Which came first the head or the brain?

Mar 28, 2013 by John Hewitt report
Which came first the head or the brain?

(Phys.org) —A fundamental question in the evolution of animal body plans, is where did the head come from? In animals with a clear axis of right-left symmetry, the bilaterians, the head is where the brain is, at the anterior pole of the body. Little is known about the possible ancestor of bilaterians. Fortunately their sister group from that same progenitor, the cnidarians, can be studied in parallel today to give some clues. Cnidarians are creatures like jellyfish, hydra, and sea anemone which possess rudimentary nerve nets, but no clear brain. They all have just a single orifice to the external world, which basically does it all. In a recent paper published in PLOS Biology, researchers from the University of Bergen in Norway compared gene expression patterns in sea anemone (Nematostella vectensis, Nv) with that from a variety of bilaterian animals. They found that the head-forming region of bilaterians is actually derived from the aboral, the opposite-oral, side of the ancestral body plan.

Pioneering developmental biologist Lewis Wolpert, is often credited with having observed: "It is not birth, marriage, or death, but gastrulation which is truly the most important time in your life." Almost all animals undergo a similar gastrulation process early in their development. The point where the cells first invaginate during gastrulation, the blastopore, uniquely defines an embryonic axis. After this stage however, all bets are off—attempts to define phyla according to hardline criteria, like blastopore = anus, are invariably met by counterexample where it instead becomes the mouth. Gene expression, while not always constrained into single contiguous areas, therefore provides a baggage-free way to assign homology across species.

Wolpert's concept of positional information in development has been largely vindicated by the discovery of hox gene codes in a wide variety of animals. While are the critical regulators of axial patterning, in most bilaterians they are not expressed in the anterior head-forming region. The researchers focused instead on the genes six3 and FoxQ2, which have been shown to regulate anterior-posterior development. Six3 knockouts in mice, for example, fail to develop a forebrain. In humans six3 regulates forebrain and eye development.

, like Nematosella, are curious creatures. As larvae they swim about with their aboral pole forward. As adults they plunge this region into the sea floor, and permanently anchor themselves in. Their bodies then undergo various changes but their oral pole remains intact for feeding. By using knockdown and rescue experiments in Nemostella, the researchers were able to show that six3 is required for the development of the aboral region, and the expression of further regulatory genes. This suggests that the region distal from the cnidarian mouth parallels development of the bilaterian head.

The researchers also looked at the expression of the forkhead domain protein foxQ2, which functions downstream of six3. Forkhead box genes are an important class of transcription factors which frequently lack the signature homeodomains and zinc-finger regions common to other transcription factors. Instead they have a unique DNA-binding region that has the shape of a winged helix. The forkhead gene, fox2p, in humans has recently garnered a lot of media attention for its apparent role in neural development, and in even more esoteric functions like speech development.

FoxQ2 is known to be a well-conserved marker for the most anterior tip of a variety of bilaterians including sea urchines, drosophila, and cephalochordates. The researchers established that before gastrulation in cnidarians, foxQ2a was expressed in the aboral pole, and in a small number cells resembling neurons. Afterwards the expression of this "ring gene" was excluded from a central spot.

In conclusion, the expression of genes for anemone head development, away from the mouth region, suggests that head development came first and was a separate event from mouth development. Secondarily, the head and a coalescing brain appear to have merged to become a centralized control center.

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More information: Sinigaglia C, Busengdal H, Leclère L, Technau U, Rentzsch F (2013) The Bilaterian Head Patterning Gene six3/6 Controls Aboral Domain Development in a Cnidarian. PLoS Biol 11(2): e1001488. doi:10.1371/journal.pbio.1001488

