(via NatGeo)
Pharyngula
Evolution, development, and random biological ejaculations from a godless liberal
Another feathered dinosaur has been found in China, prompting Ken Ham to dig in his heels and issue denials.
Yet another supposed “feathered dinosaur” fossil has come to light, again in China. (Dr. Elizabeth Mitchell, AiG–U.S., reported on another Chinese fossil of a supposed feathered dinosaur in April 2012) Now, one headline described the fossil as “almost birdlike,” and the authors of the report in Nature Communications note many features the fossil shares with living birds, particularly those that live on the ground. In fact, Dr. Elizabeth Mitchell and Dr. David Menton (AiG–U.S.) both examined the photos of the fossil and the criteria the authors used in classifying the fossil as a dinosaur. They agreed that it is a bird, not a feathered dinosaur.
Oh, really? It’s just a bird? Take a look at this image of Eosinopteryx, and you tell me.
Notice a few things about this animal: it’s got teeth. The forelimbs have clawed digits. It has a long bony tail. It lacks the bony keel that anchors breast muscles in modern birds.
The only thing that might cause you to question its dinosaur nature (and it’s a criterion that’s proving more and more inappropriate) is that lovely gray fringe of feather impressions that surround the whole fossil. And look at those forelimbs! It looks like it has stubby wings. It does not, however, have the skeletal and muscular structure to allow for extended flapping flight, and the wings are way too short for it to have been an adequate flyer.
But Mitchell and Menton and Ham looked at that and said ‘ALL BIRD’. They’re idiots.
Ham goes on: there are no transitional forms, he squeaks, there can be no transitional forms, transitional forms don’t exist…all while looking at a winged, feathered reptile with teeth and claws and a bony tail.
The fossil record doesn’t reveal any kind of dinosaur-to-bird evolution—and it certainly does not show a molecules-to-man evolution. We have no proof of transitional forms, and we won’t. God’s Word says clearly that He created animals and plants according to their kinds (Genesis 1). Through genetic loss and other factors, new species have emerged over time—but birds are still birds and apes are still apes. Nothing in the history of biology has legitimately shown that dinosaurs could develop the genetic information to evolve into birds.
Pitiful. Pathetic. I’d like to see a creationist sit down in front of me with that illustration and try to defend the claim that it’s only a bird.
Godefroit P, Demuynck H, Dyke G, Hu D, Escuillie F, Claeys P (2013) Reduced plumage and flight ability of a new Jurassic paravian theropod from China. Nature Communications 4, 1394. doi: 10.1038/ncomms2389
My students are also blogging here:
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.
I mean, really, sometimes it just gets ridiculous. This guy jabbers on and on and on for almost 9 minutes about boring ol’ weather.
(via PetaPixel.)
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.
Oh gob, the stupidity. The latest wave of anti-choice legislation is based on one trivial premise: it’s got a heartbeat! You can’t kill it if its heart is beating! So stupid bills have been flitting about in the Ohio, Mississippi, Wyoming, Arkansas, and North Dakota legislatures trying to redefine human life as beginning at the instant that a heartbeat can be detected. Here’s Wyoming’s story, for instance:
About two weeks ago, state Rep. Kendell Kroeker (R) introduced a measure to supersede the medical definition of viability. Current state law says abortions are prohibited after a fetus has “reached viability,” and Kroeker sought to replace those words with “a detectable fetal heartbeat.” The Republican lawmaker said the idea for his heartbeat bill just came to him one day because “it became clear that if a baby had a heartbeat, that seemed simple to me that it’s wrong to kill it.” On Monday, a House panel struck down Kroeker’s bill because it was too medically vague. But if Ohio and Mississippi are any indication, this likely won’t be the last time that fetal heartbeat legislation shows up in Wyoming.
It’s a step back from the inanity of declaring that life begins at conception — you can’t detect the heartbeat until 5-6 weeks of gestation — but still, it’s an arbitrary and ridiculous definition that relies entirely on folk knowledge about living things. If we’re going to do that, though, I propose that we go to the One True Source of knowledge and accept the Biblical definition of living creatures: they have breath in their nostrils. Therefore, abortion is legal right up to the instant that the baby draws its first breath.
