I was reading a book by Dr. Mel Borins, where he describes the autonomic nervous system, which overreacts to stress for the fight/flight response. If it's true that this system overreacts, then why do some people's triggers seem more subdued than others? His comment follows the description of how we went from fighting wild animals in pre-historic years to modern society where the stresses are deadlines, traffic congestion and waiting in lineups.