UNM doctoral student leads groundbreaking discovery on ancient maize farmers

Maize, or corn, is a major dietary staple in Maya communities past and present because of its reliability, potential for surplus and suitability as both food and fodder. It became so important to ancient Mesoamerican communities that it even became central to many of their religious beliefs, and arguably, they built their societies on it, yet maize has a major nutritional limitation.

Although it is an excellent source of carbohydrates, it is surprisingly low in lysine, an essential amino acid that serves as a crucial building block of protein. Without enough lysine, people cannot build and maintain body tissues like muscles and bones. Previous work suggests that as much as 70% of the protein in ancient Maya diets was ultimately derived from maize. But there is a problem: an adult would have to eat over 13 pounds of dry maize kernels (nearly 40 pounds of fresh maize) every day to get enough lysine, an impossible amount.

So how, then, did early maize farmers survive and thrive as maize consumption was rapidly increasing?

This conundrum is why new research by Nadia Neff, a doctoral candidate in archaeology at the University of New Mexico, is groundbreaking. Her paper, titled Nutritional Adaptations to Early Maize Cultivation: Earliest Isotopic Evidence of Maize-Based Animal Provisioning in the Neotropics, has been published in the AAAS Science Advances Journal and shows how ancient farmers used innovative methods to adapt their primary food source to meet their dietary needs. Using cutting-edge amino acid isotope analysis and statistical modeling, Neff and team traced individual amino acids from maize through animals and into ancient human diets spanning more than 5,000 years in Central America.

The results of their study show that maize-eating animals, such as turkeys, likely acted as biological "protein concentrators." Because these animals can eat far more food relative to their body size than humans, they can obtain all the lysine they need from maize alone. When people eat those animals, they are essentially accessing concentrated maize-derived lysine converted into high-quality animal protein.

"What we found is that these early communities weren't simply adopting agriculture for calories," said Neff. "They were actually actively engineering their food systems to solve different nutritional problems."

"What we found is that these early communities weren't simply adopting agriculture for calories," said Neff. "They were actually actively engineering their food systems to solve different nutritional problems." - Nadia Neff, UNM doctoral candidate and lead researcher

According to Neff and her faculty adviser, Keith Prufer, their findings suggest that maize cultivation and animal management developed together much earlier than previously recognized. Instead of viewing maize farming and animal management as separate innovations, their study shows that they likely formed complementary parts of a greater adaptive food system as early as 6,100 years ago.

Her findings are even more interesting because this study was not what she originally set out to find when she first began data collection. She conducted a few analyses examining the carbon stable isotope ratios in the amino acids of bone collagen and was confused by how high the lysine values she measured were, given how little lysine there is in maize.

"It's just not possible for people to eat enough maize directly to result in such high carbon stable isotope ratios in their lysine," she said. Prompting her to look for other potential explanations for the patterns she was seeing.

By collaborating across multiple disciplines, including archaeology, biochemistry, ecology, nutrition science and observations of modern Maya farming practices, Neff and her team were able to demonstrate that instead of only eating maize directly, early farmers were also eating animals that ate or were fed maize, thereby "concentrating" maize-derived lysine as it moved up the food web, reconciling the stable isotope ratios she had measured, and gaining a deeper understanding of this ancient society.

Neff has been working as a bioarchaeologist on Prufer's archaeological project, Research into the Origins and Organization of Tropical Societies (ROOTS), traveling each year to rockshelters in southern Belize to conduct excavations.

Working with local communities and NGOs, they carefully excavate sites dating back 10,000 years, and at UNM's Human Ecology and Radiocarbon Lab at the Center for Stable Isotopes, Neff performed her analyses to study the isotopic signatures in individual amino acids from human and turkey bone collagen and modern plants.

"We used amino acid isotope analysis because it gives us a much more detailed picture of human nutritional biology than looking at bone collagen as a whole," Neff explained. This allowed the team to more closely examine how people in the past grew, prepared and ate food.

UNM's Center for Stable Isotopes is one of the few labs in the country capable of performing this type of analysis.

"Nadia is building on decades of our work on early diets in the American tropics and significantly expanding our understanding of these ancient community practices in the Maya communities," Prufer, the director of the Human Ecology and Radiocarbon Lab and core faculty at the Center for Stable Isotopes, explained. "Our research even shows that maize was adapted much earlier than previously believed."

Beyond rewriting the history of ancient Maya diets, Neff's work shows the power of amino acid isotope analysis to reveal relationships hidden inside ancient food webs. By showing how past societies built nutritionally resilient food systems, her work also offers new perspectives on modern discussions of food security, agricultural sustainability and overall human nutrition.

To learn more about this research, visit the AAAS Science Advances website or email Neff directly at [email protected].