As much as I dislike finding myself on the opposite end of a debate with someone as credible as Dr Fry, I'm going to continue to disagree, even if it's simply a matter of semantics.
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Venom predated fangs rather than the other way around and evolution does only one thing at a time (ie fangs and venom did not evolve simutaneously).
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Evolution does a multitude of things simultaneously, organisms do not adapt in only a single facet of their biology, but constantly and continuously in EVERY aspect to an ever changing environment.
The definition of "venom" is a toxin which is injected, has an injection method. So while the toxin can develop in ever increasing potentcy, it is not a VENOM in the strictest sense of the word until the injection method is present.
The rear fangs have been strongly evidenced to be present for reasons other than toxin injection, the ducts which carry the toxins into the mouth don't open very close to the rear teeth and those rear teeth are not hollow, not grooved and pressure exerted on them does not cause a signifigant increase in the amount of toxins present in the saliva.
Dr Fry has been pushing his evolutionary theory, one which must be noted to contradict all those which had gone before it, not to say it's not accurate, just that, being new, it's not as well evidenced. Because of the manner in which he has been looking at the evolution of venom, he has reversed the definition of "venom" as well. Rather than "Colubrids are evolving towards venom" he is working on "Colubrids are evolving away from venom" and as such it is important that others accept his definition of venom as simply being a toxin. As of yet... and again, not to detract from his credibility or intend any disrespect, he has not shown any of the environmental factors which would be responsible for the loss of an evolutionary edge, the loss of an advantage over other species and other individuals within a population. It's an important question that will have to be answered before his theories are really accepted by "the masses", in some instances I'll accept the word of an obvious expert within their own field... But for something so radically different than what was previously thought to be true, I'd suggest additional evidence. The prescence of similar toxins is important, but until it's shown otherwise, I'm still going to work off the idea that it happened the other way around.