There's a lot going on in that first paragraph, so I'll walk you through it slowly. First: moustaches, feathered hair, boy short shorts. Disgusting. How the human race didn't dress itself out of existence is beyond me. Second: butterflies. I've always wanted to use "freaky-deaky" in an article, although I have a feeling it will be relegated to words we are not to use, so I'll get it in while I can. [N.B. Not only is that the title of an Elmore Leonard book, but also an upcoming movie by Walter Matthau's son Charles. So there you go. A little culture for the day.] I'll get to the butterflies in a moment. Third: surprising PNAS article. It was surprising because (a) the theory is a bit, shall we say, not up to PNAS par; and (b) it seems as if a little editorial bias may have contributed to its publication.
Let's start at the very beginning - a very good place to start, or so says that troublesome little scamp Maria.
From the Greek, to change form, Wiki says metamorphosis is "a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and differentiation."
Butterflies are experts at this. They start off as cute little green caterpillars (larvae); hormones signal the caterpillar to form a chrysalis (or cocoon). Inside the cocoon the caterpillar "melts" into soupy formerly-known-as caterpillar goop and reforms as a lovely winged colorful butterfly. Ever see Terminator 2: Judgment Day? Yeah, kind of like that. Or, to watch it in 3-D animation, click here.
An article in Scientific American says that since Darwin, "biologists have believed that the larval and the adult forms of insects evolved from a common ancestor. Indeed, the evolution of metamorphosis is thought to have fueled the incredible diversity of insects today, allowing them to exploit different habitats at different life stages."
Butterflies Gone Wild in Mexico, a 2-DVD set
Now the butterfly world is all aflutter, thanks to a paper published in the Proceedings of the National Academy of Sciences. Donald Williamson, "a wheelchair-bound 87-year-old zoologist at the University of Liverpool in England," (as he is described in the SA article), suggests that the "ancestors of modern butterflies mistakenly fertilized their eggs with sperm from velvet worms, also known as onychophorans. 'People have been trying to find one solution that covers all of metamorphosis,' Williamson says. 'I say it's a change in taxon during development.'"
In particular, he says a type of worm and a butterfly accidentally mated. The "accidentally" threw me a bit - unless you're really really drunk, aren't you usually aware of that sort of activity? But I digress.
A male velvet worms places sperm packets on female skin tissue, which the sperm penetrates
before migrating to the ovaries. Williamson thinks a butterfly floating by accidentally picked up some of that sperm and transmitted it to another butterfly, somehow the DNA was incorporated, and now a butterfly has two life stages - velvet worm and butterfly.
"Animals have been able to hybridize since they invented sex," Williamson says. "With external fertilization, there's always the possibility that some sperm will fertilize the wrong egg." (Wait - animals invented sex? I must have missed that day in biology class.)
Scientists were less than awestruck by Williamson's theory. Insect paleontologist Conrad Labandeira said that "hybridization between closely related species sometimes occurs in the
animal kingdom, but it is highly unlikely that the sperm of a velvet worm could fertilize a distantly related insect egg and produce a viable embryo." Labandeira also questioned where the genetic program controlling metamorphosis would come from.
He said he would likely reject the paper if he was the reviewer, but acknowledged that it is sometimes good that off-the-wall ideas like this are published to broaden the discussion.
Duke University insect developmental biologist Fred Nijhouty said the article "would be better suited for the National Enquirer than the National Academy. ... The paper is hypothetical and speculative and not a single bit of evidence supports the idea." The developmental pathways that connect larvae to adults are well-established, Nijhouty says, and many structures in caterpillars map to adult butterflies.
Apparently Williamson has a history of being a few fries short of a Happy Meal, but one of his supporters is National Academy of Sciences member Lynn Margulis, who "has a fondness for weird theories." Margulis encouraged Williamson to work on caterpillars and garnered enough positive reviews to make the case for publication, SA says.
A crazy idea isn't necessarily new to science, nor is the idea of the lone protagonist. Galileo, anyone? Einstein? Etc? But some of the commenters on the SA article make the point that by publishing the paper in PNAS, a journal of repute, the theory gains pseudo-credibility without the burden of proof.
Research by Steven Greenberg, published in BMJ, notes that "citation is both an impartial scholarly method and a powerful form of social communication. Through distortions in its social use that include bias, amplification, and invention, citation can be used to generate information cascades resulting in unfounded authority of claims."
Metamorphosis-ed itself right out of the journal?
I was going to end with some analysis on why the theory is half-baked, plus a weak joke on butterfly/chaos theory, and pull out a few quotes from the PNAS article. After all, I always like to link to the scholarly article I'm discussing so you can read it for yourself. But then I was sidetracked in a major way. Here's the problem - I can't find the article. It's really bothering me. I emailed PNAS and the Scientific American author. A hoax? An article in a forthcoming edition of PNAS? A mystery! A lovely woman from PNAS emailed me back and is looking in to the issue. I'll update the article when I hear anything new!*
*Murphy's law - as soon as I posted this article, the reporter from SA wrote back and said it should appear this week; perhaps it just hasn't been posted yet. If PNAS writes back, I'll update again.
*The article can now be found here.