Fins made of straw, easily knocked down

In response to Neil Shubin’s recent paper on the subject, and Carl Zimmer’s summary, the creationist Michael Denton criticizes evolutionary explanations for the vertebrate limb. It’s a bizarre argument.

First, here’s the even shorter summary of the Shubin work. Ray-finned fish have, obviously enough, rays in their fins — rigid bony struts that provide structure. These rays are formed dermally. That is, osteoblasts deposit bone on the surface of a connective tissue matrix to build the rods of bone that prop up the fin. It’s called dermal bone because the classic example is the assembly of bony elements within the dermal layer of the skin.

Another way of making bone is endochondral. You start with a framework of cartilage, and cells within the cartilage (which is what “endochondral” means) gradually replace the cartilaginous tissue with bone. Your limb bones, for instance, are endochondral, starting out as fetal rods of cartilage that were replaced by the action of osteoblasts.

What the researchers in the Shubin lab found is that fish fins, which have dermal bone, and tetrapod limbs, which have endochondral bone, use the same cell signaling pathways and cell movements to build the cellular structure of the limb/fin, but differ in the final steps. Fish switch on the dermal bone pathway, while tetrapods use the endochondral pathway. We have a fundamental similarity than simply uses a different end-product, which ties the assembly of fins/limbs more closely together than we had thought.

Not to Denton, though! He wants to make some strangely saltational argument that these two modes of bone formation are somehow incompatible. I’ll show you his final conclusion, so you can decide to bother with the rest.

In short, my assessment is this: There never were any transitional forms making both dermal bone and endochondral bone. Organisms made one or the other.There never were any transitional forms with fin rays and digits. And I predict that no matter how extensively the fossil record is searched, the phenotypic gap between fins and limbs will remain even as the genetic gap continues to diminish.

That’s an incredibly stupid statement. You make both kinds of bone; your skull, for instance, is largely formed of dermal bone, while your limbs are endochondral. Fish have both endochondral bones (for example, in their vertebrae) and dermal bones (skull and fin rays). The ancestral fish-like form had both kinds of bones. We have fossils of transitional forms with both a central endochondral core and fin rays.

finfossils

We’re done. Denton’s claim has already been addressed and refuted. How can he not know this?

You can just stop now. His whole argument is dead in the water. But you could take a look at the thought processes that led to that stupid conclusion, and they’re kind of weird, too.

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An almost automated fish farm (but not for Minecraft)

I was following @upulie on Twitter, when I saw that she was using this app, Periscope, to give a demo of what she does in the lab. Hey, I thought, I could do that, so I tried it, and gave a tour of my cheapass zebrafish facility (you don’t need the app to watch it). This is not my fish facility.

heustisfacility

That’s the big boys’ and girls’ system at the University of Oregon. So be warned: I just have a single small rack with 8 populated tanks. Also, it’s got nonstop water gurgling and bubbling, so it’s hard to hear me over the pleasant, soothing sounds. My students and I built it out of a plastic rack from Lowe’s, a bunch of PVC pipe, some hydroponics widgets, a big pump, and a cow trough. Our tanks are plastic Kritter Keepers bought from Amazon. The whole thing cost less than $500, and it’s grossly over-engineered. We were basically collecting from two tanks at a time all summer long, and it produced 50-100+ eggs every day, routinely. We’d only need a handful for observations and experiments, and the rest got thrown into an incubator (or down the drain), and the survivors were raised to produce another generation that will be ready to pump out eggs for us next summer. Or I could collect eggs every day during the school year, except that I’m expected to teach, not just play with the fishies.

I should mention that this is also a low-maintenance system. I feed the fish twice a day — you know, the usual sprinkling of a few tasty bits of ground-up invertebrates on the surface — and top off the reservoir and check the water quality once a week. It just keeps going, and would grow and grow if I let it. Zebrafish are so easy.

