Roma

About SARS (severe acute respiratory syndrome), the virus that first surfaced in China months ago and is showing up in America... My question is: are viruses such as this one and the infamous West Nile Virus of yesteryear said to have "evolved" or merely "adapted"? Or was the virus just hidden under a rock (so to speak) all these years and something somehow suddenly unleashed it on the earth. If these viruses are a clear example of evolution, what excuses might a YEC use to say they're not?

-Roma

Paul2

*puts on his creationist thinking cap*

It's still a virus-kind. If that virus evolves into a moose, let me know.

pz

"Evolved" is the general term, referring to heritable change that has spread through a population via any mechanism. "Adapted" refers specifically to change as a consequence of selection. I'd say the virus has done both.

SARS and West Nile were almost certainly common in animal populations for a long, long time, but weren't big news because people are self-centered bastards who don't get worked up about a bunch of ducks or mosquitos who are feeling sickly. The only change here is that the viruses have evolved to affect us. Now we care.

I have no idea what excuse creationists would make to wedge yet another set of observable facts into their ridiculously distorted worldview.

Duvenoy

C'mon pz, you know exactly what they'd say. They'd say that SARs is like the AIDs virus; God's punishment for all of our ungodly messing around, and anyone who catches it hadn't ought to have been smoking that stuff.

doov

Godot

and I thought smoking that stuff was for a medicinal benefit. bugger.



I'd have to disagree with pz. SARS will definitely have adapted, but evolved? Last I checked, evolution only works on living species. One of the pre-req's for life is self-replication. Viruses can only reproduce by hijacking the machinery of the cell, and therefore do not classify as a living organism per se.

RufusAtticus

Are you sure you wanted to say that?

Evolution occurs if you have an imperfect replicator. It doesn't matter whether its a purely self-replication or not.

pz

Whoa...you want to claim that they have adapted, but have not evolved? Adaptation can only occur in "living species", too, so why don't you reject that as well?

Rufus has pointed out the flaw in your argument. Evolution is a property of imperfect replicators, whatever they may be. Tying it to a definition of "life", which is about as slippery and difficult a concept as "species", is a mistake.

Godot

Point taken, and I stand corrected. (bow)
But surely the use of both adaptation and evolution in this context is something akin to equivocating. Kind of redundant, really.
Could we not also argue that the SARS virus hasn't necessarily changed in morphology so much as having found a new vector to affect us through? (now I'm definitely talking shit. g'night)

Non-praying Mantis

Let me chime in on this one:

Adaption is usually defined as a single organism changing in response to its environment, which is not a genetic change. Evolution refers to genetic changes that happen from generation to generation.

Viruses are not considered capable of adapting because they do not respond to their environments. Only "truly" living organisms can do this. Organisms can react to changes in their environments. Viruses react in this manner as if they were non-living chemicals.

Viruses can evolve, since they do have genetic material and they do produce generations. Some viruses, such as the AIDS virus and influenza virus, which are RNA viruses, have a very high rate of mutation, and therefore a high rate of evolution.

NPM

ps418

This brings up something I've been wondering about recently. How important is/was pathogen-driven selection in human evolution? Sickle-cell 'selected' by malaria is the example everyone knows about. But surely there are many other examples of alleles that were pushed towards fixation or extinction by the relatively huge selective pressures of prehistoric pandemics. Another example is the CCR5 allele that happens to inhibit HIV infection of leukocytes, though this is probably not being strongly selected for. Can anyone point me to more information on this subject?