WASHINGTON — Archeologists have unearthed the earliest direct evidence of people smoking marijuana from a 2,500-year-old graveyard in western China.
In a complex of tombs in the Pamir Mountains — a region near the borders of modern China, Pakistan, and Tajikistan — excavators found 10 wooden bowls and several stones containing burnt residue of the cannabis plant. Scientists believe heated stones were used to burn the marijuana, and people then inhaled the smoke as part of a burial ritual.
‘‘It’s the earliest strong evidence of people getting high’’ on marijuana, said Mark Merlin, a botanist at the University of Hawaii. He was not involved in the research, published Wednesday in the journal Science Advances.
Ancient drug use has long intrigued scholars. The Greek historian Herodotus wrote of people in Central Asia smoking cannabis around 440 BC. In the past century, archeologists have found cannabis seeds and plants in tombs across Central Asia’s highlands, including in southern Siberia, and elsewhere in western China’s Xinjiang region.
But since cannabis has other uses — seeds are pressed for oil and fibers used for cloth — the presence of seeds alone doesn’t confirm drug use.
Using new techniques for chemical analysis, the study’s scientists examined residue and found evidence of THC, the compound that gives pot its high. Most wild cannabis plants have low THC levels, so researchers believe the people who built the graves selected plants with higher amounts.
‘‘During funeral rites, the smokers may have hoped to communicate with the spirit world — or with the people they were burying,’’ said coauthor Yimin Yang of the University of the Chinese Academy of Sciences in Beijing.
Excavation of the site, called Jirzankal Cemetery, began in 2013.