Using Structure from Motion Mapping to Record and Analyze Details of the Colossal Hats (Pukao) of Monumental Statues on Rapa Nui (Easter Island)

Structure 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 Pukao of Rapa Nui (Easter Island, Chile)

Structure from motion (SfM) mapping is a photogrammetric technique that offers a cost-effective means of creating three-dimensional visual representations from overlapping digital photographs. The technique has seen increasing uses for documenting the archaeological record. We demonstrate the utility of SfM through a study of the form of red scoria bodies known as pukao from Rapa Nui (Easter Island, Chile). We study 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 Ethnohistory of Freshwater Use on Rapa Nui (Easter Island, Chile)

Sources of drinking water on islands often present critical constraints to human habitation. On Rapa Nui (Easter Island, Chile), there is remarkably little surface fresh water due to the nature of the island’s volcanic geology. While several lakes exist in volcanic craters, most rainwater quickly passes into the subsurface and emerges at coastal springs. Nevertheless, the island sustained a relatively large human population for hundreds of years, one that built an impressive array of monumental platforms (ahu) and statues (moai). To understand how Rapanui acquired their scarce fresh water, we review ethnohistoric data from first European arrival (1722) through the mid-twentieth century. Ethnohistoric accounts identify a diversity of freshwater sources and describe various Rapanui freshwater management strategies. Our findings highlight the importance of coastal freshwater seeps and provide much-needed insight into how Rapanui procured this vital and necessary resource

Rapa Nui (Easter Island) monument (ahu) locations explained by freshwater sources

Explaining the processes underlying the emergence of monument construction is a major theme in contemporary anthropological archaeology, and recent studies have employed spatially-explicit modeling to explain these patterns. Rapa Nui (Easter Island, Chile) is famous for its elaborate ritual architecture, particularly numerous monumental platforms (ahu) and statuary (moai). To date, however, we lack explicit modeling to explain spatial and temporal aspects of monument construction. Here, we use spatially-explicit point-process modeling to explore the potential relations between ahu construction locations and subsis- tence resources, namely, rock mulch agricultural gardens, marine resources, and freshwa- ter sources—the three most critical resources on Rapa Nui. Through these analyses, we demonstrate the central importance of coastal freshwater seeps for precontact populations. Our results suggest that ahu locations are most parsimoniously explained by distance from freshwater sources, in particular coastal seeps, with important implications for community formation and inter-community competition in precontact times

Presenting the AfriArch Isotopic Database

AfriArch is an archaeological and paleoenvironmental data community designed to integrate datasets related to human-environmental interactions in Holocene Africa. Here we present a dataset of bioarchaeological stable isotope (C/N/O) and radiocarbon measurements from African archaeological sites spanning the Holocene. Modern measurements, when reported together with archaeological data in original publications, are also included. The dataset consists of 5568 entries and covers the entirety of Africa, though most isotopic research has been concentrated in southern Africa. The AfriArch isotopic dataset can be used in paleodietary, paleodemography, paleoclimatic, and paleoenvironmental studies. It can also be employed to highlight data gaps across space and time and set future research agendas

The Colossal Hats (pukao) of Monumental Statues: An Analysis of Pukao on Rapa Nui (Easter Island)

156 pages. A thesis presented to the Department of Anthropology and the Clark Honors College of the University of Oregon in partial fulfillment of the requirements for degree of Bachelor of Science, Spring 2015.As part of monumental statue (moai) construction during the prehistory of Rapa Nui, islanders quarried masses of red scoria, carved them into hats (pukao), and placed them atop statues measuring up to 10 meters tall. Despite overall great interest in moai and the improbable magnitude of pukao that were raised to reach their positions on the heads of statues, few studies have investigated pukao production, transport, and placement. This study seeks to analyze three-dimensional variability of pukao using 15,000 photos of 50 pukao found near statues and 13 red scoria cylinders located in the quarry. These models are used to evaluate which surface features are stylistic with related temporal and spatial variability and which are functional and relate to construction and transport of these multi-ton objects. The functional detail has the potential to shed light on how prehistoric islanders designed pukao to be placed atop moai. To this end, additional three dimensional models of statue platforms (ahu) and moai are combined with the models of pukao to test the feasibility of the hypothesis that the pukao were placed atop moai using stone ramps. The hypothesis in which relatively small numbers of Rapanui placed pukao atop moai by rolling the former up ramps is supported by physical calculations and best explains the archaeological record

Drought Coincided with, but Does Not Explain, Late Holocene Megafauna Extinctions in SW Madagascar

Climate drying could have transformed ecosystems in southern Madagascar during recent millennia by contributing to the extinction of endemic megafauna. However, the extent of regional aridification during the past 2000 years is poorly known, as are the responses of endemic animals and economically important livestock to drying. We inferred ~1600 years of climate change around Lake Ranobe, SW Madagascar, using oxygen isotope analyses of monospecific freshwater ostracods (Bradleystrandesia cf. fuscata) and elemental analyses of lake core sediment. We inferred past changes in habitat and diet of introduced and extinct endemic megaherbivores using bone collagen stable isotope and 14C datasets (n = 63). Extinct pygmy hippos and multiple giant lemur species disappeared from the vicinity of Ranobe during a dry interval ~1000–700 cal yr BP, but the simultaneous appearance of introduced cattle, high charcoal concentrations, and other evidence of human activity confound inference of drought-driven extirpations. Unlike the endemic megafauna, relatively low collagen stable nitrogen isotope values among cattle suggest they survived dry intervals by exploiting patches of wet habitat. Although megafaunal extirpations coincided with drought in SW Madagascar, coupled data from bone and lake sediments do not support the hypothesis that extinct megafauna populations collapsed solely because of drought. Given that the reliance of livestock on mesic patches will become more important in the face of projected climate drying, we argue that sustainable conservation of spiny forests in SW Madagascar should support local livelihoods by ensuring that zebu have access to mesic habitat. Additionally, the current interactions between pastoralism and riparian habitats should be studied to help conserve the island’s biodiversity

