I think that smoking has been with us since we started to control fire. When you think about it, making a fire in the wilderness, you are already “smoking” some king if vegetable. It is not a big step to start experimenting with other herbs. It looks like these people had good results with some other herbs.
“Until now, the use of specific smoking plant mixtures by ancient people in the American Northwest had only been speculated about. ”
https://www.sott.net/article/437198-Non-tobacco-plant-identified-in-ancient-pipe-for-first-time