Andean Archaeology Revealed On An Unprecedented Scale

Astounding GeoPACHA software is advancing Andean archaeology. The new and innovative web application is allowing researchers to map archaeological features in the Andes mountains of South America with heightened precision and on a larger scale than ever before.

The Geospatial Platform for Andean Culture, History and Archaeology, or GeoPACHA, collects and coordinates high-resolution satellite imagery covering broad swaths of mountainous territory in central, southern and coastal Peru. The GeoPACHA site can be accessed from anywhere by researchers who have the necessary training to spot archaeologically significant ruins and formations.

Within Andean archaeology there may be thousands of previously undiscovered features just waiting to be found. While the discovery of a single new archaeological site can be exciting, it is the opportunity to find many such sites in identifiable distribution patterns that is creating so much buzz around the new GeoPACHA application.

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“One of the most substantial challenges in archaeology is aligning the scales of our datasets with those of the social worlds that we seek to study,” explained the developers of the GeoPACHA software, Dr. Steven Wernke from Vanderbilt University and Dr. Parker VanValkenburgh from Brown University in the United States.

“Archaeologists are often asked to solve large-scale problems -- for example, to estimate the populations of ancient empires or to evaluate the effects of past climate change on settlement patterns across a continent –– but it's very hard, if not impossible, to use conventional archaeological methods to collect the kinds of systematic data needed to answer these questions.”

So far GeoPACHA has proven to be the ideal solution to this ongoing conundrum. Dr. Wernke and Dr. Van Valkenburgh have been joined by other researchers who study past Andean civilizations in their examinations of the initial GeoPACHA data sets, and already much has been learned about pre-Hispanic settlement and building patterns in Peru’s most mountainous terrain.

Map of all areas covered in the survey (Stephen Wernke / Antiquity Publications Ltd)

The Future of Satellite-Based Andean Archaeology Has Arrived

In a special collection of articles appearing in the journal Antiquity, researchers who’ve been analyzing GeoPACHA imagery report the results of their newly completed surveys of the Peruvian Andes. What has already been learned is rapidly transforming the practice of Andean archaeology and anthropology, as scientists are finally able to look at its rocky, hidden landscapes in detail and across hundreds of miles. From the vantage point provided by satellites they are tracing connections between freshly discovered sites that wouldn’t have been so obvious in the past.

“Imagery-based survey is capable of producing archaeological datasets that complement those collected through field-based survey methods, widening the scope of analysis beyond regions,” the authors of the new studies explained. “Using GeoPACHA, teams pursue problem-specific research questions through a common data schema and interface that allows for inter-project comparisons, analyses and syntheses.”

One of the most significant innovations associated with this new platform is its incorporation of artificial intelligence tools to assist in analysis. “Conducting manual surveys of satellite imagery is labor- and time-intensive, and low target prevalence substantially increases the likelihood of miss-errors (false negatives),” a team of experts led by Vanderbilt University archaeologist James Zimmer-Dauphinee wrote in one of the Antiquity articles.

They noted that their initial results using AI “suggest that future surveys may benefit from a hybrid approach—combining manual and automated methods—to conduct an AI-assisted survey and improve data completeness and robustness.”

Aerial photographs of archaeological features in the Andes. (Figure by authors; image copyright held by Maxar, reproduced under the NextView End User Licence Agreement. James Zimmer-Dauphinee / Antiquity Publications Ltd)

The First GeoPACHA Survey Results Are In, and the Implications Are Profound

The GeoPACHA system has already proven extraordinarily useful for examining and cross-referencing diverse and spatially separated surface features within Andean archaeology. In two of the newly published Antiquity studies, teams of archaeological researchers led by Dr. Giles Spence Morrow from Vanderbilt University in the first instance and Dr. Elizabeth Arkush from the University of Pittsburgh in the second describe the distribution of hilltop forts in the northern coastal and south-central highlands areas of Peru respectively.

