Did rootworms “evolve” to overcome biotech corn?
Jim League writes in the Tennessean:
The general understanding of science is lacking in our current society. This is illustrated and exacerbated by the Dec. 29 article, “Bugs may be resistant to genetically modified corn.”
The hybrid corn has been engineered to produce its own insecticide to protect it from rootworms that destroy the roots and cause the corn to die, producing no crop. The article incorrectly stated that corn rootworms have “evolved” an ability to overcome the corn’s defenses.
Now, researchers are discovering that the corn is being attacked in some locations. The explanation was that the worms had “evolved” an immunity to the insecticide, much as mosquitoes have done to DDT.
Evolution means that some new genetic characteristic has been produced. For instance, assume that I were to suffer an accident and lose the use of my right arm and learn to use my left in its place. Did I evolve an ability to function lefthanded? No. I had the ability all along, but it had not been exercised. Many people have taught themselves to use both hands with equal dexterity. This is not evolution.
Evolution would be if I grew another appendage like a third arm, or my nose lengthened to become a prehensile limb (like a monkey’s tail). That would entail (no pun intended) a change in DNA that would be passed down to future generations.
In the case of the rootworms or mosquitoes, some individual insects have the genetic characteristic that renders them immune to the pesticide. When the non-immune insects die, only the immune ones are left to reproduce and the population becomes “immune.” Previously only some of them were immune, and this was often a small minority. When only the minority reproduces, usually passing along the immunity to their offspring, the whole group eventually gains the immunity.
No new trait has been developed or evolved. An existing trait has been spread throughout the entire population by “selective breeding.” This is an example of microevolution. Another example would be if only blue-eyed parents were to have children, soon nearly the entire population would have blue eyes. But this is not an example of evolving a blue-eyed society.
Now, if the population of blue-eyed people began, over successive generations, to be able to see through solid objects (Superman’s fabled X-ray vision), that would be an evolutionary change, or macroevolution. This would be a new ability that was not in the original population.
The import of this discussion is that we occasionally hear the claim that DDT immunity in mosquitoes proves that evolution is currently and continually occurring. This is not good science. Merely expanding an existing population characteristic is no more evolution than are acquired competencies like skill on instruments or knowledge.
Learned abilities are not evolution, nor are they inheritable. Otherwise, I would be as good a pianist as my mother was, and my kids would be brilliant chemists — well, maybe just competent ones.
In the case of the root worm population, nothing new has been developed, but an existing characteristic is now evident in the majority of the population.
Sadly, our society is appallingly ignorant of science, and careless use of terms and concepts merely reinforces this deficiency.