I’ve been doing it wrong. I was looking over creationist responses to my arguments that Haeckel’s embryos are being misused by the ID cretins, and I realized something: they don’t give a damn about Haeckel. They don’t know a thing about the history of embryology. They are utterly ignorant of modern developmental biology. Let me reduce it down for you, showing you the logic of science and creationism in the order they developed.
Here’s how the scientific and creationist thought about the embryological evidence evolves:
Scientific thinking
An observation: vertebrate embryos show striking resemblances to one another.
An explanation: the similarities are a consequence of shared ancestry.
Ongoing confirmation: Examine more embryos and look more deeply at the molecules involved.
Creationist thinking
A premise: all life was created by a designer.
An implication: vertebrate embryos do not share a common ancestor.
A conclusion: therefore, vertebrate embryos do not show striking resemblances to one another.
This is their problem: the similarities between embryos is an observed fact. It was recognized in the 18th century by observers like Goethe, reinforced by the work of the German naturphilosophen of the early 19th century, and far more persuasively, documented by the most eminent embryologist of that century, Karl Ernst von Baer, and even now, you can go to any college campus, even little ones like mine, and ask the local developmental biologist to show you his prepared slides of pig, chick, mouse, and fish embryos, and they will be able to show you all of the surprisingly consistent morphological features of these embryos. We can also show you photographs that reveal the breadth of the similarities, while also showing you the interesting little differences that have accumulated in different lineages.
The similarities between embryos are simply not matters to argue over. It’s settled. Has been for almost two centuries now.
Now if I were a creationist, I would have granted that, and instead gone on to criticize step 2, the hypothesis that these similarities are evidence of common ancestry. That’s what smart people did: Karl Ernst von Baer, for instance, was a creationist who dissented from Darwin’s interpretation, and he tried to explain the similarities as the product of the generality of early embryonic form, ascribing them to the relatively undifferentiated state of that stage. Von Baer’s explanation is actually a fairly good one, and I teach my students about it, and I even think it is still part of the explanation.
Step 3 is a problem for these alternative explanations, however. We keep getting more data, and the core processes of this developmental event show deeper and deeper similarities — and we can’t just wave it off as a result of general undifferentiation, because very specific shared genes are involved.
Unlike von Baer, modern day creationists tend not to be very smart people, and are uniformly uninformed about science. That’s the only way they can come up with the peculiarly strained logic I’ve illustrated above. They have a clear difference from evolutionary thought, in that they think first of all that their premise of a designer is true, but then what they do is let that lead them in irrational directions. I would have thought the battleground in this narrow slice of the debate would have been the second step, where evolutionists hypothesize common descent as an explanation of embryonic similarities — since they don’t accept common descent, they should be working hard to propose and test alternative hypotheses for the phenomenon.
I guess “working hard” is anathema to creationists, as is using their imaginations to come up with useful alternatives, because they don’t do that. Instead, they’ve taken the incredibly stupid tack of drawing that unnecessary third step, concluding that embryos don’t resemble one another, choosing that as their sticking point. It’s unnecessary, since if they’re claiming a single common designer, they could use that as an explanation for embryonic similarities, and it’s stupid, because as I said, the similarities are an observed fact.
Another example of this twisted logic can be seen in their carping about junk DNA. It’s a fact that most of the genome is useless, repetitive, or damaged junk, and we offer as an explanation that it is an accident of history, the accumulation of relics of past errors; creationists, instead of arguing with the interpretation and offering different explanations of their own, instead try to deny the evidence and pretend it is all functional. Maybe there is a method to their madness, though, because it also puts us a bit off balance — it’s hard to believe that they are actually making an argument that crazy.
Haeckel is just an unfortunate pawn in their game. He was guilty of fudging on one illustration…what the creationists don’t tell you is that it wasn’t the illustration that the textbooks have continued to use! His contemporaries as well as modern biologists don’t argue with the thrust of the diagram — that there is a stage at which vertebrate embryos resemble one another — and we also agree that Haeckel oversimplified and reduced differences for his pedagogical purposes. This is the diagram, of a dog, a chicken, and a turtle, that Haeckel was caught faking.
As you can see in the shared error in the somites that are highlighted in the box, this is the same woodcut used three different times. He was rightly told that this is an unethical shortcut to take, but note also: this is definitely not the diagram the textbooks have been using over and over.
Haeckel’s error was not in scientific step 1, the observations — it was that he overinterpreted (step 2), making grand pronouncements about the nature of embryonic and evolutionary change that were not out of line for his time, but have since been found to be invalid. His hypothesis went too far beyond explaining similarities as a result of history, to also claim a too-linear view of evolutionary change.
But, like I said, Haeckel doesn’t matter in this argument. He’s just a convenient whipping boy for the creationists, an excuse for them to try and deny the evidence. Step three, the ongoing confirmation of evolutionary explanations, is where the action is really at, and where their attempts to focus on 18th century speculation instead of 21st century science is simply a distraction.
This was brought home to me this morning as I was reading a paper by some zebrafish researchers on the development of the ventricles of the brain. This is a familiar topic to me — I’ve been studying zebrafish nervous system development since about 1980 — and my main interest was in finding out about these fluid-filled chambers in the brain, which I’ve usually ignored while I was focused on the neural epithelium.
The vertebrate brain is like a water balloon, hollow on the inside with a shell of cells around the outside. Initially, the cellular part is fairly thin, only one cell layer thick, but it obviously gets much thicker as development proceeds, to the point where in the adult the ventricles are actually fairly small (but important!) chambers buried deep in the mass of the brain.
The embryonic nervous system also partitions itself, making constrictions that block out the major domains of the forebrain, midbrain, and hindbrain. Again, I can’t help but compare this to a balloon: it’s like making a balloon animal, where the tube is subdivided into parts. Here’s a diagram of these early events:
What I thought was interesting was that I was reading this paper as a description of zebrafish brain development, and I glanced at the diagram and thought that it was a bit cartoony, but yes, that’s my familiar embryonic zebrafish brain…and then, of course, you look at the caption and it’s describing human brain development.
It wasn’t a surprise. I knew how human brains develop, too, and if I’d been reading about human ventricles, I would have given the diagram a nod of agreement. If it had been about mouse brain, the same; likewise, if it had said chick brain, I wouldn’t have given it a second thought. They are all roughly the same at this early stage of development. The same divisions, similar flexures, roughly the same kind of organization.
Of course there are differences, and the paper discusses those. In particular, fish nervous systems are initially solid instead of hollow, and secondarily form ventricular spaces after the subdivision of the brain into regions occurs; a mammalian brain starts hollow and stays hollow. There are also some molecular subtleties that haven’t been worked out in detail in multiple species, so some other differences may emerge as we learn more. And there certainly are differences that develop later — I would never mistake the adult human brain for the adult fish brain.
