As the morning sun peeked through the trees, Roger Crum prepared for the upcoming marathon. But not the way he ran.
Crum, a physiologist at the University of Colorado at Boulder, stood next to student James Wilson at the end of a rural dirt road. Each wore a belt of nylon tape on his head. Attached to the lower part of their straps—called humps—the log rested horizontally on the duo’s lower backs.
The couple was about to embark on a 25-kilometer hike to recreate how the ancient inhabitants of Chaco Canyon may have transported wood about 1,000 years ago. At the end of the day, their successful journey showed that it would only take a few days for two men with stands to get the wood to Chaco Crum, Wilson and their colleagues reported on February 22 in Journal of Archaeological Science: Reports .
Located in northwestern New Mexico, Chaco Canyon is home to grand structures built between 850 and 1200 AD. The multi-storied stone buildings, called big houses, had roofs made of wooden beams about 5 meters long and 22 centimeters in diameter. The site contained at least 200,000 timbers of this size.
But the wood came from forests more than 75 kilometers away. There were no draft animals and no wheels at that time, and wood, it seems, was not hauled. Scientists are puzzled by how ancient people, the ancestors of the present-day Diné and Pueblo peoples, transported large logs.
A 1986 study found that each log used as a beam had a mass of 275 kilograms . But Crum suspected that number couldn’t be right.
In 2016, he cut down a section of a tree near his house—a ponderosa pine, the same species used in the Chaco—and weighed it on a scale in his bathroom. He then extrapolated that a 5 meter long piece of wood would be closer to 90 kilograms. This discovery led to a 2022 study, in to which the mass of Chaco Canyon wood was calculated to be between 85 and 140 kilograms .
“Once we found that the weight was acceptable, I wanted to carry them,” says Crum.
He and Wilson suggested that bollards may have been used to transport wood. These headbands have been found on every inhabited continent and are believed to have been in use at least around 2,000 years ago. They are still widely used for transporting heavy loads, for example by professional porters in Nepal. A cam is located on the top of the head, which is on the same line with the cervical spine, and the attached load lies on the lower back.
Although there is no evidence that the Chaco people used pipes to transport wood, there is evidence that they used them to transport other objects, such as watercraft.
To test whether human transport of wood was possible, Crum and Wilson trained for three months during the summer of 2020, gradually increasing the weight of the load and the duration of the walk. Strangers passing by could not hide their confusion.
On the last day, the pair walked 25 kilometers carrying ponderosa pine that had been air-dried, which is how the Chaco people may have prepared their wood. The 60-kilogram log was 2.5 meters long and 24 centimeters in diameter. The entire hike took nearly 10 hours, and the weight of the full timber only slightly slowed the duo’s pace.
“In the end, I felt happy that it was possible and that the 132-pound log we shared was off our necks,” says Wilson, now a medical student at the University of Colorado in Aurora. But “I never doubted that we could do it.”