We may have evolved alongside snakes as our big enemy, developing certain physical traits to better avoid becoming snake food.

http://news.ucdavis.edu/search/news_detail.lasso?id=10757
http://www.livescience.com/4183-fear-snakes-drove-pre-human-evolution.html

I remember reading somewhere that most primates are hardwired to fear snakes, and sometimes the wiring just needs activation by an encounter of the slithery type.

Next topic: snake guns -- the Taurus Judge or something else?