The similarities are real and go even deeper than what the 19th century biologists claimed. This paper also included a simple but interesting illustration comparing the organizations of the embryonic ventricles that resembles in principle the diagrams Haeckel drew — our human embryos had brains organized in the same way as those of fish embryos.
If the Discovery Institute had their way, that comparison would not be allowed to be made in our textbooks. They claim that they want better and more accurate science taught, but they really don’t: if we put more detail in the biology textbooks, it will only make the point of the similarities of vertebrate embryos stronger.
Lowery LA, Sive H (2009) Totally tubular: the mystery behind function and origin of the brain ventricular system. BioEssays 31:446-458.
http://1.bp.blogspot.com/_1maMhmutTzw/R6t63tglWLI/AAAAAAAAAGg/xDdPJrhe1ow/s400/normal_science_vs_faith.jpg
Many thanks for the additional info, and especially for the clarification about the Haeckel illustrations.
This part will stick in my mind:
“Haeckel is just an unfortunate pawn in their [the creationists’] game. He was guilty of fudging on one illustration…what the creationists don’t tell you is that it wasn’t the illustration that the textbooks have continued to use! His contemporaries as well as modern biologists don’t argue with the thrust of the diagram — that there is a stage at which vertebrate embryos resemble one another — and we also agree that Haeckel oversimplified and reduced differences for his pedagogical purposes…”
Hard to keep up creationists who are willing to lie, ain’t it? I saw Jerry Coyne’s post on this and hoped that we’d see a follow-up. I don’t have the background needed to do this kind of analysis myself, so I really appreciate your work.
Very good, clear explanation. I’m reading Shubin’s Your Inner Fish at the moment, so seeing our brain resemble a fish’s helps to make it all fit together.
… we can’t just wave it off as a result of general undifferentiation, because very specific shared genes are involved.
That doesn’t mean goddidn’tdoit. He’s a lazy schmuck, so he used the same design, slightly modified for each species. (I’m just playing devil’s advocate.)
Hmmmmm, that’d make him a good engineer, but we know he’s an incompetent, capricious, schmuck. If he even existed, which he doesn’t, outside of Bronze Age mythology.
Wow – its the intellectual piss ant PZ Myers and his very own Christian bashing hate promoting web site. If I had to bet on it I would guess your trying your hardest to replace Dawkins as the king of atheistic pricks – but I personally don’t think your up to the job. You may end up getting canned from your university position though – would not at all be shocked by that – after all, who the heck wants loud mouthed biggot driving away students? I guess time will tell.
Hey Catholics, why don’t you all flock to the classes of the Catholic bashing Myers – go to the wikipedia page and read all about it (page down to the bottom). Naturally your proud of your hate aren’t you little man!
Wow are you late the fucking party…
Yawn, another boring know-nothing Xian troll in Troy. They all sound the same, and show no evidence. What’s the matter Troy, envious of the cat-o-licks or something? Never mind, Crackergate is old news except to the delusional and paranoid fools like yourself.
Reading your thoughtful work, PZ, I am sad that asshats like Kirk Cameron and Roy Comfort are sometimes taken seriously. Can you imagine one of those clowns saying “I focused on the neural epithelium”? The facts are overwhelmingly on your side, and yet some folks are just willfully ignorant.
Ummm, Troy? If you thought that the crowd at Panda’s Thumb played too rough…
@#5:
Why is creationism synonymous with Christianity/Catholicism? Creationists who constantly argue that their beliefs are facts and that they need to be taught alongside, if not instead of, accepted science are dishonest cretins who deserve the ridicule and outright thrashing that people like PZ or Dawkins give to them.
That’s not hate. That’s smacking down outright ridiculous behavior. That’s stepping between moronic superstitions and the teaching done in schools.
If you have a problem with it, stop coming here. It’s not a requirement. If PZ’s wrong, point out where he’s wrong.
But just declaring his speech as hate without any substance to your claims, while hoping he gets fired for being honest, is just painting yourself as a troll. Back up your claims or GTFO, as it were.
Troy, with your hilariously bad spelling, it’s clear that you’ve never seen the inside of a university.
Get an education, then come back.
Someone get Troy his bah-bah, stat.
Now as for those resemblances between embryos of different species – they were a particular interest of Louis Agassiz, the well known creationist opponent of Darwin who held that species were fixed, and that varieties were species, including notoriously human races. Very popular in the Southern States in his day, for some reason the creationists don’t seem to remember him so much now.
By the way, von Baer was critical of Geoffroy’s use of embryo similarities, rather than Darwin’s. Indeed von Baer’s branching patterns matched Darwin’s novel view of common descent.
Ah Troy, you came so close but left out the fatwa envy! Come on, some of us are trying to fill out our bingo cards here!
Troy,
At least get your facts straight. PZ isn’t just a Christian basher, he also bashed Jews, Muslims, Hindus, Scientologists, Hova Joe’s, and I’m pretty sure he’s not a fan of pygmy witch doctor’s either. I could be wrong on that last one though. It’s religion in general, doof.
Nice to try to incite a Catholic mob to attack the man though. Very religious of you, fits in perfectly with the history of religious types. Glad to see you living what you preach. Ah, the smell of irony in the morning. It smells like…victory.
Incoming snark.
Whoa, time out. Are you claiming that development of the brain is like making balloon animals? Stuart Pivar owns that.
http://scienceblogs.com/pharyngula/2007/07/lifecode.php
Thanks for yet another great and informative post, PZ! I’ve long known that all vertebrate embryos go through similar stages of early development. Oddly enough, my mom (who is a Catholic, but one who thinks about this straight) first pointed it out to me, but said that in the human embryo, all the stages of evolution are gone through until we reach the top – human. Fortunately my understanding of evolution and development have complexified since then and I understand that it’s a very simplified version of what’s actually going on. Your blog and Dawkin’s books have been paramount in that.
On another note, I wish people would stay on topic in their responses and not feed the trolls. Seriously, people, you’re not supposed to argue with the idiots, you’re supposed to ignore them or say “there, there, that’s nice” pat them on the head and leave them alone. Otherwise the rest of us have to scroll through pages upon pages of nonsense that’s off topic just to find the occasional tidbit of real information.
So please, don’t feed the trolls!
B-b-b-but PZ, to these people the 18th century knowledge is WAY OUT in the future. We are dealing with Bronze Age people when it comes to scientific development. And they prove it by referring to a book written at about that time, their time in knowledge and understanding. They may dress and talk like the rest of us, but they stopped evolving ~4000 years ago, – just like Troy @ #5.
And thanks for the interesting and enlightening article, PZ!
Troy:
FYI, “pissant” is one word.
If I had known of PZ when I was applying to undergraduate universities, I would have seriously considered applying there.
Now that I’m done with my graduate education (developmental biology), I wish I had more teachers that possessed PZ’s zest for learning and teaching, and were as clear when writing.