Climate Change, Megafaunal Extinctions, and Human Colonization of Madagascar

Biodiversity provides us with a host of cultural, scientific, and economic benefits, and highly biodiverse islands such as Madagascar are the focus of many conservation efforts. History provides essential context to the current biodiversity crisis and can influence how conservation groups engage with local communities. On Madagascar, environmental history narratives since the French colonial era have emphasized past human contributions to deforestation and species extinctions. However, these inferred contributions, and even the time of initial human arrival on Madagascar, are based on limited data and subject to ongoing archaeological debate. I use chemical analyses of subfossil bone and lake sediments recovered from archaeological fieldwork and museum collections to test ideas that past animal introductions and drought contributed to the disappearance of endemic megafauna in arid SW Madagascar.Radiocarbon data from introduced ungulates (cattle, sheep, goats, and bushpigs, n=59) and endemic megafauna (pygmy hippopotamuses, giant tortoises, elephant birds, and giant lemurs n=213) demonstrate 1) that the spread of pastoralism in SW Madagascar coincided with a pulse of megafaunal extinction ~1,000 years ago and 2) that this turnover occurred hundreds to possibly thousands of years after the first directly 14C-dated trace of human activity on the island. Directly 14C-dated butchered bone suggests that humans hunted extinct Malagasy megafauna for thousands of years, yet the spread of pastoralism likely heightened the impact of this hunting as pastoralism aided expanding human populations. Moreover, stable carbon and nitrogen isotope data suggest that sheep, goats, tortoises, and hippos had broadly similar diets or exploited similar habitats, which left potential for direct forms of competition between sheep and goats and endemic megaherbivores. Introduced domestic dogs also share a mutualism with pastoralists who occasionally hunt, and 14C-dated dog bone collected from across Madagascar suggest that dogs at least briefly co-occurred with the island’s extinct megafauna ~1,000 years ago. Dogs could have facilitated human-led hunts of forest-dwelling extinct megafauna, yet relatively high stable carbon isotope values in dog collagen suggest few individuals consumed primarily forest bushmeat. The distinct isotopic niches of dogs and the endemic forest predator known as the fosa (Cryptoprocta ferox) suggest that any negative interaction between the two follows from something other than predation and exploitation competition (e.g., interference competition and disease transmission).Ongoing aridification is a major concern for agropastoralists in southern Madagascar, and it is unclear the degree to which introduced livestock and endemic megafauna were sensitive to drought. Geochemical analysis of a sediment core from SW Madagascar revealed a succession of dry intervals during the last ~1600 years. The driest interval coincided with the appearance of livestock and the disappearance of endemic megafauna around the lake. Coupled lake sediment and bone stable carbon isotope records suggest that pygmy hippos and cattle coped with vegetation changes associated with past aridification and forest clearance by consuming more xerophytic C4 and CAM plants during drier times. However, unlike the endemic megafauna, cattle may have been more sensitive to drought, as their bone collagen stable isotope values suggest they survived by strategically exploiting wet habitat during dry intervals of the past millennium. I worked with members of the Morombe Archaeological Project to excavate three additional coastal ponds in SW Madagascar (Tampolove, Ankatoke, and Andranobe), which revealed different lengths of co-occurrence among humans, introduced vertebrates, and extinct endemic livestock during the past six millennia. Although the modification of a bone from an extinct pygmy hippo and the deposition of human subsistence remains (e.g., cutmarked fish bones and processed mangrove whelk shells) recovered from these ponds likely span only the past millennium, a directly dated introduced bushpig tooth from ~4,000 years ago may help confirm that humans were present on the island by the mid Holocene. The disappearance of extinct megafauna (particularly giant tortoises and pygmy hippos) in the vicinity of these three sites matches regional extinction patterns in SW Madagascar. Together, these data clarify species-specific responses to past ecological and climatic stressors and suggest that the spread of pastoralism, rather than simply the presence of human hunters or occurrence of drought, contributed to past megafaunal extinction on Madagascar

Student Robotics Competition using Robolab and Lego Bricks

Engineering-based competitions can provide an educational environment that integrates technical skills and teamwork. While many competitions require significant activity prior to the event, an introductory competition can be designed that requires minimal advance preparation and technical knowledge. Such an event could be used as an engineering experience for precollege teachers and students, first-year engineering majors, and multidisciplinary teams. A model for an introductory robotics competition is described based on Robolab and Lego systems. The technical culmination of the competition is to build and program a Lego vehicle for a fast and slow race. The winners create the fastest vehicle for a five-meter race and the slowest vehicle for a 0.5-meter race. Other objectives such as following a line through a simple course could be used. The approach consists of an afternoon training session and an evening competition. The training incorporates fundamental concepts of engineering and software programming. This competition was implemented and assessed for precollege teachers and students at the IEEE GLOBECOM 2005 technical conference. The intent was to provide an outreach hands-on experience in engineering to complement the participation of the precollege attendees in the conference activities. Similar introductory competitions can be used as precollege outreach activities for professional and university meetings, as teamwork activities for first-year engineering students, or as social interaction among engineering student groups