Expert: Walter Hintz - 3/5/2010

Question
Mr. Hintz,

I recently read an article on Science Daily that talks about the evolution of aphids. The article: http://www.sciencedaily.com/releases/2010/02/100222200916.htm
Surprising aphids have a very weak immune system which is surprising since they are very widespread and a species with a weak immune system (I think) probably should be extinct, at least if you go by the "survival of the fittest" idea. The article hypothesizes that they get around the problem by constantly reproducing. This doesn't make sense to me because the article makes it sound like the aphids "choose" (consciously) to reproduce more. What is even more confusing is that aphids have evolved so that female aphids (from birth) have embryos and their embryos have embryos. I don't understand how the aphids were able to evolve in those ways by natural selection and  mutation alone. What do you think? Thanks!

Mark Meckstroth

P.S. Where in Ohio do you live?

Answer
Hi Mark
I read the article. It seems that statements like an "apparently weak immune system" tells me that this is an idea that has yet to be confirmed. Whether or not they do have a weak (and the term weak is arbitrary) aphids are still highly successful organisms. They do imply that aphids suddenly decided to increase the reproduction rate to offset the death rate.  This is course is nonsense. I do not believe the authors feel that aphids have chosen to do this.  The statement is a simplification. They should probably should have said something like. "The weak immune system is compensated by an increased in the reproductive rate."
The embryos within embryos does make one wonder haw natural selection has played a part but there is a lot we do not know about evolution.  Our lack of information does not negate the process however.
 In my mind there is a simple statement that can be said about why things like can occur.
"It  is as it is because that is what works best"

I live in Wickliffe on the east side of Cleveland and teach biology at Lakeland Community College