So. At the very least, please pick up _The Elements of Style_ by Strunk and White. Even if English is your second language, your writing is appalling.
There is obviously nothing anyone can do for your lack of curiosity about the natural world.
Don’t mistake scorn for hate.
Hear! Hear!
Hey PZ,
Just thought I’d let you know that I finally released the book that I’ve been working on (“Atheism and Naturalism”). Here’s where you can read excerpts and where to buy:
http://www.godriddance.com/book.php
Peace,
Ryan
If a thread were a strand of DNA, a Troy would be the making of a tandem repeat. Fortunately the brain is quite capable of splicing the misinformation.
Why is creationism synonymous with Christianity/Catholicism?
Where are the buddhist creationists on embryology? Woowoo only knows. What about the muslim creationists? Shut up or I’ll kill you. The christian creationists are the ones who are most loudly losing this particular battle so they’re the ones we keep hearing about/from. It would be fun to get a few muslim creationists on the texas school board. Just to watch the creos slaughter eachother while shrieking “god loves you!”
Raimund #17 said,
“Oddly enough, my mom (who is a Catholic, but one who thinks about this straight) first pointed it out to me, but said that in the human embryo, all the stages of evolution are gone through until we reach the top – human.”
Actually this is the part of Haeckel that is universally regarded as wrong. Part of the early stages of multiple vertebrate embryos are very similar but the rest of development certainly isn’t, and is not simply a series of linear progessions towards the ‘top’ (to regard humans as the ultimate aim of evolution is a fallacy).
By the way I disagree with PZ’s initial post about creationist thinking.
While they may indeed think embryos show no similarity to each other at an early stage of development, it is of little consequence to their overall argument whether they do or don’t. Its a similar point to that of whether different species show similar body plans. It is just as easy to explain this as the creator having a similar basic plan that he might or might not utilize. The same type of thinking neatly gets around the problem of transitional fossils – any new species discovered was simply another example of God poofing species into existence (that is why no series of transitional fossils will be enough to convince a dedicated creationist.
Just like Lifecode predicted! I bet Pivar is beside himself.
http://scienceblogs.com/pharyngula/2007/07/lifecode_from_egg_to_embryo_by.php
Good post. Here’s my question (if stupid, apologies in advance …): I always thought that the human brain was an evolutionary kludge of three separate systems doing different things, i.e., the reptilian hindbrain, the mammalian midbrain, and the human forebrain. So why does the developing human brain look so much like the fish brain, with the same three sections?
Bugger. Beaten to the Pivar quip. I hate this place. Makes me feel (and appear) stupid.
@Sigmund #24
Yes, I know that. I was saying that my understanding has grown about evolution and embryology since then and I recognized a very long time ago that the “straight to the top” understanding of evolution is false. This Haeckel explanation is what my Mom used when I was a child as proof that we are evolved. Unfortunately I don’t know if her understanding has grown very much since then but I don’t really see why it would have since as a sheep farmer, there isn’t a great need to understand evolutionary theory at a doctorate level. Also, please note that my Mom, not me, is Catholic. I’m an atheist and have been since I was in my early teens.
That’s as much a myth as ‘ontogeny recapitulates phylogeny’. Fish have very good midbrains and forebrains. Humans expand the forebrain greatly, but it isn’t something new to us.
This is a really nice post (added to favorites).
@Troy:
What is wrong with promoting hatred of ignorance, lies and manipulation?
Try to hang around for a bit and maybe you will actually learn something useful.
…course Luskin et al. provide evidence that some mammalian brains stay hollower than others.
I have to take issue with one thing, though:
Everybody knows that creationist thought doesn’t evolve. It was created exactly as it is, six thousand years ago.
Nice post, PZ. Thanks.
Troy: Get an education . .go ahead and plunge ahead . . finish the seventh grade! Ignorant asshole.
@4
let us not think lazy but efficient. Perhaps this is a better illustration: architecture. An architect can be recognized by a particular set of core elements which he habitually uses. (or similar, we identify the particular culture of a structure by its elements.)
Just a thot.
http://www.greatjourneyblog.blogspot.com
I love these posts!
Another superb PZ post! Thanks for this additional clarification tool. It’s really valuable for real high school biology teacher’s fights against those anti-science IDiots.
Nice post. I’m confused about one thing though: I’ve been told that it was a different set of embryo drawings that Haeckel fudged. Wikipedia shows the set of “infamous” embryo illustrations that I’m thinking of. Anyone got any insights?
If you think the attacks on the embryo drawings are bad, you’d better hope they never find out about Haeckel’s exotic artwork. Especially al those paintings of mushrooms that look like big dicks.
My great surprise in this is that in the famous video of Disco Tuters going around the shop crowing about “Biology books still showing Haeckel’s illustrations” got the wrong illustration!
Well, I also learned something about the development of the brain, too.
In my teenage years as a creationist Haeckel was often meantioned. The similarities in embryonic development were usually acknowledged, but this was supposed to be due to a common designer. He apparently had a limited imagination.
“In particular, fish nervous systems are initially solid instead of hollow, and secondarily form ventricular spaces after the subdivision of the brain into regions occurs; a mammalian brain starts hollow and stays hollow.”
Remember, you’re dealing with intelligent design – there’s a reason for this difference. Like a banana fitting a hand, the hollow is clearly so that God has room to put a soul inside human babies.
In particular, fish nervous systems are initially solid instead of hollow, and secondarily form ventricular spaces after the subdivision of the brain into regions occurs;
<wince>
What do you mean by “fish”? Vertebrates except tetrapods? Gnathostomes except tetrapods? Osteichthyans except tetrapods? Actinopterygians? Teleosts? Perciforms or whatever?
In other words, is this the plesiomorphic condition (so the tetrapod condition is derived from it) or an apomorphy (the other way around)?
You misunderstand. Over here, we feed the trolls till they explode. It’s more fun that way – and more informative, because it regularly generates long posts full of explanations.
Dance, trollboy! Dance!
Hmmmm. Should I really have laughed that loud at 1 in the morning?
(Eh, never mind. Last night at 2, my neighbor vacuumed her room…)
<wince>
Stop mixing your metaphors in such a misunderstandable way, please…
Till Harun Yahya opens his pseudonymous mouth.
You’re mixing three tripartitions of the brain here. The fore-/mid-/hindbrain thing is a real anatomical partition common to all vertebrates. The other one you’re thinking about is the more psychological one between the reptilian, paleomammalian and neomammalian parts of the brain. These are sometimes represented in schematic drawings as three layers that surround each other, but that’s stupid, because they are not supposed to be single coherent spatial entities. Their names are bafflingly silly, because… for instance… all chordates, not just mammals, have for example a limbic system, part of the paleomammalian part of the brain.
Efficient?
How moronic does a Designer need to be to believe that the use of DNA as the material of heredity is efficient?
