the western Melanesian islands of New Guinea, the Bismarck Archipelago, and possibly the Solomon Islands were settled in the late Pleistocene by small hunter-gatherer populations (Downie & White, 1979; Specht, Lilley & Normu, 1981; Groubeet al, 1986), discovery and occupation by humans of the more remote island chains to the east required sophisticated voyaging and colonization strategies. That the Austronesian-speaking Lapita people possessed long-distance voyaging craft is suggested both by lexical reconstructions, and by the archaeological evidence of long-distance transport of obsidian and other exotic materials over distances of up to 3...
American journal of physical anthropology, Oct 30, 2017
The Rapa Nui "ecocide" narrative questions whether the prehistoric population caused an... more The Rapa Nui "ecocide" narrative questions whether the prehistoric population caused an avoidable ecological disaster through rapid deforestation and over-exploitation of natural resources. The objective of this study was to characterize prehistoric human diets to shed light on human adaptability and land use in an island environment with limited resources. Materials for this study included human, faunal, and botanical remains from the archaeological sites Anakena and Ahu Tepeu on Rapa Nui, dating from c. 1400 AD to the historic period, and modern reference material. We used bulk carbon and nitrogen isotope analyses and amino acid compound specific isotope analyses (AA-CSIA) of collagen isolated from prehistoric human and faunal bone, to assess the use of marine versus terrestrial resources and to investigate the underlying baseline values. Similar isotope analyses of archaeological and modern botanical and marine samples were used to characterize the local environment. Re...
High resolution satellite photographs offer a new picture of the tracks along which the Easter Is... more High resolution satellite photographs offer a new picture of the tracks along which the Easter Island giant statues were hauled from the central quarry to the exhibition sites. The survey traced 32 km of seven major roads, confirmed by features on the ground, where their current condition gives reasons for concern. The authors suggest that the radial pattern implies social division into small groups.
Recent archaeological excavations in Miloli‘i Valley, Kaua‘i are discussed to provide data from a... more Recent archaeological excavations in Miloli‘i Valley, Kaua‘i are discussed to provide data from an isolated and marginal hinterland, far removed from the island’s political centres. We develop a chronological sequence of site construction and use and discuss the nature of pre-contact Hawaiian settlement and subsistence. We also outline elements of human–environment interactions from the settlement period to the protohistoric era, and provide tentative comparisons of the Miloli‘i hinterland sequence with those from core areas in the late prehistoric political hierarchy. Our case study highlights the degree to which inter- and intra-island variability remain relatively under-studied in the Hawaiian context.
Submarine groundwater discharge (SGD) is an important component of many coastal environments and ... more Submarine groundwater discharge (SGD) is an important component of many coastal environments and hydrologic processes, providing sources of nutrients to marine ecosystems, and potentially, an important source of fresh water for human populations. Here, we use a combination of unpiloted aerial systems (UAS) thermal infrared (TIR) imaging and salinity measurements to characterize SGD on the remote East Polynesian island of Rapa Nui (Easter Island, Chile). Previous research has shown that coastal freshwater seeps are abundant on Rapa Nui and strongly associated with the locations of ancient settlement sites. We currently lack, however, information on the differential magnitude or quality of these sources of fresh water. Our UAS-based TIR results from four locations on Rapa Nui suggest that locations of variably-sized SGD plumes are associated with many ancient settlement sites on the island and that these water sources are resilient to drought events. These findings support previous work indicating that ancient Rapa Nui communities responded to the inherent and climate-induced hydrological challenges of the island by focusing on these abundant and resilient freshwater sources. Our results highlight the efficacy of using UAS-based TIR for detecting relatively small SGD locations and provide key insights on the potential uses of these water sources for past and current Rapa Nui communities.
Examining how past human populations responded to environmental and climatic changes is a central... more Examining how past human populations responded to environmental and climatic changes is a central focus of the historical sciences. The use of summed probability distributions (SPD) of radiocarbon dates as a proxy for estimating relative population sizes provides a widely applicable method in this research area. Paleodemographic reconstructions and modeling with SPDs, however, are stymied by a lack of accepted methods for model fitting, tools for assessing the demographic impact of environmental or climatic variables, and a means for formal multi-model comparison. These deficiencies severely limit our ability to reliably resolve crucial questions of past human-environment interactions. We propose a solution using Approximate Bayesian Computation (ABC) to fit complex demographic models to observed SPDs. Using a case study from Rapa Nui (Easter Island), a location that has long been the focus of debate regarding the impact of environmental and climatic changes on its human population, we find that past populations were resilient to environmental and climatic challenges. Our findings support a growing body of evidence showing stable and sustainable communities on the island. The ABC framework offers a novel approach for exploring regions and time periods where questions of climate-induced demographic and cultural change remain unresolved.