Abstract
The origin of the bilaterian head is a fundamental question for the evolution of animal body plans. The head of bilaterians develops at the anterior end of their primary body axis and is the site where the brain is located. Cnidarians, the sister group to bilaterians, lack brain-like structures and it is not clear whether the oral, the aboral, or none of the ends of the cnidarian primary body axis corresponds to the anterior domain of bilaterians. In order to understand the evolutionary origin of head development, we analysed the function of conserved genetic regulators of bilaterian anterior development in the sea anemone Nematostella vectensis. We show that orthologs of the bilaterian anterior developmental genes six3/6, foxQ2, and irx have dynamic expression patterns in the aboral region of Nematostella. Functional analyses reveal that NvSix3/6 acts upstream of NvFoxQ2a as a key regulator of the development of a broad aboral territory in Nematostella. NvSix3/6 initiates an autoregulatory feedback loop involving positive and negative regulators of FGF signalling, which subsequently results in the downregulation of NvSix3/6 and NvFoxQ2a in a small domain at the aboral pole, from which the apical organ develops. We show that signalling by NvFGFa1 is specifically required for the development of the apical organ, whereas NvSix3/6 has an earlier and broader function in the specification of the aboral territory. Our functional and gene expression data suggest that the head-forming region of bilaterians is derived from the aboral domain of the cnidarian-bilaterian ancestor.

Synopsys: www.plosbiology.org/article/in… journal.pbio.1001484

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verkle
1.2 / 5 (26) Mar 28, 2013
Duh! They both came first.
Evolution is a dying theory that just doesn't pan out.
The more we know, the more we can see its ridiculousness.

baudrunner
2.6 / 5 (5) Mar 28, 2013
In earliest prepermanently defined monocellular forms the membrane must evolve to encapsulate the protoplasm and contents and becomes a selective passage for useful proteins used to support the functions of that self-contained biomass. The amoeba simply wraps its self, by using two concentrated areas of development commonly referred to as the feet, around prospective food and ingests it via its food vacuole, expelling the unused material through its contractile vacuole, in a sequential passage of events.

Perhaps we should ask whether the feet came before the head or did the head come before the feet?
xel3241
4.1 / 5 (15) Mar 28, 2013
Duh! They both came first.
Evolution is a dying theory that just doesn't pan out.
The more we know, the more we can see its ridiculousness.



It's hardly dying. Support for it by scientists is at 99%, only the uneducated general public is unable to accept it.

Mutation occurs, therefore evolution must occur. Add to this natural selection, horizontal gene transfer, and other sources of genetic change, coupled with the evidence from the fossil record, and we have very strong evidence for evolution.

Add to this, I'm religious and supporting evolution, if that hopefully will convince you. In my view, [insert supreme being(s)] created the diversity of life on Earth and throughout the Universe by means of evolution, which was to some extent directed by genetic engineering via retroviruses (which, by the way, are ≥8% of the human genome). It is a view which is not contradictory to evolutionary theory or religion at all, so why haven't you and your creationist ilk accepted it yet?
Lurker2358
2.1 / 5 (11) Mar 28, 2013
There are better things to do then argue over process.

Let me ask:

Once God determined whatever mechanics and chemistry laws he was going to make for the universe, don't you think there are certain boundaries with which things are made in that context?

If DNA were analogous to a computer program, then all classes (representing organism types) have certain subsets of their "code" which would look very much the same, and may even be identical for some portions. Why? Because if it works once and it will work again, then why change it?

The reason so many organisms have so much DNA in common is because there are only a limited number of possible combinations for a strand of any given length, and since many combinations might be "garbage" in the context of the particular organism the creator had in mind, then there are only a few combinations that are appropriate to certain classes of life functions. These, or slight variations of these, would logically appear in wide variety of life.
xel3241
3.3 / 5 (3) Mar 29, 2013
There are better things to do then argue over process.


In the context of this forum, yes. However, in the context of the broader world, solid science needs to win over literalism and creationism. Only once the public is scientifically literate will we again begin to make major advances at a rapid rate.

