by Sarah Parcak
In case you are wondering, that is insane. When I saw the news, I yelled so loudly my husband thought our cat had jumped on my back.
Those results are all part of a three-year project run by the PACUNAM LiDAR Initiative. which has plans to map 14,000 square kilometers of Guatemala. Fundación PACUNAM is a not-for-profit focused on conservation and research in the Maya Biosphere Reserve. Francisco Estrada-Belli, one of the project co-directors, described to me the perils of ground work near Holmul.
In the middle of the night, he was awakened by something moving beneath his air mattress. Lifting it up, he found a five-foot-long snake coiled beneath where his head had just rested. The worst part: he had to put the mattress back down over the snake to get his pants on before getting help. And you thought only the archaeology was exciting!22
Assuming similar densities of features, there could be as many as 400,000 previously unknown structures in the surveyed area alone. Maya civilization covered more than 300,000 square kilometers at its peak in about 800 AD, which means nearly 8.6 million potential sites and features could be hidden beneath the lush rainforests of Central America. And that’s not even counting the vast landscape reshaping the Maya achieved. As my students say, I can’t even.
The Secrets of the Amazon
After so many new sites to see, relax onboard ship for a while, while we sail along the coast of Brazil, and past the Amazon rainforest, which has an area of around 6 million square kilometers.23 Starting more than a hundred years ago, a new age of archaeological exploration took root in its diverse regions. The disappearance of Percy Fawcett in 1925 in his quest to discover the city of “Z,” as he called it, a mythical place somewhere in the Amazon, is one of the most well-known tales.24
Whatever happened to him, Fawcett was partially right, as Michael Heckenberger of the University of Florida found. Working with Indigenous groups, he and his team located 28 previously unknown plaza towns and villages in the Upper Xingu headwaters of the Amazon.25 These settlements included a series of ditches and could be connected by ancient roads.26 Though the team did not make these discoveries using satellite imagery, they showed the intensity of pre-Columbian occupation in the Amazon. We can only imagine what remote sensing will show in the region.
Also in Amazonia, in the Acre district of western Brazil, a team led by Martti Pärssinen of the University of Helsinki used aerial photographs and Google Earth to identify more than 200 new geoglyphs. Like the Nazca lines, these figures or geographic patterns are created on the ground by humans out of natural materials such as stone, or by clearing away stones, on a sometimes epic scale. In Acre, they are signs of a “new” civilization dating between 200 and 1283 AD. The satellite imagery, taken after deforestation occurred, allowed the team to map the sites in great detail and revealed curious shapes with diameters from 90 meters to 300 meters—one to three American football fields—which could have been ceremonial, defensive, or both. Work on the ground led researchers to suggest a population of more than 60,000 in a region once considered too marginal for intensive exploitation. With the limited coverage of Google Earth, the team believes they’ve found only 10 percent of the features in the region. That means there may be nearly 2,000 other monumental structures there.27
It shows the region’s extraordinary potential for archaeological discovery. The Amazon might once have been as densely occupied as the Maya region in Central America. I hope LIDAR can be applied broadly there soon, and I expect big headlines.
As we sail around Cape Horn, things could get a little dicey on-board. Load up on the seasickness tablets, because we’re on our way to Peru! You might be familiar with the epic tale of Hiram Bingham’s 1912 investigation of Machu Picchu, which is now considered to be the top tourist destination in South America, but that was a hint of what was to come.28
Across Peru, high-resolution satellite imagery and drones have allowed both archaeological discoveries and the mapping of looting across many ancient sites.29 Peru has a long history of looting, and, sadly, you can see thousands of looting pits at many ancient cemeteries. Looters sift through graves looking for bright colored textiles to sell, and they’re often successful. Recently, I made a quick search of eBay under “antiquities Peru textiles,” and it revealed dozens, from the Chimú, Huari, and Chancay cultures. None of the listings had site locations, which suggests very strongly their sketchy origins.
