[hexag1]

think about the experiment with human babies and heights. scientists have placed babies on glass tabletops. they start out on a solid opaque surface and in front of them is a glass table with nothing beneath. babies even at 6 months, WILL NOT CLIMB ONTO THE GLASS. even if their mother calls them. even if they are shown toys. why? did they learn the hard way by falling and injuring themselves? (Ill never do that again!) no. its hardwired in to the brain.
someone above said that they would find it hard to believe that there was a first spider to freeze at a threat. would it be difficult to believe that there was a first baby to fear heights? maybe the truth is somewhere in between. perhaps our infant ancestors were born with a few hardwired behavioral choices.
1. ignore heights altogether
2. be cautious of heights, but explore your surroundings
3. be fearful of heights and cling to anything solid for your life!
same thing with the spider
when confronted with a looming threat you can:
1. do nothing and keep moving
2. keep moving but slow down
3. FREEZE!
perhaps in both cases the creature could have been equally inclined to all 3 choices. but any creature that had a tendency to go toward choice 3 would be more likely to survive and reproduce