As I keep saying: creationists are blasphemers by its own criteria.
Thanks PZ. This is why I loved my embryo course long ago. Things worked out differently, but this was the one area I wanted to follow on with.
It has been asked in previous threads – where is the scientist who is able to stand up, give the media the red meat they crave, and confront this creotard bullshit?
Kraid @ 37:
The caption on the drawing on Wikipedia say’s it’s a copy by “Romanes”, but doesn’t really clarify. I’m guessing it’s George Romanes, a friend of Darwin (now there’s a despicable euphamism if I ever heard one…). It does mention Haeckel’s drawings were on a black background with lighter shading, so the one in this article appears to be an original. That drawing, the “Romanes” copy, is the one I always see creationists touting as faked.
Offer not valid in all religions, your mileage may vary, see your local cleric for details.
Thanks, other Dave M, that’s helpful. I should go read a book about the brain now. Any suggestions?
Troy, May 9, 2009 4:41 PM
I thank God you have delivered yourself into the hands of PZ Myers and his hounds. For they are a hard and cruel people who suffer fools no whit. They will learn who you are, they will expose your identity, and they will show the world how you are a bounder and traitor who deserves no consideration, nor any trust.
Did it ever occur to you the Paul Zachery Myers PHD (Biology) just might be one of God’s Hounds, sent to the world to draw out people like you, expose them, and destroy them? That their purpose in life is not just to teach and instruct, but to reveal to the world those like you who would keep Man lost and afraid in shadows of ignorance and fear? Wouldn’t it be funny if PZ was one of the hounds of the Wild Hunt, and you his latest prey?
Hear that moaning in the wind? Hear the shrieks of rusty nails as boards are torn asunder by the storm gales rising in the distance? Do you hear the baying of the hounds as the tempest approaches? Do you see a distant, squamous shape, as of a cephalopod headed man leading great dogs that dance between the angles of reality? That is PZ Myers and his closest, most ardent defenders; and you have just gotten their attention. Pray they are only angry, for they will hurt you if they are amused.
Off topic but I believe you’ll find this interesting. A story just came out on Yahoo about the places on earth where people tend to feel the happiest and experience the most contentment with their lives. The top countries are scandanavian where atheism is hot stuff.
http://travel.yahoo.com/p-interests-27761674;_ylc=X3oDMTFzODRwOWZjBF9TAzI3MTYxNDkEX3MDMjcxOTQ4MQRzZWMDZnAtdG9kYXltb2QEc2xrA2hhcHB5cGxhY2VzLTUtOS0wOQ–
Now there’s something you might want to throw in the face of believers. We’re happier than they are. Take that, Igmar Bergman, you pretentious, whiney mope!
PZ:
I would think it’s very hard work and would take a very vivid imagination to
think ofconcoct so many ways to explain away reality.Those creationists would rather believe what they’re told — that the embryos don’t resemble each other — than believe their own lying eyes.
I wrote this to an ID biologist:
I suppose you have been reading the latest evolution vs ID stuff on the biology blogs. What is the ID position on when man became “man”….like where exactly was the cut-off point when God said only those above this biped evolutionary track were worthy of heaven? Was there some tapering allowed (e.g., numerous primitive heavens for the pre-Adams) or, did God’s knife completely sever whole generations from their immediately proximate generations?
PZ –
Thanks for posting this. My Animal Development final is going to cover some very similar stuff and it’s nice to have a little extra background on it
Huh – and I thought the loonies would say “OK, they’re similar; that’s proof that goddidit.”
Troy #5:
Yeah, particularly pay attention to the part where Webster Cook receives death threats for, basically, wanting to show the Eucharist to a friend. Oh, and Troy, get it right – PZ Myers doesn’t single out Catholics, he lambasts all religiously motivated insanity, no matter what religion is involved, such as that depicted in this very article.
I’m waiting for troy to ask for a camera…
I guess “working hard” is anathema to creationists, as is using their imaginations to come up with useful alternatives, because they don’t do that.
Working hard, using their imaginations, studying science, thinking – creationists have never done any of these things, which is exactly what should be expected from insane, gullible, bloody stupid, god-soaked idiots.
Don’t worry Charlie, anything you say is considered a lie even if backed up with a citation that probably doesn’t really back up your inane ideas. So quit bothering us, ye of the dungeon. You have no credibility here.
huh. But the CNS forms by rolling up into a tube (DHNC), right? Then it solidifies and re-hollows out? I didn’t know that.
Curiously enough, if you watch Fantasia’s famous Chinese Mushroom Dance, and track the movements of any but the littlest of the mushrooms, you’ll notice that among their properties is the capacity to grow suddenly long and tall, and shrink just as suddenly. Odd, that… perhaps the littlest one hasn’t yet been in Daddy Dobson’s shower.
charlie, I ask again…
why do you want to crap here, when you have a perfectly good living room to crap in already?
*hits charlie on the nose with rolled up newspaper*
Bad dog!
go home!
You have no credibility anywhere Charlie, that’s why you are relegated to pushing your crackpot conjectures on the internet as opposed to fighting for them where it matters… in academia. It must really suck to not be taken seriously
I can’t believe anyone would be so insecure that he has to post his Mensa membership card. I would have taken your word for it, dude. Mensa, at least in my experience, is infested with Trekkies and Libertarian crackpots.
The funny thing about that Nature article is, even if additional functionality is found in that DNA, the creationists will accept is as their own without noticing that it was found with the slightest bit of fucking help from them, by people who almost certainly think their ideas are bullshit.
*hits charlie on the nose with rolled up newspaper*
What I want to know is why didn’t Isaac Asimov throw the sock-puppeting dungeon denizon out of his apartment through the window?
Charlie, anything you cite or link is considered a lie. As I said, you have no credibility here. If anybody else believes you, that is their problem in comprehension, not ours.
You know, I have seen a few creationists who really seem to think, in all honesty, that “Ontogeny recapitulates phylogeny” is the Great Law of Evolution, and who presumably think that Haeckel is Evolution’s Great Prophet. So, they think that undermining the credibility of Haeckel is God’s work–once we realize that Haeckel fudged his pictures, we know that “ontogeny recapitulates phylogeny” can’t be true; and once we know that, the whole evolutionary edifice falls.
Needless to say, this view of things is missing more than a little bit in the way of understanding. But when I have argued the point with creationists it has seemed to me that they never really do get it. They never “get” that the credibility of Ernst Haeckel is not really the linchpin of modern biological thought. They often conflate the idea of homology with the old “ontogeny recapitulates phylogeny” bit and conclude that because biologists don’t like the latter anymore, the former is dead. I got involved in a discussion over at Amazon on the misrepresentation, in Wells/Dembski’s awful tome The Design of Life, of the evidence for the mammalian jaw having evolved from its reptilian predecessor, and when I started talking about the demonstrable homology between the mammalian ear bones and reptilian jaw bones, suddenly the whole creationist response was all about Haeckel, bad embryo drawings, and how ontogeny doesn’t really recapitulate phylogeny…weird. Not a word, of course, about the underlying question “are the bones really homologous,” because that’s not really a winner for creationists, and they wouldn’t probably understand the evidence anyway…requires book-larnin’, and from the wrong book.
