Evolution of poisonous vs. non-poisonous snakes

I had looked this up recently last year due to a creationist asking this question, and from what I learnt, have to look up more specific details in morning but the venom's found in snakes, is actually simular to something else already in snakes in another part of the body some other proteins that has a few mutations and differences in it.Link here The Evolution Project: 276: Snake venom evolutionI know it's a simular case with the platypus venom, it's simular and likly co-opt'd from proteins found within the platypus imune system link here.Page not foundDoesnt' say how they safly or such evolved but does show they are modifications of whats already in the body.PS just joined :> And read this and remembered my previous reserach so had to join and add my two cents.