A few years ago, the media was abuzz over the scare of the avian flu virus, which led me to write a post titled Avian Flu: An Example of Evolution?. At the time, it wasn't clear whether the avian flu would evolve and "jump" into a highly virulent form that easily infected humans. Had the avian flu virus made the jump, then we would have witnessed a sort of evolution where viruses swap genetic material in a process known as "reassortment" and can then more easily infect new hosts, such as humans. As I explained at that time:
So our fight to combat the Avian flu is undoubtedly a fight against evolution. The question is, has there been a net increase in genetic information through this "evolution"? The Avian flu is essentially the swapping of genes--but its genes probably came from other pre-existing viruses.If you've read the news lately, you're aware that many are presently concerned about the threat from the swine flu virus. In this case, we're looking at precisely the same type of evolution: As an article on Physorg.com explains, this new virus has bird, pig and human components:
Pigs are well-known crucibles for mixing viruses, able to harbour strains of flu that normally are specific to pigs, birds and humans. When present in the same animal, these viruses are able to swap genes as they replicate, which can result in a new strain and leap the species barrier to humans.At best, the origin of this new swine flu virus represents a virus that is composed of pre-existing genes that have been swapped into a new "mixture" in the swine flu virus. This is of course "evolution," when we understand evolution as "change over time," but it involves the origin of no new genes.
After All This "Evolution," It's Still a Virus
In his 2007 book The Edge of Evolution, Michael Behe observed that after our attempts to kill disease-causing bacteria and viruses, some can evolve via Darwinian selection to evade our disease-fighting strategies. Yet despite this evolution, they remain bacteria and viruses — with very little net change. As Behe writes:
Indeed, the work on malaria and AIDS demonstrates that after all possible unintelligent processes in the cell--both ones we've discovered so far and ones we haven't--at best extremely limited benefit, since no such process was able to do much of anything. It's critical to notice that no artificial limitations were placed on the kinds of mutations or processes the microorganisms could undergo in nature. Nothing--neither point mutation, deletion, insertion, gene duplication, transposition, genome duplication, self-organization nor any other process yet undiscovered--was of much use. (Behe, The Edge of Evolution, pg. 162)Similarly, we wrote in response to David Hillis that the evolution of certain influenza viruses entails a trivial degree of evolution:
To further show the alleged utility of evolution, Hillis discussed how mutations in one particular protein of the influenza virus allow it to escape detection by our immune system, stating “phylogenetic analysis … is a critical tool for developing flu vaccines every year,” and asserting that “knowledge of evolution helps millions of human lives be saved every year.” While there is no doubt that influenza “evolution” is a real phenomenon, we must ask the crucial questions: What degree of evolution is this? And can this sort of “evolution” be legitimately extrapolated to explain large-scale evolutionary changes? In other words, if we were teaching students about this type of “evolution,” should we teach them that it implies large scale macroevolutionary change that could explain the origin of complex biological features, such as new body plans?Indeed, as soon as one's immune system produces an antibody that can successfully target the hemagglutinin molecule in a flu virus, that virus can be effectively targeted by its host. Because it is readily recognized by our immune system, there is a tremendous amount of selection pressure on the hemagglutinin protein that makes it a huge liability to the virus. The cat-and-mouse game between the adaptive immune systems of higher vertebrates and viral hemagglutinin proteins has been going on for near-countless generations. If viruses could function without the hemagglutinin protein, evolution would have jettisoned it long ago. Long, long ago. But it hasn't. There are limits to evolution, and we see that in constraints upon viral evolution.
The answer is clearly no. The truth is that the mutations in the hemagglutinin molecule testified about by Dr. Hills represent small-scale changes in a limited number of amino acids in one domain of the protein that do not change the virus’s function for this protein (it resides on the surface of viruses and its function is to bind the flu virus to the infected cell).3 Nothing in Dr. Hillis’s comments alters the fact that the flu virus remains a virtually identical virus after the microevolutionary changes he describes. Lives may be saved by studying functionally trivial amino acid changes in this protein, but it is not due to knowledge of any kind of evolution that can explain the origin of new species or body plans.
And it's a good thing that there are limits to evolution, because our flu-fighting strategies rely on it remaining a flu virus. This allows preventative measures that work to be implemented, vaccines to be developed using standard flu virus culture techniques in eggs and the treatment of patients suffering from infection with drugs like Tamiflu. In other words, the incredibly trivial changes that Dr. Hillis was commenting on are of some significance, but clearly don’t make the point he was trying to make: We rely on the limits of evolutionary processes to fight the flu, not the purported ability of evolution to generate new biological features.
The Evolutionary Origin of Viruses? "Forever Obscure"
Evolution appears tightly constrained, yet we see a suite of complicated micro-killers like viruses. How did viruses arise in the first place? After reviewing some of the speculative, vague, and detail-free ideas about how viruses might have arisen, an article in Scientific American admitted last year, "At the end of the day, however, despite all of their common features and unique abilities to copy and spread their genomes, the origins of most viruses may remain forever obscure."
Let's just hope that a cure for the swine flu virus is less obscure than its ultimate origin.