Vox Day has Mensa membership. Being intelligent is no foil against being a crackpot, Shermer explains this well in “Why People Believe Weird Things”
An architect can be recognized by a particular set of core elements which he habitually uses.
Like I keep tellin’ ya all…
the designer is a fish!
All hail Dagon.
Alan Kellog #49
Do you know the blog, Newshounds? Their motto is:
“We watch FoxNews so that you do not have to.”
http://www.newshounds.us/
You have a poetical style of writing. I like it.
Many people who could join Mensa don’t because of jerks like Charlie and Vox Dei. Being a crackpot gives the organization a bad name with more normal intelligent people, who don’t want to be associated with them.
I think the non-linear concept throws them every time. Creationists conflate all life with linear concepts and assume evolution must conform to this assertion.
“God zaps” is linear. Morphology over millenniums is not.
Awww that’s cute.
People who feel the need to tell us they are MENSA members, always a sign of a overly stimulated feeling a self worth.
I can’t believe anyone would be so insecure that he has to post his Mensa membership card.
If I read it correctly, it’s an expired one at that.
sad, pathetic little man.
In zebrafish, it doesn’t form a tube. Cells zipper up together along the midline, so the cell movements are very similar, but they are so closely adherent that no opening forms, not even during neurulation.
This didn’t make sense the last time you tried to argue for it. But I doubt that’ll stop you. What’s next — characterizing a gas by its temperature and pressure is like believing in God?
(And isn’t “Marshall Nelson” Charlie Wagner?)
“People who boast about their IQ are losers”
– Stephen Hawking [Source]
*gasp!*
A scan of Charlie Wagner’s Mensa card?!!!
Think of what the Internet-history collectors of the future will pay for that shit.
I mean, just the fact that Charlie Wagner scanned his Mensa card is first-rate Intertubez gold IMO. Thanks, Rev, for immortalizing the URL before Charlie’s comments got their usual and well-deserved disappearance.
@ 71,re Alan’s 49:
Yeah,these SSRI are marvelous.
AN not a
sheesh
Correct. He has been using that pseudonym for three months or so.
Huh. That’s what I didn’t know, then.
the fact that Charlie Wagner scanned his Mensa card is first-rate Intertubez gold IMO.
It’s almost as funny as if Kwok had scanned and posted his Bed-Stuy diploma.
PZ gets all the stalkers, as if this blog were their springboard toward internet kook status.
What textbooks are being used in developmental biology classes? Recommendations appreciated.
Stephanurus
I think it is traffic envy. PZ gets a lot of traffic. Their blogs don’t.
Yay brains (said the mouse developmental neurobiologist)!
DaveM #27:
This is something of an oversimplification (and of course PZ already noted that the forebrain certainly isn’t human- or mammalian-specific), but as the more primitive parts of the brain develop first and the more derived parts develop relatively later in an embryo, brains of different species look more alike early than they do late.
That’s less surprising than it probably sounds, because it’s the basal developmental programs that are (and probably have to be) relatively similar, while the more derived programs are free to vary after the basic brain scheme has been set up.
In this way, I can happily identify anatomy in embryonic human brains from my knowledge of the mouse embryology, but adult human brains look pretty foreign to me.
Stephanurus #85:
Developmental Biology, which I like quite a bit, is available for free full-text search at the NCBI website: http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=dbio.TOC&depth=2
thanks for the link to Gilbert’s devbio text.
That’s the one I used to carry around with me.
As a late comer to the Pharyngula Fold, I was unaware of the entire story of Stuart Pivar and his wondrous balloon drawings as pointed out by PZ. [Seems his book has not exactly been a best seller at Amazon, and with only two comments, the complimentary one evidently a complete fake].
Two fascinating accounts on Science After Sunclipse – ‘Stuart Pivar Sues PZ Myers’ [ http://www.sunclipse.org/?p=242 ]
Yeah, I have my lab’s copy, and my rabbit has chewed on it, and now I’m too embarrassed to give it back. At least that’s the story I’m telling.
Creationist “thinking” on the evidence for evolution from comparative embryology can be expressed in a basic syllogism:
The evidence for evolution from comparative embryology = Haeckel’s drawings and/or Haeckelian recapitulation.
Haeckel’s drawings are, very inaccurate or deliberate frauds and the recapitulation theory has long been discredited.
Therefore the evidence from comparative embryology = deliberate fraud and long discredited theory.
Haeckel’s mostly minor exaggerations are a convenient excuse for them to never have to actually deal with the facts of comparative embryology.
Yet another way to avoid thinking or learning.
P.S. Please don’t confuse me with the other “Troy” commenting in this thread.
@ 91,
good point,but syllogism validity fail.
Now I’m wondering what really chewed on it…
Nice post, PZ. An elegant lucid explanation. Thanks!
PZ brushed up to the junk DNA argument at the end of this post, and I’ve been waiting to ask about something concerning that so here goes.
Oh the philosophical caveats first-
*there exists an external reality
*ideas must change to fit that reality; not reality denied to fit ideas
*It is a natural reality, no need for magic
If everything exists in a state of tension and compression (thanks Bucky for clearing up that whole tensegrity thing), then isn’t DNA also a structure capable of holding information beyond what is encoded?
Maybe this idea has more to do with accessing certain regions of the DNA for expression, but couldn’t that “junk” DNA serve a purpose at a larger organizational scale? Making it only “junk” relative to coding, but not to the overall “use” of the DNA?
Now, if I were to make the creationist argument, I’d go past Von Baer and say they looked similar because God, bein’ all smart and everything, saw he’d come up with a good way to “get ‘er dun.” No need to reinvent the early-development wheel and all that…
1. Nobody cares what you think. You’re not even an interesting troll with an argument to engage.
2. Get a spellchecker. They’re free.
The way PZ deals with junk DNA seems to perilously close to making a dogma of its junkiness. In the May Scientific American there’s a fascinating article on differences between human and chimp DNA which argues that there are significant differences in non-encoding regions. The implication seems to be that these differences must be functional. The author concludes “studies ….promise to elucidate what is going on in the 98.5 % that does not code for proteins. It is looking less and less like junk every day.”
Can’t help feeling PZ is giving a hostage to fortune with his insistence.
denial’s easier. complex apologetics have to change as more data is acquired. denial doesn’t.
Junk DNA is, by definition, DNA that doesn’t appear to do anything. If evidence showed that all DNA has a purpose, then PZ would have no problem with that, I’m sure. What PZ does have a problem with (I think) is people who aren’t looking at the evidence, but insist that things must be a certain way because of an ideological or religious belief, and hence ignore all evidence to the contrary.
