. Scientific Frontline: Ancient grains

Monday, May 16, 2022

Ancient grains

Laura Motta, University of Michigan paleoethnobotanist, shows peas excavated from the Karanis site in Egypt.
Image credit: Eric Bronson, Michigan Photography

For a long time, researchers believed the diets of ancient people were nutritionally poor.

Everyday ancient Mediterranean civilizations relied on a diet of grains and pulses (chickpeas, lentils and other members of the bean family). Researchers thought this food lacked micronutrients such as zinc and iron, while also containing components that inhibit the uptake of what nutrients the food did have.

But a University of Michigan pilot study on crops grown in Egypt during Roman times suggests that ancient grains were more nutrient dense than grains grown in the same region today. Now, building on that study, U-M is part of a five-university consortium to receive a €3.7 million grant (about $3.85 million), called the AGROS project, awarded by the Belgian program Excellence of Science.

The researchers will use cutting-edge technologies to examine the nutritional profile of the food and how its nutrients changed based on the historical methods of food preparation.

“In the first century, Egypt was the breadbasket of Rome. The village of Karanis, in Egypt, was one of the main suppliers of food to the city of Rome, its army and its public granaries,” said paleoethnobotanist Laura Motta, principal investigator of the U-M portion of the grant and assistant research scientist at U-M’s Kelsey Museum of Archeology. “They were producing, in the premodern time, at the early industrial scale here, and they were able to do so at the margin of the desert.”

But as the Roman Empire began to collapse, the city began to struggle. By the sixth century, Karanis had been abandoned. As its citizens left, the storehouses of the city were left empty—but in the homes of the city were baskets and bins of grains, the bodies of animals that had been eaten, and recipes and food preparation techniques recorded on papyri. Archaeologists call it a “veritable ‘Egyptian Pompeii.'”

In the 1920s, the city was excavated, and since, stores of grains, pulses and animal bones have been preserved at the Kelsey Museum of Archaeology.

Motta previously led the pilot study to do an initial assessment of the nutritional content of crops in the Karanis collection. That pilot study, currently in the final publication stage, examined the trace element content of these ancient crops and compared it to modern samples collected from the same area. It found that some of the crops’ trace elements, such as iron, were 45% higher in the ancient grains compared to the modern specimens.

Identifying ancient food’s trace elements is just the first step in determining its nutritional value. The researchers need to consider the food’s bioavailability, or how well a person’s body can absorb the nutrition in a particular food. For example, calcium limits the uptake of iron—but the way food is prepared can affect the way nutrients are absorbed.

That’s why, Motta says, it’s important to consider these ancient grains in their historical context rather than estimating the nutritional value of these diets based on modern grains.

“There is this general assumption that there was chronic malnutrition in most people whose diets were based on grains and pulses,” she said. “But these crops may have had a much higher nutritional content than their modern counterparts, which are the result of selection for the purpose of higher crop yields. And the higher crop yields, the less nutrient in the same plant. It’s more complex than that—but you can imagine that the more seeds a plant has, the less nutrient in each seed.”

Under the first pillar of the grant, Motta and fellow U-M researchers will identify the different kinds of grains, pulses and animal products, determine the contexts where these foods have been found, and radiocarbon date them. They will also select samples of the crops and animal bones for stable isotope analysis.

Motta’s work will reconstruct local food production, including some aspects related to agricultural practices, such as irrigation and soil fertility. Once the grains have been fully identified and carbon dated, Paul Erdkamp and Frederic Leroy of the Free University of Brussels will use biochemistry analysis to determine their nutrient content.

Richard Redding, zooarchaeologist and research scientist at the Kelsey Museum of Archeology and chief research officer of Ancient Egypt Research Associates, will study the animal bone and tissue excavated from Karanis. He will identify animal bones using the comparative collection in the bioarchaeology lab at Kelsey.

The study of the bones will help the researchers understand what proportion of the ancient diet was fish and what proportion of the diet was domesticated animals, such as sheep, pigs and poultry. His work will also focus on body part identification, age structure, evidence of pathology and evidence of other human activities on the bone.

Team members will also use isotopic identification to examine oxygen, nitrogen, strontium and carbon isotopes in the bones and tissue.

“The overall goal is to get a really good view of what animal products were used, and the nutritive contribution of animals to the diet,” Redding said. “Examining the isotopes will give us a good bit of information on water usage and whether they’re moving animals seasonally. Examining strontium isotopes will be a way of looking for evidence of pastoring animals in different environments and moving them back and forth.

“We’re really trying to get a good view of the seasonality of movement, how movement was going on, and between what areas. All of this feeds into your ability to control and use animals in the long run.”

Redding says one of the grant’s intentions is to challenge current thinking about the level of nutrition ancient diets contained.

“We have this normative view about plants and animals that these ancient diets were similar to those today, and that’s clearly not the case,” he said. “There’s been a lot of change over the years. The Green Revolution of the 1950s introduced high yield varieties of wheat. But it was at the cost of probably a lot of the nutritional value.

“It may behoove us to look at some of these older varieties of wheat and older processes that were more nutritionally advantageous, and maybe productivity is not the major factor we should be looking at, as we have a burgeoning problem of shortages of nutrition.

“We maybe should look at and advocate for reconsideration of the nutritive value of the foods we are eating, and we can look to the past to see how that’s changed. The past is a really nice record for that, and as much as it gives us insight into climate change, it also gives us insight into diet change. Not all change is good.”

The second pillar of the grant, conducted by Marie-Louise Scippo of the University of Liège and Katelijn Vandorpe at KU Leuven, will examine how the nutritional profile of food changes based on how the food was processed.

To do this, the researchers will use ancient recipes written on papyrus excavated from Karanis, as well as other texts and papyri from the wider Greco-Roman Egyptian world. They will then recreate these recipes and processing methods in a lab setting, after which they will study how the nutritional profile might change.

Finally, René Preys of the University of Namur will study the literary and artistic context of the diet.

The research is funded by the FWO (Fonds Wetenschappelijk Onderzoek-Vlaanderen) and the F.R.S.-FNRS (Fonds de la Recherche Scientifique-FNRS).

Source/Credit: University of Michigan


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