In the mid-1980s archaeologists and students from New Mexico State University excavated a dozen ancient rock shelter sites in the southern part of the Organ Mountains. The most notable discovery from these excavations was nearly 200 corncobs, also known as maize, which seemed to represent at least five different varieties of corn, one of the specimens approximately 3,000 years old.
The prehistoric corncobs have been preserved for more than 30 years at NMSU’s University Museum awaiting new technologies that could unlock their secrets without destroying the samples.
“Many of the studies of ancient corn in the Southwest focus on the Four Corners area and southern Arizona,” says Kelly Jenks, anthropology professor in the College of Arts and Sciences and one of the co-principal investigators on the grant. “We had these collections early on but because we didn’t have the technology needed back then, we weren’t able to date a lot of them. As a consequence, these sites are often left out of conversations about early corn cultivation in the Southwest.”
Today, an interdisciplinary team of NMSU anthropologists and botanists led by Rani Alexander, anthropology professor and department head, is using a grant from the New Mexico Bureau of Land Management to study this ancient corn through 3D imaging and DNA analysis to reveal clues about how ancient peoples domesticated corn in the Southwest. Corn actually started as a grassy plant called teosinte. NMSU researchers hope to learn more about how these tiny corncobs contribute to the diversity of corn, including sweet corn found in the grocery story today.
“We hope to learn more about the different landraces of corn that were cultivated by people living here thousands of years ago, where these varieties came from, how they changed over time and what they can tell us about early agriculture in the Chihuahuan Desert,” Jenks says.
“The term we use is ‘dry farming,'” says Fumi Arakawa, co-principal investigator, anthropology professor and director of the University Museum. “People here in this area didn’t have irrigation; they just relied on the rain to grow their corn. That is just amazing.”
Amanda Semanko, an anthropology graduate student, will work with Jenks and Arakawa to pull the corn specimens from the collections, carefully recording the labels so that they can reconstruct where each specimen was found within each site. Once the specimens have been pulled, Sara Fuentes-Soriano, college associate professor in the College of Agricultural, Consumer and Environmental Sciences, will identify the different varieties present in the collection. Then, the researchers will work together to select four samples for more advanced studies.
To help see the minute differences in the anatomy of each ancient corn specimen, Fuentes-Soriano, who is also director of NMSU’s Herbarium and curator of NMSU’s Range Science Herbaria, will characterize morphological variation among the samples. Using data derived from a device similar to the medical CT-scan, used to see inside the human body, she will create 3D models of the corn, inside and out.
“We are bringing in missing clues of how we domesticated corn in the past.” Fuentes-Soriano says. “From this we learn more about domestication in different environments, in this case in the desert environment. This is information that isn’t readily available, we can provide it and then we can jump into the aspects of breeding.”
Donovan Bailey, biology professor in the College of Arts and Sciences, will then analyze the genetic composition of the samples.
“We will be using modern genome sequencing to explore genetic variation in these New Mexico derived samples and then comparing the variation uncovered from other historical samples from Mexico and other parts of North America,” Bailey says.
“For every base in the genome we’ll be asking, ‘Is our sample the same or different?’ and from that, we will try to identify what groupings (landraces) of maize exist and how our samples fit into or even modify those major groupings.”
Corn isn’t thought to have started out like the modern sweet corn we are all used to today. Bailey and Fuentes-Soriano are decoding the early corncob’s shape and genetic makeup to see how prehistoric farmers may have selected for traits like drought tolerance, sweetness, and related features.
“If we understand how we as humans modified maize over time, plant breeders may be able to take advantage of some of these elements through crop improvement programs,” Bailey says. “We know part of the story from south Mexico, north Mexico, but there are still gaps in our knowledge, including southern New Mexico.”
To figure out where these samples fit within the history of maize domestication, the four samples will also be dated using a new, improved method of radiocarbon dating. This will allow the team to figure out which varieties of maize were being cultivated when, and to add this to what we already know about the ancient occupants of these rockshelter sites.
Arakawa sees this new study opening doors for other researchers to benefit from these types of perishable collections at the museum.
“This is a pilot study, but other archaeologists and researchers are also interested in the domestication of maize in the American Southwest, so I hope we might be able to contribute to a greater understanding of the topic of domestication and human-nature interactions,” says Arakawa.
During the three-year study, researchers will utilize the latest technology to extract as much information as possible from the tiny prehistoric corncobs. The $25,000 from the BLM will cover testing costs and support graduate students’ work. With the help of a number of graduate students, NMSU researchers will analyze the data and publish their results.
