The technology uncovering humanity's past -- and perhaps its future.
- By Douglas PrestonDouglas Preston is the author of many books, including Cities of Gold: A Journey Across the American Southwest.
Archaeologists discovered the Maya city of Caracol, hidden in the jungles of Belize, in the 1930s. In the 1980s, the husband-and-wife team of Arlen and Diane Chase began the daunting project of mapping Caracol and its environs. With teams of assistants and students, they tramped through the rain forest, recording and measuring every archaeological feature they could find. By 2009, after 25 years of labor, they had some of the most detailed maps ever made of a Maya city.
Then they tried a new mapping tool: "light detection and ranging" technology, or lidar. Although lidar had been used for years to survey large-scale features for projects such as urban planning and planetary exploration, only recently had it gained the resolution necessary for archaeological mapping. The Chases joined forces with NASA and the National Center for Airborne Laser Mapping at the University of Houston, which supplied a plane retrofitted to carry a million-dollar lidar machine that flew five missions over Caracol and its environs, mapping the ground with lasers.
When the images came back, the Chases were stunned. The lidar maps showed that in the quarter-century they had spent roaming the rain-forest floor, they had found only about 10 percent of what was actually there. The new maps revealed tens of thousands of previously unknown features, large and small-structures, houses, roads, reservoirs, terracing, sinkholes, caves (some with burials and artifacts), and even open and looted tombs. In a little more than nine hours, the lidar mission had revealed that Caracol was a far larger area than previously imagined, an urban landscape covering 200 square kilometers.
The Chases declared lidar the greatest archaeological advance since carbon-14 dating, which won its discoverer a Nobel Prize and transformed the science of archaeology. It’s true that archaeology is on the verge of another revolution because of lidar. The technology will soon strip away the world’s jungles to reveal their lost civilizations and hidden treasures, a prospect recently demonstrated in dramatic fashion by Bill Benenson and Steve Elkins.
A few years ago, the two filmmakers had the crazy idea of mapping a large swath of unknown rain forest in the rugged interior mountains of Mosquitia, a region in Honduras. These mountains have the distinction of being among the last archaeologically unexplored regions on Earth, cut off by dense jungles, malarial swamps, roaring torrents, steep ravines, deadly snakes, and the even more formidable Honduran bureaucracy.
Benenson and Elkins were looking for a legendary lost city, known as La Ciudad Blanca (the White City), long rumored to be hidden in the area. They persuaded the National Center for Airborne Laser Mapping to undertake the speculative project, the first to use lidar for pure exploration. (Previously, it had only been used to survey known sites.) And in May 2012, they spent a number of days flying over the Mosquitia mountains, logging a little more than eight hours of actual mapping time.
I accompanied Benenson, Elkins, and their team to Honduras as a journalist — a trip I later wrote about for the New Yorker — even though I believed their chances of finding something were small. Nothing much happened in the first few days, as the plane gathered raw data. But on the morning of the fourth day, the chief mapping engineer had crunched enough data to create maps of an isolated valley in the targeted area. Previously a skeptic, he burst out of his bungalow, running like a madman, waving his arms and yelling, "There’s something in the valley!"
When we crowded into his room, we could see that the maps were covered with blurry, unnatural features that even to our inexpert eyes looked like ruins. Later analysis by archaeologists specializing in Mesoamerica revealed two, possibly three, unknown cities in those images, encompassing pyramids, plazas, roads, canals, terracing, rectangular mounds, and walls. This wasn’t just a solitary city; it was a society. The prehistoric inhabitants of the Mosquitia rain forest — they do not have a name yet — had cleared the vegetation to create open areas, monumental architecture, roads, canals, dense housing settlements, and intensive agriculture. In a few hours, lidar had mapped an area that would have taken perhaps a century or more to survey using traditional methods, and in far greater detail.
Lidar doesn’t just do faster and better what traditional archaeology can. By mapping hundreds of square kilometers in one fell swoop — impossible in a ground survey — it reveals how ancient civilizations organized themselves on the largest scales, how the hinterlands were connected to the cities, how the cities were connected to each other, and how people farmed, traded, and engaged in religious activity. All without turning over a spade of earth.
The use of lidar as an archaeological tool comes at a crucial time for the field. Over the past two decades, archaeologists have realized that most of their ideas about prehistoric settlement in the rain forests of the Americas were wrong. These jungles are not virgin: Prior to European contact, they were heavily cleared and the terrain extensively altered. Nor were these areas populated with scattered hunter-gatherer tribes, as we see today, but with advanced, sophisticated farming civilizations. The old idea that rain-forest soils are nutrient-poor and unable to support large-scale farming is now known to be false.
Given that, outside of Caracol and Mosquitia, the rain forests of Central and South America are untouched by lidar, I would expect surprising, if not mind-blowing, discoveries as other archaeologists begin their own swoops over the jungle canopy.
And this won’t just happen in the Americas. The very first archaeological use of lidar in the Asian tropics led to the discovery of an ancient Khmer city hidden in the Cambodian jungle and revealed canals, roads, dikes, a score of unknown temples, a cave full of ancient carvings, and hundreds of mysterious mounds that may be ancient tombs. Not long ago, I met a young anthropologist at the School for Advanced Research in Santa Fe, New Mexico, who mentioned that she had started using lidar to map Penobscot Indian sites in Maine. I asked her what she thought of it as a tool. "Oh my God," she said, "lidar is crack."
Why does this all matter to the rest of us? Understanding how ancient civilizations organized themselves and why they collapsed is crucial to understanding many of the challenges we face today. The inhabitants of Mosquitia experienced a decline around the 13th century, a few hundred years after their more famous neighbor — the Maya — utterly collapsed, never to rise again. Long a mystery, the Maya collapse now appears to have been caused by environmental degradation and the growth of a wealthy class that hogged an ever-larger share of a dwindling pool of resources. Does this sound familiar? The story of archaeology is thick with cautionary tales that speak directly to the 21st century: from the demise of the Roman Empire (corruption, tax evasion, and military overspending) to the 12th-century fall of the Anasazi in the U.S. Southwest (clear-cutting, overfarming, and overreaching by the priestly class).
Civilizations change; problems endure. Our foreign-policy establishment would do well to heed the sometimes chilling lessons of the ancients.