June 9th, 2011
Texas State archaeologist digs up clues to rock art painters’ lives

Student archaeologists cook desert plants in an earth oven. COURTESY PHOTO

by ANN FRIOU

The discovery of a large prehistoric earth oven on a ranch in southwest Texas is giving an archaeologist at Texas State University the opportunity to answer questions about the lives of the ancient people who painted the famed rock art along the Texas-Mexico border.

Students survey a Lower Pecos Canyonlands archaeological site. COURTESY PHOTO

Dr. Stephen Black and students enrolled in Texas State’s Summer Archaeological Field School will spend the month of June excavating the earth oven, on the Ryes ‘N Sons Ranch in Val Verde County, near Comstock. The oven, called a “burned rock midden” by archaeologists, is about three-quarters of a mile from a well-known rock art site. The area is part of the Lower Pecos Canyonlands, the name archaeologists give to the rugged, deeply incised canyons formed by the Rio Grande and its major tributaries, the Pecos and Devils Rivers.

Earth ovens are layered arrangements of earth for sheltering the red-hot limestone cobbles used to bake local desert semi-succulent plants such as agave, lechugilla and sotol hearts. The plants were baked for two days to render the complex carbohydrates into edible sugars. Prehistoric peoples—hunter-gatherers whose tribal names have been lost—began baking plants some 7,000 years ago or earlier, a practice that intensified 3,000-4,000 years ago and peaked about 1,000 years ago. (The oldest pictographs in the rockshelters date to 4,000-5,000 years ago).

“By excavating the burned rock midden—which contains a large accumulation of cooking debris—we hope to learn more about why the prehistoric peoples intensified their cooking of plants over time,” Black said. “It takes time and energy to harvest and cook plants. It’s not that they’d rather eat desert plants than venison and berries: they harvested desert plants because they had to. It’s a sign that more people are on the landscape making do with what they have.

“Some archaeologists argue that the intensified use of baked plants occurred during major drought periods,” Black continued. “Others argue that this is a local reflection of a continental pattern of land use intensification over time. In other words, the use of baked plants intensified in the Lower Pecos area as bands of people grew and territories shrank, making less food available.

“The midden we will excavate was used intermittently for centuries or perhaps thousands of years. We hope that its excavation and radiocarbon dating will tell us whether people in the Lower Pecos Canyonlands were responding to a period of drought or to a more widespread food shortage,” Black said.

While some 2,000 archaeological sites have been documented in Val Verde County—including hundreds with burned rock middens—few have been studied because archaeologists usually have been more interested in rock art sites and in the dry rockshelters and caves.

“The middens represent the more mundane part of life, but they can contribute valuable information about the people who used them,” Black said. In addition to excavating the midden, Black and his students will survey the Ryes ‘N Sons Ranch to record its numerous rock art and plant-processing sites. Black expects that the survey will uncover many sites that were previously unknown.

ANN FRIOU writes for Texas State University’s College of Liberal Arts.