How a Biotoxin Evolved
What do shrews and lizards have in common? Not much, but two species developed the same toxin in their digestive enzymes, giving them both a poisonous bite. Science Daily said a harmless digestive enzyme became overactive through three related changes. “What had been a mild anticoagulant in the salivary glands of both species has become a much more extreme compound that causes paralysis and death in prey that is bitten.” That similar “catalytic enhancement” occurred within two unrelated species suggests that the path to this toxicity is not extremely improbable. It could be selected if it enhances the ability of the species to survive and reproduce. This was also reported by PhysOrg.
This case might provide a test of Michael Behe’s ideas about limits to evolutionary change. It appears the changes to this enzyme are minor – something like opening up the active site a little wider and allowing the substrate easier access. If so, it is no more the “evolution of new protein function” than changing the concentration or pH of an existing acid. It does not involve adding new functional information. This is “horizontal evolution” that enhances and distributes existing traits according to the environment.
Christians might take note of this story as a possible insight into the origin of natural evil. This toxin appears to be a slight modification of an existing digestive enzyme. It did not have to be created de novo. Perhaps many things that cause pain and suffering, including thorns, are not far removed from original beneficial designs.