A creature that eats its own brain | Hacker News Reader

A creature that eats its own brain

goodheartextremescience.wordpress.com

81 pointsjelliclesfarm44 comments

The headline evoked my twisted like a Monty Python youth. Or the Haggis Poem aka Horace

  Much to his dad and mum's dismay 
  Horace ate himself one day 
  He didn't stop to say his grace 
  He just sat down and ate his face 
  "We can't have this!" his dad declared 
  "If that lad's ate he should be shared" 
  But even as he spoke they saw 
  Horace eating more and more: 
  First his legs and then his thighs, 
  His arms, his nose, his hair, his eyes 
  "Stop him someone!" Mother cried 
  "Those eyeballs would be better fried!" 
  But all too late for they were gone, 
  And he had started on his dong... 
  "Oh foolish child!" the father mourned 
  "You could have deep-fried those with prawns, 
  Some parsely and some tartar sauce..." 
  But H was on his second course; 
  His liver and his lights and lung, 
  His ears, his neck, his chin, his tongue 
  "To think I raised himn from the cot 
  And now he's gone to scoff the lot!" 
  His mother cried what shall we do? 
  What's left won't even make a stew..." 
  And as she wept her son was seen 
  To eat his head his heart his spleen 
  And there he lay, a boy no more 
 Just a stomach on the floor... 
  None the less since it was his 
  They ate it - and that's what haggis is

thanks for mentioning the haggis poem!it brings to mind another of my favourites..the reluctant cannnibal by flanders and swann...altho it has an happier(and tastier) ending...roasted leg of insurance salesman

https://www.youtube.com/watch?v=dZ6LzqV1ebk

The juvenile sea squirt wanders through the sea searching for a suitable rock or hunk of coral to cling to and make its home for life. For this task, it has a rudimentary nervous system. When it finds its spot and takes root, it doesn't need its brain anymore, so it eats it! It's rather like getting tenure.

Daniel Dennett

A classic, and my first thought when I saw the headline.

"The sea squirt larvae begin absorbing all the tadpole-like parts that made them chordates. Where the sea squirt larva once had gills, it develops the intake and exist siphons that will help it bring water and food into its body. It absorbs its twitching tail. It absorbs its primitive eye and its spine-like notocord. Finally, it even absorbs the rudimentary little "brain" (cerebral ganglion) that it used to swim about and find its attachment place."

By that measure, I suppose a caterpillar also "eats its own brain" during its transformation in to a butterfly.

It may be overstated for effect (which the author acknowledges), but it's a little more dramatic than a caterpillar in that it ends up without a brain, while a butterfly doesn't.

I also don't think current thinking holds that the organs of a caterpillar disappear completely during metamorphosis, though I could easily be wrong.

One of my favorite Radiolab episodes[1] was about just this:

MOLLY: What do you think happens inside the chrysalis?

JAD: I think that -- I actually have never thought about it, to be honest.

MUSEUM GUEST: I don't know. I don't -- I don't understand how it works.

MOLLY: Not many people have.

MOLLY: Are you, like, surprised that you actually don't know?

MUSEUM GUEST: Yeah, I'm surprised. I thought, like, I knew and I don't.

MOLLY: Those are folks I met at the museum.

JAD: Hey, hold up. Now that I've thought about it for a second, isn't it simply that the caterpillar is inside the shell, it sort of snuggles up, and then it grows a wing off of its right side and then off of its left side, and it just pops wings out?

MOLLY: No. That is actually what I thought, but that's not right at all...

[1] - https://www.podtrac.com/pts/redirect.mp3/audio.wnyc.org/radi...

A caterpillar becomes a soup of cells, fats, and proteins. Some species do not retain any multi-cellular structures- others only a tiny few.

Interestingly, the still exhibit learned avoidance behaviors after complete this near complete disassembly and reassembly.

Are you an expert? If so I defer, but if not I think you're repeating an old understanding of the process. From a bit more reading a substantial portion seems to dissolve, but far from everything.

Here's a paper tracking the metamorphosis of painted lady butterflies in considerable detail:

https://royalsocietypublishing.org/doi/10.1098/rsif.2013.030...

Are you an expert? If so I defer

Don't. An expert is the person most likely to be able to provide good support for their claims.

I agree. The stance "I defer to the experts" is potentially very damaging to the growth of knowledge, and can quickly lead to what philosopher of science, Imre Lakatos, called a 'degenerative paradigm,' where increasingly elevated credentials represent increasingly less actual skill and knowledge.

While credentials perform a necessary function, they are a placeholder, an IOU, and not themselves final grounds to accept a claim. They ought not to be treated as a primary source, and a claim based on a bare assertion of expertise should be accepted provisionally and only on the understanding that support can, in fact, be provided if the matter is pressed.

In short, your definition is a pretty good one.

I can see the argument for it, but I think that, especially at present, more harm is being done by a belief that expert opinion should be subject to obsessive outside scrutiny (by whom?) than this fairly academic concern about damaging the growth of knowledge.

For all that people like to point out the conservativeness of past experts rejecting ideas ultimately proven correct, few like to engage with the fact that almost all of those ideas were ultimately championed from within the establishment, not by radical outsiders.

It is not a matter of a political who:whom, but of an impersonal, objective 'what' i.e. the process of rationality.

Arguments should be able to stand on their own merit irrespective of whether their origin is 'outsiders', or the credentials of the originator. Again, it is very damaging to the institution of knowledge to say: "I accept your thesis on the basis of your credentials alone, and will investigate no further, either to increase my understanding, or to test its veracity."

