Seems cannabis usage predates Christianity 
advances.sciencemag.org/content/5/6/eaaw1391
Wooden burners unearthed from ancient Chinese tombs dating back 2,500 years have revealed the earliest evidence of humans smoking cannabis yet.
THC residue, the main psychoactive constituent in cannabis, was found on incense burners buried at the Jirzankal Cemetery in the Eastern Pamirs, a mountainous region in Central Asia. It was discovered by eggheads from Germany's Max Planck Institute for the Science of Human History, the Chinese Academy of Sciences, and the Chinese Academy of Social Sciences.
The team took ten wooden fragments and four burnt stones from burners recovered from the burial site, and analyzed them using gas chromatography-mass spectrometry. The test revealed surprising results: a clear signature of THC.
What’s more, the level of THC in the burners was higher than what’s typically found in wild cannabis plants, suggesting folks back then knew which particular variants of cannabis plants packed more of the feel-good chemical.
“Ancient people chose the cannabis with a high content of THC, so we think they knew the effects,” Yimin Yang, a researcher at the University of Chinese Academy of Sciences, told The Register on Wednesday.