It’s the mindless opposition to reality that is so galling.
No, not my field at all, sorry :-(
B-) =8-)
“Valid Thru
3/31/2003”
Is that the date when he got religion and his IQ dropped 40 points…? Or does the causality run the other way around? Is our little moron old enough to be senile?
Repeated for truth.
Whut?
What do you mean?
Cell size is correlated to genome size, and metabolism is (via the ratio of surface to volume) correlated to cell size, so the sheer amount of junk has an effect, but, well, it might as well be styrofoam.
Oh, come on, please. That figure includes all the regulatory regions!
Together, however, the protein-coding and the regulatory regions make up at most 15 % of the genome. The rest consists of retrovirus corpses in all stages of decay (a bit over half), decayed former genes of your own (at least 10 %), and tandem repeats (the things used in paternity tests, originating from errors in copying).
You’ve got 18,500 genes of your own, and 34,000 retrovirus genes. Any more questions?
The creationist method involves less thought than that. It’s more like a method:
1) Evolution is a lie.
2) Find instances where a scientist lied.
3) Falsely claim that modern evolutionary theory is based on those lies. (e.g. falsely claim Haekel’s illustrations appear in biology textbooks).
ThirtyFiveUp, May 9, 2009 10:04 PM
When I posted that comment it was #49. But given PZ’s habit of randomly deleting comments that rile him in some fashion, it wouldn’t surprise me if by now it’s some lower number. One thing I am fairly certain of is that my name is Alan Kellogg, not Alan Kellog.
I do know of people who spell the family name in some odd fashion, but most of them have the basic nomenclatural decency to spell it Kellough or Kellock or something like that. Spelling it Kellog is just gouche.
As for the prosody. Just started on Prozac again, and am now at 60mg a day. Might be going to a crisis house fairly soon for a bit, so the overblown rhetoric may intensify or even fade after a bit. No matter what happens, I remain fairly sure that PZ and Jesus would’ve gotten along famously had they ever met. Like PZ Jesus was monumentally self-important, sarcastic, and loved giving authority figures a hard time.
This just occurred to me. Anybody have any good leads to information on Pineal Bodies in mammalian, avian, and reptilian brains? As I understand it, some passerine birds have pineal bodies with a lense, rods, and cones. One small song bird (who’s name I’ve autistically forgetten) has about three distinct cones in the cells of its pineal eye in addition to the four found in its visual eyes.
Good luck Alan !
Define self-important.
And regarding this Jesus person,how do you know? Dont tell me….the Bible? Awwwwwww
So, IS the secondary ventricle formation in zebrafish a ancestral state? I’d Think it is an apomorphy for teleosts (and relatives?), like I also think about the meroblastic discoidal cleavage.
Books about brains: I like “Development of the Nervous Sytem” By Sanes DH. It’s and undergraduate developmental biology / neuroscience textbook, but somewhat easy to understand.
They may be the famous crackpots. But there are plenty of cranks, crackpots and woo-spreaders in the rank-and-file.
“The similarities are real and go even deeper than what the 19th century biologists claimed.”
This “deeper” extends beyond appearance and cell motions, down to signalling and gradient molecules and to the shared genes for brain development itself, the very definition of relatedness. The creationist’s apologia for this similarity are “just so” stories, not science.
I wonder if the discussion we recently had regarding the similarity of the cow genes to humans vis’a’vis the rat and mouse genes, might represent another problem for creationism. Evolutionary theory has a ready explanation and mechanism. Creationism will have to strain for another ad hoc “just so” story. Nothing is going to convince the creationists, but strained explanations plugging more gaps continues the erosion of their credibility, and helps embarrass away scientists they might be trying to woo.
What purpose can an error-ridden retrovirus genome possibly have?
What? Only comments by people who are already banned are deleted.
vis-à-vis.
It’s not random. Wagner was banned long ago, and still persists in trying to post here — he gets deleted as soon as I notice him. He’s pretty much in the same category as David Mabus.
I know a high school student who chose UMM because of PZ. She had other, more ‘prestigious’ options and the credentials for them. Still creationists claim that he’s a liability to the university. We know it’s a lie because of the moving lips, but I wonder if anybody’s checked just how many students make the same choice. And it occurred to me that the “atheists damage” argument springs from the same backward thinking that started this post, so I’m not even off topic.
ice
Y’know, I went to Catholic school (gradeschool and high school), and creationism was never seriously discussed. Evolution was taught in our biology classes as fact.
okay MosesZD @95 says it a little better than I did (pop culture ref). What I really like is this: God was/is involved in evolution!
Think on it. Comment intellegently. ( Seriously, not baiting anyone here. )
Ah, the problem is that god doesn’t exist, so the statement is false. No good hard physical evidence for god exists, so science can’t use god for anything. Most people are confused on this. They presume god, and wonder why science doesn’t.
“What purpose can an error-ridden retrovirus genome possibly have?”
It may be a source of genetic variation available to natural selection. While not an error ridden example, did you catch the recent finding that certain wasp toxins are identical to some viral DNA. Unfortunately, the sciencenow report is defunct for nonsubscribers:
http://www.crome.org/wp/2009/02/another-cross-species-gene-transfer/
The nonfunctional human gene for vitamin C synthesis is another example of junk DNA.
What’s your evidence for conflating a mythological sky pixie with reality?
In response to:
David Marjanović, OM | May 10, 2009 8:20 AM @ 101
Let me clarify. If you had a garage full of old styrofoam pieces but you knew that 15% of that volume contained areas of information you really needed to get at and often (or at very specific times) lets say a few hundred CD’s in a couple cases spread around, wouldn’t it be really nice to be able to find those areas without having to remove all the styrofoam in the way every time.
The DNA is a physical structure “un-wound” occupying the nucleas, it is interacting with all the DNA, other nuclear molecules, and their charges, constantly. This physical occupation and interaction of structures is information which can be conveyed at distance.
In the analogy above it would be like each piece of space-filling-material (styrofoam from your suggestion) was connected in a very specific way, and with a very specific shape such that by looking at what pieces where arranged around the outside of the garage space you could “feel” where those CD cases were within the larger mass.
It would be another layer of organizational information at a larger scale allowing for access to those areas of information we call genes.
The actual code of DNA is the fundamental layer of information, but with mutation and the “sloppiness” of biology wouldn’t multiple layers of information be a good way to back up where at least that information is stored?
For instance; do we know the molecular machinery that provides the global nuclear organization for opening and expressing genes? How is a gene buried within the expanded DNA found for expression? How does the RNA polymerase locate promoter regions for expression? Is it random; Is it random, but the areas to be transcribed are “opened up” for greater access? Is a network of molecular machinery at this “global” scale needed to explain these questions of expression?
