There are venomous reptiles with less advanced versions of the same system. Other snakes have less effective fangs than the cobra. Gila monsters just have poisonous saliva, and have to gnaw on you for a while to get even a little into your blood. If the "perfect" system in a cobra was designed by a deity, why didn't they all get it? More importantly, if there was no death before the supposed fall, why do cobras have fangs at all - for subduing and eating tomatoes? Or did they instantly develop them, or evolve them over time, after they left the garden? How much of this change can you pack into the few hundred years between the garden and the old cultures that coexisted with cobras as we know them today?
The questions could just go on and on, but I don't see the point.
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