National Geographic magazines and Indiana Jones movies might make you imagine archaeologists digging near the Egyptian pyramids, Stonehenge and Machu Picchu. And some of us work in these famous places.
But archaeologists like us want to learn how people of the past lived around the planet. We rely on the artifacts left behind to complete the picture. We have to dig in places where there is evidence of human activity; however, those clues from the past aren’t always as obvious as a giant pyramid.
Finding this evidence can be as simple as wandering through clearly distinguishable ruins; ah, there are some broken vases or carved stones right there.
It can be as complex as using lasers, satellite imagery, and other new geophysical techniques to reveal long-lost structures. The right skills and tools are helping researchers identify traces of the past that would have been overlooked even a few decades ago.
Open eyes, open ears, open minds
The simplest and oldest method of identification is a pedestrian survey, looking for evidence of human activity, both on unstructured walks and when walking on a grid. Unless the evidence is very clear, such as those broken ships, such investigations generally require a trained eye to read the clues.
In Belize, where one of us (Gabe) works, the remains of houses and even great pyramids of temples that were abandoned more than 1,000 years ago are usually covered with trees and plants; the exposed sections look like piles of stone.
I took my father to a site where the workers had removed the thick foliage so the archaeologists could draw a complete map of the site. Another archaeologist and I enthusiastically discussed the visible architectural features: courtyards, terraces, the pieces of wall. Finally, my father raised his hands in the air and said, “All I see are rocks!”
But our trained eyes recognized that the piles of stone or mounds of earth we saw were lined up suspiciously. Observe the archaeological sites long enough and you will notice them too.
Understanding what you see may also require familiarity with the local geology and flora. And who is more familiar than people living in a region? It pays for archaeologists to make friends with the locals and be very respectful of their knowledge. In my work in Belize, most of the ritual caves and settlement sites my students and I work in were initially identified by local hunters who are intimately familiar with the forest and its landmarks.
Once, I was hiking in the jungle in Belize when a local friend of mine suddenly stopped in front of what looked like a random cluster of trees. He said, “This must have been somebody’s farm.” He had seen specific houseplants commonly found in the gardens of his village. Not being so familiar with the local flora, you would never have noticed this subtle difference. So even living plants can be considered part of man-made archaeological sites.
High-tech remote sensing
In recent years, archaeologists have begun to use new methods to find archaeological sites that had previously been overlooked. These techniques, widely known as remote sensing, allow us to peer through dense forests without cutting them down, digitally removing jungle growth and centuries of soil to reveal lost structures hidden beneath. High resolution scans using lasers or 3D photos can even detect subtle ripples in ground surfaces that are not visible to the human eye.
For example, LiDAR (light sensing and range) fires pulsed lasers to determine distance based on what is being reflected and speed. When used by an airplane, millions of points are collected, resulting in a detailed topographic map of the landscape. Specialists working with this data can remove trees and other objects to digitally expose terrain surfaces.
A recent example in the ancient Mayan city of Tikal, Guatemala, revealed some 61,000 structures in the jungles surrounding the city center. The settlement density came as a shock because, despite extensive pedestrian studies in the past, even experienced archaeologists have failed to recognize most of these ephemeral remains.