Which one? Aeolus, Aesculapius, Aether, Amor, Anadyomene, Aphrodite, Apollo, Aquilo, Ares, Artemis, Asklepios, Ate, Aurora, Auster, Bacchus, Bellona, Boreas, Ceres, Cupid, Demeter, Diana, Dionysus, Discordia, Eileithyia, Enyo, Eos, Eris, Eros, Eurus, Eurus, Fama, Fauna, Faunus, Favonius, Flora, Fortuna, Hades, Hebe, Hecate, Helios, Hephaestus, Hera, Hermes, Hespera, Hestia, Hygea, Hymen, Hypnos, Ilithyia, Inuus, Iris, Janus, Jove, Juno, Jupiter, Juturna, Juventus, Kora, Liber, Libera, Libitina, Lucifer, Lucina, Luna, Lycaeus, Maia, Mars, Mercury, Minerva, Morpheus, Mulciber, Nemesis, Neptune, Nereus, Nike, Notus, Orthia, Pales, Pan, Peitha, Persephone, Persipina, Phoebe, Phosphor, Pluto, Poena, Polydectes, Pontus, Poseidon, Priapus, Priapus, Pyschopompus, Saturn, Selene, Sol, Somnus, Suadela, Sylvanus, Terminus, Triton, Trivia, Tyche, Venus, Vesta, Victoria, Voluptas, Vulcan, Zephyr, or Zeus?
@119
You forgot Eric Clapton.
Blasphemer! We are all children of Huitzilopochtli!
Or is it Tezcatlipoca and Quetzalcoatl?
Why didn’t somebody tell me? I’ve spent years trying to fill that hollow with beer.
gimme my, gimme my, gimmie my baby back tail back.
@africangenesis, up about 108.
Creationists don’t provide “just so” stories; they’re “just ain’t so” stories.
Transcription factors.
The zebrafish is ray-finned. Would you happen to know if the more closely related lobe-finned fishes have ventricles and what their embryonic origin is?
To paraphrase myself in a previous thread
Creationist theory in action
Phase one: The bible
Phase two: ???
Phase three: Prophet
Regarding:
Sven DiMilo | May 10, 2009 11:06 AM @125
said: Transcription factors.
*consults Wiki*
Ooh
#128
No, you’re banned because you continue to break the blog’s commenting rules. People who disagree do not tend to be banned here. If they break the rules that they agree to by posting in PZ’s house, as you have, they do.
Charlie Wagner, SUPER GENIUS
Do you think that’s an original idea? I hope not.
Anyway, it’s in principle possible, but there’s no evidence that requires this hypothesis for explaining it, so we can just drop it. As Laplace allegedly said to Napoleon when he presented his book on the solar system and Napoleon allegedly asked why God wasn’t mentioned: Sire, je n’ai pas besoin de cette hypothèse – “I don’t need that hypothesis”.
That would require junk to be able to mutate into something useful. This does happen – the genes for the antifreeze proteins of icefish are former junk that happened to get a start codon at one end and a stop codon at the other, and happened to lack stop codons in between –, but it’s exceedingly rare.
Unfortunately that blog post doesn’t say what kind of viral DNA (a viral gene, a gene that the virus had picked up somewhere, a promoter…?), and it doesn’t say if the gene was junk DNA in the meantime.
Yep, it’s one of the pseudogenes that make up some 10 % of our genome. They were functional at one time or another and then got a mutation that made them kaputt.
Most of it is very tightly wound, actually. That’s what all those histones and stuff are for.
Could be, but isn’t.
Would be neat, but it’s not the case.
Sure it would. It’s just not the way it’s actually done.
Sort of.
I’ll start at the simplest level. In front of each gene (and the less decayed pseudogenes*), there’s a stretch of noncoding DNA called a promoter (or several – can get very complicated in eukaryotes, never mind the enhancers, which are similar stretches that can be pretty far away). Proteins called transcription factors drift around aimlessly (Brownian motion), and when they happen to hit a promoter, they stick to it more likely than not (simple electrostatic attraction). RNA polymerase, too, drifts around by Brownian motion, and when it happens to encounter a transcription factor, the transcription factor basically takes it and sits it down on the DNA, where it binds to a specific sequence (electrostatic attraction again) and automatically gets to work.
The next level is that genes that are not often transcribed get methylated (certain bases get modified by an enzyme), which makes transcription factors and RNA polymerase stick less well.
Then comes the packaging. DNA is wound around histones, little balls of protein (which stick to it by, guessed it, electrostatic attraction). The stretches between two balls are more accessible than those that are glued to a histone. Certain proteins attached to the transcription machinery can move the histones or even throw them off completely, making the DNA more accessible, and there’s a lot of regulation going on concerning how tightly the DNA is bound to the histones (methylation, acetylation and phosphorylation of histones).
So, in sum (and keep in mind I’ve simplified it all drastically; the transcription machinery is huge, for instance, and I didn’t even mention the operators and silencers, which have the opposite effect of promoters and enhancers…), it’s biased random: RNA polymerase drifts around aimlessly, and when it happens to encounter a transcription factor, it (likely) starts working; and the transcription factors got there the same way. The RNA polymerase is not directed to a transcription factor.
* Headline: “Cells awash in useless RNA”.
No, and more importantly I don’t see where junk DNA even enters that question.
wow, this thread is pure comedy gold.
#120, 122, and 127 all win.
Charlie, either publish your work in the peer reviewed scientific literature, or shut the fuck up. Otherwise, you are an unscientific crank. Welcome to science.
So then transcription factors just randomly float around until they find their coded-for region then the RNA Polymerase just randomly floats around until it finds the transcription factor. But those genes must be on the exposed “hetero-chromatin” side. How did the entire Chromatin-ball open correctly for the right genes to be exposed for the transcription factors to attach? Or are they small enough to float in and “find” the right region,…then that area is somehow opened?
Is there a molecule that works at a scale larger than topoisomerase for resolving opening of the chromatin from eu-to-hetero?
Oh and thanks for the heads up with the transcription factors Sven.
Charlie, you projecting little narcissist, here are the rules. You broke too many of them too often; good riddance.
You? Smart? You’re not even smart enough to notice that the argument from ignorance is a logical fallacy! :-D
(That’s the less tightly wound euchromatin, not the more tightly wound heterochromatin.)
To some degree that’s heritable… but:
To some degree, yes. The “somehow” is the enzyme machinery (histone methylase, acetylase, phosphorylase). There’s feedback: the more open something is, the more easily it stays open. I don’t know all the rest by heart and don’t have time to look it up, but it’s explained in (very recent!!!) textbooks in quite some detail.
Various signal transduction pathways influence transcription factors respectively the histone modification machinery. Keyword “epigenetics”.
David Marjanović, Thanks for the one intellegent comment. (Laplace I knew (french being one of my languages), the quote I did not.)
