I agree with you. Irrational phobies should have a plain scientific explanation concerning their origin. I still believe that this genetic secular fear is gave to (human) offspring, next reactivated, overstated and hijacked by religious environmental mediators.
Animal venomous apparatus are not recent functional novelties. I bear in mind that venomous animals existed long time before the human lineage was separed from apes in Africa. Venom was a limitative environmental parameter but completely different than Felidae or Crocodile predation. Casualties were heavy to support for the primitive human population but the signification is different.
I mean that you must do an intelligent relationship between a bite and a later fatal issue. For snakes, scorpions, the bite (or sting) is painful so this association is quite easy to consider but this is not true for spiders. World toxicologic statistics are unable to tell how much people really die each year due to spider envenimation.
Snakes are fully integrated (bad or good) to beliefs. Not spiders yet...
Any guess?
Denesha