ABSTRACTStructure from motion (SfM) mapping is a photogrammetric technique that offers a cost-eff... more ABSTRACTStructure from motion (SfM) mapping is a photogrammetric technique that offers a cost-effective means of creating three-dimensional (3-D) visual representations from overlapping digital photographs. The technique is now used more frequently to document the archaeological record. We demonstrate the utility of SfM by studying red scoria bodies known as pukao from Rapa Nui (Easter Island, Chile). We created 3-D images of 50 pukao that once adorned the massive statues (moai) of Rapa Nui and compare them to 13 additional pukao located in Puna Pau, the island's red scoria pukao quarry. Through SfM, we demonstrate that the majority of these bodies have petroglyphs and other surface features that are relevant to archaeological explanation and are currently at risk of continued degradation.
The archaeological record of Rapa Nui (Easter Island, Chile) is noteworthy for its massive statue... more The archaeological record of Rapa Nui (Easter Island, Chile) is noteworthy for its massive statues (moai) that were transported over long distances with relatively small numbers of people and minimal use of resources. Equally impressive are the colossal bodies of red scoria (pukao) placed on the heads of many of the moai. In this study, we use three-dimensional models of 50 pukao found across the island and 13 red scoria cylinders from Puna Pau, the island's pukao quarry, to study the process of pukao manufacture, transport, and placement atop statues. Our analysis identifies surface features that are explained by the process of construction and transport of these multi-ton objects. Based on shared physical features of pukao, evidence in the archaeological record, and the physics necessary for pukao movement, we propose a falsifiable hypothesis in which relatively small numbers of people rolled pukao up stone ramps to place pukao atop moai. We conclude that activities of pukao production and transport did not require oversight by a centralized political authority, nor do they support notions of a large population that collapsed with " ecological suicide " on Rapa Nui.
Three decades of archaeological excavations in Melanesia and Western Polynesia have led to a cons... more Three decades of archaeological excavations in Melanesia and Western Polynesia have led to a consensus among Oceanic prehistorians that the initial human colonization of the southwestern Pacific (east of the Solomons) was effected by populations of the Lapita Cultural Complex (Green, 1979; Kirch, 1982, 1984; Allen, 1984; Spriggs, 1984). Although the western Melanesian islands of New Guinea, the Bismarck Archipelago, and possibly the Solomon Islands were settled in the late Pleistocene by small hunter-gatherer populations (Downie & White, 1979; Specht, Lilley & Normu, 1981; Groubeet al, 1986), discovery and occupation by humans of the more remote island chains to the east required sophisticated voyaging and colonization strategies. That the Austronesian-speaking Lapita people possessed long-distance voyaging craft is suggested both by lexical reconstructions, and by the archaeological evidence of long-distance transport of obsidian and other exotic materials over distances of up to 3...
American journal of physical anthropology, Oct 30, 2017
The Rapa Nui "ecocide" narrative questions whether the prehistoric population caused an... more The Rapa Nui "ecocide" narrative questions whether the prehistoric population caused an avoidable ecological disaster through rapid deforestation and over-exploitation of natural resources. The objective of this study was to characterize prehistoric human diets to shed light on human adaptability and land use in an island environment with limited resources. Materials for this study included human, faunal, and botanical remains from the archaeological sites Anakena and Ahu Tepeu on Rapa Nui, dating from c. 1400 AD to the historic period, and modern reference material. We used bulk carbon and nitrogen isotope analyses and amino acid compound specific isotope analyses (AA-CSIA) of collagen isolated from prehistoric human and faunal bone, to assess the use of marine versus terrestrial resources and to investigate the underlying baseline values. Similar isotope analyses of archaeological and modern botanical and marine samples were used to characterize the local environment. Re...
High resolution satellite photographs offer a new picture of the tracks along which the Easter Is... more High resolution satellite photographs offer a new picture of the tracks along which the Easter Island giant statues were hauled from the central quarry to the exhibition sites. The survey traced 32 km of seven major roads, confirmed by features on the ground, where their current condition gives reasons for concern. The authors suggest that the radial pattern implies social division into small groups.
Recent archaeological excavations in Miloli‘i Valley, Kaua‘i are discussed to provide data from a... more Recent archaeological excavations in Miloli‘i Valley, Kaua‘i are discussed to provide data from an isolated and marginal hinterland, far removed from the island’s political centres. We develop a chronological sequence of site construction and use and discuss the nature of pre-contact Hawaiian settlement and subsistence. We also outline elements of human–environment interactions from the settlement period to the protohistoric era, and provide tentative comparisons of the Miloli‘i hinterland sequence with those from core areas in the late prehistoric political hierarchy. Our case study highlights the degree to which inter- and intra-island variability remain relatively under-studied in the Hawaiian context.
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