Massimo Pigliucci has reviewed Mike Lynch's book on genome evolution for Science [Postgenomic Musings]. In his review, Pigliucci writes the following:
One of the central theses of the book is that natural selection is not necessarily the central evolutionary mechanism, as quite a bit of the details of genomic structures and evolution can be accounted for by invoking the neutral mechanisms of mutation, recombination, and drift. Lynch is certainly correct on this point, and he backs his argument with much empirical and theoretical detail. Yet, we must be hanging around with different crowds, because I hardly know anybody who would seriously contend that evolution is just a matter of natural selection.
Dr. Pigliucci, I'd like you to meet Julie Dunning Hotopp.
As for the title of this blog post, it means "the way forward" in Swedish. Mike Lynch likes to include a picture like this or this in his talks. It makes people laugh, and it's a good way of *cough* framing his point.
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Glad to see the citation to Dunning Hotopp, J. C., et al. Science doi:10.1126/science.1142490 (2007).
Over on News @ nature.com the story begins:
Published online: 30 August 2007; Corrected online: 31 August 2007 | doi:10.1038/news070827-6
Bacterial genome found within a fly's
DNA transfer from bacteria to animals is more common than thought.
Ewen Callaway
Researchers have found a surprise hidden in the DNA of a fruitfly: what seems to be the entire genome of a parasitic bacterium called Wolbachia. Smaller bits of the promiscuous parasite's genetic material turned up in worms and wasps, too.
The size of the Wolbachia insertion in the fruitfly Drosophila ananassae -- more than 1 million base pairs -- has caught researchers by surprise. If bacterial DNA is so common in other creatures, they caution, researchers should be careful not to mistake it for contamination and accidentally throw it away when doing genome sequencing.
It has long been known that organisms can sop up foreign genes, the most usual example being bacteria swapping DNA with each other. DNA from mitochondria and chloroplasts -- cell structures thought to have evolved from specialized bacteria -- have also made their way into the genomes of multicellular eukaryotes (a category including plants and animals). And a worm parasite of plants has been found to contain a gene from nitrogen-fixing soil bacteria. But transfer of bacterial genes into animals has been thought rare.
The new work, published today in Science, suggests that gene flow from bacteria to animal hosts happens on a larger scale and more commonly than suspected.
The discovery also hints that the bacterial genome must have provided some sort of evolutionary advantage to its host. "You're talking about a significant portion of its DNA that is now from Wolbachia," says Julie Dunning Hotopp, a geneticist at the J. Craig Venter Institute in Rockville, Maryland, who led the study. "There has to be some sort of selection to carry around that much extra DNA."...
I've been snickering about that chapter title since the book came out.
I find Pigliucci's comments in the review to be misleading, as Lynch hasn't talked about spandrel-like panselectionism, and the spandrels paper didn't talk about pop gen nor about population thinking. And Pigliucci just doesn't convincingly argue against using non-selective forces as null hypotheses. Selection *is* different, and the reasons for this are inherent in population thinking.
So I'm wondering if Pigliucci just doesn't get that. Pigliucci has been arguing for the abandonment of the population context in his recent work (e.g., doi:10.1093/aob/mcm069), and I've found his presentation of the new approach to be pretty uninspiring. So what if G matrices are messy, this indicates messy underlying genetic architecture. It would be most useful to continue to quantify and attempt to explain the stochasticity and contingency inherent in evolution, something that pop gen helps to do, rather than skip over it in an artificially blinded search for determinism.
Would it be possible for somebody to email me a PDF copy of Pigliucci's review? I'd be very interested in reading it, but don't have a Science subscription. My address is someotherguy86 at gmail dot com. Thanks!
Actually, "genomfart" means thoroughfare, or a smaller street or path that is open at both ends and leads from one main street to another. But I guess "the way forward" is a bit more... poetic. Swedish can be fun but look up Danish if you're really in for laughs.
It's my impression that speciation events in animals are thought generally to be allopatric or parapatric events involving small seperated populations. Selection is a statistical thing: generally more fit does better than less fit. But statistics do not predict well with small populations. It seems to me that initial sampling eror, inbreeding, chance events, etc., might have more influence the evolution of a small population (so long as it is small) than selection.