Wednesday, August 20, 2008

HIV macroevolution?

I'm still thinking about the objection I wrote about in my recent T-Rex to Tweety post. It's the concern that many people, religious or not, raise along the lines of, "I don't buy evolution because I don't see it happening around me." As I was doing research for chapter 5 of the book, I began seeing the emergence of HIV as an example of macroevolution at work. I'm wondering, though, if I'm off base on this, and I would appreciate any input you can give.

From the research I've done, I've learned that HIV developed from SIV, a non-fatal disease affecting mainly chimps in Africa. In that part of Africa, humans eat chimps; so, that's the probable pathway of the virus into humans. But, the virus had to mutate so that it could infect humans, and in doing so, it also became lethal. Several descriptions of this process can be found on-line, but one I've been using recently is "The origin of AIDS and HIV and the first cases of AIDS". (It's posted by an advocacy organization, but I think they got the basic facts correct.) The thing I like about the page is how it is referenced with scientific articles; so, they're tying down their explanation with actual science.

But, is this a good example of macroscopic evolution? Am I ok in saying that this is evolution from one kind to another? As I look at it, it's an example right in front of our eyes of a virus becoming significantly different, but would people say that it's actually microevolution because it's still a virus, similar to Darwin's finches still being finches after thousands of years of evolution?


JNoah said...

Okay, I'm stepping WAY outside the bounds of what I know and, frankly am comfortable with here, but that's never stopped me before so. . . my question is, why don't we refer to all viruses that change in this way? In other words, is your basis for thinking, supposing it's evolution because it jumped from chips to humans or because it changed significantly? It seems like we have viruses that "change significantly" fairly regularly, which is why the antibiotics that worked last year don't work this year. Maybe those changes are in reality small. Again, I'm far outside any realm of usual thought here.

Anonymous said...

As I was thinking about the post and reading the article a thought occured to me. Can we say that something that is not alive(virus) evolve in the darwinian sense of the term?

I have heard many people use bacteria and their "evolving" as proof of evolution happening now. The question is what has actually happened. Did they gain some new trait (antibiotic resistance) through a random mutation? Did they gain it through a form of reproduction? Maybe we killed all of the type of bacteria that is susectible to that drug leaving only the resistant bacteria to grow and reinfect us? I think the how they got it question is most important.


Lee said...

Sorry I'm so slow in responding. It's been a busy couple of weeks, especially with classes starting up at UAB.

Both of your comments helped me think through the issue, and that's what I really appreciate about all of you who are helping me out here. Josh, that's a really good point about viruses not being alive. It's interesting to me that HIV is used as an example of evolution in the college text I have on evolutionary biology. I wonder if the biologists themselves disagree on this.

JNoah, I'm really glad you continue to step out of your comfort zone. Please keep doing so. Your comment helped me to see that we probably need a clarification of terms when we talk about the evolution of new life forms. I'm wondering now if we could use classic taxonomy to clarify terms. No one really has a problem with the evolution of new species (as in "genus" and "species"). This is just natural selection and the original of Darwin's finches become 14 or so different species as they adapted to new environment.

Is the real question for people, though, at a higher taxonomic level? In an earlier post, I talked about the evolution of birds from dinosaurs. So, this is the change from dinosaurs to birds at the class level (or from "Reptilia" to "Aves" in the Latin). I wonder where most people begin to get uncomfortable with evolution producing new life forms. "Canis" is the genus that contains jackals, wolves, dogs, coyotes, and wolves. Would most be OK with the idea that natural selection, acting over a long time, could have caused the first "Canis" to reproduce to the variety of the kinds of wolves, dogs, and jackals we see today? Or would they only feel comfortable with evolution adequately describing the very narrow subspecies of dogs? The first dog gave rise to all the different kinds of dogs we see today.

I would think that if we back up two taxonomic levels to order, a bunch of people get uncomfortable with evolution. At this level, we're saying that given time + natural selection, a common ancestor produced wolves/dogs, pandas, skunks, seals, and bears, as well as the cat family, mongooses (mongeese?), hyaenas, and others.

Am I on to something here with the idea of clarifying in terms of taxonomy?