Some researchers are investigating the volume of THC that is contained in modern strains, but also the delivery method.
Smoking a high THC strain, even 1 or 2 puffs will knock first timers out. But, doing a dab hits or from vapor pens has a much higher concentration. We may not be wired to be taking in so much THC at one time.
Sativas like Amnesia Haze will significantly impair most humans for over 3 hours.