These solid defensive structures were built by Andes people living in Peru during the Middle Horizon Period (500-1000 AD) and the Late Intermediate Period (1000-1450 AD), or in the last few centuries preceding the Spanish Conquest (the Spanish invasions of Peru began in 1526 AD).

Two hilltop forts or pukaras identified by Arkush in the survey. (Ryan Smith and ChristopheDelaere / ALTI-plano / Antiquity Publications Ltd).

In the second of these two related studies, the researchers analyzed hilltop fortresses distributed over a 58,000 square mile (151,103 square kilometer) area. This demonstrates the immense range of both satellite surveying technology and the new GeoPACHA coordinating system that is harvesting and processing its imagery.

In another intriguing GeoPACHA study freshly published in Antiquity, researchers led by anthropologist Dr. Giancarlo Marcone from Peru’s University of Engineering and Technology in Lima reveal a wealth of new details about the settlement patterns of ancient peoples who lived in scattered Andes oases known as ‘lomas’.

Until now very little has been known about how many people actually lived in these lush, green areas in pre-Spanish times. But GeoPACHA imagery has shown signs of human activity and settlement in quite a few of these patches of vegetation along the Andes coastline near Lima, revealing how the indigenous people survived in what was mostly an arid and desolate region.

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“Lomas settlements are under-represented in archaeological datasets due to their tendency to be located in remote inter-valley areas,” Dr. Marcone and his associates explained. By employing satellite imaging to map the locations of human-built structures, they were able to identify “two categories of archaeological features, large corrals and clustered structures, and document a concentration of settlement features within lomas landscapes that suggests a pre-Hispanic preference for both short- and long-term occupation of these verdant oases.”

In yet another fascinating GeoPACHA study discussed in Antiquity, Drs. Van Valkenburgh and Wernke and their colleague Dr. Bethany Whitlock from Brown University disclosed extensive new information about the distribution of pre-Spanish pastoralist settlements in the Huancavelica region of Peru’s central interior.

“Recent archaeological research in the Andes suggests that Indigenous herders carefully managed their environments through the modification of local hydrology and vegetation,” the study authors wrote. “However, the limited geographical scale of previous research makes it challenging to assess the range and prevalence of pastoralist land management in the Andes.”

Through their examination of GeoPACHA imagery, the researchers discovered that indigenous corrals and pastoralist settlements “cluster around colonial and present-day settlements and that a statistically significant relationship exists between pastoral infrastructure and perennial vegetation.” This shows that the ancient inhabitants of the Peruvian Andes successfully identified the most fertile areas in the region for cattle grazing and for human settlements, and that later occupants simply followed their lead.

A Revolutionary Technology Unleashed

One of the early surprises of the GeoPACHA surveys is the discovery that ancient communities in the Peruvian Andes were not scattered evenly across the landscape. Approximately 95 percent of the area surveyed so far has revealed no signs of human occupation or activity.

“Because many of these areas are also not currently inhabited and are difficult to reach, they are also places where pedestrian surveys are less likely to be conducted,” Drs. VanValkenburgh and Wernke said. “The result is that our current models of settlement distribution are biased in favor of densely inhabited areas.”

It therefore seems that GeoPACHA is already upending some previous assumptions about the activities of ancient Andean peoples within Andes archaeology, which highlights the technology’s revolutionary implications.

The newly obtained GeoPACHA data is just the tip of the iceberg of what this type of archaeologically oriented application is capable of accomplishing. Satellites are now photographing every area of the arth, and as news of the success of GeoPACHA spreads archaeologists elsewhere will inevitably begin working on their own versions of this highly efficient and impressively effective technology.

Top image: Hillforts (pukaras) in the south-central highlands of Peru. Source: Elizabeth Arkush, Lauren Kohut, Romuald Housse, Ryan Smith, & Steven A. Wernke / Antiquity Publications Ltd

By Nathan Falde