Pseuoscientific forum members, while individually not a large number of people, could certainly be convinced as a start.
dan42day
4.6 / 5 (13) Mar 29, 2013
I would say the head came first based solely on anecdotal evidence. I have never met a person with a brain but no head, however the reverse situation is exceedingly common.
Whydening Gyre
2.6 / 5 (5) Mar 29, 2013
I would say this somehow relates to the phrase "He's got his head up his ass...",
TheGhostofOtto1923
2.6 / 5 (9) Mar 29, 2013
The reason so many organisms have so much DNA in common is because there are only a limited number of possible combinations for a strand of any given length, and since many combinations might be "garbage" in the context of the particular organism the creator had in mind, then there are only a few combinations that are appropriate to certain classes of life functions. These, or slight variations of these, would logically appear in wide variety of life
Lurkers ass-born explanation works much better in the context of evolution but he fails to realize this because of his a priori (shit - I used a philo word) certainty that there is a god who designed it all.

If true then he is a faulty lying god who designed faulty creatures despite claiming to be perfect.

Lurker can only be convinced that his god made it all because of the evidence he is willing to IGNORE.
xel3241
2.3 / 5 (3) Mar 29, 2013
The reason so many organisms have so much DNA in common is because there are only a limited number of possible combinations for a strand of any given length, and since many combinations might be "garbage" in the context of the particular organism the creator had in mind, then there are only a few combinations that are appropriate to certain classes of life functions. These, or slight variations of these, would logically appear in wide variety of life
Lurkers ass-born explanation works much better in the context of evolution but he fails to realize this because of his a priori (shit - I used a philo word) certainty that there is a god who designed it all.


You do realize that natural selection, mutation, and divine genetic engineering *all* play a role in Lurker's (and my) opinion? If you want to think we are "ignoring the evidence" then you don't understand what theistic evolution is, and are a belligerent atheist, no better than a creationist.
VendicarE
4.2 / 5 (5) Mar 29, 2013
I was talking to GOD last night, and he told me that his plan is to see anti-evolutionists burn in eternal hell fire.

I thought his feelings on the matter are quite appropriate.
TheGhostofOtto1923
2.6 / 5 (8) Mar 29, 2013
You do realize that natural selection, mutation, and divine genetic engineering *all* play a role in Lurker's (and my) opinion? If you want to think we are "ignoring the evidence" then you don't understand what theistic evolution is
Theistic evolution. Another attempt to reconcile the Xian creator with scientific evidence.

Your god SAID the universe was created in 6 days and that a worldwide flood covered the highest mountains for 40 days. These things arent true. Chances are he knows just as little about evolution.

Your god sanctioned a book which says there was an exodus, a genocidal rampage which destroyed 400 cities, towns, and villages, great hebrew kingdoms, and a completely unique and unprecedented godman. These things arent true. If he doesn't know history how could he be expected to understand evolution?

Perhaps he has as little regard for evidence as you?
xel3241
3 / 5 (2) Mar 29, 2013
Theistic evolution. Another attempt to reconcile the Xian creator with scientific evidence.

Your god SAID the universe was created in 6 days and that a worldwide flood covered the highest mountains for 40 days. These things arent true. Chances are he knows just as little about evolution.

Perhaps he has as little regard for evidence as you?


When did I ever state I was Christian? I said religious, and that does not necessarily entail Christianity. Most religious people (Christians included) who have an interest in science aren't stupid literalists, and know what represents the views of the people at that time, what is metaphor, and what is universal truth.

Your comment only proves that your inner belligerent atheist is showing. My theistic evolution mechanism isn't magic (involving the retroviral genetic-engineering method which is right now being used in research trials), now how do you support your ayatollah Dawkins?
Whydening Gyre
2.8 / 5 (6) Mar 30, 2013
Yeah... but what if -

oh, never mind...
TheGhostofOtto1923
2.7 / 5 (7) Mar 30, 2013
arent stupid literalists, and know what represents the views of the people at that time, what is metaphor, and what is universal truth
I know, religionists all reserve the right to decide what is literal and what is metaphor. If course none of you can agree on which is which and what is what.

The gods are very specific however. They say unequivocally that these things all happened, and that the books which describe them are infallible.