To map threatened Peruvian sites enables archaeologists to begin safeguarding them. One team, led by Rosa Lasaponara, used a combination of QuickBird and WorldView-1 satellite imagery to reveal evidence of potential buried adobe features at the Piramide Naranjada, which they later confirmed with ground-penetrating radar and magnetometry.30 Elsewhere, archaeologist and former vice-minister of culture for Peru, Luis Jaime Castillo, has used drones to create beautiful and awe-inspiring 3-D models of dozens of sites, making Peru perhaps one of the most thoroughly drone-mapped countries in the world.31
Polynesian Preconceptions
We have some time to rest as we cross the ocean, so a bit of an introduction before we disembark for our next site tour at one of the most well-known archaeological islands in Polynesia. Today a part of Chile, Easter Island has more than 900 large stone statues called moai, the famous standing humanoid sculptures, located within a landscape of only 163.6 square kilometers. One of the reasons I love the story of work here is that it shows how satellite technologies have upended long-held assumptions about how and why the Rapa Nui civilization “collapsed.” Things are often more complex than they seem.
Walking around the island, you’ll be struck by its light green landscape outlined starkly against the backdrop of the Pacific. It seems so cut off, especially after what you saw in Guatemala. The stone sentinels themselves are square-jawed, stoic, and challenging, daring us to wonder how they came to be.
Europeans came to the island for a day in 1722 and again in 1770, and found a population of 3,000 people. The general assumption about the Rapa Nui was said to be a lesson for us today: when they occupied the island, they overexploited its natural resources, destroyed the forest, and drove their animals to extinction. Earlier archaeologists had assumed Easter Island was first occupied between 400 and 800 AD, but using radiocarbon dating of seeds, archaeologists Carl Lipo of Binghamton University and Terry Hunt of the University of Oregon have found evidence for a much later colonization, after 1200 AD.32
Using high-resolution satellite imagery, Lipo and Hunt mapped the roads on which the ancient moai were transported across the island.33 During their survey work, they discovered 62 moai along roads leading from the source quarry. Based on the resting positions of the statues, the team proved the hypothesis that they were “walked” upright by groups of people on either side—not dragged—to their final positions.34 The discovery dispenses with the fixed idea of mass deforestation just to create rollers to move the moai. The Rapa Nui exploited their own ingenuity, not their forests, to move their greatest works of art.
Where deforestation happened for agricultural purposes, the people preserved the land’s productivity by crushing volcanic rocks and adding them to their gardens like mulch.35 Based on recent geospatial analysis, it appears the Rapa Nui built their ahu, or megalithic platforms on which one or more moai can be found, close to freshwater sources, potentially indicating a display of territories connected to a limited natural resource.36 Rather than bringing about their own demise, the Rapa Nui were decimated by disease brought by the Europeans.37
As we leave the island behind us, alone in the wild sea, you can wonder what else the West has misinterpreted about Indigenous groups across the globe to fit preconceived notions rooted in a colonialist mentality. Remote sensing, it seems, could provide a more factual interpretation.
The Silk Road
Across the ocean, west into Asia, we see endless landscapes unroll in front of us, with equally extensive opportunities for remote sensing. It’s a huge area: vast regions of the Silk Road remain unmapped, yet Chinese archaeologists have
already created a database of 51,074 sites dating from 8000 BC to 500 AD, taken from site maps of 25 Chinese provinces.38
The Silk Road, used for over 1,500 years, stretched across land and sea from China, to India, into Indonesia, across Iran, through the Middle East, to East Africa, and on to Europe. Not one road, it was many routes that fluctuated over time based on access to water and other resources. The full scale of the sites along the Silk Road, and the number of roads in this network, are still emerging. Many sites along the Silk Road can be differentiated according to time period by their shape and size from space, without a ground survey, which throws open the potential for future remote-sensing efforts to reveal and date many hundreds of additional archaeological treasures there.
