Tobacco's center of origin was in the Peruvian/Ecuadorean Andes about 5 thousand years ago according to Geneticists. That was the variety we call Nicotiana rustica.
This Olmec stone artifact, c.1500 BC, represents a Shaman on a vision quest. Mesoamerican Shamans smoked profuse amounts of tobacco to induce religious trances.
Therefore this artifact and others like it from southern Mexico may be the earliest known representations of people using tobacco.