Early nomadic sheepherders played an important role in spreading domesticated crops along the Silk Road, according to a new study.

About 5,000 years ago in the high plains of Kazakhstan and Turkmenistan, sheepherders spread the seeds of barley, millet and wheat along the mountainous east-west corridor that leads along the Silk Road, suggesting that several strains of ancient grains and peas were being propagated across Eurasia thousands of years earlier than initially believed.

The evidence, as reported by Washington University in St. Louis researchers, was found in the charred remains of the grains uncovered at for Bronze Age campsites excavated in Kazakhstan and Turkmenistan.

"Our findings indicate that ancient nomadic pastoralists were key players in an east-west network that linked innovations and commodities between present-day China and southwest Asia," said study co-author Michael Frachetti, an associate professor of archeology at Washington University.

"Ancient wheat and broomcorn millet, recovered in nomadic campsites in Kazakhstan, show that prehistoric herders in Central Eurasia had incorporated both regional crops into their economy and rituals nearly 5,000 years ago, pushing back the chronology of interaction along the territory of the 'Silk Road' more than 2,000 years," Frachetti said.

While these crops have been known to exist much earlier in ancient China and Southwest Asia, evidence of the seed remains in Kazakhstan and Turkmenistan provide some of the earliest concrete evidence of east-west interaction in the expanse of the Eurasian mountains and the first botanical evidence of farming by Bronze Age nomads.

"Bread wheat, cultivated at least 6,000 years ago in Southwest Asia, was absent in China before 2500 B.C. while broomcorn millet, domesticated 8,000 years ago in China, is missing in southwest Asia before 2000 B.C," Washington University reported in a statement. "This study documents that ancient grains from eastern China and southwest Asia had made their way to Kazakhstan in the center of the continent by 2700-2500 B.C."

Paleoethnobotanist Robert Spengler, the study's first author, said that the findings support a call to "rewrite the model for economic change across Eurasia."

"It illustrates that nomads had diverse economic systems and were important for reshaping economic spheres more generally," he said.

The research is published in the Proceedings of the Royal Society B: Biological Sciences.