Alan Sullivan, archaeologist at University of Cincinnati. Photo: Andrew Higley/UC Creative Services

The “eureka moment” emerged from the ashes, as Alan Sullivan, a University of Cincinnati archaeologist recounts.

For years the survival of the ancient peoples of the Southwest, the ancestors of the modern Pueblo, were believed to have lived primarily off of corn crops. But in many parts of the region, there was little to no evidence of actual corn growth – and the soil in much of the region appeared to be too poor for cultivating maize.

But he received a call last year from a colleague at the scene of Scott Fire – and what could be the key puzzle piece for a centuries-old mystery fell into place, he recounts now.

“I just about leaped out of my chair,” he told Laboratory Equipment in an interview. “I said, ‘Send me pictures. Send me everything.’”

The ground in the incinerated 2,660 acres of the Coconino Rim was covered in Chenopodium, commonly known as goosefoot, just months after the blaze. The aftermath of that all-consuming fire had produced a new avenue for life. Instead of the old-growth forests of pines, junipers and sagebrush, there now stood tiny sprouts of the ruderals, the first plants to grow in a cleared forest. And those first growths may point toward what fueled native societies for centuries before Europeans arrived in North America.

After decades of research that included meticulous excavation and analysis, Sullivan has a new theory that could upend much of the traditional thinking about the lives of peoples like the Pueblo and their Anasazi ancestors. The natives used fire for a kind of farming, according to this theory. The controlled blazes would clear away the forests of juniper and pinyon trees. Out of those ashes would quickly appear the ruderals, high in nutrition, which would sustain the peoples before they moved onto another area that could be “planted” and “harvested” by setting the small fires.

“I did have a ‘eureka moment,’ quite honestly,” Sullivan recounts. “I told a couple of my friends, and they told me ‘You need to get out there.’ Which I did – I just blasted out there as soon as I could find some flights.”

Sullivan presented his theory at a major presentation last month at Boston University.

The center of the research is in and around the Grand Canyon, including the Kaibab National Forest. About 30 years ago, Sullivan and colleagues began trying to understand how corn could have sustained the peoples of northern Arizona. Little evidence of corn appeared in the layers of earth, and parts of the soil indicated regular fires. For instance, he published about a dozen papers assessing the maize – or lack thereof – at nearly 2,000 sites that otherwise show human settlement from centuries ago, including broken pottery and other artifacts. 

The conclusions: few, if any, grains of pollen are found at the sites. Burning traces showed around settlements, but they represented many small fires; the oldest juniper trees and ponderosa pines in the region showed no burn scars that would indicate the largest fires. At the same time, the geologic layers at the human settlements showed huge concentrations of wild edible plants when humans were there, which dropped off considerably after the camps were abandoned.

The work, with papers still pending publication, is expanding its scope. The archaeologists are calculating the per-capita calories needed by prehistoric residents, compared to the crop yields of a single ruderal called amaranth. That in turn will be compared to the agricultural output of corn, and how much would have to be grown to support the estimated population of the times.

Sullivan thinks he has cracked the code of ancient life for many natives of the Southwest.

“It’s definitely a paradigm-threatening opinion,” said Sullivan. “It’s not based on wild speculation. It’s evidence-based theorizing. It has taken us about 30 years to get to the point where we can confidently conclude this.” 

Some colleagues have already started to seriously consider the “fire farming” theory.

Neil Weintraub, the archaeologist for Kaibab National Forest, was the person who first noted the ruderals growing after last year’s all-consuming fire, and relayed the observations to Sullivan. What Weintraub and colleagues found was an ecosystem recovering with the ruderals – but especially with goosefoot, a wild relative of quinoa that is minty and chewable, and contains considerable nutrients.

Weintraub told a University of Cincinnati magazine that the nomadic life of the ancestral Puebloans would lend itself to fire farming – and even current abundance of wild crops seems to bolster the concept.

“It’s a fascinating idea because we really see that these people were highly mobile,” said Weintraub. “On the margins where it’s very dry we think they were taking advantage of different parts of the landscape at different times of the year.

“In a good year we (researchers) didn’t need to bring lunch in the field when we were out at our archaeological surveys,” Weintraub added. “We’ve be cracking pinyons all day.”

Sullivan said he is still working on testing and documenting his theory – and potentially rewriting parts of the history of the Southwest.

But it all came back to that moment of realization, with the sprouting flowers in the ashes.

“It was just one of those moments when as a scientist… things fall into place, and the keystone finishes off the entire project,” said Sullivan. “In this case, that was the fire – and the aftermath of the fire.”

Sullivan Fire excavation site. Photo: Alan Sullivan