But we know that this is simply not true. And so any attempts at trying to explain physical phenomena in light of book-derived gods is nonsense.

You all struggle to do this only because you can't let go of those sick ideas of favored status, wishes granted, and escape from death with your teddy bear in heaven. Don't be too ashamed there are billions if people just like you all over the world. Many many of them are quite willing to kill and die for these fantasies because their gods DEMAND it.

And this is where the problem lies. Doesn't it?
xel3241
4 / 5 (4) Mar 30, 2013
Otto, you are correlating specific religious books to be what religionists construe as the absolutely true nature of God. Then you rail on about how these religious books spread a message of hate.

Again, you need to realize that in a sense there are as many religions as people. Some are nearly indistinguishable from others, but everyone has a slightly different conception of God and nobody is perfectly right. The truth is, very few people believe in the God you speak of, so your arguing against him is moot for me.
TheGhostofOtto1923
2.3 / 5 (3) Mar 30, 2013
I didnt say anything about hate did I? The judeo/Xian/Moslem, Hindu, Buddhist, Sikh, etc religions all have books which describe their gods in intricate detail. They all relate histories that didn't happen, about people who didn't exist. They use these stories to convince believers that their gods are real, and just, and merciful.

These books all describe what believers must do to earn the favor of their gods. This invariably includes rejecting others who do not share their beliefs as morally corrupt. These books also encourage and demand that believers increase the flock by proselytism and procreation.

It is these requisites which lead to the kind of hate you refer to. Every religion is blasphemy to every other religion because the books SAY they are. This is how religions divide the people, create animosity, generate scarcity, and result in VIOLENCE time and again.

The books all demand violence in defense of their gods as these gods are incapable of defending themselves.
TheGhostofOtto1923
2.3 / 5 (3) Mar 30, 2013
Some are nearly indistinguishable from others, but everyone has a slightly different conception of God and nobody is perfectly right. The truth is, very few people believe in the God you speak of, so your arguing against him is moot for me
And you CANNOT absolve yourself of responsibility for the actions of other religionists. You INSIST your god is real just as they do. This makes you complicit in the perpetuation of the whole concept, that superstition is real, and valuable, and worth killing and dying for.

Your pleasant fantasies enable others to commit the crimes they do in the name of the very same god you both believe in. A god who is simply NOT THERE. Because his books are full of easily exposed LIES.

Time to grow up. Time to let go and let god... go.
Torbjorn_Larsson_OM
not rated yet Apr 01, 2013
Creationists shouldn't comment on science, it is hilarious and makes deconverts from religion, see Dawkins's Convert's Corner.

"Evolution is a dying theory". Except that it is the major theory and basis of biology, and they are all expanding exponentially as measured by published works. So that was an exceedingly stupid claim.

"In earliest prepermanently defined monocellular forms the membrane must evolve to encapsulate the protoplasm and contents".

Indeed, and it did that either from spontaneously formed lipid vesicles and/or within inorganic compartments of alkaline hydrothermal vents.

The real bottleneck was energetics, but that is now solved too. (Electron bifurcating enzymes, with reduction potential modulated by the pH in alkaline hydrothermal vents. See Lane's & Martin's latest paper.)

"don't you think there are certain boundaries with which things are made in that context?".

Claim in need of reference. As is the preceding magical agent "gods" claim.
Torbjorn_Larsson_OM
not rated yet Apr 01, 2013
"The reason so many organisms have so much DNA in common is because there are only a limited number of possible combinations for a strand of any given length,".

So you _do_ acknowledge growth and loss of function, as there must be under strand length variation? Good, under that observation the reason for common DNA is inheritance under selection.

Also, _all_ cellular organisms have DNA and genes for its processing in common - one root.
ValeriaT
1 / 5 (1) Apr 01, 2013
Creationists shouldn't comment on science, it is hilarious and makes deconverts from religion
All people should be welcomed in discussion, until they're using rational arguments. The call for censorship isn't such an argument and it's actually as nonscientific, like the religion itself.