Lynn Margulis weblog tour

Here’s an interesting opportunity: Lynn Margulis, the controversial scientist, is going on a ‘blog tour’ to promote her new imprint of science books called Sciencewriters Books. What does that mean? She’s going to hang out for a little while on a few blogs and chat and answer questions. If you’ve wanted to have a conversation with the author of the endosymbiont theory and critic of neo-Darwinian theory, here’s your chance.

The tour will kick off on Monday, 12 March, at Pharyngula. She’ll be sending me a short article that I’ll post that morning, and we’ll collect comments and questions. Later that afternoon or evening, she’ll browse through those comments and answer the ones she finds interesting.

In addition, she’ll be available in the Pharyngula chat room (channel #pharyngula on irc.zirc.org; if you don’t have an IRC client, that link will let you use your browser to join in) from 12:00-1:30pm ET.

So mark it on your calendars: an online conversation with Lynn Margulis, next Monday, 12 March, at Pharyngula.

What is science?

Vox Day asks a question: what is my definition of science? It’s a bit weird coming from him — he is not usually that lucid or civil — but OK, I’ll take it seriously.

Unfortunately, “science” is one of those hugely polymorphic terms that carries a tremendous amount of baggage, and any one definition is going to be inadequate. This is one of those subjects where a smart philosopher (Janet? John?) could go on at amazing length, and even then, everyone will argue with their summaries. I’ll just charge in, though, and give a couple of shorter definitions off the top of my head.

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Report from Planet Righty

Tim Lambert summarizes an informal survey of 59 right-wing bloggers: 100% of them deny the idea that humans are the primary cause of global warming, contradicting the scientific evidence. They were also asked about other issues—the majority approve of the “surge” in Iraq, think Bush is doing an acceptable job in foreign policy, and believe Democrats like the idea of losing the war in Iraq, but only on global warming is their unanimity.

It’s too bad the survey didn’t ask about other science issues. I’d like to know if they are similarly wrong about evolution, HIV as the cause of AIDS, and whether the earth goes around the sun rather than vice versa.

Orthozanclus

i-418e0b95a0ed69a876105edf26600940-orthrozanclus.jpg
(click for larger image)
Reconstruction of O. reburrus by M. Collins. The precise arrangement of the anteriormost region remains somewhat conjectural.

Halkieriids are Cambrian animals that looked like slugs in scale mail; often when they died their scales, called sclerites, dissociated and scattered, and their sclerites represent a significant component of the small shelly fauna of the early Cambrian. They typically had their front and back ends capped with shells that resembled those we see in bivalve brachiopods. Wiwaxiids were also sluglike, but sported very prominent, long sclerites, and lacked the anterior and posterior shells; their exact position in the evolutionary tree has bounced about quite a bit, but some argument has made that they belong in the annelid ancestry, and that their sclerites are homologous to the bristly setae of worms. One simplistic picture of their relationship to modern forms was that the halkieriids expanded their shells and shed their scales to become molluscs, while the wiwaxiids minimized their armor to emphasize flexibility and became more wormlike. (Note that that is a very crude summary; relationships of these Cambrian groups to modern clades are extremely contentious. There’s a more accurate description of the relationships below.)

Now a new fossil has been found, Orthozanclus reburrus that unites the two into a larger clade, the halwaxiids. Like the halkieriids, it has an anterior shell (but not a posterior one), and like the wiwaxiids, it has long spiky sclerites. In some ways, this simplifies the relationships; it unites some problematic organisms into a single branch on the tree. The question now becomes where that branch is located—whether the halwaxiids belong in a separate phylum that split off from the lophophorate family tree after the molluscs, or whether the halwaxiids are a sister group to the molluscs.

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Basics: Gastrulation, invertebrate style

The article about gastrulation from the other day was dreadfully vertebrate-centric, so let me correct that with a little addendum that mentions a few invertebrate patterns of gastrulation—and you’ll see that the story hasn’t changed.

Remember, this is the definition of gastrulation that I explained with some vertebrate examples:

The process in animal embryos in which endoderm and mesoderm move from the outer surface of the embryo to the inside, where they give rise to internal organs.

I described frogs and birds and mammals the other day, so lets take a look at sea urchins and fruit flies.

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Basics: Gastrulation

That guy, John Wilkins, has been keeping a list of presentations of basic concepts in science, and he told me I’m supposed to do one on gastrulation. First I thought, no way—that’s way too hard, and I thought this was all supposed to be about basic stuff. But then I figured that it can’t be too hard, after all, all you readers went through it successfully, and you even managed to do it before you developed a brain. So, sure, let’s rattle this one off.

In the simplest terms, gastrulation is a stage in early development; in human beings it occurs between two and three weeks after fertilization. It is that stage when a two-layered cell mass undergoes a set of specific movements and interactions that establish the three germ layers of the embryo (endoderm, mesoderm, and ectoderm) and the beginnings of a three-dimensional structure. The end result doesn’t look like much of an animal, but it has set up pools of cells that will contribute to specific future cell types, and has laid down the rough outline of tissues along the body axis.

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What use is an appendix?

Here’s an excellent and useful summary of the appendix from a surgeon’s perspective. Creationists dislike the idea that we bear useless organs, remnants of past function that are non-functional or even hazardous to our health; they make up stories about the importance of these vestiges. Sid Schwab has cut out a lot of appendices, and backs up its non-utility with evidence.

The study I cited most often to my patients when asked about adverse consequences of appendectomy is one done by the Mayo Clinic: they studied records of thousands of patients who’d had appendectomy, and compared them with equal thousands who hadn’t. (Back in the day, it was very common during any abdominal operation to remove the appendix. Like flicking a bug off your shoulder. No extra charge: just did it to prevent further problems: took an extra couple of minutes, is all.) The groups were statistically similar in every way other than presence of the worm. There were no differences in incidence of any disease. It’s as convincing as it gets, given the impossibility of doing a prospective double-blind study.

I have a personal interest in this: I was nearly killed by my appendix at the age of 9, and had it removed. I haven’t missed it since.

The Haeckel-Wells Chronicles

Lately, the Discovery Institute has stuck its neck out in response to the popularity of showings of Randy Olson’s movie, Flock of Dodos, which I reviewed a while back. They slapped together some lame critiques packaged on the web as Hoax of Dodos (a clunker of a name; it’s especially ironic since the film tries to portray the Institute as good at PR), which mainly seem to be driven by the sloppy delusions of that poor excuse for a developmental biologist, Jonathan Wells. In the past week, I’ve also put up my responses to the Wells deceptions—as a developmental biologist myself, I get a little cranky when a creationist clown abuses my discipline.

In case you are completely baffled by this whole episode, here’s a shorter summary.

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Would Chuck Terhark like a job writing science abstracts?

One of the subjects I mentioned at the Thursday Flock of Dodos discussion was that an obstacle to getting the public excited about science is the state of science writing. It’s a very formal style in which the passive voice is encouraged, caution and tentative statements are demanded, adverbs are frowned upon and adjectives are treated with suspicion, and all the passion is wrung out in favor of dry recitations of data. Now that actually has a good purpose: it makes it easy to get to the meat of the article for people who are already familiar with the subject and may not need any pizazz to get excited about nematode cell lineages or connectivity diagrams of forebrain nuclei. It makes the work impenetrable to those not already inculcated with the arcana of the discipline, however.

The City Pages illustrates the difference. On Tuesday, the Café Scientifique is going to be given by Cynthia Norton of College of St. Catherine in St. Paul, on the subject of snails. Just for comparison, I’ve put an example of a scientific abstract and the publicity copy for the talk below the fold, and you’ll see what I mean.

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