Ever since Herodotus, we've been aware that the nomadic pastoralists of Asia Minor known as the Scythians burned marijuana as part of religious rituals and ceremonies. Now comes evidence that not only does human commerce with the pot plant extend back even further, it could have helped stimulate the rise of Western civilization.

At the end of the last Ice Age, roughly 10,000 to 12,000 years ago, Stone Age people on both sides of the Eurasian land mass independently discovered and made use of marijuana, according to new research published in the academic journal Vegetation History and Archaeobotany. That same research also links an upsurge in marijuana use in East Asia with the rise of transcontinental trade at the beginning of the Bronze Age, some 5,000 years ago.

While the traditional view has been that cannabis was first used and possibly domesticated in China or Central Asia and then spread westward, a new database tracking the academic literature on trends and patterns in prehistoric pot use suggests that marijuana showed up in both Japan and Eastern Europe at almost exactly the same time, between 9,400 BCE and 8,100 BCE.

"The cannabis plant seems to have been distributed widely from as early as 10,000 years ago, or even earlier," said database compiler Tengwen Long of the Free University of Berlin.

While it appears that different groups of people across the Eurasian landmass began using the plant around this time, it is not clear just what they were using it for. Perhaps for its psychoactive properties, but also maybe as a source of food or medicine or to make textiles from its fibers.

But the database suggests it only people in western Eurasia made regular use of the plant. Early records of its use in East Asia are rare, Long said, at least until about 3,000 BCE.

At that time, marking the beginning of the Bronze Age, East Asian use picked up again, and the researchers think nomadic pastoralists like the Yamnaya people, thought to be one of three key tribes that founded European civilization, played a key role.

By the beginning of the Bronze Age, the nomads on the steppe had mastered the art of horse riding, which allowed them greater geographical scope and led to the formation of trade networks along the same Eurasian route that would become famous as the Silk Road several millennia later. The Bronze Road facilitated the spread of all sorts of commodities between East and West, possibly including marijuana.

"It’s a hypothesis that requires more evidence to test," Long said, noting that marijuana's high value would have made it an ideal exchange item. He called it "a cash crop before cash." While it's unclear whether people were trading buds in order to obtain a Bronze Age high, there is some support for that idea. Burned marijuana seeds at archaeological sites suggest that the Yamnaya carried the idea of smoking cannabis with them as they spread across Eurasia.

David Anthony of Hartwick College in Oneonta, New York, who studies the Yamnaya, told the New Scientist the proto-nomads may have reserved weed for special occasions.

"The expansion of cannabis use as a drug does seem to be linked to movements out of the steppe," he said. "Cannabis might have been reserved for special feasts or rituals."

And archaeologist Barney Warf of the University of Kansas noted that the people whom the Yamnaya preceded, the post-Bronze Age Scythians, regularly used marijuana as a drug.

"People talk about Herodotus' accounts of hanging out in the Crimean peninsula smoking with the Scythians," he said, adding that he thinks that only scratches the surface. "I think there’s a largely untold story of cannabis in Europe from the Bronze Age up until the Renaissance," he said.