As with many psychoactive plants and foods, the adaptation here isn't so much a genetic/physiological tolerance as it is an often in-depth body of knowledge/practices for how to utilize the drug/medicine safely. Look at the notorious Datura for example which can cause you to go into a delirious state for over 2 days. The amount of preparation, processing, and knowledge that goes into administering it safely is lost on modern day kids who simply read an Erowid experience about a powerful psychoactive plant that likely grows locally.