Saturday, February 25, 2012

James Shapiro Responds to Coyne

James Shapiro responded to Jerry Coyne's criticisms, which Coyne put in the combox, instead of starting another thread, which would have been the polite thing to do. So I didn't realize that Shapiro had responded until just a few minutes ago.

 There's an interesting discussion in the combox afterwards.  I made a few observations from it:

1)  There is some agreement that environmental stress can cause an organism to increase mutation frequency to its genome, in order to solve the crisis.

2)  However, are the mutations just random attempts to solve the crisis, like a blind man trying to find his way out of a maze, or does the organism somehow "know" which mutations are more likely to solve the problem?

3)  Either way, it still leaves in place Darwin's claim that natural selection decides which variations survive.

4)  Why isn't anyone talking about (genetic) drift as an alternative to natural selection?  That, it seems to me, is the real challenge to Darwin's claim about natural selection.

Let me add a fifth point:

5)  What mechanisms cause organisms to increase their mutation rates?  Have these mechanisms  been acquired through evolution?  Or were they part of the original cells?


Crude said...

One question.

Does the standard Coyne uses here - 'natural selection fixes the change' - make it so natural selection is, essentially, bulletproof by definition? His reply seems to be that, no matter what the source of novelty may be, if natural selection touches on it in any way or plays any role, then "natural selection is the explanation for what we see".

It's a little like saying that, if flat out hopeful monster theory is true, then Coyne will just turn around and insist that natural selection is still the only game in town because the "better" hopeful monsters will survive. But that seems close to making natural selection downright trivial.

Bilbo said...

In his book, The Edge of Evolution, Michael Behe defined neo-Darwinism as consisting of three parts: Common descent, natural selection, and random mutation. Behe went on to accept natural selection, and even argued for common descent, but argued that at least some mutations are non-random. If I remember, Behe said something about natural selection being trivially true. It doesn't explain the source of variation or novelty in evolution. It just explains which ones survive.

But there are biologists who favor genetic drift as the explanation of which ones survive, instead of natural selection. Thus variation A may survive variation B, not because it survives better in the given environment, but because its offspring became the dominant form by chance.

I'm surprised no one is bringing this up in the discussion. I would, but my comments don't survive in Cousin Jerry's combox. I suspect artificial selection is to blame, but I can't prove it.

Bilbo said...

So yes, Coyne would say that Hopeful Monster A survived, and Hopeful Monster B didn't survive, because of natural selection. That doesn't explain how in the heck either Hopeful Monster arose in the first place, though.

Crude said...

Well, if you want to really cause hell, ask this question: is there a way to scientifically test between artificial selection and natural selection?

I agree that to take Coyne's route, apparently, would mean that natural selection hardly does much of anything. At least if I understand him right, I don't see him offering much of a response to Shapiro than "well, no matter why or how the mutations happened, if it was a beneficial change than that helped it survive, so natural selection is still involved and I win".

And yes, drift seems like it would complicate matters as well. I suppose Coyne's response would simply be, "Unless drift, but that's rare I bet and who cares anyway, quit talking about it".

Bilbo said...

Crude: there a way to scientifically test between artificial selection and natural selection?

Excellent question.

I'd like to know what Coyne thinks about the significance of drift.