A
recent article suggests that our fear of snakes is largely genetic because of its apparently uniform nature across all strata of people and that it was likely caused due to predation of our ancestors.
As evidence of this, the author interviewed 120 of the Agta Negrito people, a hunter-gatherer group in the Phillipines, and noted that 16 of the individuals had been attacked by giant pythons, while two had been attacked twice. In addition, individuals reported six cases of fatal snake attacks over a 39 year period (1934 - 1973). While it's not clear from the article, the snakes may not necessarily have fared much better, since they were also predated upon by humans.