Archaeologists have long maintained that people who lived in the Grand Canyon region 1,000 years ago had a diet dominated by corn.
But one researcher who studies the people who lived south of the canyon rim is now calling that assumption into question. More likely is that these ancient pueblo people started and managed low-intensity fires to spur the growth of edible native plants that were their main food source, said Alan Sullivan, a professor of anthropology at the University of Cincinnati.
Sullivan has spent the past 30 years studying the people who lived in the Upper Basin, a 85-square mile area dominated by pinyon pine and juniper trees that stretches southeast of the South Rim. People known as Ancestral Puebloans or Grand Canyon Anasazi populated the area between 900 and 1200 AD before drifting away to other places, Sullivan said.
For his research, Sullivan has done extensive surveys of excavation sites in the area looking for items like corn kernels, cobs and pollen that would indicate a culture dependent on corn cultivation, but came up with scant evidence of that sort of lifestyle, he said.
What he did find much more frequently were signs of ruderals — plants that are the first to grow back after a disturbance like fire sweeps through an area. In addition to juniper berries and calorie-dense pinyon nuts, Sullivan found evidence that people relied on a range of edible plants including nutrient-rich amaranth and chenopodium, both wild relatives of quinoa.
He found pollen from these plants inside clay pots used by the Ancestral Puebloans and studied geologic layers that show a surge in concentrations of wild edible plants between 900 and 1200, compared to the centuries before and after.
There’s also the fact that tree rings dating back to the centuries the area was occupied by humans don’t show scars that would come about from major canopy scorching fires, suggesting the area only saw low-intensity fires during that time, Sullivan said. In the absence of people, those more intense fires are the norm for pinyon juniper woodlands.
“We have tried to connect the dots to align with what we know about forest and fire ecology and the archaeological record,” Sullivan said.
Then, last spring, Sullivan saw his hypothesis play out in real time. In June and July 2016, the Scott Fire burned 2,660 acres east of Tusayan. Kaibab National Forest archaeologist Neil Weintraub returned to the site the next spring and noticed a red plant growing all over the place. The plant turned out to be high-protein chenopodium, or fetid goosefoot, that Sullivan had found evidence of in the ancient sites in the Upper Basin.
“It smelled minty and we started munching on it and it tasted really good,” Weintraub said. He called Sullivan and a few weeks later, Sullivan flew across the country to see the site for himself. It was a eureka moment, Sullivan said. Edible plants hadn’t been growing in that area before the fire and no one had planted their seeds after the blaze. Clearly the seeds had been present in the area and just needed fire to kickstart their growth.
“To me that was conclusive evidence that we were on the right track essentially,” Sullivan said.
Sullivan and others noticed the plants also appeared to be concentrated around archaeological sites, which would support a hypothesis that people were using these plants, bringing them home, processing them and eating them, with some seeds getting dropped in the process.
Why would people have relied on wild plants instead of cultivating crops like corn?
Foraging makes sense considering the area’s climate, Weintraub said.
“When you think about the Coconino Plateau, it’s a very very dry area so...people moved around a lot to collect plants from different areas at different times of the year as those wild plants flowered and fruited,” he said.
Corn needs pretty regular summer rains, making it a risky endeavor to try in this region, Weintraub said.
The area is also characterized by thin, rocky soils that can support pinyon pines, junipers and the understory plants, “but it’s not corn country,” Sullivan said.
It’s amazing to think about what fire then does to the landscape, he said.
"If you can then transform these pinyon juniper forests with the application of fire...it’s almost magical, really, when you think about effects of fire on pinyon juniper woodland,” he said.
A diet based on wild plants and pinyon nuts would have been more well-rounded and nutritious than one dominated by corn as well, Sullivan said.
Several aspects of Sullivan’s research aligns with well known elements of Navajo culture and history, said Jason Nez, a freelance archaeologist who has worked for the National Park Service in the Upper Basin area.
Nez said he used to pick pinyon nuts in the area when he was younger and many Navajo families continue to do the same.
“For us modern Navajos it has been an important gathering area,” Nez said of the Upper Basin.
It is also well known among many Navajos, and especially those living in forested locations, that an area becomes more productive after a fire, he said. People tend to head to places that have recently burned, knowing, for example that certain plants and animals will come out after the fire.
Nez was at the site of the Scott Fire with Weintraub and said he recognized the fetid goosefoot as an edible plant.
Much of Sullivan’s research puts scientific backing to what native people already know, Nez said. The work is also valuable to tribes because they often don’t have the resources to study the people that inhabited the area long before them.
“It reinforces cultural connections to the past, it reinforces stories, reinforces songs,” Nez said. “We feel empowered, we feel strengthened, we feel stronger when this knowledge is proven.”
Looking at the pinyon-juniper woodlands of the Upper Basin today, Sullivan said it may be hard to imagine the area supported significant human settlement.
Fire exclusion has meant the forest has become overstocked while grazing contributed to the local eradication of much of the understory vegetation, he said.
“When you walk around the forests today, there is nothing but bare soil. They're rocky and it looks like who in the world could ever make a living here?” Sullivan said. “But if you back out the effects that we have inadvertently introduced to woodlands and introduce fire back into the equation they were probably pretty productive places to live."