I didn't say don't listen to experts. I didn't say don't respect expert opinions, only radical outsiders.

Here you have someone presenting evidence! But saying "if you're an expert, I defer". You can expect an expert to make their case and allow it to stand on its own. Beware experts who invoke their own authority as an argument.

That's an incredible paper! The supplementary materials are exquisite and can be obtained here [0]. I'd very much like to get ahold of the enormous raw dataset, but alas their margin was too small to contain it: "Owing to file size limitations, no repository capable of archiving the entirety of the voxel data for these scans currently exists".

[0] https://datadryad.org/stash/dataset/doi:10.5061/dryad.b451g

I noticed that too; hopefully in the intervening 7 years these sorts of limitations are no longer, but I suspect scientific data simply expandss to fill the archive space available, and more ;(

Absolutely not! The nervous system is retained intact.

"The juvenile sea squirt wanders through the sea searching for a suitable rock or hunk of coral to cling to and make its home for life. For this task, it has a rudimentary nervous system. When it finds its spot and takes root, it doesn't need its brain anymore, so it eats it! (It's rather like getting tenure.)" [0]

[0] Consciousness Explained, Daniel Dennett. https://www.google.com/books/edition/Consciousness_Explained...

Do you recommend that book?

If you are interested in consciousness, then yes, Consciousness Explained is a worthwhile read. If your interest lies with sea squirts, then not so much.

While I do not necessarily agree with Dennett's position in whole, I believe his arguments make a valuable contribution to the subject of consciousness -- even moreso in the context of Wigner's thought experiment and the recent empirical results.

Would you mind sharing a pointer to the recent empirical results?

Science magazine [0] and Ars Technica [1] published readable overviews. The paper on the experiment regarding Wigner's friend paradox ("A strong no-go theorem on the Wigner’s friend paradox") was published in Nature Physics. [2] [3]

[0] https://www.sciencemag.org/news/2020/08/quantum-paradox-poin...

[1] https://arstechnica.com/science/2020/08/quantum-reality-is-e...

[2] https://doi.org/10.1038/s41567-020-0990-x

[3] https://www.nature.com/articles/s41567-020-0990-x

The article is reminiscent of the some old science fiction tropes, about very different life cycles.

The article also reminded me of the chicken and egg inversion (I think from a chapter in a Richard Dawkins book) -- the observation that chickens are merely the mechanism through which eggs propagate themselves throughout the world.

I looked up what makes an animal an animal. It turns that animals have to eat another living thing to survive. It's quite interesting that the thing that makes us animals is not the brain, limbs, heart, lungs, liver, etc.

It's having a stomach. Every animal has gotta do some sort of ingesting of another lifeform. The sea squirt seems to be the prime example, it's just a stomach. Everything else is replacable.

No idea where you "looked it up", becuase that's hardly a valid definition. Modern taxonomy is rather complicated and is not particularly concerned with kingdoms (like Animalia), which are used more because they are handy to use, not because there is a real strict boundary between what is an animal and what isn't. So they have rather loose definitions.

Your statement lacks definition of what exactly is a "stomach", and I don't think you can provide such a definition for it to classify animals correctly. Sponges (which are animals), for instance, don't really have a "stomach", there is no cellular differentiation based on that function. Many carnivorous plants (which are not animals based on that they are plants, a different kingdom), on the other hand, do consume other living creatures and have something that can be considered "a stomach".

> Your statement lacks definition of what exactly is a "stomach", and I don't think you can provide such a definition for it to classify animals correctly. Sponges (which are animals), for instance, don't really have a "stomach", there is no cellular differentiation based on that function.

To be fair to sponges, they are considered the first branch of the animal kingdom - direct descendants of the first digestive tract and the first organism with any sort of cellular specialization. They're what animals would look like if they were nothing but a stomach.

> I looked up what makes an animal an animal. It turns that animals have to eat another living thing to survive.

I'm not sure where you looked up the definition, but that is very much not what defines animals.

There are plants like pitcher plants that eat living things, as well as many bacteria that eat other living bacteria. And there are animals like earthworms that only eat non-living organic material.

> Animals (also called Metazoa) are multicellular eukaryotic organisms that form the biological kingdomAnimalia. With few exceptions, animals consume organic material...

Assumes that meant living things?

Other things doing it too doesn't make a different, definitions we use for words are gonna have grey zones, such is the reality of compression.

"Organic material" as in organic chemistry as in compounds that form carbon-hydrogen bonds - stuff made up mostly of hydrogen, carbon, oxygen, nitrogen, and the halogens.

The correct term is heterotrophic but even that is a fuzzy distinction because many (if not most) plants require symbiotic bacterial/fungi colonies due to nitrogen depletion and there are plenty of parasitic plants that can't produce their own nutrition.

Clean classification of such abstract groups after billions of years of evolution is impossible.

Yeah we are basically a thinking chunk of meat that grew around a ringed worm, for it to feed itself more easily than wallowing naked in the dirt. Welcome to the depersonalization disorder.

I know it's not actually relevant. But what a horrible website to read. The grey text is soooo lacking contrast on the white.

So their larva is an almost-vertebrate (chordata) but then it changes back to an invertebrate. Neato

Is this a case of regressive evolution (devolution)?

No, it's just regular evolution. It's a mistake to assume that evolution prefers any particular direction, like increasing complexity or intelligence.

Still, a species can evolve to be more similar to some distant ancestor than to a certain more recent one. There's no mistake in asking if that is the case here.

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