In one study, CORONA and Google Earth data helped archaeologists N. K. Hu of Shaanxi Normal University and X. Li of the Chinese Academy of Sciences expose 70 previously unknown sites in northwestern China around the Juyan Oasis, dating primarily from 1028 to 1375 AD.39 Imagine the other oases, the trade posts and junctions on the routes, that still remain to be mapped.
Sailing west, we round Thailand, Vietnam, and Cambodia, filled with the magnificent temples of the Khmer. The rainforests of Thailand and Vietnam have not yet been mapped, but I’ve heard rumors that new LIDAR campaigns are about to be launched. Adventure awaits.
New Beginnings for the Indus Valley
And here we are in India. Vibrant, varied, and ancient, it’s a country with some of the greatest remote sensing potential on Earth. A big part of this tempting prospect is the Indus Valley Civilization, relatively unmapped from space, unlike similarly ancient civilizations Egypt and Mesopotamia. Larger than both, the Indus Valley Civilization swept across India, Pakistan, and beyond.
Results of recent mapping lead us to expect great things. One team, led by Cameron Petrie of the University of Cambridge, has used remote sensing and ground surveys in northwest India40 to visualize relationships between ancient sites and the rivers close to them. The team mapped more than 10,000 square kilometers of ancient river channels using medium-resolution satellite data sets. They created a 3-D model of the landscape’s topography and have very kindly provided their code for all researchers to use.41
Another team, led by Ajit Singh of the Indian Institute of Technology, Kanpur, and Sanjeev Gupta of Imperial College London, made a global splash when they used radar-derived elevation models and Landsat data to locate an ancient channel of the Sutlej River, known as the Ghaggar-Hakra, in northwest India. For over a century, archaeologists believed that the densest concentrations of Indus Valley urban settlements relied on a major river with its source in the Himalayas. They were so convinced, they claimed that when the river dried up or moved, the urban sites declined and were abandoned between 2000 and 1900 BC.
This is a tidy story, but the remote-sensing work and subsequent coring and dating efforts overturned it completely. The new research proved that the river actually dried up by 6000 BC, long before the rise of the Indus Valley Civilization around 3000 BC. This suggested that Indus Valley settlements appeared along the relic river channel because of its relative stability, free from unpredictable flooding.42
I’m very excited about what will be found right across Asia in the next few years. We can sit back and contemplate that as we sail across the Indian Ocean to South Africa. We’ll need to enjoy a few vineyards to recover.
Our Earliest Ancestors
This is where it all gets dusty, and hot. Much of the African continent remains unmapped and unexplored archaeologically. It would take volumes to even begin to describe the extraordinary diversity of cultures and peoples who have lived there since the first Homo sapiens. Going further back, our family tree looks more like a dense bush, and new ancient human ancestor fossil sites sometimes appear in unexpected places. We have barely scratched the surface in understanding our human origins, and I think Africa represents the greatest frontier for archaeological discovery in the world.
Large regions of East and South Africa are ripe for exploration using satellite imagery, and contain some of the best-known sites where early human fossils have been found. And plants, not artifacts, lay our trail here. Paleoanthropologist Lee Berger, from the University of the Witwatersrand, in South Africa, used Google Earth to find wild olive and stinkwood trees, which tend to grow near the entrances of caves in South Africa.43 Perhaps ideal sites for our early ancestors’ shelters, those caves can contain new species of early humans.
Around the Turkana Basin, in Kenya, the son of world-famous anthropologists Louis and Mary Leakey, Richard, and his wife, Maeve, made many of their famous discoveries. Today, their daughter Louise continues the family tradition. Hyperspectral cameras and other remote-sensing tools might assist such evolution explorers in the location of other sites. Fossils emerge from the ground after rains or as a result of erosion processes; when they could be scattered across areas measuring hundreds of square kilometers, a ground-based surveyor is limited to lucky finds and happy accidents.
