Axial twist theory

https://en.wikipedia.org/wiki/Axial_twist_theory

by lordnacho • 11 months ago

178 45 11 months ago

en.wikipedia.org

ahartmetz2• 11 months ago

The schematic illustrations are just adorable! Whoever did these, fantastic job.

qgin• 11 months ago

Just look at this distinguished gentleman

https://upload.wikimedia.org/wikipedia/commons/thumb/6/61/Fi...

bongodongobob2• 11 months ago

It looks like brainrot material, I love it. This has some meme potential.

frozenseven• 11 months ago

Not gonna lie, those illustrations are a bit scary. Which makes it even better.

comex• 11 months ago

I found the illustrations confusing; I had to go over them and the accompanying text over and over before I understood what was being depicted.

DC-3• 11 months ago

Not saying the theory is bunk but I think that basically everything about this on Wikipedia is written and illustrated by the researcher who devised the theory. So it's that guy.

ahartmetz2• 11 months ago

I doubt it because the guy died in 1934. There is no short, clear statement on the Wikipedia page that it was this guy, only that he "proposed a theory". https://en.wikipedia.org/wiki/Santiago_Ram%C3%B3n_y_Cajal

esafak• 11 months ago

https://en.wikipedia.org/wiki/User:Marci68

riffic• 11 months ago

surgeon Francisco Torrent-Guasp determined the human heart to be continuous, helical muscular structure like a conch shell. maybe I've been the holofractal subreddit a bit too long because folks really seem to have a thing for the twisty toroidal vortexes there.

taneq2• 11 months ago

Interesting! My pet theory about the crossover in the optic nerve is that it's the simplest way to get goal-seeking behaviour. Proto-eye activates, activates muscles on opposite side of body, organism turns towards activated proto-eye.

Fun speculation: Maybe we started with no crossover (which gives avoidance behaviour, keeping the organism free-swimming). This still works for a while as the axial angle between eyes and muscle groups increases, so there's no real penalty for having a bit of a twist. As the twist increases, it starts acting a bit like a discriminator, where we avoid small things less than large things, which seems good if we want to eat small things. Past 90°, we start spiraling towards things instead of away from them, which admittedly makes us crash into large things more, but we can chase moving things. Hunting has evolved!

admin_account• 11 months ago

That’s interesting! My mind always just assumes the reason is some “core” biological reason. I think contralateral wiring helps the brain manage signal sequencing while preserving evolutionary symmetry.

The spinal cord handles rapid reflexes (pulling away from a hot stove), leaving the brain for slower non-immediate tasks. By crossing nerves before they reach the brain a standardized delay is introduced, giving the brain a predictable offset to filter against. The optic chiasm follows the same logic.

And I think this is necessary to keep same-side brain-body pairs from over-optimizing (direct nerve connection from the right hand to the right brain hemisphere) their paths at the expense of balance, preserving biological symmetry.

polishdude20• 11 months ago

Ive always wondered if it had something to do with up being the direction of the sun and light and down being the direction of gravity, depth, darkness.

Sharlin3• 11 months ago

Invertebrates seem to have had no problems evolving hunting even though they don’t have a twisted body plan. And hunting almost certainly evolved before this change occurred in the vertebrate lineage.

OhMeadhbh2• 11 months ago

When I see a seemingly "random" post on HN I always wonder if someone happened across some random bit of info and thought it so interesting they just had to share, or if there's some other bit of related news I haven't heard about. Did we just discover space starfish on Mars? I'm guessing I would have heard about that. Or did someone post a paper challenging axial twist orthodoxy? Guess I can google that.

But there's a delightful span between seeing someone post something on HN unrelated to AI, Cryptocurrencies or startups selling VS-Code extensions and the moment when I satisfy myself something outlandish (like space starfish) hasn't happened. During that time, all things are plausible.

[Edit. Which is not to say I disparage or discourage posting cool things you've found on the net. That's kind of what many of us are here for.]

mk_stjames• 11 months ago

One of the most delightful things involving reading HN is seeing a strange, context-less post in the morning, and then, later in the day or evening, coming across another piece of information- maybe a popular article on another website or a very popular youtube video- that then leads you to some research hole, possibly wikipedia'ing and following the older, linked sources- where you wind up on the exact page linked from the random post that morning and it becomes pretty obvious that you just retraced the exact steps that a like-minded individual had done earlier that day.

