This is really, really sad. Your post has creeped me out, particularly this
But when I realize the surrounding forest has gone dead silent--no bird movements or twitters, no scurrying ground squirrels, when even the wind seems to be holding its breath--my hackles rise. I pause, sniff the air, study the woods around me, and only move on when some intuitive, instinctual part of me is satisfied.
That's happened to me in the woods in broad daylight. None of the woods I go near are far from civilisation, we don't have any predators large enough to even try to damage a person, yet that feeling of my hackles rising has happened and I always freeze and do exactly what you do. However I then go a step further and shin up the nearest shinnable tree! Fast! Then sit with my heart pounding.
I've wondered about the cause of this for years. It isn't just when I've been reading scary stories or watching scary movies. It can be in an area I know very well and have walked in many times or it can be a little off my usual beaten track. Sometimes it can be caused by the snap of a twig, but usually there's nothing to explain it, at least nothing I'm
consciously aware of.
I think you're onto something when you attribute it to survival instincts of our ancestors. We are rather puny, we don't have claws, teeth, speed, size. We have our intelligence and we use that to get or keep ourselves out of trouble. Yes, we may get false alarms, but they do no harm, however it could save our life if the threat is real.
Having said all that I have to admit that trying to explain to hubby why one minute I'm just behind him and the next minute I'm up a tree hasn't been easy.
I'm a real wus when it comes to the dark, but only indoors. It's always worse after a scary book or movie and that really is down to the power of suggestion. That's probably because it's better to learn from other people's experiences and so we have an inbuilt mechanism to make us wary of what dangerous tales, even if they are fiction. Maybe it doesn't matter that we know they're fiction, this little inbuilt mechanism can't tell the difference in some people.