Some readers raised objections to my column several weeks ago on the evolution of e coli into dangerous, toxin-producing forms. One called foul on me for using the word "evolution" to describe this phenomenon. Here's that reader's take:
By using the word "evolution" for instead of adaptation or micro-evolution for what the E. coli are producing (a human toxin)you are falsely leading readers to think that this is an example of very rapid evolution. But they are still E. coli., just a variety within that species -- no evolution has happened. My spouse has an MS degree in microbiology.
While scientists I interview rarely make the distinction between "microevolution" and "macroevolution", many creationists readers insist this is important, so they can accept the "micro" and reject the "macro" part. I called biologist Ed Dudley from Penn State University to help answer the questions posed by this reader. He kindly offered to help clear up this issue.
Sorry this has been a slow response, but still getting caught up after being away. So let's deconstruct what was stated:
"By using the word "evolution" for instead of adaptation or micro-evolution for what the E. coli are producing (a human toxin)..."
I would reiterate what the last comment in the thread said, in that adaptation is the term commonly used for short term evolution, also known as micro-evolution. Interestingly this reader doesn't appear to believe that micro-evolution a form of evolution; I guess by the same argument "microeconomics" has nothing to do with economics. Adaptation is also used to describe how organisms adjust to new environments without genetic changes; for example if you add bacteria to milk, they can adapt by expressing genes that allow them to use the milk sugar lactose but the DNA itself does not change. In the end, what happened to this outbreak strain should not be called micro-evolution, as this term tends to imply a change that has very little observable effect on the organism, and we know that what happened was evolution imparting a significant feature to the E. coli strain.
"you are falsely leading readers to think that this is an example of very rapid evolution."
This was an example of very rapid evolution. As your column stated, a bacteriophage introduces its own DNA along with the DNA for Shiga toxin in a single step, transforming a minor pathogen into a serious one. By simple vertical evolution (ie. mutations in existing DNA that get passed down to the next generation as cells divide) these organisms would likely never acquire the ability to produce the toxin.
"But they are still E. coli., just a variety within that species -- no evolution has happened."
Absolutely true they are still E. coli, but new species are rarely formed during evolution. Take the first well-characterized genetic mutation in humans: the fact that many folks of African descent have a mutation in their gene for hemoglobin that leads to enhanced resistance to the malaria parasite (and unfortunately Sickle cell anemia as well). By this reader's argument, we either need to consider these individuals to be a new species from Homo sapiens, or that acquisition of this mutation isn't evolution even though it leads to a selective advantage under certain conditions (ie. within areas where malaria is endemic).
"My spouse has an MS degree in microbiology. "
Oh, don't get me started here....
My next two Monday columns will delve more deeply into this issue. Most scientists interviewed on this topic say that it's all micro-evolution, but when you look at it over the sweep of time, some big changes will eventually occur.