Ok thanks David for the study material, now to find “very recent” used text books for sale at less-than insane prices!
Maybe thats part of the problem with science (evolution/genetics) education for the all-ready out of school, all the material is so damn expensive. Who can afford a subscription to Nature. Guess i have to spend my weekends at the library from now on.
Aren’t university libraries public where you are?
Well, there is this special textbook:
http://www.amazon.com/Epigenetics-C-David-Allis/dp/0879698756/ref=sr_1_2?ie=UTF8&s=books&qid=1241977333&sr=8-2
It’s very complete, but requires some expertise. Allis and Jenuwein are the discoverers of histone acetyl transferases and histone methyl transferases, respectively.
This is a good book on genetics and molecular biology, and transcription factors:
http://www.amazon.com/Molecular-Biology-Gene-James-Watson/dp/080539592X/ref=sr_1_1?ie=UTF8&s=books&qid=1241977802&sr=1-1
@ David Marjanovic:
It’s not true that DNA/nucleus architecture and knoformation doesn’t matter, there seem to be different compartments in the nucleus in which chromatin is pulled in or out for expression. But that could be to counter the huge amount of junk.
Review (free!):
http://genesdev.cshlp.org/content/21/23/3027.long
I also want to repeat the question Marjanovic, Micheal and I asked:
Do the ventricles also form from a solid string in non-teleost fish? Or are they formed from folding in a primarily hollow neural tube, like in tetrapods?
gnah, typos.
I don’t think it’s been established (here) that all teleosts have secondarily hollow ventricles…AFAIK this could easily be a zebrafish thing, a consequence of miniaturization, perhaps.
Never mind.
More details of comparative neurulation here, of all places.
And apparently “The Queensland lungfish (Neoceratodus forsteri) shows primary neurulation (Kemp 1982)”
Yes, five comments in a row…this just to acknowledge the unfortunately missing italics above.
@ #141, Sven DiMilo:
Yes, but I always get told that “fish” neurulate that way in developmental biology courses.
What is a “fish”? those critters are more diverse than the other vertebrates, depending on which clades you throw in.
Maybe developmental biologists only mean zebrafish and medaka when they/we say “fish”, but it also could be a feature for all teleosts or ray fins. teleosts are a somewhat advanced clade with many apomorphies, and it may be that they also have many developmental specialities.
For example, lamprey embryos cleave in a way similar to frogs, while teleosts do something wierd. So I guess that’s a new invention in that part of the phylogenic tree.
Har, wow, thx!!
“…What I really like is this…”
Yeah, that’s your first problem. Try removing your personal proclivities first, then come back and test. *That* is how it’s done, not by selecting a subjective position and then testing.
Some of us are unclear on the concept of borrowing.
We tend to go “BOOK! MINE! CAN HAS! NO! YOU, NO CAN HAS!”
Also called “doesn’t play well with others”.
David Marjanović, OM @ #131
“It’s only wafer thin.”
Quote Lowery et al., 2004:
7. Evolutionary considerations: is zebrafish neurulation primitive?
The distinction between primary and secondary neurulation is particularly apparent in the stages that bracket formation of the neural tube. For example, prior to neural tube formation, primary neurulation utilizes a flat neural plate whereas secondary neurulation begins with a mesenchymal population of cells, which condense. These early stages may best serve as comparisons for evolutionary conservation. As discussed above, details of the precise movements in different vertebrates show a variety of solutions to the problem of changing the sheet of neural plate cells into a tube, and these details may be less helpful in evolutionary comparisons.
Previous descriptions of zebrafish trunk neurulation have suggested that this process is more primitive than neurulation in ‘higher’ vertebrates. This does not appear to be true, since organisms from more primitive lineages clearly undergo both primary and secondary neurulation. For example, the sturgeon, from a more ancient lineage than zebrafish, generates the neural tube by a direct folding of neural plate epithelium (Ginsburg and Dettlaff, 1991). The myxinoids (hagfish) and elasmobranches (sharks and rays), from even more primitive lineages, use primary neurulation in the brain and spinal cord region and secondary neurulation in the tail ( Nakao and Ishizawa, 1984). Amphioxus and ascidians (both protochordates) roll up an epithelial neural plate ( Conklin, 1932; Holland et al., 1996 and Swalla, 1993), characteristic of primary neurulation.
Thus, evolutionarily, teleosts are flanked by more ancient and more modern lineages that employ primary neurulation anteriorly and secondary neurulation posteriorly. This is consistent with conclusions that teleost trunk neurulation should be described as primary.
Well, at least you’re not egotistical.
God was/is involved in evolution!
trying to become a theistic evolutionist?
well, I guess it’s some sort of progress, if you started off as a Young Earth Creationist, anyway.
or were you thinking more along these lines:
http://www.crank.net/evolution.html
scroll to:
“An Evolutionary Manifesto”
I hope not.
Ichthy, be careful. You might drawn “he who is too crazy” here.
Ichthy, be careful. You might drawn “he who is too crazy” here.
there’s no taking it back, now. Note that I DID start with the link to crank.net first; in order to establish exactly where that bit of crazy-spew belongs.
However, I think its name has to be said 3 times for it to pop out of mirror-land and attack.
just in case…
*puts on anti-crazy helmet*
there.
I thought it was 4 times in a tub of coolwhip?
This is a first for me;this card was actually shown as a tool of validation and not a drunken forenight’s misgiving…otherwise a great post for an amateur biology buff.
#156
“Stupomatron” helmet. Patented, water-resistant…
Ichthyic
NEVER was I a Young Earther. In fact since the time I became informed enough to form an opinion on such things, I have always been an evolutionist.
A theist too I admit.
Please excuse the lack of credit for the following (i can’t for the life of me remember who said it)
“The crime of holding an opinion ought to be one crime all commit.”
( I only remember it was from the late 19th cent.)
And I hope that you are also aware of the insightful: “You are entitled to your own opinions, but not to your own facts.”
Is God merely an opinion, and not a fact? Could God be a fact? If not, why not? If so, what sort of fact would God be?
Thanks a lot, I’ll read it ASAP (…which means “not soon” :-( ).
Also thanks to all those who clarified the phylogenetic and anatomic distribution of the neurulation methods. Looks like it’s at most a teleost thing, and at the minimum… zebrafish and medaka are very, very, very close relatives, you know…
TZ:
Amazing insight! But reading through the progression of blog comments is mind boggling…information overload for an undergrad such as I.
This is actually the first time I’m realizing how much the comments are part of what make blogging/(reading blogs) are fun.
And on that note….there are too many people with their heads up their arses, I think.
Access to higher technology evidently is not reflective of an advanced/evolved intelligence system.
“The crime of holding an opinion ought to be one crime all commit.”
the problems comes when one fails to distinguish informed opinion from rampant speculation.