What I taught today: Axis specification

We began today with chocolate. Always a good thing at 8am, I think — so I brought a candy bar to class. Then I told the students that I loved and respected them all equally and that they all had equal potential, but that I was going to mark just one person as special by giving them that candy bar*. So I asked them how I could decide who should get it, telling them right off that dividing it wasn’t an allowed solution, and that yes, this could be an openly unfair process.

There were lots of suggestions: we could do it by random chance. I could throw it into the middle of the room and let them fight over it. We could analyze everyone’s DNA and give it to the most average person…or the most genetically unusual. I could just give it to the first person to raise their hand, or the person closest to me, or the person farthest from me. We could have a competition of some sort, and the winner gets it. I could give it to the person who wants it most, or who needs it most.

The point I was making is that this is a common developmental problem, that you have a potentially uniform set of cells and that somehow one or a few have to be distinguished as different, and carry out a different genetic program than another set of cells. One cop-out is to invoke mosaicism: that is, they aren’t uniform, but inherit different sets of cytoplasmic determinants that make them different from the very beginning, but that even in that case, these determinants aren’t detailed enough to specify every single cell fate in most organisms. Even with an initial prepattern, you’re eventually going to end up with a field of cells, like the dorsal side of the fly wing, and within that uniform field, some cells will have to be programmed to be epithelial, others to be bristles, others to be neurons. And that means that in every organism, even the most classically mosaic, you’ll reach a point where cells have to process information from their environment and regulate to build differential structures.

And with that I went on to talk about some animals that were judged as being mostly mosaic in character: molluscs, tunicates, echinoderms, and nematodes. Even here, these animals all required complex molecular interactions to build their embryos.

For example, I’d earlier used echinoderms as classic examples of regulative development. You can dissociate them at the 4-cell stage and each blastomere can go on to build a complete embryo. But at the 8-cell stage, when the cleavage plane separates an animal half from a vegetal half, that’s no longer true: the top four cells when isolated are animalized, forming only a ciliated ball, while the bottom four cells are vegetalized, only making a static blob with a bit of a skeleton inside. Clever experiments can quantitatively juggle these cells around, removing just the bottom 4 cells (the micromeres) at the 16-cell stage, or assembling composite embryos with different ratios of the different tiers of cells, and get different degrees of development. Even when you’re discussing an organism in which you’d call the pattern of development mosaic, it absolutely depends on ongoing cell:cell signaling at every step, and the final form is a consequence of interactions within the embryo. It’s a mosaic-regulative continuum.

I also described very superficially the work of Davidson and Cameron on specification events in echinoderms. These interactions can be drawn as a kind of genetic circuit diagram, where what you’re seeing is the pattern of genes being switched on and off. We can describe a cell type as the output of mappable gene circuitry, and we can even identify modules of networks of genes associated with a particular kind of cell, and that we can also see a limited number of genes that mediate interactions.

Next week I promised to start going into more detail, when we start talking about early fly development and axis decisions. The next class we’re actually going to switch gears a bit and discuss Sean Carroll’s Endless Forms Most Beautiful.

Slides used in this talk (pdf).

*Yeah, I lied again. I brought enough candy bars for everyone, and after we’d generated a list of ways to share just one, I gave them to everyone. They’ll never trust me again.

The best and worst review of yesterday’s Superbowl

It fits my perception of the event. Tom Shales reviews the Superbowl, and talks about the half-time show, the pregame show, some weird interruption in the game, the announcers, and, of course, the commercials, and nowhere anywhere in there does he talk about the game. I don’t know who played or who won, and I don’t care, and neither, apparently, does Tom Shales. Football teams are just floating corporations whose purpose for existence is to scoop up specially fast meaty people, give them a brief period of pampering and unwarranted glory, and in return, grinds them up and gives them brain damage for the entertainment of the people.

And now the hype surrounding this Superbowl nonsense has grown so huge that it has completely drowned the game. I’m not going to watch it ever, and for that matter, I’m not interested in watching any football game.

Aryan Jesus

This isn’t Thor, it’s Jesus.

aryanjesus

There is a lot of cheesy Christian art that looks like this, and I get the same message from all of it. At worst, it’s freaking racist — these are people trying to draw the Ideal Man, and every time they fit him into the western, north European mold. Most charitably and at the very least, it tells me that Jesus isn’t a historical figure to these people, his reality isn’t a concern, and they need make no effort to put him in a place and time and people. He’s a legend, and so he’s a plastic figure with no strong attachment to history…but he can be freely warped to fit the ideology of the individual.

Either way, I feel no need or desire to worship or even respect a cartoon.

(via Zeno)

Oh, the things you’ll learn about “Science” from the interwebs!

Far right wing talk show host Kevin Swanson has a few things to say about birth control.

