A millenium ago, the Southwest's main political and ceremonial center was the place we now know as Chaco Canyon, which flourished between 850 and 1250 A.D.
The ancient site is known for large-scale structures like multi-story buildings and partially subterranean kivas, built out of stone and more than 200,000 huge logs. Studies show the timbers at Chaco came from places including Zuni and the San Juan mountains, all more than 45 miles away. There is no evidence people who lived in the area at the time had draft animals or even wheels.
So how did they get there?
It is a question that has long puzzled scientists, but now, a team from the University of Colorado, Boulder, describes an experiment in the Journal of Archaeological Science: Reports that offers a possible explanation.
The feasibility study suggests the logs were carried on straps called tumplines, as Rodger Kram, the Associate Professor Emeritus of Integrative Physiology, explains in a video made by the university.
"A tumpline is a strap that goes not really on the forehead, but over the top of the head," he said. "And then you can carry the load in the small of your back."
Tumplines are depicted in ceramic effigies recovered from close to Chaco Canyon, and yucca fiber tumplines have even been preserved in the archaeological record, thanks to the low humidity of the site. Modern people still use tumplines, notably porters or sherpas in Nepal.
To test the the tumpline hypothesis, Kram and his colleague James Wilson, then an undergraduate, spent the summer of 2020 training, and then carried a ponderosa pine log up and down a forest road for a day.
"We carried the 130 pounds timber roughly 15 miles," in one day, said Wilson.
The experiment concluded that carrying a load by tumpline was, 'surprisingly comfortable and quickly achieved'.
The report's authors conclude, 'it is entirely feasible that Chacoans could have used tumplines to transport heavy timbers, oriented transverse to the walking direction, 25 km [about 15 miles] /day'.