It's happened to me several times where I doubt it could be simply recency bias coupled with chance of topics, due to the specificity and narrow directed-ness of the graph.

parpfish• 11 months ago

same. it happens to me all the time on HN.

on one hand, i feel like this is a text-book example of the Bader-Meinhoff illusion [0].

but... there's an actual causal mechanism that could drive it.

show an interesting article to the HN crowd -> some subset of HN readers are inspired to go down a wikipedia rabbit hole and post some cool thing they found back on HN -> people that saw the original interesting post will not only see the related followup post, but they'll upvote it and cause even MORE to see it

[0] https://en.wikipedia.org/wiki/Frequency_illusion

adamjb• 11 months ago

axial twist orthodoxy

My impression is that this isn't exactly settled science. If you look in the history for the article you can see that it's mainly written by the lead author of the main citations. He also did the cute illustrations that everyone loves

https://commons.wikimedia.org/wiki/User:Marci68

monkeycantype5• 11 months ago

can you be my collective memory for a minute, I remember the existence of a very satisfying engineering explanation for why the representation of various body parts needs to be flipped left/right in the brain that came down to the topology of the wiring, and explained why unflipped isn't feasible / or perhaps it was just less efficient, it was one of those 'mind explodes' moments, but now I can't recall the logic.

bongodongobob2• 11 months ago

I always thought it was so if an organism takes head damage on one side, the limbs facing the danger will have a better chance to still work, giving it a better chance to fend whatever off and survive.

topaz0• 11 months ago

That has the smell of an evolutionary just so story

monkeycantype5• 11 months ago

no there is a very specific reason, related to mapping the 2d surface of your body to a 2d mapping on your brain that allows the areas of your brain that process sensory input from your skin to be adjacent to the processing of the areas that are adjacent on the skin that only works with a flip, I can remember what that is, I only remember the tingle of understanding it at the time

Sharlin3• 11 months ago

That would be an incredibly unlikely adaptation anyway, but this change occurred in vertebrates before they even had limbs.

andrewflnr• 11 months ago

I have a similar dim memory, but (at least according to this article) invertebrate bilaterians don't have that swap at all, so it can't be too strong a constraint.

renewiltord• 11 months ago

I recall this. The original idea is from decades ago but perhaps you read it in the Quanta article here https://www.quantamagazine.org/why-the-brains-connections-to... or perhaps that will lead you to what you want.

monkeycantype5• 11 months ago

Ah! That's the thread, not the source I read but I beat if I read the referenced paper I get there , thank you

ragazzina• 11 months ago

Are you referring maybe to the "Visual map theory"?

https://en.wikipedia.org/wiki/Contralateral_brain#Visual_map...

monkeycantype5• 11 months ago

I wasn't but that's intriguing Thank you

adrian_b• 11 months ago

There is no doubt that the body of the vertebrates posterior to the head is rotated in comparison with that of most animals, so that what is up in other animals is down in vertebrates and vice-versa. Evidence for this has been known and it has continued to accumulate for about two centuries.

Where there is uncertainty is about what has happened to the head.

According to the supposition presented in the linked article, most of the head has preserved the same orientation as in most other animals, either because it never took part in the rotation of the rest of the body, or because later it has made an additional half-turn rotation, which has brought it back to the initial orientation. Among these 2 alternatives, I think that the first is more plausible, because in that case the environment would have retained a constant orientation with respect to the principal senses, even if the posterior body rotated.

While this theory supposes that most of the head of the vertebrates has the original orientation, also all competing theories must accept that at least a few parts of the head either have never participated to the body rotation, or a subsequent rotation has brought them back in the original position, e.g. the mouth.

qoez• 11 months ago

I feel like these whimsy diagrams will eventually be taken down or replaced with something more formal and corporate. That's a shame imo. I wish there was a place for a wiki style community edited resource that allowed more whimsy.

Razengan• 11 months ago

Can someone TL;DR? What does this mean?

It just made me think, whether it's related or not, shouldn't the "natural" resting position of human heads be "upwards" like the rest of the animal world?

I mean if you consider the worm/fish template, it's

    o--->

where "o" is the "tail end" and ">" is the head. It points in the "direction" of the body. All other mammals and birds are also

    o--->
     | |

whereas we weirdos are

    o—--v

Sharlin3• 11 months ago

No. We’re talking about axial twist that occurred very early in vertebrate evolution. The hypothesis aims to explain why each brain hemisphere is associated with the opposite side of the body, including the eyes, in vertebrates (but not in invertebrates).

samirillian• 11 months ago

Is it possible that lefties twisted in the opposite direction

danw1979• 11 months ago

Wouldn’t that result in the organs of lefties being flipped too though ?

taneq2• 10 months ago

I don’t know about southpaws but I went to school with a guy whose heart was on the right side of his chest. I’m not certain about the rest of his organs though.

Axial twist theory

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