What Can We Learn from an Ancient Pea?

What can a few grains of charred grit in a plastic vial tell us about our ability to adapt to a warming world? Boston University environmental archaeologist John M. Marston studies ancient human agriculture: which crops did our ancestors grow for subsistence, which farming techniques did they use, and how did they adjust their behavior to adapt to a changing environment?

One of the regions Marston studies is modern-day Uzbekistan, known for having been agriculturally rich before, during, and after the Medieval Warm Period, which stretched from 950-1250 and saw temperatures rise to heights that had not been seen for millennia before, and were not seen again until the 20th century.

Marston’s team excavated previously undug sites in the Khorezm region of Uzbekistan, collecting samples of ancient soil from across a range of time periods that they have brought back to BU for analysis. “We’re interested in how their agricultural system might have changed across this really important climatic boundary,” says Marston.

Archaeological material from each soil sample is meticulously itemized by hand, using tiny brushes and tweezers, with particular attention paid to what might be ancient burned seed fragments. “If something is burned to the point where it becomes charcoal, it’s carbonized,” he says. “Then it becomes chemically inert….Bacteria don’t attack it, fungi don’t attack it, and it can preserve in soils for an extremely long period of time.”

Sydney Hunter (CAS’19), an undergraduate researcher working in Marston’s lab, found one seed fragment that struck the team as particularly unusual, seeming to resemble the end of a snap pea pod with one of the pea seeds still intact.

“We very rarely get these fleshy kinds of tissues because it’s much less likely that they would end up accidentally in fire and char exactly the right way so that they don’t burn up or explode into nothing,” says Marston. “For this pea pod fragment to be so well preserved is pretty unique.”

So what does the discovery of a single pea tell him about agricultural practices in ancient Uzbekistan? By itself, perhaps not a lot. “But it’s one piece of the puzzle,” he says.

The relative distribution of subsistence crops like peas, in comparison to cash crops like cotton, can give Marston insight into decisions ancient farmers were making during this period of climatic change. And because traditional agriculture practices in this part of Uzbekistan share many similarities with modern agricultural practices, understanding the decisions, both successful and unsuccessful, made by ancient farmers can potentially help inform better agricultural decision-making today.

“These types of trade-offs are the kinds of decisions that farmers have to make all around the world all the time,” Marston says. “They made them thousands of years ago, and they make them today.”

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