(CNN) Cannabis has been cultivated as a crop for millennia, but there's been little historical or archeological evidence showing when humans began to use the plant for what it's best known for today: getting high.

However, an excavation of a 2,500-year-old tomb in western China has revealed the earliest clear evidence of humans using cannabis for its psychoactive properties.

Scientists from China and Germany analyzed wooden fragments and burnt stones from pots in the tombs, and the results showed an exact match to the chemical signature of cannabis -- particularly that with a high amount of tetrahydrocannabinol (THC), the most potent psychoactive agent in the plant.

The authors of the study, which was published Wednesday in journal Science Advances , suggested that cannabis was probably used during burial ceremonies, perhaps as a way to communicate with the divine or the dead.

The brazier and burnt stones.

However, it was unlikely that cannabis was smoked in the same way it is today. More likely, it would have been burnt like incense in an enclosed space to release vapors.

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