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Arizona Researcher: Shift In Sourcing Material Allowed Ancient People To Build Massive Structures

Tree, tree-ring, Baisan
(Photo courtesy of Christopher Guiterman)
Chris Baisan of the University of Arizona's Laboratory of Tree-Ring Research samples a dead tree in New Mexico's Chuska Mountains.

In a remote canyon in northwestern New Mexico, large pueblos made from stone and wood nearly a millennia old still stand. A new study from the University of Arizona Laboratory of Tree-Ring Research suggests when the canyon dwellers changed where they sourced materials from, it turned their small buildings into massive structures.

The arid Chaco Canyon protects some of the largest pre-Columbian buildings in North America. From 850 to 1020, these Puebloans harvested timber from the Zuni Mountains, about 50 miles to the south. Then for the next 100 years, research suggests the ancient society shifted material sourcing to the Chuska Mountains 50 miles to the west.

However, the study's lead author, Christopher Guiterman, said, “We did not know the Zunis were also a source and the system shifted in time.”

Guiterman said there was a construction boom once the shift to the Chuskas took place. One house grew from a few a rooms to a five-story structure with hundreds of rooms. The testing of 170 wood beams and their chronological tree ring order led to the discovery.

“The process was to compare the pattern of the beams to the patterns in the mountain ranges," said Guiterman. "And we used correlation with living trees of known origin, so modern trees. We did that for all 170, times eight chronologies (eight different mountain ranges), so we did a lot of correlating and this pattern arose.”

Guiterman said cultural objects like pottery and weapons containing stone from the Chuskas also appeared around 1020, giving further evidence to the shift. While the research may answer where the Chaco materials came from, it raises more questions as to how and why the shift took place.

EDITOR'S NOTE: This story has been updated to clarify where material sourcing shifted to and the number of moutain range chronologies studied.

Updated 12/15/2015 at 11:29 a.m.

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Andrew Bernier was a senior field correspondent at KJZZ from 2014 to 2016.