However, high-resolution maps, created by hyperspectral cameras, showing exactly where other fossils might emerge, would better target their search. In a collaborative project with Louise Leakey and her team in the Turkana Basin, I was proud to help develop such mapping. While the results are largely preliminary, the cameras did detect areas with the same spectral signatures as other fossil-rich deposits. The mind boggles at how such new data might assist in our understanding of our own evolution.
Zimbabwean Achievements
It’s a long, long trek overland, north and east to our next stop. The massive stone-built ruins of Great Zimbabwe, capital of the Zimbabwe people, is a UNESCO World Heritage site and has recently been remapped using high-resolution satellite imagery. From 300 BC to 1900 AD, Great Zimbabwe had five phases of occupation. Unfortunately, archaeological work had to stop altogether in the 1990s because of the political situation there.
Thanks to Shadreck Chirikure and his team at the University of Cape Town, work has recently resumed, and already, satellite data has shown previously unknown terracing, unmapped walls, and three routes up the main hill complex of the site.44 Perhaps an additional satellite survey will add to our knowledge of the 200 or so smaller Zimbabwes, other stone enclosures such as Mapela Hill in southwestern Zimbabwe, showing that the region had a far greater political importance than previously assumed.45
We’re back into tree cover again in Central Africa, where a rainforest measuring millions of square kilometers stretches through Cameroon, Gabon, Congo, Uganda, and up into the Central African Republic. In West Africa, too, dense vegetation blankets the landscape. It’s largely unexplored for archaeology, with work beginning only in the last 50 years.
Exploration on the ground is difficult in the region because of ongoing wars, disease, and lack of infrastructure. Given the region’s rich history, though, and recent discoveries of new sites and features in the rainforests across the Atlantic, the area is crying out for LIDAR work. Who knows what could be found; maybe even large-scale farming or other signs of entirely undefined civilizations. If I could pick anywhere in the world to turn my archaeological all-seeing eyes, this would be it. Discoveries there could shake up our perceptions of the continent.
Familiar Territory
Northward up the east coast of Africa, we come to the great snorkeling opportunities of the Red Sea. Its crystal waters are rich with coral and brightly colored parrotfish and angelfish, and the seafood is great. A project led by Matthew Meredith-Williams using radar and high-resolution satellite images has revolutionized our understanding of more than 4,200 shell-midden sites in the Farasan Islands and Dahlak Archipelago, off the coasts of Saudi Arabia and Eritrea, respectively.
These middens show up as hills of hundreds of thousands of shells, measuring up to 6 meters in height, and they are common throughout the world where people depended heavily on the fruits of the sea. Archaeologists knew of only 20 before, so this is a wealth of new information. The mounds range in age, but m
ost probably formed more than 5,000 years ago,46 which suggests that there could have been many more people than were previously assumed living in the area.
Inland, through the dry desert river wadis carved down through the sand and rock, we come to ancient Nubia, in modern Sudan and the far south of Egypt. It was one of the greatest civilizations in Africa, and has received less attention and less satellite imagery analysis than its more famous northern neighbor. Rising waters from dam projects in Sudan prompted major surveys in the 1960s, leading to numerous archaeological discoveries. Today, similar dam projects threaten vast tracts of land, which archaeologists once more have limited time to survey.
The promise of satellite imagery for detecting sites shines at the archaeological sites of Karima and Gebel Barkal, 350 kilometers north of Khartoum. Archaeologists located relic courses of the Nile, created high-resolution 3-D site maps, and found a wealth of features for investigation in future seasons at Gebel Barkal.47 I cannot stress enough the urgency of using satellite imagery here—this part of Sudan may contain hundreds of unknown sites, and development, including gold mining, also represents a serious threat.48
As we pass by Egypt through the Suez Canal, we can look west to the Nile Delta. I had adventures to last me a lifetime of dinner parties during my survey work there, including the time when a man demanded that I marry his toothless son. I told him his son would not be able to enjoy my cooking, and the father answered, without missing a beat, “Do not worry! He can enjoy your soup!”