In recent years it has becoming increasingly obvious that there is a considerable amount of lateral, or cross phylogenetic, transfer of genetic material. In bacteria, this happens by several mechanisms, such as uptake of gene fragments from cells that have disintegrated, or by mechanisms such as conjugation ("bacterial sex"). Sometimes genetic material has transferred this way from bacteria into mammal cells. How important this turns out to be for the novelty of evolutionary processes remains to be seen.
But until recently there has been little evidence of lateral transfer (apart from sex, which is almost always within-species) in vertebrates. Now comes a paper in PNAS (USA) in which transfer of genetic material from a snake into a gerbil via a DNA poxvirus has been documented, and we might expect more of this now people are looking.
The origins of novelty almost always turn out in evolution to be due to the recombination of genetic mutations from elsewhere. As Darwin put it, we see why Nature is profligate in variety but niggard* in innovation.
Piskurek, Oliver, and Norihiro Okada. “Poxviruses as Possible Vectors for Horizontal Transfer of Retroposons from Reptiles to Mammals.” PNAS 104, no. 29 (2007): 12046-51.
*This word no more has to do with racial epithets than "history" has to do with gender or stories.
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Wow!
Ah, looks like they were hit by that Shakespearean curse - "A pox on both your houses!"
The one thing that's missing is direct evidence that the snake does indeed carry the virus. But I'm not going to go to West Africa and ask the snakes to give samples.
Bob
Funny, but this sort of thing was being talked about back in the 70s and 80s; Lewis Thomas is where I found out about it. The earlier talk is why I had my Dragon Earth Gnomes (descended from Homo floresiensis) pick up the gene complex for creativity from the Orcs (descended from Homo neanderthalensis) via a flu bug. :)
Unfortunately, it's just a SINE, which doesn't code for anything, but is expert at jumping in and out of DNA. It would be really exciting to find evidence of horizontal transfer of real genes into the germline.
If I read it correctly, the paper provides good evidence that a snake SINE popped into the viral genome, which is interesting in itself, but the virus->rodent transfer is more speculative.
I'm guessing the IDers will be a bit confused to hear that their beloved junk DNA might be crossing species boundaries.
So far as I am aware, almost exactly no coding DNA has made the jump for verts and there is little evidence that it is very important for their evolution. But the mere fact that it happens is evidence that it might do.
Look out, the species barriers are falling! ... Oh.
Indeed. "Middle English nigard, perhaps from nig, stingy person, of Scandinavian origin".
A "niggard person" is nowadays the antiquated term "njugg person" in swedish. (Um, yes, "person" is the same, and very much in use. I suspect more lateral transfer, in the other direction. :-P )
What does this discovery do for phylogenetic trees based on molecular sequence data? Do we just have to be really, really careful which sequences we pick to compare?
Lateral transfer shows up just like homoplasy (convergent evolution), and has to be ignored. In such cases it shows up as an unresolved cladogram (with more than two edges coming from a single node) and can be dealt with by removing characters until the cladogram resolves again.