High up on the Colorado Plateau, in what is today the state of New Mexico, sit the remains of what was once a city of epic proportions.
From the 9th to the 12th century CE, the tens of thousands of ancestral Puebloan people who lived in Chaco Canyon occupied massive buildings stretching up to four stories high, many of which feature hundreds of rooms.
Made from sandstone blocks and heavy timbers, the buildings in and around Chaco Canyon were the largest structures ever built in North America prior to the 19th century. And yet without the assistance of wheels or draft animals, the transport of such massive pieces of material from nearby mountains would have been a challenge many find hard to imagine.
Researchers at Colorado University (CU), Boulder have now put their heads together to figure out the mystery… quite literally.
The team showed the human skull, neck, and spine are more than capable of acting together to support a 60-kilogram (130-pound) wooden beam 100 kilometers (60 miles) or more.
All that's required to schlep this impressive load is a pair of willing humans, a couple of head straps, and a bit of determination.
"Some people baked sourdough bread during COVID. Instead, we carried sand and heavy logs around using our heads," laughs Rodger Kram, an integrative physiologist at CU Boulder.
In today's world, where backpacks are ubiquitous, you might be wondering how scientists settled on head-packs for such heavy timber loads.
At first, Kram and two of the study's co-authors, neurophysiologist Joseph Carzoli and biochemist James Wilson, tried to heft the logs on their shoulders, but they quickly came to realize how inefficient that was.
"It was just debilitating," Kram recalls. "It's just a dumb way to carry a heavy object."
Humans have known that for millennia, yet today, this ancient hack is too often overlooked. Waist straps are instead regularly attached to hiking backpacks to help give our shoulders a break and redistribute some of the weight to our core.
A much easier option, as it turns out, is to strap the weight to the top of your head using a tumpline.
Tumplines are simple tools with ancient roots that have been used around the world for millennia.
In and around Chaco Canyon, archaeologists have found ceramic effigies illustrating Puebloan people using tumplines to carry resources, as well as yucca fiber wraps that could be the remains of ancient tumplines.
