More than a century after the great sandstone monuments of New Mexico’s Chaco Canyon were first studied, archaeologists are finally learning about the Ancestral Puebloan leaders who built them.

Researchers have recently analyzed more than 60 sets of human remains that are thought to represent Chaco’s elite, found in tombs within the famous “great house” known as Pueblo Bonito, some of the graves lavished with turquoise beads, pendants, and pottery.

By studying the chemistry of the remains, researchers have been able to determine where these elite figures were born and raised.

And the results reveal that the vast majority of them were from the Chaco Canyon area itself, and not from more distant regions, as many experts expected.

The discovery has big implications for archaeologists’ understanding of the origins of what they call the Chaco phenomenon — the rapid fluorescence around 1,100 years ago of a sophisticated society in this remote desert canyon, which wielded widespread cultural influence and developed trade networks extending into Mesoamerica.

While many experts had theorized that this sudden burgeoning was the result of migration from what’s now southwestern Colorado, the new research shows that the phenomenon was led by home-grown leaders, said Dr. Stephen Plog, anthropologist with the University of Virginia.

“[Our research] suggests the most prominent developments for which Chaco is known, such as great houses, were largely initiated by the people belonging to the same people or culture that had lived in or near Chaco for many generations,” said Plog, a co-author of the new study, in an interview.

“There likely were some people who moved into Chaco from regions to the west, northwest, or north, as other scholars have hypothesized, but our study suggests those newcomers were not the ones who created what people have come to call the ‘Chaco phenomenon.’”

Plog and his colleagues studied 61 sets of human remains — originally exhumed in the early 1900s from two interior chambers of Pueblo Bonito — as part of a broader initiative to better understand the migration patterns and relationships among the key cultures of the Southwest.

“We … included the Bonito burials because there has been so much discussion of why and how Chaco developed,” Plog said.

“[M]any have proposed Chaco began after movements into the region by people leaving southwestern Colorado. We thought isotope analysis would be a great way of testing that hypothesis.”

Since their removal from Pueblo Bonito, the human remains have been housed in various museums around the country, from Harvard’s Peabody Museum to Chicago’s Field Museum.

The researchers tested samples from these remains, taken from the teeth, using a technique known as isotope analysis.

This method analyzes the samples for various isotopes — that is, atoms of different masses — of elements like oxygen and strontium.

The ratios of these isotopes vary from place to place, in the soil and in local drinking water. So as our teeth form, these ratios get laid down in our tooth enamel, creating a chemical record of where we lived for the first ten or so years of our lives.

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By comparing the levels of these isotopes with the levels found around the Southwest, the team was able to pinpoint the regions where those buried in the elite graves had been reared.

“In regard to the 61 burials in Pueblo Bonito, we believe the isotopes show that almost all of them had been born near Chaco Canyon,” Plog said.

Of those remains, 58 bore chemical signatures that were indicative of the area immediately surrounding Chaco Canyon, he added.

The results from this group were also remarkably consistent, he added.

“The 61 burials in Pueblo Bonito that we analyzed are much more similar to each other than to burials in areas west, northwest, or north of Chaco,” Plog said.

“That is, collectively they form a relatively homogenous group which, along with the differences from other areas we considered, implies they were born either in or near Chaco Canyon, or perhaps in not too distant areas to the south.”

As for the three outliers that didn’t match Chaco’s chemical profile, their places of origin remain unknown.

“More isotopic analysis of more burials is needed to answer that question with any degree of certainty,” Plog said.

“It appears unlikely they were from southwestern Colorado, but we cannot absolutely eliminate that possibility.”

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From here, some of the researchers hope to explore some other physical traits among the remains, ones whose further study might be explain how Chaco’s home-grown residents differed from outsiders, or how elites compared with the rest of Chaco’s population.

Dr. Steven LeBlanc, for example, observed that many of the elites exhibit a distinctive form of cranial deformation, their skulls apparently having been shaped in infancy to feature a slope at the top rear of the cranium.

Likewise, the elites also include an unusual example of polydactyly — a woman who had six fingers instead of five.

While these and other prospects are being explored, Plog and his colleagues suggest that their findings may make archaeologists reconsider the origins of the Chaco phenomenon.

(See new insights into Chaco’s early influence: “Bones of Exotic Macaws Reveal Early Rise of Trade, Hierarchy in Chaco Canyon“)

“Southwestern archaeologists have a tendency to explain major culture changes such as the construction of Chaco great houses as a result of either climate change or migration,” he said.

“Our study suggests migration was not significant, that the people who had lived in Chaco Canyon for generations were creative innovators who, for a variety of reasons that we are still trying to understand, initiated the path from exclusively small settlements of 25 to 75 people with minimal social hierarchy and little to no long-distance trade, to the construction of large, complex great house structures; the acquisition of cacao and scarlet macaws from southern Mexico or Central America; and the creation of significant social hierarchies.”

The team reports their findings in The Journal of Archaeological Science: Reports.