Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Thursday, September 08, 2005

Crossing the line - HGT and [Paul] Nelson

For some time now, there has been an increasing awareness that evolution is not always tree-like in structure. Lyn Margulis and her collaborators identified cases of endosymbiosis, where one life form was captured by another and integrated into the cell. Our organelles are examples. Mitochondria were once free living organisms. Same with chloroplasts in plants, which photosynthesise light. Moreover, retroviruses can copy parts of the DNA of one organisms and then infect the sex cells of another, entirely distinct species. As much as 45% of mammalian genomes are the end result of such "horizontal transfer", including ours, and who knows how much of this ends up providing useful genetic material for the new host?

And hybridisation of sexual species has been known since Aristotle - it is a common source of new species, and looks, in the genetic "fossil record" just like crossover. Genes can also "introgress" from one species into another, a process that's common also in plants.

So lateral transfer is not exactly something "paradigm breaking" in evolutionary biology. In fact, it is one of the oldest of all known ways in which novel hereditary material is added to an evolving lineage. But it does tend to undercut the "textbook" view of evolution, which gets taught to undergraduates, that evolution is a branching tree. It is only nearly always a branching tree. There is resistance to the idea, though, and so advocacy of this is sometimes thought to be an indicator of crackpottery amongst biologists (rarely amongst those who study it, though). The leading names here are Carl Woese, Ford Doolittle, and their collaborators.

One person who has advocated this since the mid 1980s is Mike Syvanen, a professor of molecular genetics at UC, Davis. So, since we evilutionists are often accused of not "teaching the controversy" with respect to ID and creationism, I suggested that it might be a good idea for him to discuss an actual controversy in evolution - this one - in a guest article at the Panda's Thumb blog. This he did. All that there was left was to wait for the IDevotees to quote mine and spin it. And so they did.

Most concerning was not that this happened - in the blog discussion list it was predicted that it would. The worry is that this was done by one of the few IDevotees who I had some respect for, Paul Nelson. Paul s a graduate of Chicago's excellent history and philosophy of science program, and, if memory serves, his advisor was Bill Wimsatt, one of the most influential, if underpublished, philosophers of biology out there.

Paul has a history of being a nice guy - in email he is polite and respectful, unlike the less pleasant Wells and Dembski, whose idea of debate is to make dismissive insults. But this piece is abysmal. It is simple misdirection, and knowing what Nelson knows, it can only be put down to a deliberate attempt to lie.

It's in the context of another article by Mooney and Nisbett in the Coumbia Journalism Review, on how journalism ought not take a "fair and balanced" view when one side is incompetent or wrong, in debating evolution. Nelson tries to make the existence of a tangled root and occasional vine in the evolutionary tree reason to think there is no tree. He cites, misleadingly and quoteminingly, the Syvanen article. It's pure deception, and nicely dissected on the evolutionblog.

Meanwhile, Carl Zimmer's Loom trumpets lateral evolution as interesting science (with a fascinating picture). Oh what a tangled web we weave, Paul...