Wednesday, September 07, 2005

Nelson on Mooney/Nisbet

Of course, the ID folks weren't going to take the Mooney/Nisbet article lying down. It wasn't long before they had dispatched one of their flacks to say something stupid. The flack in question was Paul Nelson, and his comments can be found here. He begins with an excerpt from the Mooney/Nisbet article, the most relevant portion of which I produce below:


What Dobzhansky calls “evolution,” Charles Darwin himself often called “descent with modification,” but the basic idea is the same — that the wide variety of organisms occupying the earth today share a common ancestry but have diversified greatly over time.


From here Mooney/Nisbet go on to describe the way virtually all scientists and professional scientific organizations view this subject.

Seems unobjectionable enough, but here's Nelson:


The safe strategy, then, if one doesn't want to be tossed into the lowly bin labelled “hack reporters trying for phony scientific balance on a story where there is none,” would be to paste something resembling Mooney and Nisbet's Orthodox Position on Evolution into one's article.

Problem is, if scientists love to make discoveries, reporters love to break stories. As in, tell their readers something new (i.e., newsworthy): “You and most people think P, but I've learned Q; and here's why Q is significant and deserves your attention.” So let's suppose you're a science reporter who wanders over to the Panda's Thumb blog to see what's cooking that day. Turns out Mike Syvanen is explaining why Darwin's tree of life -- Mooney and Nisbet's orthodox “common ancestry of all organisms on earth” -- may not be the case, because life may have arisen from multiple independent starting points.


Let us begin with the obvious: Mooney and Nisbet make no reference to the tree of life. They talk only about common ancestry. Those are two different things. Since Nelson is about to make hey out of the fact that many biologists argue that trees are not the best models for evolution at the earliest stages, this equation is highly significant.

Now let's turn to the Syvanen post to which Nelson refers. Does Syvanen write that common ancestry is on the way out? Of course not:


As an example for how profound the notion of HGT [horizontal gene transfer] has changed our thinking concerns the notion of the last universal common ancestor (LUCA). This is an idea that was central to the hypothesis that life shared common ancestors. Though the idea of common ancestry remains valid (indeed evidence for common ancestry is everywhere in the sequence of our genes) there is no longer a need to postulate that all life evolved from a single last universal common ancestor. Rather, we can entertain common descent from multiple ancestors.


Hard to get much clearer than that. At the very earliest stages of evolution (where HGT is now known to be an important mechanism of evolution) it becomes inaccurate to view evolution as a tree. Instead of tracing our heritage back to a single ancestor, we find instead a community of simple organisms that were trading genetic material with each other via HGT. Thus, a differemt metaphor is called for.

And Nelson thinks this is relevant to an article about evolution and ID?

The ID folks want us to believe that the very possibility of a naturalistic explanation for the evolutionary process is so ridiculous that it is more plausible to concoct, from nothing, an unbelievably powerful intelligent designer. Now it turns out that there is a previously underappreciated mechanism of evolution that provides yet another naturalistic way for genetic complexity to increase. Why does Nelson think this is helpful to his cause?

To put it another way, the discussion has gone like this: Evolutionists of a bygone era used the metaphor of a tree of life, in which any pair of modern organisms can be said to have a common ancestor. They pushed this tree back all the way to its root, hypothesizing that there was a single organism residing there. More recent work has shown that, especially among relatively simple organisms, genetic transfer can, and frequently does, take place by mechanisms other than descent. Consequently, instead of viewing the tree being rooted at a single organism, it is more accurate to view a community of many organisms at the root. Further, a metaphor other than a tree should be used to describe evolution at this level.

And here's Nelson saying, “See! Evolution's all nonsense. There's real controversy here! ID works better.”

Nelson gives a second example:


Hot on the scent now, you click over to Entrez PubMed and put “Tree of Life” into the search box. Up pops a recent paper about the shortcomings of “tree thinking,” which also appears to challenge another of Mooney and Nisbet's What Every Sane Biologist Knows For Sure points of orthodoxy.

Now you've got a couple of problems. You know what you're supposed to say, per Mooney and Nisbet, to stay out of the disreputable hack bin. What you really want to do, however, is to call Mike Syvanen, or W.F. Doolittle's lab, to arrange an interview.


If you're interested, the paper Nelson is referring to can be found here. In this case, however, there isn't even any need to quote from the article. The authors are making precisely the same point as Syvanen. “Tree thinking” is not a good way of thinking about the earliest stages of evolution.

According to Nelson, reporters writing stories about evolution and ID should make a point of discussing how new discoveries are showing that evolutionists have an embarrassment of riches at their disposal for explaining major aspects of evolution. Fine with me. But this fact contradicts nothing that Mooney and Nisbet wrote, and it is positively damaging to the ID case. Why Nelson thinks he has scored a point here is beyond me.

4 Comments:

At 11:07 AM, Blogger Salvador T. Cordova said...

Jason wrote,

" Instead of tracing our heritage back to a single ancestor, we find instead a community of simple organisms that were trading genetic material with each other via HGT. Thus, a differemt metaphor is called for."

In the interest of representing your position and that of others fairly, does that mean we have multiple, possibly independently-originated organisms at the start? Possibly meaning abiogenesis happened multiple times independently, and then these organisms started exchanging material?

I've not seen that point explicitly addressed anywhere (it does not mean it hasn't been written about, I just haven't seen it).

Thanks.
Salvador

 
At 11:21 AM, Blogger Jim said...

Since the root systems of trees are often as complex as their branches, "tree thinking" is only inapt as a misunderstanding of real trees.

 
At 11:39 AM, Blogger JM O'Donnell said...

In the interest of representing your position and that of others fairly, does that mean we have multiple, possibly independently-originated organisms at the start? Possibly meaning abiogenesis happened multiple times independently, and then these organisms started exchanging material?

The general concept is pretty much that. Because microorganisms aren't quite as restrained in what they are able to do with the DNA of other organims, it's very unlikely we could ever find a 'common' ancestor of all life. In fact, such a notion is possibly dead now as there has been so much evidence that bacterial genomes are the product of multiple horizontal gene transfer events as to make such a search meaningless.

Of course, this isn't the case once you start getting higher up, but the tree of life has actually been dead for a really long time. It's more like a horrible looking fungus, which does branch like a tree at the top (that is with metazoans like us) but at the bottom it's pretty much a mess. There are bits and pieces going everywhere as bacteria, viruses and other organisms throw their genes all over the place.

It gets somewhat more difficult when you put plants in there as well, because bacteria can also exchange genes with plants (for example, in nodulation and nitrogen fixation).

I just don't see the point in these silly 'tree of life' analogies really. It's clear that there are common ancestors that can be clearly determined at the higher taxonomic regions, but trying to apply such basic notions to bacteria is a futile excercise and misses the real story of how these organisms actually evolved.

 
At 4:11 PM, Anonymous Anonymous said...

Salvador asked In the interest of representing your position and that of others fairly, does that mean we have multiple, possibly independently-originated organisms at the start? Possibly meaning abiogenesis happened multiple times independently, and then these organisms started exchanging material?

I'm not so sure about that "independently-originated" part.

RBH

 

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