Periscope is also really easy. I’ll probably try it again later this week; I thought I’d give another tour, this time of my nice Leica scope with epifluorescence and DIC and a Jenoptik cooled CCD camera, which is also a little farther away from the gurgling water system, so maybe I’ll be more audible. Later still maybe I’ll set up some embryos/cells on the scope and give a close-up look at how baby fish are made.

Oh, and if anyone else wants to try some small scale zebrafish production, there are lots of sources. I stole many of the ideas from my pal, Don Kane, who has instructions for a similar little system for zebrafish. Or you can read Lawrence and Mason, who give an overview of basic principles. Kim et al. also published a detailed description of their homebuilt system. Or, if you have lots and lots of money, there are companies that build specialized racks and water systems just for zebrafish, and you don’t even have to get your hands wet or sniff PVC solvent or buy a bunch of interesting valves and widgets that will put you on a DEA list somewhere.

I guess I’m going to have to believe it now

Some people say we’re all standing on a giant rocky ball, which is spinning around — a ludicrously silly claim. But now I guess I have to accept it, because someone actually made a video recording showing it, by stabilizing the image to the stars. When you do that, you can actually see the earth moving.

You know what else is silly? The idea that I evolved from a rock. LaughingSquid is going to have to meet the creationist standard of evidence and show me a movie of that happening.

I know, this happened a long long time ago, which makes it more difficult, but I still have a VHS tape player, so I’ll even accept that antique medium.

Hey, I think my mother still has my grandfather’s old 8mm movie projector, so I’m willing to go even that far back. Checkmate, evilutionists.

Creationists skittering about in the background

Would you believe an angry creationist tried to get Jeffrey Shallit fired for critically reviewing some creationist books? Of course you would. It’s what they do. I’ve had a couple of loons do the same thing, rifling through my university’s faculty list to get all the email addresses they could, and then send off bulk email to everyone documenting my crimes. It’s annoying, but it’s also incredibly stupid; every time it has happened, there’s a bit of a laugh among the people targeted, and it’s an uncomfortable laugh at these sad people with their weird delusions.

It doesn’t help their case that their arguments are always so awful. Here’s another example: David Klinghoffer, the Discovery Institute hack, is claiming that Proxima B calls evolution into question. How? I don’t know. But as Matthew points out, the logic is ridiculous.

If life is common, that’s evidence for intelligent design. But if life is rare, that’s evidence for intelligent design. Everything is evidence of your theory when you haven’t internalized the concept of falsifiability.

It doesn’t help that the Proxima B story is an example of ridiculously over-hyped nonsense: the observation that there’s a big rock orbiting a star almost 5 light years away does not imply that it is habitable or that anyone will be colonizing it soon. It doesn’t help that Klinghoffer quotes Mr Indiscriminate Hype himself, Michio Kaku.

It’s a “game changer,” the “holy grail,” only a “hop, skip, and a jump” away, physicist Michio Kaku tells CBS, which characterizes the planet as a possible “Earth 2.0.”

Jebus, but that guy is a pandering twit — it’s gotten to the point where, if I see his face appearing on the television, I turn it off, confidently secure that I’ve spared myself another trickle of bullshit. And really, life is contingent on a set of circumstances that we haven’t mapped out yet, so discovering that another planet either has no life on it or has independently evolved it (and neither of these things are known for Proxima B) says absolutely nothing about the validity of evolutionary theory.

Field scientists get all the fun

Here’s a series of illustrations of funny mistakes by scientists.

​Jim Jourdane

​Jim Jourdane

They all seem to be about awkward things that occurred while doing field work, and I’m feeling left out. I sit in a lab with air conditioning and fluorescent lights, staring into a microscope. Nothing amusing ever happens to me.

Maybe I need to bring in a few crocodiles or let a troop of monkeys loose.

Dangerous business

SpaceX blew up on the launch pad this morning. There were no casualties, at least, and we do get a spectacular explosion video out of it, but this is an unfortunate setback.

Human beings sometimes sit on top of those kinds of infernal devices? I don’t think I could do that.