Don’t argue with me! It’s in the Bible! Do you want to go to hell?
But the heart thing? Nonsense. Here’s what I routinely see:
Zebrafish embryos have a heartbeat one day after fertilization. That one above is a two-day embryo, and it’s even more special and sacred because it carries a heart-specific GFP, so it’s heart glows green. We don’t suddenly think of the organism as complete and inviolate because cardiac cells are twitching.
Or even better, you can dissociate the heart tissue of just about any animal, including humans, and culture single cells in a dish…and look! They beat!
If that were a human cell, does that means we could never throw that petri dish away? Speaking of human, let’s jack up the consequences. Here’s a clump of induced pluripotent stem cells, adult cells forced into an embryonic state by transfection with a few genes that reprogrammed this population into a cardiac cell state. It’s the religious right’s nightmare, transformed by the hand of scientists into living embryonic tissues, growing in a lab under a microscope…and it’s alive! IT’S ALIVE!
Is anyone seriously going to decide that that is human and deserving of all of the rights and protections we accord to adult people?
I suppose it depends on whether those cells are derived from a female or not.
My students are also blogging here:
You really can’t teach a class by lecturing at them…especially not an 8am class. But sometimes there is just such a dense amount of information that I have to get across before the students know what to ask that I have to just tell them some answers. My compromise to deal with this eternal problem is to mix it up; some days are lecture days, others are discussion days. And today was a discussion day.
I’ve been talking at them for the past two weeks, basically working to bring them up to a 1950s understanding of the field of developmental biology, with a glimmering of the molecular answers to come and some of the general concepts, so that they’re equipped to start thinking about the contemporary literature. So I had them read this paper before class:
Kerszberg M, Wolpert L (2007) Specifying Positional Information in the Embryo: Looking Beyond Morphogens. Cell 130(2):205–209.
And then today they got into small groups and tried to explain it to each other. I primed them by suggesting that they try to define the terms positional information, gradient, morphogen, and polarity, and mentioned that I was playing a dirty trick on them, giving them a paper to introduce a basic concept that at the same time was pointing out some of the difficulties and problems of the idea, so I expected them to also do some critical thinking and question the concepts.
So they went at it. It went well; they had some lively conversations going on, which I always worry won’t happen with early morning classes. I find it helpful to ask students to try to poke holes in an idea, rather than just recite by rote what the paper says — it sends them hunting rather than gathering.
Several students noted that having a simple continuum of a molecule begs the question of how that gets translated into many discrete cell types; why does having one concentration of a morphogen make a cell differentiate into a thorax, while a very slightly lower concentration means it differentiates into an abdomen? It’s all well and good to suggest that a couple of overlapping gradients can specify position, like laying out a piece of graph paper with coordinates on it, but it doesn’t explain how that gets translated into position-specific tissues. I was most pleased that several of them, while groping for an answer, related it to the lac operon in E. coli, and brought up the idea of thresholds of gene activation. Yay! That so sets up future discussions about early fly embryogenesis, where that is exactly the answer.
I think they also got the idea that an explanation for general specification of body parts, for example, may not apply for explaining polarity within a body part; we may have to think about some kind of hierarchy of regulation, where we progressively partition the embryo into smaller and smaller units, with different mechanisms at different scales. They might be catching on to the depths of the problems to come.
Another way the paper primed the students was that it very briefly introduces a whole bunch of specific molecules: dpp, bicoid, sonic hedgehog, activin. They got a very general idea of the broad roles these molecules play, all part of my devious grand plan. When we start talking about the details of how animals set up dorsal-ventral polarity, for instance, and dpp/BMP start coming up in more specific contexts, I want them to be familiar old friends — molecules they already knew casually and informally, and now see doing very specific things, and interacting with another set of molecules, which now also joins their circle of pals. Before I’m done with them, they’re all going to regard these developmental signals and regulators as part of their family!
You Twin Cities folk will have to drive like maniacs to get here in time, but you can do it: I hear the roads are slick as glass so you can just slide all the way here. At 6pm we’re doing another science for the community event, this time with Michael Ceballos talking about biology and biofuels. I’ll be heading over in a little bit to set everything up — I get to be the emcee. It does mean I’ve got a long evening ahead of me, though, and I haven’t had a nap.