I’m beginning to get some evidence from certain doctors and certain scientists that have done research on women’s wombs after they’ve gone through the surgery, and they’ve compared the wombs of women who were on the birth control pill to those who were not on the birth control pill. And they have found that with women who are on the birth control pill, there are these little tiny fetuses, these little babies, that are embedded into the womb. They’re just like dead babies. They’re on the inside of the womb. And these wombs of women who have been on the birth control pill effectively have become graveyards for lots and lots of little babies.

I am astonished at the specificity of that citation: “some evidence from certain doctors and certain scientists”. If anybody can track down the scientific paper in which that was published, I’ll not only post the verification, but I’ll reproduced the illustrations of the uteruses with the little tiny baby graveyards in them.

For now, this is the best I can do. I’ve taught histology, we even have slides of sections of uteruses (which, unfortunately, do not have the information about whether the source was a godless fornicator on the label), and this is what they look like.

Uterus

What Swanson said wasn’t science. It’s something different. I think the technical term is making shit up.

Stupid is as stupid does

One of the points made in that discussion yesterday is sometimes the “trolls” are just people trying to make an argument contrary to our own, and that they should have a right to express themselves; I was also told that dismissing disagreement as stupid or wrong was a prejudicial value judgement.

I would agree that there certainly are boundary conditions where that might be true; we’re looking at a continuum, not a sharp black and white world, where one side is uniformly bright and stellar and the other is dark and dim. But even on a continuum there are extremes; sometimes one side really is stupid.

Free speech is not an automatic good. Stephanie Zvan has done a fabulous job of documenting the tactical mode of some of our opponents, the ones who claim to dwell in “a bastion of the most free of free speech”, where they are totally free to say whatever they like, and where the shoddy operations of their lazy, slimy brains are openly exposed for all to see. These are the people who think the argument “YOUR FAT AND UGLY” is cogent, and who think spicing it up with a photoshopped image makes it more persuasive.

There’s a reason I automatically ban those people. They’re assholes, as they demonstrate over and over again.

Another really stupid argument from William Lane Craig

Craig is not one of the clever ones. He’s one of the glib, superficial ones, and he impresses a lot of superficial people. Here’s one of his latest, the Argument for God from Intentionality.

God is the best explanation of intentional states of consciousness in the world. Philosophers are puzzled by states of intentionality. Intentionality is the property of being about something or of something. It’s signifies the object directedness of our thoughts.

For example, I can think about my summer vacation or I can think of my wife. No physical object has this sort of intentionality. A chair or a stone or a glob of tissue like the one like the brain is not about or of something else. Only mental states or states of consciousness are about other things. As a materialist, Dr. Rosenberg [the interlocutor] recognizes that and so concludes that on atheism there really are no intentional states.

Dr. Rosenberg boldly claims that we never really think about anything. But this seems incredible. Obviously I am thinking about Dr. Rosenberg’s argument. This seems to me to be a reductio ad absurdum of atheism. By contrast, on theism because God is a mind it’s hardly surprising that there should be finite minds. Thus intentional states fit comfortably into a theistic worldview.

So we may argue:

1. If God did not exist, [then] intentional states of consciousness would not exist.

2. But intentional states of consciousness do exist!

3. Therefore, God exists.

The link is to a philosopher’s debunking, pointing out the obvious fallacies and some of the more subtle arguments against it from serious, non-superficial philosophers. It doesn’t bring up the first counter-argument that came to my mind, though.

We know what the physical nature of intentional states are; they are patterns of electrical activity in a network of cells with specific physical properties. We don’t know how to read that pattern precisely, but we can measure and observe them: stick someone in an MRI and ask them to think about different things or engage in different cognitive tasks, and presto, blood flows shift in the brain and different areas light up with different levels of activity. These are properties not seen in chairs or stones, which lack the neuronal substrates that generate these patterns.

Intentional states are ultimately entirely physical states; they are dependent on organized brain matter burning energy actively and responsively in different patterns. There is no evidence that they require supernatural input, so Craig’s first premise that these could not exist without supernatural input is not demonstrated.

One way to deal with a troll

John Scalzi had a troll infestation from someone he’s now calling the Racist Sexist Homophobic Dipshit; Scalzi is one of those notoriously liberal egalitarian people, and RSHD would whip up his Racist Sexist Homophobic followers and send them off to rampage through Scalzi’s comment threads.

So what he’s done is announced that he’ll donate money to non-racist non-sexist non-homophobic non-dipshit organizations every time RSHD issues one of his calls to arms against Scalzi. He encouraged other people to join in: he now has pledges for $26,000, all going to organizations RSHD hates.

It’s very amusing. It probably won’t silence RSHD at all, but at least all the hate gets churned into dollars for good causes.

Actually, I know it won’t shut RSHD up, because it’s easy to find out who RSHD is. It’s Vox Day, or Theodore Beale, and Racist Sexist Homophobic Dipshit is an extremely accurate title for the guy.